Annual Meeting, 2013/Réunion annuelle, 2013 The Canadian Phytopathological Society

Cytological analysis of Pyrenophora tritici-repentis in barley. R. ABOUKHADDOUR AND S. E. STRELKOV. Department of Agricultural, Food and Nutritional Science, 410 Agriculture/Forestry Centre, University of Alberta, Edmonton, AB T6G 2P5, Canada

Pyrenophora tritici-repentis (Died.) Drechs., the causal agent of tan spot disease of wheat, is a destructive fungal pathogen worldwide. This fungus produces several host-selective toxins, also known as pathogenicity effectors. These toxins interact in a highly specific manner with the host plant, and the ability of isolates of P. tritici-repentis to cause disease on specific wheat genotypes is related directly to their ability to produce particular toxins. Recently, we reported the ability of a Ptr ToxB-producing isolate of the tan spot fungus to cross the species boundary and cause chlorosis on certain barley genotypes in a similar manner as it does on susceptible wheat. On wheat, chlorosis is a characteristic symptom of infection with Ptr ToxB-producing isolates of P. tritici-repentis. A cytological analysis of the infection process in susceptible and resistant barley genotypes, using light, fluorescence and confocal laser microscopy, revealed that germinated conidia develop germ tubes that form appressoria and penetration pegs, which then penetrate through the epidermal cells and develop intracellular vesicles. The invading hyphae advance further to colonize the mesophyll layer intercellularly, causing damage to the cells beyond the advancing hyphae. These results indicate that the cytology of barley infection by P. tritici-repentis closely resembles the cytology of infection in susceptible wheat. Further studies on the P. tritici-repentis-barley interaction are underway.

Effect of seeding date, seed size, seeding depth and seed treatment on pythium seedling blight of canola. H. U. AHMED, Q. ZHOU, G. D. TURNBULL, S. F. HWANG AND S. E. STRELKOV. Crop Diversification Centre North, Alberta Agriculture and Rural Development, 17 507 Fort Road N.W., Edmonton, AB T5Y 6H3, Canada; and (S.E.S.) Department of Agricultural, Food and Nutritional Science, 410 Agriculture/Forestry Centre, University of Alberta, Edmonton, AB T6G 2P5, Canada

Seedling blight, caused by the soil-borne pathogen Pythium ultimum Trow, reduces canola stand establishment and productivity in the Canadian prairies. The effects of seeding date, seeding depth and seed size on pythium seedling blight of canola were evaluated under greenhouse and field conditions. Under field conditions, early seeding reduced canola seedling emergence and seed yield in 2 out of 3 trial-years. In a greenhouse study, the sowing of large seed (>2.0 mm in diameter) resulted in consistently greater seedling emergence, plant height and shoot dry weight compared with smaller seed (<0.7–2.0 mm). The effect of seeding depth was generally not significant on seedling emergence, plant growth parameters, disease severity or seed yield in greenhouse or field trials. Thus, the data suggest that late seeding has some potential to reduce losses due to seedling blight in fields infested with P. ultimum.

Aetiology of Pyrenophora teres isolates from the Canadian Prairies causing intermediate symptoms of net blotch of barley. A. AKHAVAN, T. K. TURKINGTON, B. KEBEDE, I. S. STRELKOV, K. XI, K. KUMAR, A. TEKAUZ, R. KUTCHER, J. TUCKER, C. KIRKHAM, K. DUNFIELD AND S. E. STRELKOV. Department of Agricultural, Food and Nutritional Science, 410 Agriculture/Forestry Centre, University of Alberta, Edmonton, AB T6G 2P5, Canada; (T.K.T.) Lacombe Research Centre, Agriculture and Agri-Food Canada (AAFC), 6000 C & E Trail, Lacombe, AB T4L 1W1, Canada; (K.X., K.K.) Field Crop Development Centre, Alberta Agriculture, Food and Rural Development, 6000 C & E Trail, Lacombe, AB T4L 1W1, Canada; (A.T.) Cereal Research Centre, AAFC, 195 Dafoe Road, Winnipeg, MB R3T 2M9, Canada; (R.K.) Crop Development Centre, Department of Plant Sciences, University of Saskatchewan, 51 Campus Drive, SK S7N 5A8, Canada; (J.T.) Brandon Research Centre, AAFC, 18^th Street North and Grand Valley Road, P.O. Box 1000A, R.R. #3, Brandon, MB R7A 5Y3, Canada; and (C.K.) Melfort Research Farm, AAFC, P.O. Box 1240, Melfort, SK S0E 1A0, Canada

Net blotch caused by Pyrenophora teres Drechs. is the only foliar disease of barley in western Canada with two morphologically similar but genetically distinct forms: P. teres f. teres (Ptt) and P. teres f. maculata (Ptm), causing the net form of net blotch (NFNB) and spot form of net blotch (SFNB), respectively. A collection of 30 isolates recovered from Canadian Prairie (Alberta, Saskatchewan and Manitoba) barley crops was assessed to address the aetiology of symptoms that were not visually distinguishable as NFNB or SFNB. Isolates were identified as P. teres based on morphological characteristics and by polymerase chain reaction (PCR) with species-specific primers. Form-specific PCR primers further differentiated isolates into two distinct Ptt and Ptm groups with 19 and 11 isolates for each form, respectively. Thirteen polymorphic simple sequence repeat (SSR) primers developed from the P. teres genome assembly were used to detect evidence of possible recombination between the two forms. Applying the SSR data and employing the unweighted pair group method with arithmetic mean (UPGMA) procedure and Jaccard's similarity coefficient, cluster analysis revealed that all isolates clustered in two distinct divergent groups conforming to either Ptt or Ptm. No intermediate clade between the two forms was found when the same analysis was repeated with a larger population consisting of 217 P. teres isolates from western Canada. In contrast to studies that suggested the occurrence of natural hybridization between the two forms of P. teres in the field, these results suggest hybridization between the two forms is unlikely to occur in western Canada.

Occurrence of forms and mating type idiomorphs in western Canadian Pyrenophora teres (net blotch of barley) populations. A. AKHAVAN, T. K. TURKINGTON, I. S. STRELKOV, K. XI, K. KUMAR, A. TEKAUZ, R. KUTCHER, J. TUCKER, C. KIRKHAM, K. DUNFIELD AND S. E. STRELKOV. Department of Agricultural, Food and Nutritional Science, 410 Agriculture/Forestry Centre, University of Alberta, Edmonton, AB T6G 2P5, Canada; (T.K.T.) Lacombe Research Centre, Agriculture and Agri-Food Canada (AAFC), 6000 C & E Trail, Lacombe, AB T4L 1W1, Canada; (K.X. and K.K.) Field Crop Development Centre, Alberta Agriculture, Food and Rural Development, 6000 C & E Trail, Lacombe, AB T4L 1W1, Canada; (A.T.) Cereal Research Centre, AAFC, 195 Dafoe Road, Winnipeg, MB R3T 2M9, Canada; (R.K.) Crop Development Centre, Department of Plant Sciences, University of Saskatchewan, 51 Campus Drive, SK S7N 5A8, Canada; (J.T.) Brandon Research Centre, AAFC, 18^th Street North and Grand Valley Road, P.O. Box 1000A, R.R. #3, Brandon, MB R7A 5Y3, Canada; and (C.K.) Melfort Research Farm, AAFC, P.O. Box 1240, Melfort, SK S0E 1A0, Canada

A collection of 220 isolates of the barley net blotch fungus [Pyrenophora teres Drechs.] from the Canadian Prairies (Alberta, Saskatchewan and Manitoba) was assessed for form and mating type (MAT) idiomorph distribution and frequency. Net blotch form (net form: P. teres f. teres or spot form: P. teres f. maculata) was determined with form-specific polymerase chain reaction (PCR) primers. It was common to find both the net and spot forms of the fungus in the same field, on the same plant and on the same leaf. The net and spot forms were found in approximately equal numbers in Saskatchewan and Manitoba, but the net form was more than twice as frequent in Alberta. Analysis with mating type-specific primers revealed that the MAT1 and MAT2 idiomorphs of the net blotch pathogen could be identified within the same field, on the same plant, and on the same leaf. However, while both mating types could be identified within a single lesion caused by P. teres f. teres, only one mating type was typically found within a single lesion caused by P. teres f. maculata. For both forms, there was no significant departure from the expected 1:1 MAT1/MAT2 ratio in each of the three provinces and in the entire western Canadian population. Therefore, we conclude that P. teres likely goes through regular cycles of sexual and asexual reproduction on the Prairies. Given the frequency of both forms, breeding programmes should continue to incorporate resistance to both the net and spot forms of the net blotch pathogen.

Anthracnose of lentil – is race related to incompatibility group? C. ARMSTRONG-CHO, J. MENAT AND S. BANNIZA. Crop Development Centre, Department of Plant Sciences, University of Saskatchewan, 51 Campus Drive, SK S7N 5A8, Canada

Anthracnose (Colletotrichum sp. ex lentil) is an important disease of lentil in western Canada. Two pathogenic races are present in the pathogen population, designated race 0 and race 1. At present, cultivar resistance is available only to race 1. The sexual phase of the pathogen can be induced in the laboratory, and perithecial production requires the presence of isolates from two incompatibility groups, IG1 and IG2. Of the four possible combinations of two races and two IGs, the combination of race 1 and IG1 was absent among 37 field isolates. The possibility of these two traits being genetically linked was investigated by phenotyping the progeny of a cross between a race 0/IG1 isolate and a race 1/IG2 isolate. An equal frequency of each race-IG combination was observed among the 24 progeny, indicating that these traits are not linked. This result provides additional support for the hypothesis that sexual recombination of this pathogen is not occurring under field conditions (Menat, 2012).

Isolation, identification and disease severity assessment of Ralstonia solanacearum isolates on potato. N. A. ASHMAWY, A. F. EL-BEBANY, M. G. HASSOUNA, L. R. ADAM, F. DAAYF, K. A. LASHIN AND A. S. AOWN. Department of Plant Pathology, Faculty of Agriculture, Alexandria University, El-Shatby, 21545, Alexandria, Egypt; and (L.R.A., F.D.) Department of Plant Science, 222 Agriculture Building, 66 Dafoe Road, University of Manitoba, Winnipeg, MB R3T 2N2, Canada

Brown rot (also bacterial wilt) disease of potato is a destructive and major obstacle of potato production in several areas worldwide. Brown rot disease is caused by the bacterium Ralstonia solanacearum (Smith) Yabuuchi et al. In this study, 20 isolates of R. solanacearum were recovered from infected potato tubers collected from local markets of Alexandria, Ismailia and Menufia Governorates. The specific medium, triphenyl tetrazolium chloride (TZC), was used to isolate and detect the level of virulence of R. solanacearum isolates. Eighteen isolates of R. solanacearum were identified at the molecular level through polymerase chain reaction (PCR) using specific primers OLI1 and Y-2 that produced the 288 bp specific PCR product. From the identified isolates, nine isolates were assessed on three potato cultivars 'Cara', 'Hermes' and 'Lady Rosetta'. Wilting symptoms were evaluated on the three potato cultivars using disease severity index (0–4). Root and shoot fresh and dry weight were recorded. Potato cultivar 'Lady Rosetta' was the most sensitive one to all the R. solanacearum tested isolates. Two isolates were highly virulent on all potato cultivars. Further analyses of the genetic variations of the R. solanacearum isolates are being examined.

Purification and characterization of Phaeosphaeria nodorum toxins and mapping of toxin insensitivity. P. BAJRACHARYA, C. RAMPITSCH, F. DAAYF AND C. MCCARTNEY. (P.B., C.R., C.M.) Cereal Research Centre, Agriculture and Agri-Food Canada, 195 Dafoe Road, Winnipeg, MB R3T 2M9, Canada; and (P.B., F.D.) Department of Plant Science, 222 Agriculture Building, 66 Dafoe Road, University of Manitoba, Winnipeg, MB R3T 2N2, Canada

Stagonospora nodorum blotch (SNB) is a leaf spotting disease of wheat caused by the ascomycete Phaeosphaeria nodorum (Müll.) Hedjar. Phaeosphaeria nodorum belongs to the order Pleosporales with other plant pathogens like Pyrenophora tritici-repentis (Died.) Drechs., Leptosphaeria maculans (Desmaz.) Ces & de Not., Cochliobolus victoriae Nelson and Cochliobolus heterostrophus (Drechsler) Drechsler. In the field, P. nodorum often occurs in conjunction with other leaf spotting pathogens like P. tritici-repentis, Mycosphaerella graminicola (Fuckel) Schröt. in Cohn, and Phaeosphaeria avenae (Weber) Erikss. Therefore, this group of pathogens is often referred to as the leaf spot complex. Phaeosphaeria nodorum relies on host selective toxins (HSTs) for its pathogenicity. A compatible interaction results when one of these toxins interacts with its corresponding sensitivity gene in wheat. Hence, the pathogen follows inverse gene-for-gene interaction. Four HSTs (SnToxA, SnTox1, SnTox2 and SnTox3) have been identified to date and have been found to be proteinaceous. This study focuses on purification and identification of new HSTs, and mapping of the corresponding sensitivity gene(s) in the Kenyon/86ISMN 2137 mapping population. Fungal cultures are processed using chromatography techniques to identify a potential HST. Once the potential protein has been identified, it is tested in differential lines of wheat to confirm bioactivity. This method has led to the identification of a putatively new toxin. Currently, the gene corresponding to this candidate protein is being heterologously expressed in yeast cells. This will allow confirmation of the bioactivity of this putative new toxin and precise mapping of the corresponding toxin sensitivity gene in wheat. In addition, other fungal cultures from different isolates are at various stages of purification.

Broadening the spectrum of biocontrol: long-term survival of sclerotia of Botrytis squamosa, Sclerotinia sclerotiorum and Sclerotium cepivorum treated with three biological controls under field conditions. L. C. BARBISONN, M. R. MCDONALD AND G. J. BOLAND. School of Environmental Sciences, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada; and (M.R.M.) Department of Plant Agriculture, Crop Science Building, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada

The primary overwintering inoculum of Botrytis squamosa Walker, Sclerotinia sclerotiorum (Lib.) de Bary and Sclerotium cepivorum Berk are sclerotia. Management of these pathogens is difficult due to the resilience of sclerotia within the soil; however, this common life stage is an ideal target for a multi-host biological control agent (BCA). The objective of this research was to determine the impact of three BCAs, Coniothyrium minitans Campbell, Microsphaeropsis ochracea (Carisse & Bernier), and Trichoderma atroviride (Karsten), on the survival of sclerotia of B. squamosa, S. sclerotiorum and S. cepivorum under field conditions within a 2-year time span. Laboratory-produced sclerotia of B. squamosa, S. sclerotiorum and S. cepivorum were treated with spore suspensions of the individual BCAs. All sclerotia were buried 5–10 cm deep in pots containing muck (organic) soil and placed in the field on 12 December 2011. Per cent survival was assessed at 1–3 month intervals post-burial. Once recovered, sclerotia were surface disinfested, plated onto acidified PDA, and observed for germination and formation of daughter sclerotia. Fourteen months post-burial, per cent survival of untreated control sclerotia decreased by 42%, 16% and 1% for B. squamosa, S. sclerotiorum and S. cepivorum, respectively, compared with 1 month post burial. Sclerotia of all three pathogens treated with T. atroviride demonstrated the lowest per cent survivals at this time. Per cent survival of B. squamosa, S. sclerotiorum and S. cepivorum were reduced to 26%, 27% and 0%, respectively. Assessments will continue until November 2013.

Identification and functional characterization of CtToxB from the lentil anthracnose pathogen Colletotrichum sp. ex lentil. V. BHADAURIA AND S. BANNIZA. Crop Development Centre, Department of Plant Sciences, University of Saskatchewan, 51 Campus Drive, Saskatoon, SK S7N 5A8, Canada

Lentil is one of the top three legume crops in Canada. Anthracnose caused by Colletotrichum truncatum (Schwein.) Andrus & Moore is the most devastating fungal disease on lentil. The Colletotrichum species of lentil is likely different from the C. truncatum type specimen and efforts in our lab are underway to clarify its taxonomic status. This ascomycete fungus employs a biphasic infection strategy to colonize lentil plants. The biotrophic infection is characterized by thick primary hyphae and the necrotrophic infection is characterized by thin secondary hyphae. This morphological transition, also known as the biotrophy-necrotrophy switch (BNS), is essential for anthracnose development. We identified an effector gene encoding a putative Toxin B (named hereafter CtToxB) from the BNS-specific cDNA library. The full-length cDNA (GenBank Accession: JZ350031) of CtToxB is 555-bp in size with an open reading frame of 282-bp encoding a preprotein of 94-aa containing a signal peptide of 19-aa and four cysteine residues in the mature protein (75-aa). Quantitative RT-PCR analysis showed that the expression of CtToxB peaked during the BNS, suggesting a potential role in anthracnose development. No differential expression and polymorphism was observed between isolates of the two pathogenic races described in this species from lentil. A gene-silencing approach was used to determine the biological function of CtToxB in C. truncatum, which showed that CtToxB is a potential virulent determinant. Taken together, our data indicate that unlike PtrToxB, the CtToxB may not play a significant role in the quantitative virulence variation of C. truncatum races.

Optimization and standardization of nucleic acid extractions from field collection and bulk samples for sensitive direct detection. G. J. BILODEAU, T. CHECKLAND, G. P. ROBIDEAU AND E. TREMBLAY. Canadian Food Inspection Agency, P.O. Box 11300, 3851 Fallowfield Road, Ottawa, ON K2H 8P9, Canada

For protection of Canadian biodiversity and trade from the impacts of global change, improving the ability to monitor invasive alien and quarantine species is really important. The quality and yield of a DNA extraction is the key in the development of reference collection and direct detection in field and bulk samples of quarantine and invasive species and is sometime difficult to evaluate. Different DNA extraction methods and optimization for standardization for sensitive direct detection are evaluated in order to achieve selection of the best DNA to use and understand the limit of detection. Real-time PCR was employed for detection and quantification of target organisms. Internal controls were developed, tested and evaluated with our species-targeted primers and probes: Phytophthora and Verticillium, to determine PCR inhibition. Various soil types were prepared and inoculated with the different species targeted to evaluate the best DNA extraction procedure for DNA yield and quality. The qPCR was used to assess the ability to detect the DNA while the internal control monitored inhibition of the PCR reaction. Our results clearly indicate that the methods giving the highest concentration in DNA also have the most PCR inhibitors. A second purification step is required (magnetic beads) to remove inhibition for quantitative analysis by real-time PCR. High yield and low inhibition are necessary for amplification of DNA for direct detection as would be needed for metagenomic analysis. Similar work with other crop pests and matrices and other methods to capture targeted DNA is underway.

Tools to manage leaf spot diseases of barley in Saskatchewan. G. S. BRAR, C. KIRKHAM, A. KIRK, G. PENG, S. A. BRANDT AND H. R. KUTCHER. Crop Development Centre, Department of Plant Sciences, University of Saskatchewan, 51 Campus Drive, Saskatoon, SK S7N 5A8, Canada; (C.K.) Melfort Research Farm, AAFC, P.O. Box 1240, Melfort, SK S0E 1A0, Canada; (A.K.) Western Applied Research Corporation (WARC), Box 89, Scott, SK S0K 4A0, Canada; (G.P.) Saskatoon Research Centre, Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, SK S7N 0X2, Canada; and (S.A.B.) Northeast Agriculture Research Foundation, Box 1240, Melfort, SK S0E 1A0, Canada

Barley (Hordeum vulgare L. emend. Bowden) is an important cereal crop in western Canada. Net Blotch [Pyrenophora teres Drechsler] and spot blotch [Cochliobolus sativus (Ito & Kurib.) Drechsler ex Dastur] are two common foliar diseases that cause economic losses for barley growers by reducing yield as a result of decreased photosynthetic area of the leaf surface. Variety selection and fungicide application are two important disease management tools. The purpose of this study was to evaluate the effectiveness of varietal resistance and foliar fungicides on disease severity and yield of barley. Experiments included three malt barley varieties that varied in resistance to net blotch and spot blotch: ‘Newdale’ (resistant to moderately resistant), ‘AC Metcalfe’ (moderately resistant to moderately susceptible) and ‘Harrington’ (susceptible); and two foliar fungicides: propiconazole (Tilt^®) and prothioconazole (Proline^®) and an unsprayed check. Treatments were arranged in a RCBD with four replications at two locations: Melfort and Scott, for four and two years, respectively. Results indicated the beneficial effects with leaf spot resistant varieties and fungicides. Disease severity was reduced and yield increased for the resistant barley variety ‘Newdale’ compared with ‘AC Metcalfe’ and ‘Harrington’. Foliar fungicides also reduced disease severity and increased yield, but the benefit was greatest for the susceptible variety ‘Harrington’. We conclude that the benefit of foliar fungicide application depends on the variety grown; a leaf spot resistant variety may benefit little from a fungicide treatment. These results indicate that variety selection and fungicide application are important tools available to barley growers to manage leaf spot diseases.

Penicillium bilaiae grows on roots and increases plant phosphorus uptake. C. CALDWELL, S. STECKLER, K. PRIEST AND D. GREENSHIELDS. Novozymes BioAg Limited, 3935 Thatcher Avenue Saskatoon, SK S7R 1A3, Canada

Phosphorus (P) is an essential nutrient for plant growth. Up to 90% of applied phosphate fertilizer is quickly bound to soil constituents and rendered unavailable for plant uptake. Some soil microorganisms are able to solubilize this inorganic phosphate, increasing availability for crop uptake. We isolated 180 new P solubilizing microbes from across Western Canada and 89% of these were either Aspergillus or Penicillium. Penicillium bilaiae Chalab. was the strongest P solubilizer that we isolated. Inoculation of soybean seeds with P. bilaiae resulted in increased rhizosphere gluconic acid concentrations and leaf tissue P concentrations. Root colonization of soybean by P. bilaiae was confirmed using a fluorescent protein-tagged isolate. These results suggest P. bilaiae solubilizes phosphate and increases P uptake in soybean by colonizing plant roots and secreting gluconic acid into the rhizosphere.

Race structure of Pseudomonas syringae pv. phaseolicola from dry bean fields in western Canada. S. CHATTERTON, P. M. BALASUBRAMANIAN, D. L. MCLAREN, R. L. CONNER AND R. J. HOWARD. Lethbridge Research Centre, Agriculture and Agri-Food Canada (AAFC), 5403–1 Avenue South, Lethbridge, AB T1J 4B1, Canada; (D.L.M.) Brandon Research Centre, AAFC, 2701 Grand Valley Road, Brandon, MB R7A 5Y3, Canada; (R.L.C.) Morden Research Station, AAFC, Unit 100-101 Route 100, Morden, MB R6M 1Y5, Canada; and (R.J.H.) Crop Diversification Centre South, Alberta Agriculture and Rural Development, 301 Horticultural Station Road East, Brooks, AB T1R 1E6, Canada

Bacterial diseases of dry bean, such as common blight [Xanthomonas axonopodis pv. phaseoli Smith; Xap)] and halo blight [Pseudomonas syringae pv. phaseolicola (Van Vuurde and Van den Bovenkamp) Jansing and Rudolph; Pph], can significantly impact production in western Canada. Dry bean cultivars in several market classes with moderate resistance to Xap have recently been developed. Nine races of Pph have been identified based on their virulence on a differential set of dry bean cultivars. In order to accurately screen breeding lines for resistance to both bacterial diseases, the races of halo blight present in western Canada need to be determined. The objectives of this study were to assess the incidence of multiple bacterial diseases on dry beans in southern Alberta using a multiplex PCR diagnostic assay and to determine the prevalent halo blight races in western Canadian dry bean fields. Seventy-one Pph isolates were recovered from symptomatic dry bean fields surveyed in Alberta, Saskatchewan and Manitoba in 2010–2012. Virulence testing of these isolates on the dry bean differential set is currently ongoing. Results to date indicate that Pph isolates from Southern Alberta bean fields belong to race 2, while isolates from Manitoba bean fields belong to race 2 or 6. Polymerase chain reaction was used to confirm the presence of specific avirulence genes that determine Pph race structure. The presence of the avirulence gene PphE, and absence of genes PphF and PphB indicated that all collected Pph isolates belong to either race 2 or 6. Assessing the virulence of race 2 and 6 isolates to dry bean lines with resistance to common bacterial blight is currently underway.

Our current understanding of stripe rust and effective management. X. M. CHEN. USDA-ARS Wheat Genetics, Quality, Physiology, and Disease Research Unit; and Department of Plant Pathology, Washington State University, Pullman, WA 99164-6430, USA

Stripe rust, caused by Puccinia striiformis Westend. (Ps), is one of the most important diseases of wheat and barley. Our recent studies together with collaborators have resulted in a better understanding of the biology, genome and pathogenicity of the pathogen, epidemiology of the disease, and molecular mechanisms of host plant resistance and plant-pathogen interaction; and have led to an effective management of the disease. Numerous Berberis and Mahonia species have been identified as alternative hosts, providing a system for genetic studies of Ps. The whole genome and cDNA sequences of several Ps isolates have allowed us to compare the species with those causing leaf and stem rusts; and the Ps sequence data have allowed us to develop SSR and EST markers. Using the co-dominant SSR markers, we have determined the population structures and virulence distributions of Ps in the USA and several other countries, differentiated the formae speciales causing wheat and barley stripe rusts, and possibility of their somatic hybridization on grasses. A new set of differentials have been established to identify races of the wheat stripe rust pathogen, which provides virulence information directly related to resistance genes in cultivars and used in breeding programmes. New genes for effective resistance have been identified and resistant germplasm lines possessing different resistance genes have been developed for breeding resistant cultivars. New fungicides have been identified and responses of cultivars to fungicide application are determined each year to implement appropriate management based on disease pressure forecast using newly developed prediction models and field surveys, and resistance levels of individual cultivars.

Transcription factors in Ustilago maydis pathogenesis and meiosis. H. Y. K.CHEUNG, C. E. DOYLE, M. E. DONALDSON AND B. J. SAVILLE. Environmental and Life Sciences Graduate Program, DNA Building, Trent University, 2140 East Bank Drive, Peterborough, ON K9J 7B8, Canada; and (B.J.S.) Forensic Science Program, DNA Building, Trent University, 2140 East Bank Drive Peterborough, ON K9J 7B8, Canada

Ustilago maydis (DC.) Corda is the model basidiomycete plant pathogen. Its infection of corn (Zea mays) results in tumour formation in all aerial plant tissues. The tumour is the ultimate stage of the fungal/plant interaction and it is the location of teliospore formation. Teliospores are the dispersal agent for the fungus and the cell type where meiosis is completed. Key to understanding smut pathogenesis is determining how the fungus controls developmental changes during growth in the plant. Three U. maydis transcription factors have been identified that may influence these transitions (Zfp1, Mcg1 and Ztf1). Deletion of the gene for the zinc finger protein Zfp1, in SG200, reduces virulence; deletion of mcg1, coding an Ndt80 related protein, leads to altered teliospore development and blocks the completion of meiosis; and ztf1, coding an APSES domain protein, is up-regulated during growth of the fungus in the plant. The functions of these proteins are being further investigated by seedling pathogenesis assays, creation of over-expression lines, targeted mutagenesis, bioinformatic identification of potential target genes, and cDNA subtraction library creation. The data suggests a role for Zfp1 in pathogenic development and a role for Mcg1 as a positive and negative regulator of transcription. These investigations provide new insight regarding the U. maydis developmental transitions within the host.

Identification of avirulence genes in the Leptosphaeria maculans population in Manitoba and Saskatchewan in 2010. D. J. CROSS, S. H. LIBAN, G. PENG, W. G. D. FERNANDO AND H. R. KUTCHER. Melfort Research Centre, Agriculture and Agri-Food Canada (AAFC), P.O. Box 1240, Melfort, SK S0E 1A0, Canada; (S.H.L., W.G.D.F.) Department of Plant Science, 222 Agriculture Building, 66 Dafoe Road, University of Manitoba, Winnipeg, MB R3T 2N2, Canada; (G.P.) Saskatoon Research Centre, AAFC, 107 Science Place, Saskatoon, SK S7N 0X2, Canada; and (H.R.K.) Department of Plant Sciences, University of Saskatchewan, 51 Campus Drive, Saskatoon, SK S7N 5A8, Canada

Blackleg disease, caused by Leptosphaeria maculans (Desmaz.) Ces. & De Not. is responsible for significant yield loss of canola/rapeseed (Brassica napus L.) in many parts of the world. In western Canada, the disease was controlled successfully with the use of varietal resistance and a 4-year crop rotation since the 1980s. However, severely diseased fields have been reported on R-rated cultivars in the last several years, which may be related to changes in L. maculans race structure and shortened crop rotation in favour of canola production. Diseased canola stubble from commercial fields in Manitoba and Saskatchewan were analysed using a set of host differentials with 11 known specific blackleg-resistance genes to determine the frequency of avirulence (Avr) alleles in the pathogen population. A total of 299 L. maculans isolates were tested, and AvrLm1, AvrLm3, AvrLm9, AvrLepR1 and AvrLepR2 showed a frequency of 0–8% in the samples collected. The low frequency of these Avr genes indicates that the corresponding resistance genes Rlm1, Rlm3, Rlm9, LepR1 or LepR2 are ineffective against blackleg in these two provinces. In contrast, AvrLm2, AvrLm4, AvrLm5/6, AvrLm7 and AvrLmS were found in most of the L. maculans isolates analysed, which would imply that canola cultivars carrying any of the corresponding resistance genes will still be effective. By profiling the frequency of Avr alleles, we may be able to identify which resistance genes in canola cultivars are effective against the pathogen population.

In vitro sensitivity of Leptosphaeria maculans to azoxystrobin. L. E. DEL RIO MENDOZA AND S. RUUD. Department of Plant Pathology, NDSU Department 7660, P.O. Box 6050, North Dakota State University, Fargo, ND 58108-6050, USA

Increasingly serious blackleg epidemics have been recorded in North Dakota in recent years. These epidemics are caused by Leptosphaeria maculans (Desmaz.) Ces. & De Not. strains against which commercial cultivars are no longer resistant. Azoxystrobin is one of three fungicides registered to manage this disease in North Dakota. Azoxystrobin belongs to a chemical group with a history of fungicide resistance. This study was conducted to characterize the sensitivity of 131 L. maculans isolates to azoxystrobin. Isolates were collected in 2004 from canola stems at harvest time. Fungicide sensitivity was estimated by quantifying spore germination in solutions containing 50 μg mL⁻¹ of SHAM and 0, 0.1, 0.025, 0.05, 0.1 or 1.5 μg mL⁻¹ of analytical grade azoxystrobin. Sensitivity was expressed as 50% effective concentration (EC₅₀). Each concentration was evaluated in triplicate and the study was conducted twice. Sensitivity to azoxystrobin ranged between 0.02 and 0.13 μg mL⁻¹ with a mean of 0.07 μg mL⁻¹. Since the isolates used in this study were collected at a time when azoxystrobin use for blackleg control was minimal in the state, this information could be considered a baseline of sensitivity. Efforts are underway to evaluate sensitivity of isolates collected at later times.

Pathotype reaction in clubroot-resistant canola cultivars in Canada. A. DEORA, B. D. GOSSEN AND M. R. MCDONALD. Department of Plant Agriculture, Crop Science Building, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada; and (B.D.G.) Saskatoon Research Centre, Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, SK S7N 0X2, Canada

Clubroot [Plasmodiophora brassicae Woronin] was reported first on canola (Brassica napus L.) in western Canada in 2003. Since then, several clubroot-resistant cultivars have been developed. The timing and expression of resistance to each of the major pathotypes (pathotypes 2, 3, 5, 6, Williams’ system) in Canada was examined in four resistant cultivars. Root hair infection occurred at high levels in each resistant cultivar, but developed more slowly than in the susceptible control. Secondary infection and development in cortical cells was inhibited in each resistant cultivar; only a few bi-nucleated plasmodia were observed at 12 days after inoculation (DAI), and plasmodia were rarely observed at 18 and 24 DAI. In contrast, development in the susceptible cultivar had progressed to resting spores by 24 DAI. In addition, a dense ring of reactive oxygen species (ROS) accumulated in and around the endodermis of non-inoculated controls and inoculated plants of each of the resistant cultivars. However, the ROS ring disappeared rapidly in infected plants of the susceptible control. No specific points of ROS accumulation or lignification were observed in any of the resistant cultivars, which indicates that a hypersensitive response did not occur. Resistance to clubroot is generally pathotype specific, so the uniform response of the resistant cultivars to several pathotypes is one line of evidence indicating that the resistance in these cultivars is conditioned by a gene(s) from a single non-specific source. If so, this may pose a threat to the durability of this resistance for clubroot management on canola in this region.

High throughput pathotyping of common osier willow rust [Melampsora larici-epitea] in Poland. X. DU, J. CISZEWSKA-MARCINIAK, J. PRZYBOROWSKI AND M. JEDRYCZKA. Institute of Plant Genetics, Polish Academy of Sciences, Poznan, Poland; and (J.P.) University of Varmia and Mazury, Olsztyn, Poland

Common osier willow (Salix viminalis L.) and its hybrids can be used as bioenergy crops in temperate regions worldwide. However, yield of its biomass can be greatly reduced by pests and diseases. One of the most damaging pathogens of common osier willow is rust, caused by the fungi of the genus Melampsora. The disease can lead to plant defoliation and decrease biomass production. Rust fungi are strict biotrophs, which live only on host-plants. Most of them need alternative hosts to complete their life cycle. The aim of this work was to evaluate the number of pathotypes of rust of common osier willow in Poland. To fulfil this task 20 differentials of willow species and their hybrids and 401 pathogen isolates were investigated. The isolates were collected from three geographically distant regions of Poland, including Wielkopolska, Varmia and Lubuskie regions. Naturally infected leaves of common osier willow and its hybrids with Salix schwerinii were collected in 2008–2012. Single uredinium cultures were obtained and multiplied in a series of propagation cycles on susceptible willow genotype. Species identification was based on Scanning Electron Microscopy, light microscopy, sequencing of the ITS region and comparison of RAPD banding patterns. All isolates were identified as Melampsora larici-epitea Kleb. A series of inoculations was performed in controlled environment conditions. None of the willow genotypes was fully resistant, but the genotypes greatly differed in their susceptibility (1.9–85.1%). Among 401 tested isolates, 262 pathotypes were found, which proves high polymorphism and great genetic diversity of the M. larici-epitea population in Poland.

Managing leaf spot diseases of wheat to maximize production. V. P. EDIRISINGHE, C. KIRKHAM, A. KIRK, G. PENG, S. A. BRANDT AND H. R. KUTCHER. Department of Plant Sciences, University of Saskatchewan, 51 Campus Drive, Saskatoon, SK S7N 5A8, Canada; (C.K.) Melfort Research Farm, Agriculture and Agri-Food Canada (AAFC), Box 1240, Melfort, SK S0E 1A0, Canada; (A.K.) Western Applied Research Corporation, Box 89, Scott, SK S0K 4A0, Canada; (S.A.B.) Northeast Agriculture Research Foundation, Box 1240, Melfort, SK S0E 1A0, Canada; and (G.P.) Saskatoon Research Centre, AAFC, 107 Science Place, Saskatoon, SK S7N 0X2, Canada

Wheat (Triticum aestivum L.) is one of the main sources of nutrition and a staple in the human diet. Canada produces over 2.5 million tonnes annually, but yield and quality can be reduced by leaf spot diseases caused by Septoria tritici Roberge in Desmaz. and Septoria nodorum Berk. and tan spot caused by Pyrenophora tritici-repentis (Died.) Drechs. Cultivation of resistant varieties, crop rotation, residue management and fungicide application are used to control these diseases. The objective of this study was to assess the effect of varieties and foliar fungicide application on leaf spot disease severity, yield and quality. Three varieties, ‘5603 HR’ (resistant), ‘Infinity’ (moderately resistant) and ‘AC Barrie’ (susceptible) were grown in an RCBD with four replicates for 4 years at Melfort, SK and 1 year at Scott, SK. Two fungicides, propiconazole (Tilt®) and pyraclostobin (Headline®) were applied along with an unsprayed check. Results revealed that both cultivation of resistant varieties and fungicide application contributed to reduction of leaf spot diseases and yield increase. Both fungicides were significant in reducing disease symptoms and increasing yield in comparison to the unsprayed check, particularly on ‘AC Barrie’, but fungicide treatment was not warranted on ‘5603 HR’. Both fungicide treatment and selection of a leaf spot resistant variety increased thousand kernel weight. These findings suggest that selection of leaf spot resistant varieties and the use of foliar fungicides can assist wheat growers to maximize production.

Pathogenicity and diversity of Rhizoctonia solani isolates collected from Egypt on three potato cultivars. A. F. EL-BEBANY, N. A. ASHMAWY, S. S. ABOSHOSHA, L. R. ADAM, F. DAAYF, S. S. HUSSIEN AND A. G. GAD. Department of Plant Pathology, Faculty of Agriculture, Alexandria University, El-Shatby, 21545, Alexandria, Egypt; and (L.R.A., F.D.) Department of Plant Science, 222 Agriculture Building, 66 Dafoe Road, University of Manitoba, Winnipeg, MB R3T 2N2, Canada

Rhizoctonia solani Kühn (teleomorph Thanatephorus cucumeris (A.B. Frank) Donk) is a soilborne fungus affecting many crops worldwide. It is the causal agent of stem canker and black scurf disease on potato. In the current study, 35 isolates of R. solani were retrieved from infected potato plants and soil samples on potato dextrose agar (PDA). The diseased samples were diagnosed and collected from Noubaria, Badr, Hoosh Issa and Kafr El-Sheikh regions, Egypt. All isolates were maintained on PDA. Specific primers for the internal transcribed spacer (ITS) regions were used in polymerase chain reaction (PCR) for molecular identification of the R. solani isolates. Twenty isolates were used to assess their pathogenicity on three potato cultivars 'Cara', 'Hermes' and 'Lady Rosetta'. Fifty days after inoculation, Rhizoctonia disease severity was assessed using a scale of 0–4, where 0 = no damage, no lesions on stem, and 4 = all sprouts killed. Length, fresh weight and dry weight of root and shoot as well as the number of stolons of the inoculated plants were measured and statistically analysed. The tested R. solani isolates showed variations in their aggressiveness on the potato cultivars. Isolate Rs12–10 was the most aggressive one on the three potato cultivars. Genetic diversity of the 35 R. solani isolates using random amplified polymorphic DNA (RAPD) molecular marker is being investigated.

A novel strategy for managing blackleg of canola on the Canadian prairies. W. G. D. FERNANDO, X. ZHANG, S. H. LIBAN, D. J. CROSS, G. PENG AND H. R. KUTCHER. Department of Plant Science, 222 Agriculture Building, 66 Dafoe Road, University of Manitoba, Winnipeg, MB R3T 2N2, Canada; (D.J.C.) Agriculture and Agri-Food Canada (AAFC), Melfort Research Farm, Agriculture and Agri-Food Canada (AAFC), Box 1240, Melfort, SK S0E 1A0, Canada; (G.P.) Saskatoon Research Centre, AAFC, 107 Science, Saskatoon, SK S7N 0X2, Canada; and (H.R.K.) Department of Plant Sciences, 51 Campus Drive, University of Saskatchewan, Saskatoon, SK S7N 5A8, Canada

Blackleg, caused by Leptosphaeria maculans (Desmaz.) Ces. & De Not., is an economically important disease of oilseed brassicas with recent epidemics observed in Australia and France. This disease is a renewed concern to canola (Brassica napus L.) production in western Canada and severe damage has been reported in some R- or MR-rated cultivars in past several years. Tighter rotations, low resistance diversity and changes in pathogen race structure may all have to do with the increased problem. To develop an effective management strategy, our research has been focusing on better understanding of avirulence (Avr) genes in the pathogen population and specific resistance (R) genes in commercial varieties and elite germplasm/lines from seed companies. The specific-gene resistance to blackleg generally follows the gene for gene model in which R genes defend against the pathogen isolates with corresponding Avr genes. No single R gene can remain effective forever, due to a changing pathogen population. The results have shown that pathogen adaptation has rendered the most common Rlm3 gene (in 65% of lines examined) ineffective, due possibly to the widespread selection pressure against the isolates carrying AvrLm3 (in only 6% of isolates). Based on this information, it may be possible to establish a resistance rotation guideline that switches among varieties in different resistance groups to deter pathogen adaptation and mitigate the risk of blackleg outbreak. With the present knowledge we have on the R-genes, five resistance groups may be deployed initially, and additional resistance groups can be incorporated as more R genes are identified. Ongoing monitoring of the pathogen population will provide early warning of potential R-gene breakdown and allow us to pre-emptively switch cultivars before significant yield losses occur.

Evaluation of seed and foliar fungicides for blackleg [Leptosphaeria maculans] control in canola. M. C. FRASER, S. F. HWANG, G. D. TURNBULL, H. U. AHMED, W. BARTON AND S. E. STRELKOV. Department of Agricultural, Food and Nutritional Science, 410 Agriculture/Forestry Centre, University of Alberta, Edmonton, AB T6G 2P5, Canada; (S.F.H., G.D.T., H.U.A.) Crop Diversification Centre North, Alberta Agriculture and Rural Development, 7000-113 Street, Edmonton, AB T5Y 6H3, Canada; and (W.B.) BASF, Research & Commercial Development, 100 Milverton Drive, Mississauga, ON L5R 4H1, Canada

Blackleg disease of canola, caused by Leptosphaeria maculans (Desmaz.) Ces. & De Not., can cause significant yield losses due to seedling death, stem cankers and lodging. As a consequence of shortened canola rotations in Canada, blackleg levels are increasing and growers are turning to fungicides as a control method. The aim of this study was to evaluate the efficacy of fungicide treatments as a tool in blackleg disease management. In 2012, field experiments were conducted in northeast Edmonton and Camrose, Alberta. The experiment was designed as a randomized complete block and included the seed treatments BAS 720 F (pyraclostrobin and fluxapyroxad) at the half and full rate, and Prosper FX (carbathiin, trifloxystrobin and metalaxyl). Foliar treatments, applied in combination with the seed treatment BAS 720 F, included Priaxor (pyraclostrobin and fluxapyroxad) and Tilt 250 EC (propiconazole). Treatments were applied to a susceptible and moderately resistant canola cultivar. Plots were artificially inoculated with L. maculans. At the Edmonton location, all treatments significantly reduced stem infection in the resistant cultivar compared with the control. At both locations, the Priaxor treatment significantly reduced stem infection in the susceptible cultivar relative to the control and BAS 720 F full rate. There were no significant differences in yield within cultivars at either location. These preliminary results suggest that there is a potential for a combination of seed and foliar treatments to manage blackleg, particularly when a susceptible cultivar is cropped. This study will be repeated in 2013.

Heating things up for seed-borne anthracnose in dry beans. A. P. FRIESEN, D. E. ROBINSON, R. L. CONNER AND C. L. GILLARD. Department of Plant Agriculture, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada; and (R.L.C.) Morden Research Center, Agriculture and Agri-Food Canada, Unit 100-101 Route 100, Morden, MB R6M 1Y5, Canada

The seed-borne disease anthracnose [Colletotrichum lindemuthianum (Sacc. & Magn.) Bri. & Cav.] causes significant losses in yield and seed quality in dry bean (Phaseolus vulgaris L.). Various controls exist but thermotherapy treatment may provide an alternative method. In 2012 and 2013, laboratory studies were conducted to evaluate the effect of microwave radiation on germination and control of anthracnose in navy (cv. Navigator) and pinto (cv. AC Ole) bean seed. A maximum microwave exposure time of 40–60 s caused minimal decrease (< 10%) in germination. This loss was considered acceptable, if significant disease control was obtained. A linear decrease in pathogen growth was observed on potato dextrose agar as length of microwave exposure increased. Microwave radiation efficacy was evaluated further using the full (maximum) exposure rate and a half rate in field studies near Exeter and Ridgetown, ON in 2012. Microwave treatments were evaluated alone and in combination with two chemical seed treatments; a BASF experimental and thiamethoxam, metalaxyl –M, fludioxonil + azoxystrobin, the standard seed treatment for dry bean in Ontario. Each study consisted of 10 treatments including non-infected and infected controls. Emergence, vigour, disease control and yield were evaluated and treatment means compared using orthogonal contrasts. In 2012, the microwave treatments did not affect emergence or vigour compared with the infected control. Anthracnose control and yield were similar to the infected control in the microwave treatments, and the combination of microwave and chemical seed treatment provided the same level of control as the chemical seed treatments on their own. Further field testing will be conducted in 2013.

The use of imaging technologies to assess plant disease and develop a high throughput screening platform for biocontrol agents. M. FRODYMA, M. FURLAN, M. SCHULTE AND E. PRUSINKIEWICZ. Novozymes BioAg Limited, 3935 Thatcher Avenue, Saskatoon, SK S7R 1A3, Canada

Over the last decade, interest in sustainable agriculture has increased significantly. Microbial yield and fertility enhancers help farmers attain healthier crops and higher yields. Novel biocontrol organisms reduce the need for chemical pesticides. However, true innovation lies in identifying new organisms with novel benefits and showing their effectiveness in the field. In order to bridge the gap from laboratory to true field efficacy we have developed high throughput plant phenotyping assays using the ScanalyzerHTS system from LemnaTec GmbH. The assay is based on Arabidopsis thaliana, which can be grown in the space of a microtitre plate, and whose short growth cycle allows for a higher number of experiments and replicates to be performed. Colletotrichum higginsianum Sacc. is used as the model pathogen. Experiments are imaged in the ScanalyzerHTS, and then processed using a number of filters that take the raw image and convert it to an analysed and quantified image. Analysed images are used to extract colour classification and object area data which are quantitative indicators of plant health. Experiments using a commercial biocontrol organism based on Bacillus amyloliquefaciens subsp. plantarum validated the assay’s ability to discern differences in the level of pathogenicity of the fungus.

Characterization of Streptomyces spp. causing common scab disease in Newfoundland. J. K. FYANS AND D. R. BIGNELL. Department of Biology, Memorial University of Newfoundland, 232 Elizabeth Avenue, St John’s, NL A1B 3X9, Canada

Potato common scab disease is caused by several members of the bacterial genus Streptomyces (Waksman & Henrici), with infection typically manifesting as scabby lesions on the tuber surface. As this devalues the crop, development of consistently effective control strategies is vital to minimize economic losses suffered by growers. All potato growing regions worldwide are affected by common scab, with previous studies reporting prevalence in eastern Canada. However, this is the first investigation into scab-causing species found specifically in Newfoundland. Knowledge of the species and their mechanism of infection are required to develop effective control strategies. Sixteen Streptomyces spp. were isolated and purified from scab lesions of potatoes harvested in 2011 from a single location in Newfoundland and assessed for virulence using a rapid and sensitive radish seedling bioassay. Five plant pathogens were recognized whose species identification is being undertaken using genetic analysis of 16S rRNA and rpoB genes. Polymerase chain reaction (PCR) analysis revealed the absence of several known virulence-associated genes in the pathogenic strains. Most notable was the absence of the biosynthetic genes for thaxtomin A, the predominant phytotoxin produced by scab-causing streptomycetes. Thaxtomin A production was assessed by analysing organic extracts of culture supernatant by HPLC, and this revealed that these isolates are non-producers. Bioactivity in culture supernatants indicates production of an alternative phytotoxin, the identity of which is currently being investigated. Continuation of this work will focus on broader characterization of isolates from different growing seasons and locations across Newfoundland.

Rapid identification of four Phytophthora ramorum lineages using cellulose binding elicitor lectin (CBEL) gene region and real-time PCR. M.-C. GAGNON, M.-J. BERGERON, R. C. HAMELIN, N. J. GRUNWALD AND G. J. BILODEAU. Canadian Food Inspection Agency, 3851 Fallowfield Road, P.O. Box 11300, Ottawa, ON K2H 8P9, Canada; (M.-J.B., R.C.H.) Natural Resources Canada, Laurentian Forestry Centre, 1055 rue du P.E.P.S., P.O. Box 10380, Québec, QC G1V 4C7, Canada; (R.C.H.) Faculty of Forestry, Forest Sciences Centre, University of British Columbia, 2424 Main Mall, Vancouver, BC V6T 1Z4, Canada; and (N.J.G.) Horticultural Crops Research Laboratory, USDA-ARS, 3420 NW Orchard Avenue, Corvallis, OR 97330, USA

Phytophthora ramorum Werres et al. is a pathogenic oomycete responsible for causing sudden oak death (SOD) in the Western USA and sudden larch death in the UK, where millions of trees have died. Until recently, three genetically divergent clonal lineages of this microorganism were recognized (EU1, NA1 and NA2), each named according to the continent on which they were first detected. In 2009, a fourth lineage was discovered in the UK. Sequencing and microsatellite genotyping revealed that the EU2 lineage is genetically distinct from all other lineages. The objectives of our study were (1) to develop Allele Specific Oligonucleotide-PCR (ASO-PCR) assays using real-time PCR allowing the identification of the new EU2 lineage and (2) to validate a combination of ASO-PCR assays in the CBEL gene region to rapidly identify all four P. ramorum lineages. Sequencing of the CBEL gene region revealed eight single nucleotide polymorphisms (SNPs) distinguishing EU2 from other lineages. Four ASO-PCR assays were developed, and two of these assays yield constant and successful genotyping, allowing the identification of EU2 over EU1, NA1 and NA2 samples. These new assays were combined with two existing assays in the same gene region to allow for identification of all four lineages. Tests performed with a blind panel, including samples of each lineage in varying proportions, revealed unique profiles for each lineage, allowing their rapid identification. These markers can be used with field samples, which make them well suited for routine diagnostic procedures in regulatory laboratories.

Identification and molecular characterization of Canadian strains of potato late blight and potato wart. M.-C. GAGNON, L. KAWCHUK, X. LI, T. A. J. VAN DER LEE, P. J. M. BONANTS, C. A. LÉVESQUE AND G. J. BILODEAU. Canadian Food Inspection Agency, 3851 Fallowfield Road, P.O. Box 11300, Ottawa, ON K2H 8P9, Canada; (L.K.) Lethbridge Research Centre, Agriculture and Agri-Food Canada (AAFC), 5403-1 Avenue South, C.P. 3000, Lethbridge, AB T1J 4B1, Canada; (X.L.) Canadian Food Inspection Agency, 93 Mount Edward Road, Charlottetown, PEI C1A 5T1, Canada; (T.A.J.v.d.L., P.J.M.B.) Plant Research International, Droevendaalsesteeg 1, 6708 PB Wageningen, the Netherlands; and (C.A.L.) Eastern Cereal and Oilseed Research Centre, AAFC, 960 Carling Avenue, Ottawa, ON K1A 0C6, Canada

Phytophthora infestans (Mont.) de Bary (potato late blight) and Synchytrium endobioticum (Schilb.) Percival (potato wart) are plant pathogens with devastating impact on potato crops worldwide. For example, P. infestans was the causal agent of the Irish potato famine in 1845, while S. endobioticum is one of the most important quarantine pathogens infecting potato. Both pathogens are present in Canada, and more diagnostic tools are needed to detect, identify and characterize them. The objective of this project is to develop single nucleotide polymorphisms (SNPs), microsatellites and allele specific oligonucleotides (ASO) from genomic and transcriptomic data to identify and characterize Canadian strains of P. infestans and S. endobioticum. Mining of P. infestans genome revealed several regions containing SNPs, both in genes and in flanking sequences of microsatellites loci. Nine ASO-PCR assays were developed from these SNPs, allowing the unambiguous identification of the five Canadian genotypes of this pathogen. Markers for 20 microsatellite loci were also developed from the draft genome sequence of S. endobioticum, obtained by NGS of a Dutch isolate of race 1. Until now, six loci were tested on a panel of samples from the Netherlands and Canada. Genotyping revealed that four loci were variable, and that our samples comprised at least five multilocus genotypes. The two Canadian DNA samples tested were identical, and similar to the most frequent genotype found in our samples. Additional markers are needed to improve resolution and to determine if all the S. endobioticum strains found in Canada have the same multilocus genotype.

Mapping clubroot resistance genes in Chinese cabbage and turnips. F. GAO, A. HIRANI, J. LIU, Z. LIU, G. FU, C. WU, P. B. E. MCVETTY AND G. LI. Department of Plant Science, 222 Agriculture Building, 66 Dafoe Road, University of Manitoba, Winnipeg, MB R3T 2N2, Canada; and (J.L., G.F., C.W.) Monsanto Canada Inc., 900 – One Research Road, Winnipeg, MB R3T 6E3, Canada

Five Chinese cabbage cultivars obtained from China, four ECD turnips from the European clubroot differential (ECD) set that contain clubroot resistance genes and a susceptible B. rapa accession were used. In Chinese cabbage, two F₂ and three BC₁ mapping populations were produced. A 3 : 1 ratio of resistant individuals to susceptible ones in both F₂ populations and a 1 : 1 ratio in all three BC₁ populations were found, suggesting that one Mendelian gene controls the clubroot resistance in all five Chinese cabbage cultivars. Using a high density genetic map in B. napus with over 10 000 SRAP markers, two SRAP markers were found to co-segregate with the resistance gene in Chinese cabbage. By comparing these two SRAP markers with the SRAP molecular markers on the genetic map, the resistance gene was mapped on N3 linkage group. In the ECD set, four turnips accessions, ECD1, ECD2, ECD3 and ECD4 with resistance to clubroot were used as donor male parents to cross with a susceptible B. rapa rapeseed and backcrossed to the susceptible parent to produce four BC₁ segregating populations. All four BC₁ segregating populations were phenotyped and genetic analysis in all four segregating populations indicated that single and two gene models explained well the segregation patterns of clubroot disease resistance in these four mapping populations. Some ECD accessions were confirmed to contain the mapped locus in Chinese cabbage while all ECD accessions were showed to have two resistance loci. Mapping all the clubroot resistance loci in all ECD turnips is underway.

Control of stripe rust in western Canada. D. A. GAUDET, B. PUCHALSKI, H. RANDHAWA, T. DESPINS AND A. LAROCHE. Lethbridge Research Centre, Agriculture and Agri-Food Canada, 5403 1^st Avenue South, Lethbridge, AB T1J 4B1, Canada

Stripe rust [Puccinia striiformis Westend.] is an important pathogen of wheat in western Canada and worldwide. Severe epidemics are associated with extensive yield and quality losses and fungicides are recommended to reduce losses. However, studies are required under Western Canadian production conditions to associate disease severity levels with thresholds for spraying recommendations. The spring wheat cultivars ‘Barrie’ (susceptible), ‘Imagine’ (intermediate) and Lillian (resistant) were seeded on 21 May and 4 June 2012 at Lethbridge, AB. The winter wheat cultivar ‘Radiant’ was inoculated with a local isolate on 2 June in spreader rows among plots. The systemic fungicide Folicur^® (Bayer Crop Sciences) was sprayed at the recommended rate as individual treatments on 17 July, 6 August or 12 August, and one treatment received all three sprays on these dates whereas control treatments remained unsprayed. Plots were scored for disease severity five times during the growing season using a Modified Cobb Scale and were harvested on 8 September. Plant height, maturity, yield, test weight (TW) and thousand kernel weights (TKW) were recorded. Final severities of 77% and 56% were recorded on control treatments of ‘Barrie’, for the 21 May and 4 June seeding dates, respectively, whereas severities on corresponding treatments of ‘Imagine’ were 16% and 12%. Only trace levels of stripe rust were observed on ‘Lillian’. While no significant reductions in yield due to rust were observed in either planting date on ‘Barrie’, reductions in height, maturity, TW and TKW were observed on specific planting dates.

Defence signalling pathways associated with hardening-induced snow mould resistance in winter wheat. D. A. GAUDET, D. RYABOVA, B. PUCHALSKI, M. FRICK, N. GAUDET AND A. LAROCHE. Lethbridge Research Centre, Agriculture and Agri-Food Canada, 5403 1^st Avenue South, Lethbridge, AB T1J 4B1, Canada

The Low Temperature Basidiomycete (LTB) is the most important snow mould fungus in northern Canada and can cause extensive winterkill of winter wheat in regions prone to deep persistent snow during the winter. Early work demonstrated that genetic resistance to LTB was only expressed after extended exposure of plants to cold hardening temperatures. Cold-induced resistance has been shown to be effective against other plant pathogens. Our previous microarray analyses demonstrated that jasmonic acid and ethylene (JA/ET) related defence genes were up-regulated during cold hardening while the expression of salicylic acid (SA) related genes remained unchanged. In the present study, we assayed cold hardened winter wheat for JA and SA using GC/MS, but observed that levels were near the limits of detection. Using qPCR, we then studied the expression of key genes involved in the biosynthesis pathways for JA, SA and ET following hardening and inoculation of wheat plants with snow mould in ‘PI181268’ (resistant) and ‘Norstar’ (susceptible). JA/ET biosynthesis genes were significantly up-regulated during hardening. Expression levels were higher in ‘PI181268’ compared with ‘Norstar’, whereas SA biosynthesis genes were generally down-regulated in these same treatments. Additionally, the expressions of the JA/ET genes were higher in treatments inoculated with LTB compared with non-inoculated treatments at incubation temperatures of −3 °C.

Assessment of genetic diversity in Verticillium dahliae isolates from olive trees in Tunisia using AFLP, SSR and PCR. Y. GHARBI, M. A. TRIKI, R. GDOURA, L. R. ADAM AND F. DAAYF. (Y.G., L.R.A., F.D.) Department of Plant Science, 222 Agriculture Building, 66 Dafoe Road, University of Manitoba, Winnipeg, MB R3T 2N2, Canada; (Y.G., R.G.) Department of Life Sciences, Faculty of Sciences, Sfax University, BP 1171, 3000 Sfax, Tunisia; and (M.A.T.) Institut de l’olivier, Unité de Recherche Protection des Plantes Cultivées et Environnement, Sfax BP 1087, Tunisie

Verticillium wilt of olive, caused by Verticillium dahliae Kleb., is a very serious disease that has been reported in all important olive cultivation areas in the world. In Tunisia, the first record dates from 2006 when it was detected in Sfax region. In fact, changes in olive cultivation practices contributed to the expansion of the disease and severity of pathogen attacks. To study the genetic variation in local populations of V. dahliae, 42 isolates collected from olive trees and from different geographical areas were selected for molecular analyses. Diversity among the isolates was assessed by different approaches, including Simple Sequence Repeat (SSR), Amplified Fragment Length Polymorphism (AFLP) and Polymerase Chain Reaction assays for specific fragments associated with the Defoliating (D) and non-defoliating (ND) pathotypes, and with Vegetative Compatibility Groups (VCG). AFLP, SSR and PCR-VCG data were used to generate matrices of genetic distance among the isolates for cluster analysis using the neighbour-joining method. Results indicate that V. dahliae isolates are divided into two main groups. Those from the coastal area of Tunisia (Sousse, Monastir) are grouped in sub-clusters clearly distinct from those collected from the central part of the country (Sidi bouzid, Kairouan and Sfax). This suggests that a combination of different molecular approaches can be applied to differentiate the isolates based on their geographical origin. Further pathogenicity and host range experiments will be useful to decipher potential relations between geographical distribution of certain strains and their impact on the production of olive in Tunisia and elsewhere in the Mediterranean rim.

Limitations of qPCR to quantify gDNA of Plasmodiophora brassicae in young seedlings. T. V. GLUDOVACZ, B. D. GOSSEN AND M. R. MCDONALD. Department of Plant Agriculture, Crop Science Building, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada; and (B.D.G.) Saskatoon Research Centre, Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, SK S7N 0X2, Canada

Microscopic examination of stained root hairs, image analysis of cortical sections and qPCR of pathogen genomic DNA (gDNA) were used to quantify the effects of temperature on development of Plasmodiophora brassicae Woronin in seedlings in studies on cabbage (Brassica oleracea L.) and canola (B. napus L.). There was a correlation between gDNA of P. brassicae and root hair infection at 4 and 8 days after infection (DAI) in an initial study on cabbage. However, there was no clear association between gDNA and root hair infection on canola when assessed at 10 DAI. In canola at 10 DAI, gDNA of P. brassicae was highest at 10 °C, 12.5 °C, and 25 °C, but low at 15–22.5 °C and 27.7 °C. This result was unexpected based on visual assessment of total root hair infection, where development occurred more quickly with increasing temperature to a maximum at 25 °C and then declined at higher temperature. The discrepancy between visual assessment and gDNA may be associated with developmental stage of the pathogen. At 10 DAI and 25 °C, the pathogen is in transition between its primary (root hairs) and secondary (root cortex) infection cycles. Secondary zoospores are released from root hairs, but have not yet begun to colonize the root cortex. gDNA might decline dramatically during the transition, only to increase quickly in subsequent assessments. Users need to be aware that assessments of gDNA during the transition could substantially underestimate infection levels in young seedlings.

Potential for degree day modelling of clubroot on canola. T. V. GLUDOVACZ, B. D. GOSSEN AND M. R. MCDONALD. Department of Plant Agriculture, Crop Science Building, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada; and (B.D.G.) Saskatoon Research Centre, Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, SK S7N 0X2, Canada

The main environmental factors identified as contributing to clubroot [Plasmodiophora brassicae Woronin] development on vegetable Brassica crops are temperature and soil moisture (rainfall). A project was initiated to predict the development of clubroot severity on canola (Brassica napus L.) based on temperature (degree days above 14 °C) and rainfall. Cultivar ‘InVigor 5030’ was seeded at 2-week intervals in 2011 and 2012, and plants were sampled and assessed weekly for clubroot severity (0–3 scale). Also, data on Chinese flowering cabbage (B. rapa subsp. chinensis (Rupr.) var. utilis Tsen and Lee) from previous trials at the same site were included to provide a wider range of conditions. Flowering cabbage was selected because its disease reaction to clubroot is similar to that of canola. Using a base temperature of 14 °C, the best predictive parameters during crop growth were accumulated air degree days (R² = 0.61), and accumulated soil degree days (R² = 0.54) using a 1-week delay to account for a lag in symptom development. The best combination of parameters to predict clubroot severity at plant maturity was soil degree days accumulated over the 2 weeks before the sampling date plus rain in the first 2 weeks after seeding (R² = 0.45). The bias of each analysis generally increased as severity increased. Base temperatures of 12 °C and 17 °C were also assessed, but they resulted in lower R² or higher bias. This approach appears promising, but additional years of data and an expansion of the modelling approach are required.

Metabolic cost of resistance to Plasmodiophora brassicae when inoculum pressure is high. B. D. GOSSEN, M. R. MCDONALD, K. SHARMA, A. DEORA AND G. PENG. Saskatoon Research Centre, Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, SK S7N 0X2, Canada; and (M.R.M., K.S., A.D.) Department of Plant Agriculture, Crop Science Building, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada

Clubroot [Plasmodiophora brassicae Woronin] is spreading rapidly on canola (Brassica napus L.) on the Canadian prairies. Management options were initially limited, but almost no clubroot symptoms develop on the clubroot-resistant cultivars that have recently been developed. However, there is evidence that the yield of resistant cultivars of canola and other Brassicas is reduced when inoculum pressure is high. In growth cabinet trials, biomass was reduced and plant development was delayed in plants of resistant cultivars inoculated with an avirulent pathotype, relative to non-inoculated controls. Similarly, growth and yield of resistant cultivars of canola and several Brassica vegetables in field trials were substantially lower at sites where inoculum pressure was high compared with nearby sites where inoculum pressure was low. In a crop rotation study that compared 1-, 3- and 11-year intervals between canola crops at a heavily infested site, development of resistant canola cultivars was delayed and yield was reduced by about 20% in the 1-year interval compared with the 3-year interval. Severity in a susceptible cultivar was 100%, irrespective of cropping interval, but no clubroot symptoms developed in the resistant cultivars. Secondary infection occurs but does not persist in resistant canola cultivars, which indicates that an active process of pathogen recognition and suppression is involved. We conclude that there is a metabolic cost associated with expression of resistance that results in reduced plant size, delayed development, and reduced yield when inoculum pressure is high.

A preliminary greenhouse study for the host status of spring wheat and canola to parasitism by the stem nematodes, Ditylenchus weischeri and D. dipsaci. A. HAJIHASSANI, M. TENUTA AND R. H. GULDEN. Department of Soil Science, Ellis Building, University of Manitoba, 13 Freedman Crescent, Winnipeg, MB R3T 2N2, Canada; and (R.H.G.) Department of Plant Science, University of Manitoba, Winnipeg, MB R3T 2N2, Canada

A greenhouse study was conducted to determine the host status of two major crops commonly grown in the Canadian Prairies; spring wheat (Triticum aestivum) and canola (Brassica napus), against the newly described stem nematode species, Ditylenchus weischeri Chizhov et al., of Canada thistle (Cirsium arvense), and the quarantine pest, D. dipsaci (Kühn) Filipjev. Our previous studies confirmed the presence of D. weischeri on Canada thistle in Manitoba and Saskatchewan. Freshly obtained J4 stage individuals of D. weischeri, from infested Canada thistle, and a population of D. dipsaci, from infested garlic (Allium sativum) in Quebec, were used in this study. Young crop plants as well as Canada thistle and garlic were challenged with 100 individuals of both species in 15 μl of 1.5% carboxymethyl cellulose applied to the axils of the first true leaves. Plants inoculated with water alone were used as a control. All plants were then grown for an additional 8 weeks prior to extraction for the nematodes. The reproductive factor (R_f) for D. dipsaci was 6.2, 1.0, 0.1 and 0 on garlic, Canada thistle, spring wheat and canola, respectively. The R_f for D. weischeri was 3.3, 0.6, 0.5 and 0.4 on Canada thistle, garlic, spring wheat and canola, respectively. These preliminary results provide evidence for further differentiation of the two stem nematode species based on plant host preference. Ditylenchus dipsaci was very capable of reproducing (R_f > 1.0) on garlic whereas D. weischeri was on Canada thistle. Further evaluations are being done for both nematode species on other crops.

Root rot disease caused by Fusarium cuneirostrum in dry bean in Canada. M. A. HENRIQUEZ, D. L. MCLAREN, R. L. CONNER, P. M. BALASUBRAMANIAN, K. F. CHANG, S. F. HWANG AND S. E. STRELKOV. Brandon Research Centre, Agriculture and Agri-Food Canada (AAFC), 2701 Grand Valley Road, Brandon, MB R7A 5Y3, Canada; (R.L.C.) Morden Research Station, AAFC, Unit 100-101 Route 100, Morden, MB R6M 1Y5, Canada; (P.M.B.) Lethbridge Research Centre, AAFC, 5403 – 1 Avenue South, Lethbridge, AB T1J 4B1, Canada; (K.F.C., S.F.H.) Alberta Agriculture and Rural Development, 17507 Fort Road NW, Edmonton, AB T5Y 6H3, Canada; and (S.E.S.) Department of Agricultural, Food and Nutritional Science, 410 Agriculture/Forestry Centre, University of Alberta, Edmonton, AB T6G 2P5, Canada

Root rot is a major disease of dry bean in Manitoba and is capable of causing significant yield reductions due to compromised root systems and reduced plant stands. An in-depth study on root rot pathogen identification on commercial dry bean from the major production areas in Manitoba was assessed during 2011. Pathogen species were identified based on their morphological characteristics. Of 844 Fusarium isolates identified, 74 isolates were identified as Fusarium cuneirostrum O’Donnell & Aoki. Species identity was confirmed by sequencing the translation elongation factor 1 alpha (EF1-α) gene, the internal transcribed spacer (ITS) region and the nuclear ribosomal intergenic spacer (IGS). The isolation of F. cuneirostrum from symptomatic dry bean roots has not been previously reported in Canada. These new findings provide critical information for plant breeders who will be able to select for resistance to this Fusarium species, and develop root rot resistant bean cultivars which are considered to be the best long-term and most cost-effective component for integrated control of root rot.

Evaluation of methods for cleaning and disinfesting equipment contaminated with clubroot. R. J. HOWARD, D. A. BURKE, S. E. STRELKOV, D. C. RENNIE, C. A. PUGH, S. L. I. LISOWSKI, M. W. HARDING AND G. C. DANIELS. Crop Diversification Centre South, Alberta Agriculture and Rural Development, 301 Horticultural Station Road East, Brooks, AB T1R 1E6, Canada; and (S.E.S., D.C.R.) Department of Agricultural, Food and Nutritional Science, 410 Agriculture/Forestry Centre, University of Alberta, Edmonton, AB T6G 2P5, Canada

The transportation of infested soil or infected crop residues from one field to another has the potential to spread the clubroot pathogen (Plasmodiophora brassicae Woronin). Farm machinery, especially large tillage equipment, may carry hundreds of kilograms of soil and crop residues. Sanitization (sanitation) is the process of cleaning and disinfecting hard surfaces (machinery, equipment, vehicles, tools, footwear), seed, plant materials, water and/or soil infested with pathogens. It has been used for clubroot management in vegetable operations for many years, but its use in canola production systems has been a recent innovation. Equipment sanitization involves three key steps: (i) rough cleaning using scraping, brushing or blowing to remove bulk soil and crop debris; (ii) fine cleaning using pressure washing, scrubbing or compressed air to remove remaining residues; and (iii) disinfection with an effective biocide applied to the cleaned surfaces with ≥20 min of contact time to ensure any remaining resting spores are killed. The most critical steps in sanitizing clubroot-infested farm machinery, equipment and vehicles are the rough and fine cleaning, which should render the surfaces free of visible soil and plant material and aim to remove up to 99% of the contamination. Ten chemical disinfectants and seven thermal treatments were evaluated for the final sanitization step. Amongst 10 chemical disinfectants tested, sodium hypochlorite, hydrogen peroxide, acetic acid, and potassium peroxymonosulphate were the most effective. Thermal treatments of ≥80 °C for 30 min were required to induce substantial spore mortality, but some even survived exposure to 100 °C for up to 3 h.

Evaluating procedures for the sanitization of potato storages. R. J. HOWARD, G. C. DANIELS, S. L. MOBBS, D. A. BURKE, B. E. ROBINSON, S. L. I. LISOWSKI, M. W. HARDING, S. H. DE BOER AND T. C. SHINNERS-CARNELLEY. Crop Diversification Centre South, Alberta Agriculture and Rural Development, 301 Horticultural Station Road East, Brooks, AB T1R 1E6, Canada; (S.H.D.B.) Charlottetown Laboratory, Canadian Food Inspection Agency, 93 Mount Edward Road, Charlottetown, PE C1A 5T1, Canada; and (T.C.S.-C.) Peak of the Market, P.O. Box 2032, Carman, MB R0G 0J0, Canada

Research was conducted to determine the relative effectiveness of 10 chemical disinfectants against Clavibacter michiganensis subsp. sepedonicus (Spieck. & Kotth.) Davis et al. (Cms), the causal agent of bacterial ring rot (BRR), a destructive disease of potato tubers. Previous disinfection studies have dealt mainly with Cms in its planktonic (solitary or free-floating cells) form and relatively little research has focused on the reduction or eradication of the pathogen growing as a biofilm (aggregated cell population encased in a self-produced slimy matrix). Biofilm eradication was the main emphasis of the current study. Stable biofilms of Cms were generated utilizing BEST™ assay plates (Innovotech Inc., Edmonton, AB). Eleven hard surface materials common to potato storages and associated equipment were studied for ease of Cms biofilm decontamination and included both porous and non-porous substrata. The most effective biocides were Bleach, Thymox, Hyperox, Virkon and SaniDate; however, relative effectiveness varied depending on the type of surface being decontaminated, with porous surfaces being the most difficult to sanitize. Pilot-scale evaluations with live steam and 11 disinfectants were carried out in commercial potato storages in Alberta, Saskatchewan and Manitoba in 2010–12. None of these facilities was naturally infested with Cms, so the effectiveness of the various treatments was assessed by measuring total populations of bacteria, yeasts and fungi prior to and after cleaning and disinfection. Biocide effectiveness varied with the type of surface being decontaminated. Overall, bleach was the most effective disinfectant, but Thymox was also a strong performer against both bacteria and fungi.

Diversity in population structure of the late blight pathogen, Phytophthora infestans, in Manitoba. M. R. ISLAM, H. ALKHER, M. BEZZAHOU, C. GODEE, L. R. ADAM, L. M. KAWCHUK, K. F. DOBINSON, K. L. CONN, R. D. PETERS, K. I. AL-MUGHRABI, T. C. SHINNERS-CARNELLEY AND F. DAAYF. Department of Plant Science, 222 Agriculture Building, 66 Dafoe Road, University of Manitoba, Winnipeg, MB R3T 2N2, Canada; (L.M.K.) Lethbridge Research Centre, Agriculture and Agri-Food Canada (AAFC), 5403 1^st Avenue South, Lethbridge, AB T1J 4B1, Canada; (K.F.D., K.C.) Southern Crop Protection and Food Research Centre, AAFC, 1391 Sandford Street, London, ON N5V 4T3, Canada; (R.D.P.) Crops and Livestock Research Centre, AAFC, 440 University Avenue, Charlottetown, PE C1A 4N6, Canada; (K.I.A) Potato Development Centre, New Brunswick Department of Agriculture, Aquaculture and Fisheries, 39 Barker Lane, Wicklow, NB E7L 3S4, Canada; and (T.C.S.-C.) Peak of the Market, P.O. Box 2032, Carman, MB R0G 0J0, Canada

The oomycete Phytophthora infestans (Mont.) de Bary is the causal agent of late blight in several Solanaceous crops. In fact, it is considered one of the most destructive diseases of potato and tomato worldwide. In recent years, genetic changes in the population structure of this pathogen in North America and elsewhere have been recorded along with an increased frequency of late blight epidemics. In Canada during the mid-1990s, the US-1 genotype was displaced by its US-8 counterpart, which rapidly became the most dominant genotype and remained so until 2007. In 2009–11, new outbreaks in Canada of late blight on both potato and tomato were caused by new strains of P. infestans (US-22, US-23 and US-24). In 2012, 10 P. infestans isolates were confirmed as A1 mating type and one was undetermined. In vitro assays with isolates from 11 diseased samples showed that only four isolates were sensitive to mefenoxam whereas seven were resistant. Allozyme banding patterns at the glucose 6-phosphate isomerase (Gpi) locus indicated 100/100 and 100/100/111 profiles consistent with US-6/US-23 and US-11/US-24 genotypes, respectively. Restriction fragment length polymorphism (RFLP) analysis of representative isolates was performed using the RG-57 probe and resulted in banding patterns which confirmed US-23 as the dominant genotype and also confirmed the presence of US-24 in 2012. Mitochondrial DNA (mtDNA) haplotyping confirmed both US-23 and US-24 genotypes as Ia haplotype of P. infestans in Manitoba. Taken together, the US-23 and US-24 genotypes of P. infestans dominated the population in Manitoba during 2009–12, suggesting clonal reproduction and long-distance migration in seed tubers and garden centre transplants. Monitoring pathogen movement and population composition will improve our ability to understand and possibly predict further population changes, and hopefully improve late blight management strategies in Canada.

A cupin domain containing protein (VdQase) is required for optimum virulence in Verticillium dahliae. M. R. ISLAM, A. EIHARDAMI, L. R. ADAM, K. DOBINSON, M. BEZZAHOU AND F. DAAYF. Department of Plant Science, 222 Agriculture Building, 66 Dafoe Road, University of Manitoba, Winnipeg, MB R3T 2N2, Canada; (A.E.) OMEX Agriculture Inc, Oak Bluff, MB, R4G 0A5, Canada; (K.D.) Southern Crop Protection and Food Research Centre, Agriculture and Agri-Food Canada, 1391 Sandford Street, London, ON N5V 4T3, Canada

Verticillium dahliae Kleb. is a serious soilborne fungal pathogen causing wilt in many crops and increasingly emerging as a threat to potato production. Rutin (quercetin-3-rutinoside), one of the flavonoids released by plant roots in the rhizosphere, is part of the potato response to V. dahliae. In an earlier study, potato treated with Canada milk vetch (CMV) extract showed higher protection against V. dahliae through a substantial accumulation of the flavonol glycoside rutin. Here we identified a cupin domain containing protein (VDAG_02250.1) in the Verticillium genome database which was induced when V. dahliae was grown in a medium containing rutin. We renamed the gene ORF as VdQase as one of the V. dahliae dioxygenases. To analyse the possible role of VdQsae in V. dahliae-potato interaction, a knock-out mutant of VdQase was generated using an Agrobacterium-mediated transformation system. Pathogenicity testing revealed that mutation of VdQase gene reduced pathogenicity significantly on susceptible potato and tomato cultivars. Higher flavonols accumulation in the potato stem infected with the mutant indicated that V. dahliae may be utilizing such flavonols using VdQase. Higher residual non-utilized quercetin in presence of the knock-out mutant, as quantified by HPLC in vitro, strongly suggests the involvement of VdQase in quercetin’s metabolism. Verticillium dahliae may dioxygenically oxidize quercetin aglycone, a derivative from the rutin catabolic pathway, into its by-products viz. phloroglucinol and a protocatechuoyl moiety during infection, which may trigger the antagonism of salicylic acid (SA) and jasmonic acid (JA) pathways in countering potato defences and in becoming more competitive in the rhizosphere.

Monitoring of Leptosphaeria and Fusarium spore concentration in the air of different climatic regions of Poland. J. KACZMAREK, A. BRACHACZEK AND M. JEDRYCZKA. Institute of Plant Genetics, Polish Academy of Sciences, 34 Strzeszynska, 60-479 Poznan, Poland; and (A.B.) DuPont Poland Ltd., 17b Postepu, 02-676 Warsaw, Poland

Numerous diseases of plants are broadcast by air, what allows pathogens to be dispersed over very large areas. Aerobiology offers tools and methodologies allowing monitoring of airborne inoculum. Fungal propagules dispersed by wind can be monitored in fields when captured on rotating tapes within 7-day volumetric spore traps. Tapes from traps can be processed for spore counts followed by DNA diagnostics and quantification by Real-Time PCR to estimate more accurately the particular fungal species. In Poland starting from autumn 2004 a network of 9–10 volumetric spore samplers located in different geographic locations has been constantly operating. The monitoring of airborne spores is currently done for Leptosphaeria maculans (Desmaz.) Ces. & de Not. and L. biglobosa that cause stem canker of crucifers or blackleg on oilseed rape as well as for Fusarium spp. responsible for fusarium head blight on cereals. In this study we found considerable differences between experiment sites and years. The dynamics of the abundance of airborne spores corresponded to fluctuations in the levels of DNA originating from either Leptosphaeria spp. or Fusarium spp. In all cases, positive correlations were found between spore counts, obtained by light microscopy and molecular detection based on the amounts of DNA. We also found that the ratio between airborne propagules of both Leptosphaeria species greatly differed between the seasons and sampling sites. Detection and quantification of pathogen inoculum by classical aerobiological methods combined with molecular tools helps in precise management of epidemics caused by plant-pathogenic fungi.

Fine mapping of Ug99 stem rust resistance gene SrCad. M. T. KASSA, C. HIEBERT, F. M. YOU, M. JORDAN, P. FOBERT, A. SHARPE, C. POZNIAK, T. ZEGEYE, T. FETCH, J. MENZIES AND C. A. MCCARTNEY. Cereal Research Centre, Agriculture and Agri-Food Canada, 195 Dafoe Road, Winnipeg, MB R3T 2M9, Canada; (P.F., A.S.) National Research Council Canada, 110 Gymnasium Place, Saskatoon, SK S7N 0W9, Canada; and (C.P.) Crop Development Centre, Department of Plant Sciences, University of Saskatchewan, 51 Campus Drive, Saskatoon, SK S7N 5A8, Canada

Wheat stem rust, caused by the fungus Puccinia graminis f. sp. tritici Eriks. & Henn., is a serious disease that can cause huge economic losses. The evolution and emergence of new highly virulent races TTKSK (Ug99) (Pretorius et al. 2000) and its variants has alarmed the wheat community. High levels of resistance to Ug99 and its variants are present in Canadian wheat cultivars ‘Peace’ (BW90*3/BW553) and ‘AC Cadillac’ (BW90*3/BW553//BW90’S’/Katepwa). The resistance gene SrCad, which confers Ug99 resistance, was mapped to chromosome 6DS in both cultivars (Hiebert et al., 2011). A lack of polymorphic markers in the 6DS region has hampered the fine mapping of SrCad. Thus, using bioinformatic tools we identified single nucleotide polymorphisms (SNP) associated with SrCad resistance using an Infinium 90K iSelect assay, publicly available SNP databases, the wheat survey sequence and Aegilops tauschii genomic resources. The SNPs were converted to Kompetitive Allele Specific PCR (KASP) assays and were mapped in two populations: 345 DH lines from RL6071/Peace and an F₆‐derived recombinant inbred line population of 1872 lines from BW278/AC Foremost. The SNP markers delineated SrCad to a 1.5 cM interval using the two populations. Using these markers, we have identified Resistance Gene Analogues (RGAs) in the region and are now pursuing developing RGA-based markers to identify candidate genes for SrCad. The goal of this project is to develop diagnostic molecular markers useful for wheat breeding programmes, and to characterize SrCad gene expression on a molecular basis.

Population diversity and segregation analysis of genotype specific loci of the Irish potato famine pathogen. L. M. KAWCHUK, R. D. PETERS, K. I. AL-MUGHRABI, K. F. DOBINSON, K. L. CONN AND F. DAAYF. Lethbridge Research Centre, Agriculture and Agri-Food Canada (AAFC), 5403 1^st Avenue South, Lethbridge, AB T1J 4B1, Canada; (R.D.P.) Crops and Livestock Research Centre, AAFC, 440 University Avenue, Charlottetown, PE C1A 4N6, Canada; (K.I.A.) New Brunswick Department of Agriculture, Aquaculture and Fisheries, 39 Barker Lane, Wicklow, NB E7L 3S4, Canada; (K.F.D., K.L.C.) Southern Crop Protection and Food Research Centre, AAFC, 1391 Sandford Street, London, ON N5V 4T3, Canada; and (F.D.) Department of Plant Science, 222 Agriculture Building, 66 Dafoe Road, University of Manitoba, Winnipeg, MB R3T 2N2, Canada

Late blight, caused by Phytophthora infestans (Mont.) de Bary and responsible for the Irish potato famine, remains a devastating disease of potatoes and tomatoes that occurs worldwide. In recent years, late blight has been very severe in Canada and the USA, causing localized epidemics and considerable yield losses. A national survey conducted in Canada during 2012 revealed that the P. infestans US-23 genotype dominated pathogen populations in most provinces. In addition, several isolates of the P. infestans US-22 and US-23 genotypes showed increased resistance to the systemic fungicide mefenoxam in in vitro assays. Asexual (clonal) reproduction appears to be the primary method of propagation and has contributed to the P. infestans US-22, US-23 and US-24 genotypes becoming established in Canada. However, in some situations, both A1 and A2 mating types of the pathogen were found in the same production region thereby increasing the potential for sexual recombination within pathogen populations. Sexual recombination of P. infestans contributes to the rapid generation of new strains and production of oospores that can potentially overwinter and survive in the absence of host tissue. In 2012, evidence for sexual recombination in the P. infestans population was detected in British Columbia on potato, producing a new A1 mating type genotype resembling both US-8 and US-11 but with a gpi allozyme 100/100/111 and RG57 RFLP 1,5,10,13,14,17,20,21,24,25 profile. Successful prediction and management of late blight will require continued monitoring of pathogen populations and measures to address the characteristics associated with these new P. infestans genotypes.

Investigation of microorganisms in the imported culture medium of anthurium plants. S. H. KIM, H. W. KWON, J. Y. KIM, M. CHOI, S.-K. YOON AND S. W. JANG. Department of Microbiology, Dankook University, Cheonan, Chungnam, 330-714, Korea

The production of anthurium in Korea has depended on the import of its seeds and young plants. Because it is distributed in neotropical areas such as South American and Asian rain forests, the plant is potted and imported. The plant pot contains culture media composed of agricultural by-products or natural plant residues such as coco-peat, coconut bark, moss and peat moss. Culture media can be contaminated by pathogenic fungi and bacteria and damaging insects. For these reasons, many countries have guidelines to control plant pathogens for exportation and importation. In an effort to examine the status of culture media, we investigated fungi and bacteria from culture media of imported anthurium pots. We isolated seven species of fungi and nine species of bacteria from the anthurium’s culture media. One of the isolated fungi has been classified as Myrothecium roridum Tode. Because this species was known as an anthurium pathogen and found to be an unrecorded species in Korea, in the present study we report its morphological, physiological, biochemical and pathological characteristics.

Development of a real-time nano-antibody sensor for forecasting blackleg in canola. X. LI, J. YANG AND J. CHEN. Alberta Innovates – Technology Futures, Highway 16A 75^th Street, Vegreville, AB T9C 1T4, Canada; and (J.C.) National Institute for Nanotechnology, 11421 Saskatchewan Drive NW, Edmonton, AB T6G 2M9, Canada

The objective of this study was to determine the possibility of measuring conductivity of gold nanoparticle-antibody-pathogen spore complexes. We hypothesize that there is a correlation between the number of pathogen spores and the conductivity resulting from binding spores to their antibody-gold nanoparticle conjugates. If this hypothesis is true, a device can then be made to detect the number of spores in the crop field in a real-time fashion to forecast disease severity. In this study, a blackleg disease fungus, Leptosphaeria maculans (Desmaz.) Ces. & de Not. and its antibody were used as a model to test this hypothesis. A nanoelectronic sensing array was used to quantitatively measure the changes of conductivity. The anti-L. maculans antibody was linked to the gold nanoparticle and increasing amounts of L. maculans spores: 45, 45 × 10¹, 45 × 10², 45 × 10³, 45 × 10⁴, 45 × 10⁵ were added as test samples. We found a linear relationship (R² = 0.8956) between spore quantity and conductivity signal index. The conductivity of the nanoparticle-antibody-pathogen spore complex decreased as the spore number increased. Based on the results generated to date, we conclude that the development of a nanoparticle-antibody based sensor for in-field, real-time forecasting of plant disease is feasible.

Association mapping of stripe rust resistance in durum wheat using high-density SNP markers. X. LIN, A. N’DIAYE, Y. RUAN, H. R. KUTCHER, H. RANDHAWA, J. M. CLARKE, A. SHARPE AND C. J. POZNIAK. Crop Development Centre, Department of Plant Sciences, University of Saskatchewan, 51 Campus Drive, Saskatoon, SK S7N 5A8, Canada; (H.R.) Lethbridge Research Centre, Agriculture and Agri-Food Canada, 5403 1st Avenue South, Lethbridge, AB T1J 4B1, Canada; and (A.S.) Saskatoon Research Facilities, National Research Council, Saskatoon, 110 Gymnasium Place, Saskatoon, SK S7N 0W9, Canada

Stripe rust, caused by fungal pathogen Puccinia striiformis f. sp. tritici Eriks. & Henn., is an important disease of durum wheat (Triticum turgidum L. var. durum) worldwide. Epidemics of stripe rust can result in yield losses of 10–70% and total yield loss has been reported when severe epidemics occur. Thus, breeding of resistant varieties is a priority. The goal of this study was to identify DNA markers for stripe rust resistance using an association mapping (AM) approach that could be utilized in marker assisted breeding. Ninety-two durum accessions collected from major durum wheat breeding programmes globally were genotyped with an Infinium 90K iSelect assay and 245 simple sequence repeats (SSR) markers. Population structure was estimated using a combination of genetic similarity matrix (Rogers’ coefficient) and Bayesian analysis using the software STRUCTURE. Seedling resistance was assessed in replicated trials conducted under controlled conditions using two pathogen races obtained from naturally infected plants in Saskatchewan and Alberta, Canada. Significant differences in disease severity were observed among accessions of the AM population. A total of 13 539 (16.6%) SNP markers were selected and scored on the AM population. Population structure as determined by Bayesian analysis indicated that the highest likelihood was K = 5. In total, 15 significant SNP markers (P ≤ 0.05) were identified for seedling resistance, 12 were located at the same site on chromosome 7B. These markers are currently being validated for association with stripe rust resistance in a bi-parental stripe rust resistant by susceptible population of durum wheat to confirm the association.

Analysis of the internal transcribed spacer (ITS) of Ditylenchus weischeri parasitizing Canada thistle. M. MADANI, M. TENUTA AND S. SUBBOTIN. Department of Soil Science, Ellis Building, University of Manitoba, 13 Freedman Crescent, Winnipeg, MB R3T 2N2, Canada; and (S.S.) Plant Pest Diagnostic Center, California Department of Food and Agriculture, Sacramento, CA 95832-1448, USA

We previously reported the stem nematode, Ditylenchus weischeri Chizhov et al., on Canada thistle (Cirsium arvense) in MB and SK, and its seeds contaminating yellow pea grain from the Canadian Prairies. Genomic molecular variation of this nematode is reported here. The whole internal transcribed spacer region (ITS) was sequenced from 10 isolates of D. weischeri from Canada thistle in MB and SK, and one from Russia. Forty-three ITS sequences from these isolates were compared with nine sequences of closely related D. gigas and 58 of the D. dipsaci (Kühn) Filipjev species complex in GenBank. After multiple sequence alignments, a 673 bp region was sequenced for intra- and inter-species variations. Twelve single-nucleotide-polymorphisms (SNPs) were specific to D. weischeri. They included two deletions and 10 substitutions. All isolates of D. weischeri differed from D. gigas with five substitutions in ITS1, and one deletion and three substitutions in ITS2. The Canadian D. weischeri isolates differed from the D. weischeri holotype in GenBank and infested Canada thistle from Russia by two substitutions. Within the MB isolates of D. weischeri, a substitution was indicative of two haplotypes. Ditylenchus weischeri differed from D. dipsaci by 23 SNPs. The SNPs were not unique to all 58 D. dipsaci accessions in GenBank though some sequences in the database are likely incorrectly attributed to D. dipsaci. The results substantiate species recognition of D. weischeri and D. gigas. The results also indicate SNP genotyping should be useful for designing species diagnostic primer sets of these species and haplotypes of D. weischeri.

Molecular identification of populations of the soybean cyst nematode (Heterodera glycines) from Ontario. M. MADANI, M. TENUTA, T. WELACKY AND A. TENUTA. Department of Soil Science, Ellis Building, University of Manitoba, 13 Freedman Crescent, Winnipeg, MB R3T 2N2, Canada; (T.W.) Greenhouse and Processing Crops Research Centre, Agriculture and Agri-Food Canada, 2585 County Road 20, Harrow, ON N0R 1G0, Canada; and (A.T.) Ontario Ministry of Agriculture, Food and Rural Affairs, Ridgetown College, Ridgetown, ON N0P 2C0, Canada

Soybean cyst nematode (SCN), Heterodera glycines Ichinohe, is a major pest of soybean in Ontario and worldwide. Current internal transcribed spacer (ITS) based primer sets do not accurately and rapidly identify all populations of the nematode by diagnostic PCR. This inconsistency hampers development of resistance varieties and consequently effective control measures. In this study, a total of 30 populations of SCN from southwestern Ontario were used to develop a diagnostic PCR method for rapid species identification. Populations of closely related H. schachtii, H. trifolli and H. glycines and more distantly related nematodes, Meloidogyne incognita and Ditylenchus dipsaci, were used as controls. The heat shock gene (Hsp90), D2A-3B expansion of 28s RNA gene, and Mt-DNA were amplified and sequenced. The species identity of the populations was verified using ITS-RFLP and ITS sequence homology to GenBank accessions for H. glycines. From alignment of available Mt-DNA sequences of Heterodera species in GenBank and Hsp90 gene sequences obtained in this study, several primer sets were designed for potential rapid species identification. The primers were used in diagnostic specific PCR for H. glycines, and in duplex PCR by adding the D2A-D3B primers as controls to the PCR reaction. The most promising primer set was from the Mt-DNA that identified all populations of SCN with no false positives for the control species. This primer set was used in real-time PCR that generated a specific melting curve for H. glycines. Melt curve analysis has advantage of eliminating need for post-PCR gel electrophoresis.

Evaluating disease reaction of western Canadian spring wheat cultivars (Triticum spp.) to natural and artificial infection with Claviceps purpurea. L. MALO AND P. HUCL. Department of Plant Sciences and Crop Development Centre, University of Saskatchewan, College of Agriculture and Bioresources, 51 Campus Drive, Saskatoon, SK S7N 5A8, Canada

Ergot [Claviceps purpurea (Fr.) Tul.] attacks the floral organs of many cereal species resulting in the production of sclerotia instead of kernels of grain. Infection results in reduced yields, downgrading, and poisoning if consumed by humans or animals. Few studies have been conducted on ergot in wheat, and there are no control measures other than prevention. In this study, 92 wheat cultivars were examined under field and under controlled conditions to determine differences in disease reaction. Disease was measured using number of sclerotia per spike and per cent sclerotia by weight in the harvest sample. In the controlled environment, data collection also included honeydew ratings and sclerotia size estimates. Results suggest that there are differences in disease reaction among cultivars and market classes, but that these differences may vary depending on the measurement variable. Pearson correlations were also calculated using cultivar means from both environments. A lack of correlation between test environments suggests conflicting resistant mechanisms and therefore has implications for future studies. Results of the indoor tests may indicate some type of genetic resistance; however, field results suggest decreased disease due to avoidance. The results of this study may provide valuable information on genotypes to use for future disease resistance breeding efforts, including selection characteristics to facilitate the process.

Mapping adult plant crown rust resistance in oat. C. A. MCCARTNEY, Y. LIN, B. N. GNANESH, A. D. BEATTIE, J. CHONG, J. W. M. FETCH, H. R. KUTCHER, P. E. ECKSTEIN, E. W. JACKSON, J. G. MENZIES AND I. A. P. PARKIN. Cereal Research Centre, Agriculture and Agri-Food Canada (AAFC), 195 Dafoe Road, Winnipeg, MB R3T 2M9, Canada; (Y.L., A.D.B., H.R.K., P.E.E.) Crop Development Centre, Department of Plant Sciences, University of Saskatchewan, 51 Campus Drive, Saskatoon, SK S7N 5A8, Canada; (E.W.J.) General Mills Agriculture Research, 150 N. Research Campus Drive, Kannapolis, NC 28081, USA; and (I.A.P.P.) Saskatoon Research Centre, AAFC, 107 Science Place, Saskatoon, SK S7N 0X2, Canada

Crown rust, caused by Puccinia coronata Corda f. sp. avenae Eriks., is the most damaging disease of oat in Canada. Host plant resistance is an important management option. Most oat breeding efforts to control crown rust have focused on race-specific seedling resistance genes. These genes have typically failed after 5 years of widespread production. Non-race-specific adult plant resistance is proposed as an alternative option for developing resistant varieties with improved durability. The oat breeding line MN841801 is believed to possess non-race-specific resistance. This resistance was studied in a recombinant inbred line (RIL) population consisting of 163 lines from the cross ‘AC Assiniboia’ × MN841801. The population was inoculated with crown rust isolate CR251 (race BRBB) in four environments and a mixture of crown rust isolates in a fifth environment. CR251 is virulent on the parents of the population at the seedling growth stage, thereby mitigating confounding effects of seedling resistance genes segregating in the population. The population was genotyped with the new 6K oat Infinium SNP array and Diversity Array Technology (DArT) markers. The resulting linkage map identified a highly significant quantitative trait locus (QTL) for adult plant resistance to crown rust in all field tests. The SNPs identified in this study will facilitate the incorporation of the adult plant resistance QTL into new oat varieties.

Reaction of canola to inoculation with primary and secondary zoospores of Plasmodiophora brassicae. M. R. MCDONALD, K. SHARMA, B. D. GOSSEN, J. FENG, A. DEORA AND S. F. HWANG. Department of Plant Agriculture, Crop Science Building, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada; (B.D.G.) Saskatoon Research Centre, Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, SK S7N 0X2, Canada; and (J.F., S.F.H.) Crop Diversification Centre North, Alberta Agriculture and Rural Development, 17 507 Fort Road N.W., Edmonton, AB T5Y 6H3, Canada

Plasmodiophora brassicae Woronin causes clubroot of canola (Brassica napus L.) and many other Brassica crops. Resting spores of the pathogen germinate and release primary zoospores that infect root hairs. Secondary zoospores are produced in infected root hairs, and infect the root cortex. Studies were conducted to investigate the role of these two spore types on cortical infection and subsequent clubroot severity in canola cv. Zephyr. Plants were inoculated with resting spores (RS, as a source of primary zoospores) or secondary zoospores (SZ) of either a virulent (P3) or an avirulent (P6) pathotype. In addition, SZ-P3 at 5 days after inoculation (DAI) with RS-P3 or RS-P6 was assessed. The area of the root cortex infected (%, based on image analysis of stained cortical sections) was assessed at 10 DAI, and clubroot severity (0–3 scale) was assessed on each plant at 42 DAI. The pattern of response was similar for cortical infection and severity. Inoculation with RS-P6 (avirulent) resulted in almost no infection (0.1%) or severity (0%), but SZ-P6 produced low levels of both infection (4%) and severity (31%). RS-P3 produced more infection (33% vs 12%) and higher severity (100% vs. 67%) than SZ-P3. Following RS-P3 with SZ-P3 did not affect cortical infection (34% vs. 33%). However, RS-P6 + SZ-P3 produced lower infection (18% vs. 34%) and severity (84% vs. 100%) than RS-P3 + SZ-P3. These results indicate that pathogen effectors may act at the root hair infection stage and suppress (P3) or induce (P6) resistance in the host.

Population study of the anthracnose pathogen from lentil fields in Saskatchewan. J. MENAT AND S. BANNIZA. Crop Development Centre, Department of Plant Sciences, University of Saskatchewan, 51 Campus Drive, Saskatoon, SK S7N 5A8, Canada

Colletotrichum sp. ex lentil has been responsible for severe yield losses in Western Canada. This ascomycete fungus is believed to reproduce asexually under field conditions, but the teleomorph has been obtained under laboratory conditions. Heterothallism was confirmed in this species and two incompatibility groups have been identified that do not correspond to the two typical ascomycete mating type genes MAT1-1 and MAT1-2. To gain a better understanding of the life cycle of the fungus under field conditions, a molecular population study based on amplified fragment length polymorphisms was undertaken on 179 isolates from different Saskatchewan locations and crop years. This set of isolates displayed a low level of diversity compared with what was observed in populations of other Colletotrichum species. Although the fungus is a sexual species under laboratory conditions and both mating types coexist in the field, a moderate level of linkage disequilibrium suggested that the population studied is mostly clonal and that sexual reproduction, if it occurs, remains a rare event. Twenty-seven isolates physically mapped in and collected from multiple sites in a single lentil field were crossed with reference isolates of both incompatibility groups. This experiment showed that isolates of different mating types coexisted in the same field and on the same plant, suggesting that geographical isolation is not a factor restricting sexual reproduction.

Field applications of composted manures and the soil fumigant Vapam for the control of potato early dying in Manitoba. O. I. MOLINA, M. TENUTA, K. BUCKLEY AND F. DAAYF. Department of Soil Science, Ellis Building, University of Manitoba, 13 Freedman Crescent, Winnipeg, MB R3T 2N2, Canada; (K.B.) Brandon Research Centre, Agriculture and Agri-Food Canada, 2701 Grand Valley Road, Brandon, MB R7A 5Y3, Canada; and (F.D.) Department of Plant Science, 222 Agriculture Building, 66 Dafoe Road, University of Manitoba, Winnipeg, MB R3T 2N2, Canada

Potato early dying (PED) can severely reduce yields in potato production areas of North America including Manitoba. PED is caused by a fungal-nematode complex. In Manitoba, however, the major causal-agent is the fungus Verticillium dahliae Kleb. Composted cattle manure has shown potential to reduce PED and increase potato yield in Manitoba. The objective of this research was to evaluate the effect of different rates (20, 40 and 80 Mg ha⁻¹) of composted separated hog slurry solids (CSHSS) and cattle manure (CCM) on V. dahliae densities in soil, PED development and potato yield. Two replicated field experiments planted to ‘Russet Burbank’ and ‘Standard Norland’, respectively, were conducted on each of three commercial potato fields in 2012. Treatments were the two compost sources and rates, the soil fumigant Vapam, applied at 375 and 560 L ha⁻¹, high inorganic fertilizer to simulate N-P-K addition with compost treatment, and standard fertility treatment (control). Although compost, fumigant and high-fertilizer treatments reduced PED severity and incidence in both experiments, PED-incidence was lower than the control only in fumigated and CSHSS-80 Mg ha⁻¹ treatments, in ‘Russet Burbank’ and ‘Norland’ (P < 0.001), respectively. The highest increase in total yield relative to the control, in ‘Russet Burbank’ and ‘Norland’ was 15 and 10%, respectively, and was with the Vapam 375 L ha⁻¹ treatment. In brief, application of Vapam at the lower rate increased potato yield, and reduced PED, possibly due to the reduction of V. dahliae in soil observed in both experiments, while CSHSS-80 Mg ha⁻¹ reduced PED only with ‘Norland’.

Impact of cytokinins on Ustilago maydis pathogenic development. E. N. MORRISON, R. J. N. EMERY AND B. J. SAVILLE. Environmental & Life Sciences Graduate Program, Trent University, DNA Building, 2140 East Bank Drive, Peterborough, ON K9J 7B8, Canada; (R.J.N.E.) Biology Department, Trent University, DNA Building, 2140 East Bank Drive, Peterborough, ON K9J 7B8, Canada; and (B.J.S.) Forensic Science Program, DNA Building, Trent University, 2140 East Bank Drive, Peterborough, ON K9J 7B8, Canada

We are using the corn smut fungus Ustilago maydis (DC.) Corda as a model to investigate the role cytokinins play during fungal development and biotrophic fungal infection of plants. Cytokinins (CKs) are a group of phytohormones that are often associated with actively dividing tissues. Infection of corn by U. maydis stimulates uncoordinated cellular division, resulting in tumour formation on all aerial organs of the plant. CK-like activity has been associated with these tumours and detected in axenic U. maydis cultures; yet control of fungal CK production has not been examined. The first and rate-limiting step in cytokinin biosynthesis in plants is catalysed by isopentenyltransferases (IPTs). In fungi, related IPTs are usually tRNA-isopentenyltransferases (tRNA-IPTs). Because U. maydis is amenable to molecular manipulation and biochemical characterization we were able to delete the sole tRNA-IPT gene in solopathogenic strains of this fungus. Subsequent biochemical profiling of these strains through liquid-chromatography-electrospray ionization-tandem mass spectrometry, LC- (ESI) MS/MS, revealed that none of the major CKs produced in wild type cultures are detectable in the tRNA-IPT deletion mutant strains. Deletion of this gene alters fungal growth in both liquid culture and filamentous growth assays. During infection of the plant, both cob and seedling assays show decreased pathogenesis by the deletion mutants relative to wild type. Results of deletion strain characterization and a proposed role(s) for CKs will be presented.

Screening for resistance to Leptosphaeria maculans in Brassica hybrids. J. NIEMANN, J. KACZMAREK, A. WOJCIECHOWSKI AND M. JEDRYCZKA. Department of Genetics and Plant Breeding, University of Life Sciences, 11 Dojazd, 60-632 Poznan, Poland; (J.K., M.J.) Institute of Plant Genetics, Polish Academy of Sciences, 34 Strzeszynska, 60-479 Poznan, Poland

Stem canker of crucifers or blackleg, caused by Leptosphaeria maculans (Desmaz.) Ces. & de Not., is one of the most important diseases of oilseed rape worldwide. The incorporation of L. maculans resistance into Brassica lines with desirable agronomic and quality traits is the major objective in breeding programmes. Although cultural practices and chemical treatments assist in reducing the spread and severity of the disease, genetic resistance remains the most reliable method of control. Screening of plant susceptibility/resistance to L. maculans was done for 130 hybrids between Brassica species and five parental genotypes. The hybrids represented F₃–F₆ generations of crossings of Brassica napus × B. carinata, B. napus × B. juncea, B. napus × B. campestris ssp. pekinensis and B. napus × B. campestris ssp. trilocularis. Oilseed rape line used to obtain these hybrids was male sterile. Screening was done using a cotyledon test based on inoculation of 2-week-old seedlings with spore suspension of four L. maculans isolates (10⁷ conidia mL⁻¹). The plants were grown in a controlled environment chamber, maintained at alternating periods of 16 h light at 20–22 °C and 8 h of darkness at 16–18 °C. Droplets of spore suspension were placed on each half of a cotyledon – four inoculation points per plant – previously wounded by puncturing with a thin needle. Host response was scored using a 0–6 scale, where a 1–3 score was recorded as a resistant reaction and a 4–6 score corresponded to susceptible reaction. The genotypes differed with their reaction to the pathogen, allowing selection of some genotypes for further studies.

Efficacy of fungicidal seed dressings to manage fusarium root rot of soybean in southern Alberta. R. NYANDORO, K. F. CHANG, S. F. HWANG, S. E. STRELKOV, G. D. TURNBULL, R. J. HOWARD AND M. HARDING. Department of Agricultural, Food and Nutritional Science, 410 Agriculture/Forestry Centre, University of Alberta, Edmonton, AB T6G 2P5, Canada; (K.F.C., S.F.H., G.D.T.) Crop Diversification Centre North, Alberta Agriculture and Rural Development (AARD), 17 507 Fort Road N.W., Edmonton, AB T5Y 6H3, Canada; and (R.J.H., M.H.) Crop Diversification Centre South, AARD, 301 Horticultural Station Road East, Brooks, AB T1R 1E6, Canada

Soybean (Glycine max (L.) Merr), a high-protein nitrogen-fixing leguminous crop has potential for inclusion in rotations in the canola cropping systems of southern Alberta owing to its relatively high returns and to the development of short season cultivars. It is, however, threatened by root rot disease caused by Fusarium spp. Experiments were conducted in the 2012 summer season both under greenhouse and open field conditions to evaluate the efficacy of nine fungicide seed treatments (Apron Maxx, Rancona Summit + Maxim 5FS, Rancona Summit, EverGol Energy, Trilex EverGol, Vitaflo 280, Rancona Summit + Maxim 5FS + Vibrance, Vitaflo 280 + Apron and Vibrance + Apron) in protecting soybeans (cv. TH29002RR) from Fusarium avenaceum (Fr.) Sacc. Greenhouse and field trials were arranged in a randomized complete block design with fungicides as treatments, along with inoculated and disease-free controls. Seeds treated with Apron Maxx had the highest rate of emergence in the field experiment, while Rancona Summit- treated seeds gave significantly high soybean yields (P ≤ 0.05). Seedling emergence was severely reduced in inoculated treatments in the greenhouse trial and where the seeds germinated, root weight was severely reduced and the root system exhibited severe discolouration. Treatment with Rancona Summit, Apron Maxx, Vitaflo + Apron Maxx or Vitaflo 280 resulted in the lowest root rot severity in the greenhouse experiment. Both the field and greenhouse experiments will be repeated in 2013 to confirm results on fungicide efficacy for the management of soybean root rot.

The role of fungicides for effective disease management in cereal crops. N. F. POOLE. Foundation for Arable Research, P.O. Box 23133, Templeton 8445, Christchurch, New Zealand

Fungicides are the last line of defence in the armoury of an integrated disease management (IDM) approach. They do not create yield, but protect an inherent yield potential that the grower may realize in the absence of disease. In the field, securing effective disease control from a fungicide application is dependent upon the disease pressure and the effectiveness of the fungicide to control that disease. Globally, the same fungicide active ingredients are used against a similar range of fungal pathogens. However, in the presence of the pathogen the level of economic response to fungicide application is primarily driven by the environmental conditions and the interaction with crop development and the pathogen. Fungicides are canopy management tools that influence the size and duration of the green leaf area (GLA) of the crop. The total number of fungicide applications links to the length of the growing season and the disease risk in that period, for example, the top three leaves of a cereal crop canopy might warrant protection for approximately 120 days in an irrigated wheat crop on the Canterbury Plains of New Zealand, but only 60 days in the dry land wheat crops of the Victorian Mallee in Australia. Combining our knowledge of fungicide effect on the crop canopy with soil water and nutrient availability enables better matching of fungicide product, dose and timing to a specific disease risk. It also enables better use of crop physiology models, such as APSIM (Agricultural Production Systems sIMulator), to assist with in-crop fungicide decisions. This paper reviews the role of fungicides, principally the triazoles (G1 - FRAC target site code), strobilurins (C3) and SDHI’s succinate dehydrogenase inhibitors (C2), in cereal disease management. It explains (i) why applying foliar fungicide by plant development stage (as well as disease threshold) confers advantages when fungicide mode of action and on farm logistics are taken into consideration; (ii) gives examples of how fungicide management strategies are adjusted in Australia and New Zealand to take account of environmental conditions; and (iii) explains the importance of green leaf retention (GLR) in the realization of an economic response from fungicides.

The microflora of tomato fruits and its relationship to post-harvest disease development – can applications of Rhapsody (Bacillus subtilis) reduce disease? Z. K. PUNJA, S. FORMBY, A. TIRAJOH AND G. RODRIGUEZ. Department of Biological Sciences, Simon Fraser University, 888 University Drive, Burnaby, BC V5A 1S6, Canada

A survey of fungi causing post-harvest decay of greenhouse tomato fruits was conducted during 2010–11. Isolates recovered were inoculated onto tomato fruits to determine their pathogenicity. Most disease at 21 °C was caused by Penicillium olsonii Bainier & Sartory, followed by Rhizopus stolonifer (Ehrenb.:Fr.) Vuill., Botrytis cinerea Pers.:Fr., Alternaria alternata (Fr.) Keissier and Geotrichum candidum Link ex Pers. To monitor microbes on fruits, cotton swabs were gently rubbed on ripening fruit, at weekly intervals during June–September, 2011 and 2012. The fungi recovered from fruit surfaces were species of Penicillium, Rhizopus, Alternaria/Cladosporium and Aspergillus. Colonies of Botrytis were recovered infrequently and Geotrichum not at all. Tomato plants in two commercial greenhouses were treated with Rhapsody (Bacillus subtilis) once a month during July–October, 2012 to determine effects on fungal populations and disease. Disease incidence and severity were both significantly reduced (to 0–5%) on fruit treated with Rhapsody compared with up to 30% infection on untreated fruit at 18–21 °C. A major source of inoculum of post-harvest fungi on fruit was stem and calyx tissues, which led to infection through the stem end. Rhapsody applications prevented spread of these fungi onto the fruit. Rhapsody applications made every 4 weeks are sufficient to maintain high populations of Bacillus on the fruit surface, resulting in significant post-harvest disease control on fresh market tomatoes.

Aster Yellows, a potential threat for flax and sunflower in western Canada. K. Y. RASHID. Morden Research Station, Agriculture and Agri-Food Canada, Unit 100-101, Route 100, Morden, MB R6M 1Y5, Canada

Aster Yellows (AY) caused by a phytoplasma was first reported in 1902 and is a common and destructive disease worldwide. It affects >300 plant species including field crops, vegetables and weeds. AY has been considered a minor disease that affects flax causing flower buds to become vegetative with star-shape appearance and produces no seed. AY affects sunflower, causing floral buds to turn vegetative, forming yellow petals in the middle of the head and no seed production in the affected buds. The phytoplasma is transmitted by several species of leafhoppers that migrate in from the south and is mostly spread by the six-spotted leafhopper Macrosteles fascifrons. The phytoplasma overwinters in perennial host plants, weeds, winter grain crops and in adult leafhoppers. Annual surveys have been conducted since 1988 of 60–100 flax crops mostly in MB and SK, and 30–60 sunflower crops in MB. AY was identified based on symptoms, and the incidence and severity were recorded. AY was prevalent in 2012 on most crops in western Canada including: canola, cereals, flax and sunflower. In flax, 60% of crops had AY with incidence ranging from trace to 5% plants affected in comparison with a prevalence of 5–30% of the crops and trace to 1% incidence in the previous 10 years. The last major epidemics of AY were recorded in 1953–1957 with 90–100% prevalence and 5–15% incidence. In sunflower, AY was observed at low prevalence and trace incidence similar to previous years. The high prevalence and incidence of AY in flax has been attributed to the early migration of the six-spotted leafhopper from the south coinciding with the warm weather in the spring. Presently, there is no recommendation to control this disease.

Evaluation of fungicides and cultivars for management of asparagus Phytophthora crown, spear and root rot. C. SAUDE, C. BAKKER AND M. R. MCDONALD. Department of Plant Agriculture, Crop Science Building, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada

Asparagus (Asparagus oficinalis L.) is an important vegetable crop in Ontario where 80% of the Canadian crop is produced. Phytophthora crown spear and root rot (PCSRR), caused by the oomycete Phytophthora asparagi Saude & Hausbeck was found on infected asparagus spears collected from production fields in Norfolk and Chatham-Kent counties in 2011. Water soaking, shrivelling of roots and spears, and spear curving are the characteristic symptoms associated with PCSRR. In 2012, field trials were conducted at the Simcoe Research Station, University of Guelph, to evaluate asparagus cultivars for resistance to P. asparagi and the efficacy of fungicides and biofungicides in controlling the pathogen. Asparagus cultivars ‘Millennium’, ‘Jersey Giant’, ‘Pacific Challenger’, ‘UC 157’, ‘UG005’ and ‘UG020’ inoculated with P. asparagi-infected millet, and the fungicides Zampro (1 L ha⁻¹), Phostrol (5.8 L ha⁻¹) Ranman (0.44 L ha⁻¹) Ridomil (25 kg ha⁻¹) and Experimental A (1400 mL ha⁻¹), and the biofungicides Sonata (9.4 L ha⁻¹), Previcur N (1.5 mL L⁻¹), Actinovate (840 g ha⁻¹), Oxidate (1.0 L per 100 L) and Prev-Am (391 mL per 100 L) were evaluated. Drench applications of the products were applied twice 30 days apart. Disease severity was rated monthly using a 0–5 scale and the disease ratings were used to calculate the disease severity index (DSI). Phytophthora crown spear and root rot of asparagus was reduced by the fungicides Experimental A and Zampro, followed by Ranman, Ridomil and Phostrol. The biofungicides were less effective in reducing PCSRR but reduced the disease when compared with the untreated check. All asparagus cultivars were susceptible to PCSRR apart from cultivars UG005 and UG020.

Pathogenicity of Discula destructiva on Cornus spp. M. STANESCU AND T. HSIANG. School of Environmental Sciences, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada

The ascomycete (Order Diaporthales) fungus Discula destructiva Redlin causes a devastating disease of dogwoods. In North America, the disease has been reported on two major dogwood species: Cornus florida L. (flowering dogwood) in the east and C. nuttallii Audubon (Pacific dogwood) in the west. Previous studies on the infection process of D. destructiva have focused only on C. florida. This study aimed to assess the ability of the pathogen to cause disease on other species of dogwood native to North America: C. alternifolia, C. amomum, C. racemosa, C. sericea and C. sericea ‘Cardinal’, as well as on the typical host, C. florida and on an introduced species, C. kousa ‘Chinensis’. Three types of fungal inoculum: mycelial plugs, sporulating colonies on media and a 10⁷ spores mL⁻¹ spore suspension, were used to inoculate detached, fully expanded leaves from the above-mentioned host species. The only inoculation method which caused anthracnose symptoms on leaves of all host species included in the study was the incubation of leaves on sporulating colonies of D. destructiva for 3 days. Spores from spore suspension inocula, however, germinated on leaves of these host species, but successful infection and formation of infection structures occurred only on wounded leaves of C. florida and C. alternifolia. Further investigations are needed to assess the resistance mechanisms involved in the defence responses to dogwood anthracnose found in the other dogwood species.

Microbial phosphate solubilization for sustainable agriculture. S. STECKLER, C. CALDWELL, K. PRIEST, M. LEGGETT AND D. GREENSHIELDS. Novozymes BioAg Limited, 3935 Thatcher Avenue, Saskatoon, SK S7R 1A3, Canada

Phosphorus (P) is an essential nutrient that is often limiting in agricultural soils. Much of the applied fertilizer phosphate becomes fixed and unavailable for plant uptake. Soil microbes can improve P use efficiency in agricultural systems by converting this fixed phosphate into available forms. Novozymes produces and markets the phosphate inoculant JumpStart, which contains the soil fungus Penicillium bilaiae Chalabuda. Our current P. bilaiae strains solubilize phosphate from a range of soils and increase crop P content and yield. We recently isolated new phosphate solubilizing microbes from 125 locations across Western Canada and found that the top 10 solubilizers were again strains of P. bilaiae. We are working to characterize the rhizosphere growth, metabolism and gene expression of P. bilaiae and other soil Penicillia to understand their contribution to the P cycle and to make better inoculants for sustainable agriculture.

Evaluation of the impact of crop rotation on clubroot severity in canola in Alberta, Canada. M. TABORI, T. CAO, V. P. MANOLII, S. F. HWANG AND S. E. STRELKOV. Department of Agricultural, Food and Nutritional Science, 410 Agriculture/Forestry Centre, University of Alberta, Edmonton, AB T6G 2P5, Canada; and (S.F.H.) Crop Diversification Centre North, Alberta Agriculture and Rural Development, 17 507 Fort Road N.W., Edmonton, AB T5Y 6H3, Canada

Clubroot, caused by Plasmodiophora brassicae Woronin, is an emerging disease of canola in the Canadian Prairies. A greenhouse experiment was conducted to evaluate the effects of six crop rotation regimes on clubroot severity. These included: (T1) continuous cropping of a clubroot-susceptible canola cultivar (S); (T2) S –fallow (F) - S – F - S; (T3) S – barley (B) - S – B – S; (T4) S – resistant canola cultivar (R) - S – R – S; (T5) continuous cropping of the same resistant cultivar; and (T6) continuous cropping of different resistant cultivars. Index of disease (ID), plant height and dry mass were recorded at the end of each rotation. Over the course of the experiment, the range of IDs in the susceptible canola cultivar grown in T1 to T4 decreased significantly from 97.0–98.6% (after the first crop) to 52.8–82.5% (after the fifth crop). In contrast, the IDs in the resistant canola cultivar grown in T5 increased significantly from 15.0% to 23.5%. In T6, in which different resistant cultivars were grown in succession, no significant changes in ID were observed. At the end of the experiment, the plant height of the canola plants in T5 and T6 was significantly higher than in T1 to T4, reflecting the much greater root infection in the susceptible canola cultivars. The data suggest some erosion of resistance after continuous cropping of the same resistant cultivar, which was not observed when different resistant cultivars were rotated. Resistance stewardship will have to be an important component of a sustainable clubroot management approach.

Pathogenic variability in Pyrenophora teres in Manitoba in 2012. A. TEKAUZ AND M. BANIK. Cereal Research Centre, Agriculture and Agri-Food Canada, 195 Dafoe Road, Winnipeg, MB R3T 2M9, Canada

Net blotch, caused by Pyrenophora teres Drechs., occurs annually on barley in Manitoba. The disease reduces grain yields and quality, thus incorporating or enhancing resistance to it is an objective of most barley breeding programmes. Screening of experimental lines must employ relevant isolate(s) of the pathogen; this requires periodic sampling of the local population and its assessment to detect novel virulence and other significant changes. The 18-member P. teres 'International Barley Differential Set' (IBDS) was used to sample a segment of the Manitoba population from 2012. Of the 10 random isolates tested, four were identified as P. teres f. teres (Ptt) and six as P. teres f. maculata (Ptm); these induce the two visual manifestations of the disease, 'netted net blotch' and 'spotted net blotch', respectively. Compared with Ptt standard isolates WRS102 and WRS858 having average infection phenotypes of 5.1 and 4.8 (1–10 scale), respectively, one of the isolates from 2012, ‘#98’ was somewhat more pathogenic (5.7); others ranged from 4.3 to 5.3. No isolate was virulent (scores 6–10) on the recognized resistant sources CI5791, CI9214, CI9819 or CI9825. One of the Ptm isolates, ‘#60’, was considerably more pathogenic (6.3 on the 1–9 scale) than standard isolate WRS857 (4.6) or others tested (range 3.3–4.8). Only IBDS barley genotype CI9214 was resistant (scores 1–3) to this isolate. The results suggest no significant new Ptt virulence likely has developed recently in Manitoba, but that new Ptm virulence may be present and should be monitored closely.

The impact of fungicide and herbicide timing on barley leaf disease severity, weed management and crop productivity. T. K. TURKINGTON, K. XI, K. N. HARKER AND J. T. O’DONOVAN. (T.K.T., K.N.H., J.T.O.) Lacombe/Beaverlodge Research Centre, Agriculture and Agri-Food Canada, 6000 C & E Trail, Lacombe, AB T4L 1W1, Canada; and (K.X.) Field Crop Development Centre, Alberta Agriculture and Rural Development, 6000 C & E Trail, Lacombe, AB T4L 1W1, Canada

Interest in tank mixing herbicides and half rates of fungicides for weed and disease management in barley has been increasing. However, little published scientific information exists regarding the impact of this practice on weed and disease management, and crop productivity. At Lacombe, Alberta, from 2010 to 2012 combinations of the herbicide Axial^® and the fungicide Tilt^® were applied to barley at the 2–3 leaf stage, 5–6 leaf stage or the flag leaf stage. Prior to seeding, the plot area was cross-seeded with tame oat as a model weed. Penultimate and flag leaf samples were collected for assessment of leaf disease severity, while crop and model weed emergence and biomass were assessed. Plots were harvested and grain yield and kernel quality assessed. Dry conditions limited crop emergence and disease development. Scald was the predominant disease and generally occurred at low severities. However, scald severity was significantly higher for the no fungicide treatments and the 2–3 leaf stage combination herbicide and half rate fungicide treatment compared with all other treatments. Yields tended to be highest for those treatments with early herbicide application and/or where the fungicide treatment included a flag leaf stage application. Weed biomass was very low and not influenced by the treatments due to poor emergence and effective control following herbicide application.

Whole genome sequencing and comparative genomics of multiple Fusarium graminearum isolates. S. WALKOWIAK, L. WANG AND R. SUBRAMANIAM. (S.W., L.W., R.S.) Eastern Cereal and Oilseed Research Centre, Agriculture and Agri-Food Canada, 960 Carling Avenue, Ottawa, ON K1A 0C6, Canada; and (S.W.) Department of Biology, Carleton University, 1125 Colonel By, Ottawa, ON K1S 5B6, Canada

The Fusarium graminearum Schwabe species complex is the principal cause of fusarium head blight in North America. These fungi produce a harmful toxin, deoxynivalenol (DON), which accumulates in infected plant tissues. The disease results in severe losses in yield and quality of cereals, such as wheat and corn. New challenges are also beginning to develop in the management of these pests. There is growing concern surrounding the emergence and spread of some highly virulent isolates that produce the toxin precursor 3-acetyldeoxynivalenol (3-ADON), which may be displacing the less virulent 15-acetyldeoxynivalenol (15-ADON) producing isolates. In addition to these differences, culture conditions used to induce 15-ADON production are unable to induce 3-ADON production. Although some of the genetic mechanisms concerning these differences among isolates are known, many of them remain to be elucidated. This project focuses on characterizing the genetic variations between isolates within the F. graminearum species complex to identify the lineage specific regions that lead to differences in toxin production and pathology. Whole genome sequencing and comparative genomics were performed on eight Fusarium isolates with profile differences in toxin production and pathology in wheat.

Genetic characterization of the causal agent of anthracnose on Lens culinaris from western Canada. R. WARALE AND S. BANNIZA. Crop Development Centre, Department of Plant Sciences, University of Saskatchewan, 51 Campus Drive, Saskatoon, SK S7N 5A8, Canada

Anthracnose, caused by the fungal pathogen Colletotrichum sp. ex lentil, is currently the most economically important disease of lentil in Western Canada. The nomenclature of the pathogen has been up for debate from the time it was first identified. Several previous morphological and genetic studies of Colletotrichum spp. strongly suggest that the pathogen reported to cause anthracnose of lentil in Western Canada has been incorrectly classified as Colletotrichum truncatum, and it has been suggested that it belongs to the Colletotrichum destructivum clade. The objective of this study is to infer inter- and intra-specific diversity among closely related Colletotrichum spp. and a selection of isolates of Colletotrichum sp. ex lentil. Seven molecular markers (ACT, β-TUB, CHS-1, EFIα, GAPDH, HIS3 and ITS) will be used to characterize and establish the phylogenetic relationships among 18 Colletotrichum isolates from lentil, three isolates from soybean, a single isolate from scentless chamomile and 10 reference isolates of closely related Colletotrichum spp. including the type specimen of C. truncatum. This study will clarify the relationship of the lentil anthracnose pathogen with other closely related species and lay the foundation for assigning a proper species name.

Emerging diseases of intensive organic greenhouse vegetable production in British Columbia. A. C. WYLIE AND Z. K. PUNJA. Department of Biological Sciences, 8888 University Drive, Simon Fraser University, Burnaby, BC V5A 1S6, Canada

An increasing trend in British Columbia has been the conversion of hydroponic cucumber, tomato and bell pepper production in greenhouses to intensive organic management. This refers to cropping in soil-based media, without the use of chemical fertilizers or pesticides, using management practices similar to hydroponic (soil-less) production, with the goal of similar yields. Organic production potentially harbours soilborne pathogens over successive crops, including bacterial canker of tomato caused by Clavibacter michiganensis subsp. michiganensis Davis, verticillium wilt of tomato caused by Verticillium dahliae Kleb, postharvest black spot of tomato caused by Penicillium olsonii Bain. & Sart., and crown rot of cucumber suspected to be caused by a Pythium uncinulatum-like species. The pesticide-free greenhouse environment is also prone to prolific reproduction of pests such as greenhouse millipede Oxidus gracilis Koch, and housefly Musca domestica L. that can damage plants or spread disease organisms, as well as occasional infestation by potato psyllid Bactericera cockerelli Sulc for which biological control is difficult. Our research is focused on the potential for biological control of these diseases, and developing a novel model soil system in which to study root rot pathogens in hybrid soil-hydroponic production. Control strategies will require an integrated approach of close monitoring, expert growing methods and biological control of both diseases and pests.

Understanding the development and management of stripe rust in central Alberta. K. XI, K. KUMAR, M. D. HOLTZ AND T. K. TURKINGTON. Field Crop Development Centre, Alberta Agriculture and Rural Development, 6000 C & E Trail, Lacombe, AB T4L 1W1, Canada; and (T.K.T.) Lacombe Research Centre, Agriculture and Agri-Food Canada, 6000 C & E Trail, Lacombe, AB T4L 1W1, Canada

In central Alberta, wheat stripe rust caused by Puccinia striiformis Westend. f. sp. tritici Eriks. (Pst) has resulted in substantial yield losses, while barley stripe rust caused by Puccinia striiformis Westend. f. sp. hordei Eriks. (Psh) has been increasingly observed. Stripe rust was surveyed in commercial fields and monitored in nurseries across central Alberta. Stripe rust inoculum had the potential to survive on winter wheat in central Alberta and then spread to other winter and spring cereals the following growing season. One hundred and sixty-five field samples collected during 2007 to 2011 were identified to forma specialis and pathotype using wheat and barley differentials. Both Pst and Psh isolates were virulent on highly susceptible wheat and barley cultivars and lines. Nearly one third (18 of 60) of Psh isolates were virulent on many wheat differentials. These overlapping virulence spectra may result from hybridization between the two formae speciales. Genotyping of Psh isolates using simple sequence repeats markers provided the evidence of hybridization. Foliar application of fungicide was effective for control of stripe rust and prevention of yield losses in susceptible wheat cultivars. Germplasm and breeding lines of barley and triticale were screened for stripe rust resistance in international nurseries. The majority of winter and spring triticale lines were resistant, while more two-row hulled barley lines were resistant than six-row and hull-less lines.

Impacts of biochar on plant diseases of hydroponically grown cucumbers and tomatoes. J. YANG, R. GIBSON AND G. SMITH. Alberta Innovates – Technology Futures, Vegreville, AB T9C 1T4, Canada; and (G.S.) Alberta Newsprint Company, Whitecourt, AB T7S 1P9, Canada

Biochar made from woodchips was used as a growth medium to grow cucumbers and tomatoes in an open hydroponic system and its impacts on plant pathogen development and disease severity were evaluated and compared with that of commercially used coconut coir medium in greenhouses. Pythium ultimum Trow was inoculated to the growth media in the cucumber experiment and Fusarium oxysporum Schlecht. emend Snyder & Hans. was inoculated to the growth media in the tomato experiment. Root diseases were recorded 2-, 4- or 8-weeks after inoculation. Results showed that cucumber plants grown in biochar had significantly lower Pythium disease incidence and lower disease severity compared with the plants grown in coconut coir. The same result was obtained from tomato–Fusarium evaluation trials. The Fusarium population in biochar was lower than that in coconut coir based on a dilution-plating test 4- and 8-weeks after inoculation. Total microbe counts obtained from biochar media were lower than counts from coir. Results suggest that biochar, when used as growth medium, could minimize plant losses due to root diseases and reduce disease control costs for commercial cucumber and tomato hydroponic greenhouse operations. Further work is needed to determine the mechanisms of biochar effect on plant diseases.