Sensitivity of western Canadian Pyrenophora teres f. teres and P. teres f. maculata isolates to propiconazole and pyraclostrobin. A. AKHAVAN, S. E. STRELKOV, H. ASKARIAN, S. V. KHER, M. FRASER, H. R. KUTCHER AND T. K. TURKINGTON. Department of Agricultural, Food and Nutritional Science, 410 Agriculture/Forestry Centre, University of Alberta, Edmonton, AB, T6G 2P5, Canada; (H.R.K.) Crop Development Centre, University of Saskatchewan, 51 Campus Drive, Saskatoon, SK S7N 5A8, Canada; and (T.K.T.) Lacombe Research and Development Centre, Agriculture and Agri-Food Canada, 6000 C & E Trail, Lacombe, AB T4L 1W1, Canada
Pyrenophora teres Drechs. f. teres Smedeg. (Ptt) and Pyrenophora teres Drechs. f. maculata Smedeg. (Ptm), the causal agents of the net and spot forms of net blotch of barley, respectively, can be managed in western Canada with fungicides containing propiconazole and pyraclostrobin. Given the potential for development of fungicide resistance, the sensitivity of a collection of Ptt and Ptm isolates to propiconazole and pyraclostrobin was evaluated using microtitre plate bioassays. The concentration of propiconazole needed to inhibit fungal growth by 50% (EC50) was 1.5 mg L−1 for Ptt and 2.3 mg L−1 for Ptm, while the EC50 of pyraclostrobin was 0.015 mg L−1 for Ptt and 0.024 mg L−1 for Ptm. Subsequently, 39 Ptt and 27 Ptm isolates were screened with discriminatory doses of 5 mg propiconazole L−1 and 0.15 mg pyraclostrobin L−1. Inhibition of growth as a result of propiconazole ranged from 12–95% for Ptt and from 48–92% for Ptm; growth inhibition as a result of pyraclostrobin ranged from 40–100% and from 24–100%, respectively. Two Ptt isolates were insensitive to propiconazole, while one Ptm isolate was insensitive to pyraclostrobin. The latter also showed decreased sensitivity to propiconazole. The identification of net blotch isolates insensitive to these fungicides emphasizes the need for farmers to employ integrated crop management strategies to avoid fungicide resistance.
Pathotype structure of Plasmodiophora brassicae single-spore isolates from Alberta, Canada, and their virulence on canola (Brassica napus). H. ASKARIAN, S. F. HWANG, V. P. MANOLII, T. CAO, A. AKHAVAN 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 Forestry, 17507 Fort Road NW, Edmonton, AB T5Y 6H3, Canada
Clubroot, caused by Plasmodiophora brassicae Woronin, is a soilborne disease of canola (Brassica napus L.) managed mainly by planting clubroot resistant (CR) cultivars. Clubroot resistance has been overcome in 42 fields in Alberta. Since P. brassicae populations are often pathotype mixtures, 37 single-spore isolates were purified from eight populations of the pathogen collected from CR canola. The pathotype composition of two populations and 16 single-spore isolates was evaluated on the differential hosts of Williams, Somé et al., and a putative Canadian clubroot differential series. While the field populations were classified as pathotypes 5, P4 and P, or 3, P2 and A, respectively, on the differential sets, a much wider range of pathotypes was found among the single-spore isolates, suggesting significant diversity in the virulence of P. brassicae in Alberta. Further testing on a suite of seven CR canola cultivars showed that while both populations were highly virulent on all of the cultivars, only 10 of 16 single-spore isolates were virulent on all or some of the hosts. The remaining isolates were avirulent, indicating that field populations can consist of a mixture of virulent and avirulent P. brassicae genotypes. Breeders should therefore use caution when interpreting resistance screening results obtained with field populations, as opposed to single-spore isolates, of P. brassicae.
Development of a TaqMan PCR assay for quantification of Aphanomyces euteiches from field soils. S. CHATTERTON, A. ERICKSON AND S. BANNIZA. Lethbridge Research and Development Centre, Agriculture and Agri-Food Canada, 5403 1st Avenue South, Lethbridge, AB T1J 4B1, Canada; and (S.B.) Crop Development Centre, University of Saskatchewan, 51 Campus Drive, Saskatoon, SK S7N 5A8, Canada
Aphanomyces root rot, caused by Aphanomyces euteiches Drechs., was first detected in pea fields in Saskatchewan and Alberta in 2012 and 2013, respectively, and can cause significant crop loss in both provinces. The only management strategy is field avoidance by extended rotations away from susceptible host crops (peas, lentil and alfalfa). To develop a DNA-based quantification tool to determine Aphanomyces root rot risk of field soils, a specific and sensitive molecular detection protocol from soil is first required. To achieve this, primer and hydrolysis probe sets were designed following bioinformatics analysis of the ITS region of related oomycetes and tested against known A. euteiches isolates. The best assay was then tested against non-target fungi including Aphanomyces, Fusarium and Pythium spp. The qPCR assay detected all A. euteiches positives, but at later cycles, also amplified Aphanomyces cochlioides, a closely related species of A. euteiches. All other non-target species were not amplified. The assay was then tested against oospore soil dilution curves prepared in grey and brown soil types. Detection limit in soil was 100 oospores/g of soil, which is also the threshold level for disease development. Future testing will focus on evaluating soil samples from known infected fields to determine the inoculum potential of field soils and validate the A. euteiches infection curve.
Distribution of Fusarium graminearum in Alberta wheat and corn fields in 2015. G. C. DANIELS, T. GRÄFENHAN, H. GELECH, J. M. BAMFORTH, T. ASHFAQ, T. B. HILL, C. J. HILL, C. A. PUGH, M. KUNDU AND M. W. HARDING. Crop Diversification Centre South, Alberta Agriculture and Forestry, 301 Horticultural Station Road East, Brooks, AB T1R 1E6, Canada; (T.G., J.M.B., T.A.) Canadian Grain Commission, 196 Innovation Drive, Winnipeg, MB R3T 6C5, Canada; and (H.G.) Biovision Seed Labs, Unit 310, 280 Portage Close, Sherwood Park, AB T8H 2R6, Canada
In 2015, samples of mature wheat heads or post-harvest stubble, and corn lower-stem nodes were collected from 1% of Alberta wheat and corn fields. In total, 883 wheat samples (817 head and 66 stubble) and 37 corn samples were collected. Each sample consisted of 500 wheat heads or 100 stubble or node pieces. Wheat head samples from individual fields were threshed separately to avoid cross-contamination and seed was evaluated for the presence of Fusarium damaged kernels (FDKs). A variety of fungal pathogens, including F. graminearum Schwabe, were identified by high-throughput, real-time PCR using quantitative assays optimized for SYBR Green-based detection. Wheat and corn stem nodes were plated to acidified potato dextrose agar and suspect Fusarium colonies were isolated and identified by multiplex PCR. When results were compared to the previous Alberta survey for F. graminearum (2010), the pathogen’s distribution was shown to have increased from 27.1 to 37.9% of the municipalities surveyed. In the central and northern regions of the province, F. graminearum was found more frequently in 2015, but the chemotype had dramatically shifted from 0 to 95.5% 3-ADON during that period. In southern Alberta, where corn acres are highest, the 15-ADON chemotype continued to be dominant.
Efficacy of agricultural disinfectants for Cucumber Green Mottle Mosaic Virus decontamination in a commercial vegetable greenhouse. W. ELLOUZE, V. MISHRA AND R. J. HOWARD. Alberta Agriculture and Forestry, Crop Diversification Centre South (CDCS), 301 Horticultural Station Road East, Brooks, AB T1R 1E6, Canada; and (R.H.) RJH Ag Research Solutions Ltd., P.O. Box 1456, Brooks, AB T1R 1C3, Canada
An effective greenhouse sanitization programme should lead to a significant reduction or elimination of active and dormant stages of pathogens and pests, as well as to disrupt their life cycles. The objectives of this study were to: (1) test the susceptibility of Cucumber Green Mottle Mosaic Virus (CGMMV), an extremely stable Tobamovirus that can cause extensive yield losses in greenhouse cucumbers, to several disinfectants in vitro, and (2) evaluate the relative effectiveness of actual sanitization/disinfection procedures performed in a CGMMV-infested commercial vegetable greenhouse. Various commercial products, including hydrogen peroxide, quaternary ammonium, potassium peroxymonosulfate, and an acid-based cleaner, were tested according to the manufacturer’s label instructions on concrete, metal, wood and plastic surfaces artificially infested with CGMMV in in vitro trials at CDCS. An extensive environmental sampling programme for CGMMV before and after each sanitization step being used in a commercial greenhouse also was undertaken. A Solar-Cult® Pre-moistened Sampling Cellulose Sponge Kit was used for collecting environmental samples from multiple infested hard surfaces within this facility. These samples were analysed for CGMMV presence by relative quantification using ELISA. The effectiveness of the disinfectants was markedly reduced when they were applied under in situ conditions as compared with in vitro experiments. The analysis of samples collected from greenhouse surfaces initially having heavy virus infestations were freed of CGMMV contamination by up to 99% following a combination of pressure washing and applying an alkaline sanitizer with foam twice post-crop removal, as compared with applying the same sanitizer with foam only once prior to disinfection.
Survey of dry bean fields for sclerotinia white mould in Alberta in 2016. M. W. HARDING, G. C. DANIELS, D. A. BURKE, C. A. PUGH AND J. M. NIELSON. Crop Diversification Centre South, Alberta Agriculture and Forestry, 301 Horticultural Station Road East, Brooks, AB T1R 1E6, Canada
A survey for sclerotinia white mould caused by Sclerotinia sclerotiorum (Lib.) de Bary in 26 commercial dry bean (Phaseolus vulgaris L.) fields in southern Alberta was conducted in 2016. White mould symptoms were observed in all fields surveyed. The incidence of disease was calculated as a per cent of infected plants with white mould symptoms, and the disease severity was estimated using a rating scale of 1 to 4 where a score of ‘1’ was given when no disease was observed, up to a score of ‘4‘, which was assigned when the disease had killed the host plant. Disease incidence ranged from 14.3 to 75.0% with an average of 60.8%. Disease severity ranged from 1.01 to 1.61 with an average of 1.25. These values are among the highest white mould incidences and severities on dry bean in Alberta for the past 7 years.
Wheat streak mosaic virus in Alberta in 2016. M. W. HARDING, M. KUNDU AND G. C. DANIELS. Crop Diversification Centre South, Alberta Agriculture and Forestry, 301 Horticultural Station Road East, Brooks, AB T1R 1E6, Canada
Wheat streak mosaic virus (WSMV) is a Group IV (+ssRNA) in the Potyviridae. It is composed of a flexible, rod-shaped genome with a helical capsid and is vectored semi-persistently by the wheat curl mite (Aceria tosichella). The virus can infect many hosts in the Poaceae family, but wheat is the most susceptible crop. Over 6.5 million acres of wheat are grown in Alberta, but WSMV is a relatively rare problem, with reports of the disease only once between 2000 and 2015. In 2015 a few wheat fields in southern Alberta were confirmed to have WSMV. In 2016 cereal leaf samples from 24 fields with suspicious symptoms were tested for WSMV. Fourteen were positive for a prevalence of 70% in suspicious fields representing more than 2000 acres confirmed and thousands more suspected. The mild winter in 2015–16, and a green bridge from the 2015 to 2016 growing seasons, may have contributed to this outbreak.
Survey for blackleg on canola in Alberta in 2016. T. B. HILL, G. C. DANIELS, D. A. BURKE, C. A. PUGH, K. ZUZAK, D. RENNIE, J. MCDONALD AND M. W. HARDING. Crop Diversification Centre South, Alberta Agriculture and Forestry (AAF), 301 Horticultural Station Road East, Brooks, AB T1R 1E6, Canada; (K.Z., D.R.) Crop Diversification Centre North, AAF, 17507 Fort Road NW, Edmonton, AB T5Y 6H3, Canada; and (J.M.) Agricultural Research & Extension Council of Alberta, #2 5304 50 Street, Leduc, AB T9E 6Z6, Canada
Blackleg is a serious disease which can cause extensive losses on susceptible host crops such as canola. The infection is caused by the phytopathogenic fungus Leptosphaeria maculans (Sowerby) Karst. Infected plants often form dry, sunken cankers at the stem base. The infection can reduce yield and quality, often due to premature senescence and lodging. A survey for blackleg was performed in Alberta in 2016 targeting 1% of the canola fields in the Province. A total of 480 canola fields in 58 municipalities were surveyed, with 100 plants/field evaluated. Symptoms included vascular discolouration at the cut surface and/or the presence of basal stem cankers. Blackleg prevalence was calculated as the percentage of fields with symptoms present. Incidence was calculated as the percentage of plants with blackleg symptoms, and severity was estimated using a 0–5 scale for rating vascular discolouration. In 2016, the prevalence of blackleg was 90%, the average incidence was 23.87% and the average severity was 0.42. When compared with previous surveys for blackleg in Alberta the prevalence, incidence and severity values in 2015 were 79.5%, 21.59% and 0.39, respectively, and the prevalence, incidence and severity reported in 2012 were 99%, 21% and 1.26, respectively. Higher than average seasonal precipitation in 2012 and 2016 co-occurred with higher blackleg disease levels.
Genes differentially expressed during pathogenesis by two Plasmodiophora brassicae pathotypes on canola (Brassica napus). J. JIANG, R. FREDUA-AGYEMAN, 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 (R.F.A., S.F.H.) Crop Diversification Centre North, Alberta Agriculture and Forestry, 17507 Fort Road NW, Edmonton, AB T5Y 6H3, Canada
Gene expression studies offer a means of understanding the pathogenesis of clubroot disease caused by Plasmodiophora brassicae. In this study, a canola (Brassica napus) cultivar ‘45H29‘ was inoculated with two P. brassicae pathotypes 5 and 5x (P5 and P5x) and the pathogen/plant biomass ratio in roots was determined 7, 14 and 21 days after inoculation (dai) by quantitative PCR (qPCR) analysis. To identify genes differentially expressed during the infection process, 205 P. brassicae genes encoding proteins with signal peptides were screened on total RNA extracted from the 14 dai samples. It was observed that the P5x/plant biomass ratio increased across the time course, while the P5/plant biomass ratio decreased. The biomass and phenotypic data confirmed that P5x was virulent on ‘45H29‘ while P5 was avirulent. At 14 dai, the qPCR results showed that only one of the 205 genes was up-regulated in samples inoculated with P5x, while 15 genes were up-regulated in samples inoculated with P5. At 21 dai, 13 of the above 16 genes were differentially expressed between the two pathotypes, with 10 being more greatly expressed in P5x and three in P5. In contrast, none of the 16 genes showed a significant (α = 0.01) difference in expression between the two pathotypes at 7 dai. Through the course, the chronological regulation of nine out of the 16 genes in P5 differed to that in P5x, i.e. genes up-regulated in P5 are down-regulated in P5x.These 16 genes present in the P. brassicae genome may offer important information on the canola–P. brassicae interaction.
Effect of irrigation and plant canopy architecture on white mould development in dry bean. K. A. KADER, P. M. BALASUBRAMANIAN AND S. CHATTERTON. Lethbridge Research and Development Centre, Agriculture and Agri-Food Canada, 5403 1st Avenue South, Lethbridge, AB T1J 4B1, Canada
Dry bean (Phaseolus vulgaris L.) is a profitable pulse crop grown under irrigation in southern Alberta. White mould (WM) caused by the fungus Sclerotinia sclerotiorum (Lib.) de Bary is a major constraint to dry bean production. Field studies were conducted at AAFC-Lethbridge in 2015 and 2016. Three levels of irrigation (high, medium and low) and five cultivars with different canopy architecture (determinate bush, indeterminate bush and prostrate) were arranged in a split-plot design and plots were evaluated for WM development. Microclimate variables were monitored using data loggers and sensors. WM incidence, severity and flower infection were significantly higher in high irrigation plots compared with medium and low irrigation plots. Higher water content within the top 5-cm of soil, prolonged leaf wetness and cooler canopy temperatures were maintained in high irrigation plots compared with medium and low irrigation plots. Highest yield and thousand seed weight (TSW) were observed in plots grown under medium irrigation in both years. WM development was significantly lower in ‘I9365-31‘ (indeterminate prostrate), and ‘AAC Burdett’ and ‘AC Island’ (indeterminate bush). Thus, irrigation schedule and choice of cultivars can be effective tools for WM management in Alberta. This trial will be conducted for another year.
Causal agents of necrotic spots on faba bean seeds: Lygus, Botrytis spp. or both? S. KAUR, J. THOMAS, S. MEERS, S. CHATTERTON AND H. A. CARCAMO. (S.K., J.T.) Department of Biological Sciences, 4401 University Drive, University of Lethbridge, Lethbridge, AB T1K 3M4, Canada; (S.K., S.C., H.A.C.) Lethbridge Research and Development Centre, Agriculture and Agri-Food Canada, 5403-1 Avenue South, Lethbridge, AB T1J 4B1, Canada; and (S.M.) Crop Diversification Centre South, Alberta Agriculture and Forestry, 301 Horticultural Station Road East, Brooks, AB T1R 1E6, Canada
Faba bean (Vicia fabae L.) seed quality and marketability is often downgraded due to the presence of necrotic spots on the seeds. Botrytis spp., cause of chocolate spot (CS) disease, and Lygus spp. are often found concomitantly in faba bean fields. The objective of this study was to determine the effect of Botrytis spp. and lygus in downgrading seed quality under field conditions. In 2015, field surveys were conducted in commercial faba bean fields in Alberta at the pod stage to quantify lygus abundance and CS severity. Seed damage was quantified by visual assessment and fungi colonizing the seeds were determined by plating on potato dextrose agar. Correlation analysis among insect abundance, CS severity and seed damage was conducted to test for possible associations. CS severity was generally low, but Botrytis was frequently isolated from seeds. Seed damage was significantly higher for seeds collected from the top of the plant, where lygus bugs were expected to be abundant as compared with the middle and bottom of canopy while it was opposite for CS severity. Lygus feeding on pods significantly affected the seed damage levels. However, Botrytis was isolated from faba bean seeds suggesting seed infestation. A correlation was not detected between lygus abundance and CS severity in the field.
Quantification of mycotoxins in FHB infected barley grains using ELISA, HPLC and NIRS. K. KUMAR, M. HOLTZ, L. OATWAY, X. S. LI, Z. HARTMAN, K. XI AND F. CAPETTINI. Field Crop Development Centre, Alberta Agriculture and Forestry, 5030-50 Street, Lacombe, AB T4L 1W8, Canada; and (X.S.L.) Alberta Innovates Technology Futures, Vegreville, AB T9C 1T4, Canada
Mycotoxins produced by Fusarium graminearum pose a health hazard in food and feed. The rapid and accurate determination of these toxins is crucial for the agricultural and food industries. Over100 field barley grain samples from a FHB screening nursery were used to detect and quantify mycotoxins including DON, 3-ADON and 15-ADON, using HPLC, ELISA and NIRS. The amount of fungal chemotype DNA in the samples was also analysed using quantitative PCR. Encouraging results were obtained from the initial NIRS calibrations with R2 values of 0.80, 0.71 and 0.60 for DON, 3-ADON and 15-ADON, respectively. There were moderate levels of correlation in the total mycotoxin content between HPLC analysis and ELISA assays (R2 = 0.64, P < 0.01). The amount of fungal and toxin-encoding DNA was moderately correlated (P < 0.01) with the mycotoxin levels determined by the three methods of analysis. The correlation between the amount of 3-ADON and the fungal and toxin-related DNA was consistently higher than with 15-ADON. Furthermore, the amount of fungal DNA determined was slightly more correlated with mycotoxin levels using ELISA than using HPLC and NIRS, indicating that ELISA was more specific in quantifying different types of mycotoxins produced by chemotypes compared with HPLC and NIRS.
Members of hypersensitive induced reaction superfamily protein involved in wheat resistance to leaf rust. L. X. LI, C. R.WEI, X. M. YU, A. LAROCHE AND D. Q. LIU. College of Life Sciences, Hebei Agricultural University, 2596 Lekai South Street, Baoding, Hebei 071001, P. R. China; and (A.L.) Lethbridge Research and Development Centre, Agriculture and Agri-Food Canada, 5403 1st Avenue South, Lethbridge, AB T1J 4B1, Canada
Hypersensitive induced reaction (HIR) proteins form a superfamily of genes involved in plant hypersensitive reaction (HR). In order to understand the role of members of the HIR superfamily in wheat resistance to leaf rust, Thatcher-Lr15 line was inoculated with virulent and avirulent leaf rust races to obtain via RT-PCR full length cDNA sequences for TaHIR1-4. TaHIR2-4 were expressed in young wheat leaves, stems and roots, while no transcripts were detected in mature seeds for all of these three genes. Transcripts of the members of HIR superfamily in wheat leaves were differentially regulated following infection by leaf rust races as more transcripts for TaHIR2 and TaHIR3 accumulated in the resistance interaction. Western blotting showed higher accumulation of TaHIR2-4 in the incompatible reaction in wheat leaves compared with the compatible reaction. For TaHIR2, the response was faster and stronger in the resistance interaction than in the susceptible one. Our results demonstrate that members of the wheat HIR superfamily are involved in resistance to infection by leaf rust pathogen at mRNA and protein levels, and provide experimental support for further investigating the roles of HIR superfamily members during mounting of the HR defence in wheat.
Quantification of Fusarium avenaceum in soil and crop residues from pea fields Alberta. S. SAFARI, S. CHATTERTON AND L. HALL. Lethbridge Research and Development Centre, Agriculture and Agri-Food Canada, 5403 1st Avenue South, Lethbridge, AB T1J 4B1, Canada; and (L.H.) Department of Agricultural, Food and Nutritional Science, 410 Agriculture/Forestry Centre, University of Alberta, Edmonton, AB T6G 2P5, Canada
Root rot is a destructive disease of field pea on the Canadian prairies. One of the main pathogens involved in the root rot complex is Fusarium avenaceum. The objective of this study was to use real-time PCR for quantification of F. avenaceum DNA in soil and crop residues collected from commercial pea fields. For this purpose, a specific primer and hydrolysis probe set was designed based on partial elongation factor alpha gene sequence. The assay was then used to quantify the pathogen in naturally infested samples collected from pea fields in Alberta. Soil, stubble (post-harvest pea) and straw (previous crop prior to pea seeding) samples was collected from field sites with and without root rot disease symptoms. The quantity of DNA detected in stubble and straw samples was relatively higher than that detected in soil samples, indicating the importance of crop residues as a source of inoculum for this pathogen. In order to correlate disease severity to inoculum levels, greenhouse experiments using different levels of F. avenaceum inoculum added to the soil was conducted and changes in disease severity recorded. Results showed that there was a positive relationship between these two factors. The outcomes from this study, combined with additional information about other pathogens involved in root rot disease and environmental parameters, will be applied toward developing a disease risk model.
Detection of stripe rust urediniospores by immune assays. F. WANG, C. SHEEDY, J. E. THOMAS AND A. LAROCHE. Lethbridge Research and Development Centre, Agriculture and Agri-Food Canada, 5403 1st Avenue South, Lethbridge, AB T1J 4B1, Canada; and (J.E.T.) Department of Biological Sciences, 4401 University Drive, University of Lethbridge, Lethbridge, AB T1K 3M4, Canada
Stripe rust caused by the fungal pathogen Puccinia striiformis f. sp. tritici is a harmful disease affecting wheat. To prevent yield losses due to stripe rust, early detection of the pathogen is essential to mitigate the effects of the disease and to achieve the most effective application of fungicides when needed. To avoid the difficult and time-consuming step of DNA extraction and to minimize time required for traditional field scouting for visual symptoms on wheat plants, a novel and sensitive assay for stripe rust urediniospores detection is required. An enzyme-linked immunosorbent assay (ELISA), direct and indirect real-time immuno-PCR (RT-iPCR) assays, and proximity ligation assay (PLA) were designed to detect stripe rust. Each assay was developed using polyclonal antibodies obtained from a rabbit immunized with P. striiformis urediniospores. The results showed that the limit of detection of ELISA assay was 679 urediniospores per well, while the indirect and direct RT-iPCR assay showed the ability to detect 30 and 20 urediniospores, respectively. The most sensitive assay currently in development is PLA, which can differentiate between samples lacking any urediniospores and those containing a single urediniospore. Simultaneously, these results confirm that the immuno-assays described above were suitable and sensitive for quantitative stripe rust detection.
Interactions of root rot pathogens and pea leaf weevil (Sitona lineatus) in field pea. T. L. WILLSEY, S. CHATTERTON, H. CARCAMO AND J. THOMAS. Department of Biological Sciences, 4401 University Drive, University of Lethbridge, Lethbridge, AB T1K 3M4, Canada; and (S.C., H.C.) Lethbridge Research and Development Centre, Agriculture and Agri-Food Canada, 5403-1 Avenue South, Lethbridge, AB T1J 4B1, Canada
Increased production of field pea (Pisum sativum L.) in Canada has led to a greater incidence of disease and instigated the range expansion of insect pests. Aphanomyces euteiches Drech. and several Fusarium spp. are soilborne pathogens responsible for causing severe root rot disease in pea and related pulse crops, while the feeding activity of the pea leaf weevil (Sitona lineatus L.) significantly reduces nitrogen fixation. The mutual association of these organisms with the roots of their host suggests a high potential for synergistic interactions that may ultimately increase yield loss. Two independent greenhouse trials indicated that simultaneous exposure of pea to F. avenaceum and S. lineatus increased both disease expression and insect survival in comparison to controls. There are currently no effective management strategies available, therefore field trials were conducted to test the efficacy of nine seed, foliar and soil treatments in slowing insect herbivory and pathogen spread. Preliminary results indicate that combined fungicidal and insecticidal treatments may suppress pathogen growth and herbivory in both pea and faba bean (Vicia faba L.), particularly at early growth stages. These results lend important insight into the design of appropriate strategies aimed at mitigating these critical threats to pulse production.
Identification of microsatellite markers linked to quantitative trait loci associated with partial resistance to aphanomyces root rot in field pea. L. F. WU, R. FREDUA-AGYEMAN, K. F. CHANG, R. L. CONNER, S. F. HWANG, D. FEINDEL, K. B. MCRAE AND S. E. STRELKOV. Department of Agricultural, Food and Nutritional Science, 410 Agriculture/Forestry Centre, University of Alberta, Edmonton, AB T6G 2P5, Canada; (R.F.A., K.F.C., S.F.H., D.F.) Crop Diversification Centre North, Alberta Agriculture and Forestry, 17507 Fort Road NW, Edmonton, AB T5Y 6H3, Canada; (R.L.C.) Morden Research and Development Centre, Agriculture and Agri-Food Canada (AAFC), 101 Route 100, Morden, MB R6M 1Y5, Canada; and (K.B.M.) Kentville Research and Development Centre, AAFC, 32 Main Street, Kentville, NS B4N 1J5, Canada
The development of partial resistance to Aphanomyces root rot of pea, caused by Aphanomyces euteiches, is considered to be the most effective method to manage this destructive soilborne disease. In this study, two recombinant inbred line (RIL) populations, obtained by single-seed descent from the crosses F6: ‘00-2067ʹ × ‘Reward’ (RIL1) and F8: ‘Carman’ × ‘Reward’ (RIL2) were used to identify the quantitative trait loci (QTL) associated with the partial resistance to the disease. There was a significant correlation for plant growth and disease severity between greenhouse and field studies. The resistant ‘00-2067ʹ remained highly resistant to A. euteiches, relative to the susceptible ‘Reward’, while the resistance in ‘Carman’ eroded as inoculum concentration increased. This indicated that ‘00-2067ʹ contained at least one major QTL for resistance that ‘Carman’ did not have. A total of 212 microsatellite markers were used to screen three parental cultivars of which 16 (RIL1) and 20 (RIL2) markers were associated with the resistance to A. euteiches. These markers were located on chromosomes I, II, III, IV, V and VII suggesting that partial resistance to A. euteiches in pea is controlled by multiple loci. Screening with more markers is needed to accurately map the QTLs.
Overexpression of an elongation factor 1-alpha (FgEF1a) in Fusarium graminearum leads to reduced fitness. W. Q. ZHAO, A. ERANTHODI, D. GONZÀLEZ-PEÑA FUNDORA, R. K. GOYAL AND N. A. FOROUD. College of Plant Protection, Hebei Agricultural University, 289 Lingyusi Street, Baoding, Hebei 071001, P. R. China; and (W.Q.Z., A.E., D.G.-P.F., R.K.G., N.A.F.) Lethbridge Research and Development Centre, Agriculture and Agri-Food Canada, 5403-1st Avenue South, Lethbridge, AB T1J 4B1, Canada
Fusarium graminearum is the causative agent in fusarium head blight (FHB) of wheat and related cereals. We have generated a F. graminearum mutant overexpressing the gene encoding for elongation factor 1-alpha (FgEF1a), and evaluated changes in pathogenicity. Disease symptoms were reduced by 77.4% in spray inoculated susceptible wheat cultivar ‘Roblin’, and by 39.1% in spray inoculated Brachypodium distachyon ecotype Bd21, when inoculated with the FgEF1a-overexpression (OX) strain compared with the wild-type. This apparent reduction in pathogenicity seems to be related to a reduction in fitness in the FgEF1a-OX strain, which was observed in mycelium growth and spore germination assays. Eukaryotic EF1a plays a vital role in protein synthesis, but has also been shown to be involved in various other cellular activities including cytoskeletal organization, cell cycle and signalling. Thus, alterations in the physiological levels of EF1a expression could theoretically impact one or more aspects of cell biology/biochemistry, explaining the reduced fitness in F. graminearum. In fact, it has been reported that EF1a overexpression in yeast leads to a similar reduction in fitness due to interactions with actin, thus affecting cytoskeletal function. Additional characterization of FgEF1a-OX is underway to identify changes in cell cycle and morphology to provide insights into the reduced fitness associated with this strain.
Identification of Fusarium spp. and F. graminearum chemotypes from corn in Alberta. K. A. ZUZAK, G. C. DANIELS, Y. YANG, D. C. RENNIE, J. FENG AND M. W. HARDING. Crop Diversification Centre North, Alberta Agriculture and Forestry (AAF), 17507 Fort Road NW, Edmonton, AB T5Y 6H3, Canada; and (G.D., M.H.) Crop Diversification Centre South, AAF, 301 Horticultural Station Road East, Brooks, AB T1R 1E6, Canada
Fungal spp. were isolated from corn stalk samples collected from 37 fields in southern Alberta in the summer of 2015. Among the obtained isolates, 145 were identified as Fusarium spp. based on colony morphology. These 145 isolates were analysed by PCR using Fusarium spp.-specific primers. Most of these isolates are F. graminearum (73) and F. culmorum (43), followed by F. avenaceum. The 74 F. graminearum isolates were further analysed by PCR using primers that can differentiate mycotoxin-producing strains. Sixty-six were 15-ADON, seven were 3-ADON and one was a NIV-producing strain. Fusarium graminearum was the targeted species in this study and accounted for more than half of all isolates. It appears that the 15-ADON chemotype continues to predominate on corn in Alberta. This is interesting to note because the newer 3-ADON chemotype has frequently replaced the 15-ADON chemotype in other provinces and in areas of Alberta where corn is less common.