Nematicides and organic products for management of stem and bulb nematode (Ditylenchus dipsaci) in garlic (Allium sativum)
T. BLAUEL, K. VANDER KOOI AND M. R. MCDONALD
Department of Plant Agriculture, Ontario Crops Research Centre – Bradford, University of Guelph, 1125 Woodchoppers Lane, King, ON L7B 0E9, Canada
Stem and bulb nematode (Ditylenchus dipsaci, SBN) is a major pathogen of garlic in Ontario. It can cause yield reduction and crop failure and easily spreads from field to field in infested seed cloves. There are currently no nematicides registered on garlic in Canada to control this nematode. The objective of this research was to evaluate the efficacy of products for control of SBN on garlic. The nematicides tested were Velum Prime (fluopyram), Agri-Mek (abamectin) and two organic products, Prev-Am (orange oil) and Promax (thyme oil). The Velum Prime treatments were applied either as a seed (clove) soak for 2 and 4 h prior to planting or an over the row drench at two rates at planting. All other nematicides were applied as a seed soak for 4 h. The trial was planted in the fall in a nematode free mineral soil field using SBN infested garlic cloves (6 SBN g−1). The Velum Prime and Agri-Mek treatments reduced nematode damage and increased marketable yield compared to the untreated check. The organic product Prev-Am resulted in higher damage and lower marketable yield than the untreated check. The 2-h soak with Velum Prime was as effective as the 4-h soak for disease severity (2.7 and 3.8%) and percent marketable yield (98.8 and 96.4%), respectively. Velum Prime was very effective for management of SBN in garlic as a soak or drench. If registered, would be a valuable tool for garlic growers in Ontario. The organic products did not protect garlic from SBN damage.
Amelioration of high salinity damage by plant growth-promoting bacterial endophyte Brevibacterium casie AL-305
J. CHEN1,2, S. ALI2, N. CLARK1,2, H. DOGRA1,2, S. SALDIAS2, S. KANDASAMY2 AND G. LAZAROVITS1,2
1Department of Biology, Western University, 1151 Richmond Street, London, ON N6A 3K7, Canada2A&L Biologicals, Agroecological Research Services Centre, 2136 Jetstream Road, London, ON N5V 3P5, Canada
Salinity of arable land is a major problem in agriculture, causing a significant loss of crop productivity each year. Plant growth-promoting bacterial endophytes have shown promising results in mitigating the effects of high soil salinity, in addition to solving many other agricultural problems. In this study, we characterized, identified, and evaluated bacterial endophyte AL-305 for its ability to improve plant growth under high salinity conditions. Wheat and cucumber seeds treated with AL-305 demonstrated significantly higher emergence than untreated control seeds when planted in soil containing 13% sodium base saturation levels. At harvest, treated plants exhibited more robust root systems, greater biomass, and higher overall plant vigour over control plants. Consequently, the study was taken to a field trial, where AL-305 treatment demonstrated an overall 10% yield increase in fava bean. Seeds treated with AL-305 have shown a shelf life of 335 days when stored at room temperature. Being natural companions of plants, bacterial endophytes may face less regulatory barriers to their deliberate release into the environment and provide an environmentally friendly method to attain sustainable agriculture.
Induced susceptibility to clubroot in split root canola plants
S. CHESNEY1, B. GOSSEN1,2 AND M.R. MCDONALD1
1University of Guelph, 50 Stone Road East, Guelph, ON NIG 2W1, Canada2Saskatoon Research and Development Centre, Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, SK Z7N 0X2, Canada
Clubroot [Plasmodiophora brassicae] is a soil-borne pathogen that can cause 100% yield losses in canola. The pathogen has different pathotypes that differ in virulence. The main management strategy against clubroot is resistant cultivars which are pathotype specific. In resistant cultivars, primary infection occurs with little or no secondary infection. It is hypothesized that primary infection initiates the resistant reaction or susceptible reaction to cortical infection. A trial was conducted using split root plants to test the hypotheses that infection with an avirulent pathotype induces resistance to a virulent pathotype and infection with a virulent pathotype induces susceptibility to an avirulent pathotype. The canola cultivar L233P, which is resistant to pathotype 6 (avirulent) and susceptible to pathotype 2 (virulent) was used. One side was inoculated on day 0 with a virulent or avirulent pathotype, and the second side inoculated 4, 7, or 14 days later, with the other pathotype. Water controls were added for each timing. Clubbing was assessed 6 weeks after the final inoculation. Induced resistance did not occur, as the second side was no different from the virulent control for all timings. However, some clubs formed on the avirulent side inoculated 4 days after inoculation with a virulent pathotype. This clubbing could indicate induced susceptibility. This is consistent with the hypothesis on balancing selection in P. brassicae, where infection by a virulent pathotype can ‘open the door’ for infection by avirulent pathotypes. More data are needed to confirm the treatment effects observed in this study.
An ACC deaminase bacterial endophyte Pseudomonas sp. strain AL-336 protects plants from transplant shock
N. CLARK1,2, J. H. CHEN1,2, H. DOGRA1,2, S. ALI2, S. SALDIAS2, S. KANDASAMY2 AND G. LAZAROVITS1,2
1Department of Biology, Western Ontario University, 1151 Richmond Street, London, ON N6A 3K7, Canada2A&L Biologicals, Agroecological Research Services Centre, 2136 Jetstream Road, London, ON N5V 3P5, Canada
Transplant shock is common among plants, in both greenhouses and in field conditions. It has been recorded that up to 50% of plants die from the shock associated with transplanting. Transplant shock occurs in vegetable seedlings, bedding plants, tree saplings and even in high-value crops such as cannabis. Huge economic losses are associated with transplant shock. Bacterial endophyte Pseudomonas sp. strain AL-336, contains 1-aminocyclopropane-1-carboxylate deaminase (ACCD) enzyme. The ACCD enzyme breaks down the ethylene precursor, aminocyclopropane-1-carboxylic acid (ACC), to ammonia and α-ketobutyrate. This results in lowering the ethylene levels produced in response of physiological stress such as transplant shock. Ethylene is a requirement for normal plant growth, however, in excess ethylene can cause further complications, such as leaf drop and wilting. Strain AL-336 is applied as liquid formulation within a substrate at the seed-planting stage. This has been tested in both tomatoes and melons. Growth room and field trials have been performed over the past three years. Data from these studies have indicated significant yield benefits. The yield increase was 13% and 20% consistently over the trials. In addition, this bacterium exhibits potentials for nitrogen fixation, phosphate solubilization, potassium solubilization, zinc solubilization, iron sequestration, indole acetic acid production, plant growth promotion and many antibiotic activities against fungal pathogens.
Bacillus amyloliquefaciens-based biocontrol formulations suppressed fusarium head blight and associated vomitoxin production in wheat under field conditions
H. DOGRA1,2, J. HOAGE2, E. MABED2, N. CLARK1,2, J. CHEN1,2, S. KANDASAMY2, S. SALDIAS2, S. ALI2 AND G. LAZAROVITS1,2
1Department of Biology, Western Ontario University, 1151 Richmond Street, London, ON N6A 3K7, Canada2A&L Biologicals, Agroecological Research Services Centre, 2136 Jetstream Road, London, ON N5V 3P5, Canada
Bacillus amyloliquefaciens is a Gram-positive, spore-forming bacterium used commercially as both a biofertilizer and biocontrol agent in many agriculture and horticulture crops. Nearly 10% of its genome is involved in synthesizing antimicrobial metabolites and their corresponding immunity genes; Surfactin is the dominant antibiotic produced. Cyclic lipopeptides and volatiles produced at sub-lethal concentrations by plant-associated Bacilli trigger pathways of induced systemic resistance (ISR), which protect plants against pathogenic microbes, viruses, and nematodes. Our studies demonstrated that B. amyloliquefaciens isolates 94, 113, and 279 as a biocontrol formulation inhibited about 61 of 65 tested species of fungal pathogens. Growth room and field studies were conducted to determine if this bioformulation could control fusarium head blight (FHB) caused by Fusarium graminearum in wheat, a serious risk to global food security due to yield losses and mycotoxin accumulation (DON) in harvested grains. This formulation strongly inhibited the fusarium mycelial growth and reduced DON levels by 83% under lab conditions. In the field, it reduced the disease incidence up to 36%, severity up to 17%, and disease index up to 49% over the control. DON levels were reduced by 36 & 55% and the yield increase was 9 & 17% alone and when co-applied with chemical fungicides respectively under field conditions. Antibiotic gene expression analysis is under progress to determine the mode of action of this biocontrol formulation.
Toward improved disease forecasting for Stemphylium leaf blight of onion
M. KOOY1, B. D. GOSSEN1,2 AND M. R. MCDONALD1
1Department of Plant Agriculture, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada2Saskatoon Research and Development Centre, Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, SK S7N 0X2, Canada
Stemphylium leaf blight (SLB), caused by the fungal plant pathogen Stemphylium vesicarium is an important foliar disease of onion in Ontario. The symptoms start as small, dark or tan water soaked lesions on the leaves that progress to severe leaf dieback. Resistance to common fungicides has been found in Ontario and could be increased with over application of fungicides. Improvements in disease forecasting are needed to identify when fungicide applications are not needed. A replicated field trial was established at the Ontario Crops Research Centre – Bradford to evaluate various spray timing models to reduce spray applications. Treatments were a Calendar spray (7–10 days), 2 TOMcast model variations, and BSPcast model. TOMcast is effective for SLB on tomatoes and BSPcast was developed for SLB on pear. Each treatment was assessed weekly after the three leaf growth stage and until the onions lodged. Assessments were completed by rating disease percentage of the three most mature leaves of 20 plants for each treatment. A final assessment was established on August 16 by pulling 20 plants from each treatment and assessing each leaf into percentage of disease categories. Disease severity was relatively low in 2021 (43% in the nontreated check). All disease forecasting models reduced disease severity, with 33% using Tomcast with a threshold of 15. This reduction in disease is relatively small and demonstrates that the models triggered more fungicide sprays than needed. Research is continuing to develop an improved disease forecasting model for SLB on onions.
Temperature regulation of the plant-rhizobia-immunity axis during induced systemic resistance (ISR)
E. J. R. MARCHETTA1, K. YOSHIOKA1,2, W. MOEDER1,2, E. DÉZIEL1,3 AND C. D. M. CASTROVERDE1
1Department of Biology, Wilfrid Laurier University, Waterloo, ON N2L 3C5, Canada2Department of Cell & Systems Biology, University of Toronto, ON M5S 3G5, Canada3Institut National de la Recherche Scientifique, Institut Armand-Frappier, Laval, QC H7V 1B7, Canada
The rhizosphere is an active site of plant--microbe interactions. Beneficial root microbiomes have demonstrated the ability to enhance nutrient uptake, improve root structure, and provide protection against abiotic and biotic stressors. For example, certain rhizobia can activate induced systemic resistance (ISR) in host plants against pathogens and pests. Although plant pathogenesis and immune responses are known to be influenced by changing environmental factors, the impacts on plant and microbial mechanisms during ISR are largely unexplored. The principal goal of this study is to determine how the physiology of ISR-inducing bacteria and the resulting systemic signalling in host plants are affected by temperature. We will first measure in vitro growth rate, phosphate solubilization ability, and direct anti-pathogenic effects of 21 ISR-inducing bacterial strains. In parallel, the in situ effect of temperature on ISR-inducing bacterial strains will be determined by investigating bacterial colonization of roots, bacterial proliferation in the rhizosphere and persistence on the rhizoplane. Finally, plant defence gene expression after colonization with ISR-inducing bacterial strains will be tested at different temperatures to determine the impact on the resulting plant immune response. Ultimately, this study aims to identify temperature-resilient rhizobacteria, which can be applied as biofertilizers or plant probiotics to protect crops under fluctuating temperature conditions caused by climate change. Our anticipated discoveries will not only benefit the agricultural industry to ensure global food security, but they also could promote environmental and human health due to reduced agrochemical usage.
Resistance of Stemphylium vesicarium in onions to azoxystrobin and fluopyram fungicides
E. MCFAUL AND M. R. MCDONALD
Department of Plant Agriculture, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada
Stemphylium leaf blight (SLB), caused by Stemphylium vesicarium, has recently become an important disease of onion in the Holland Marsh. There are no onion cultivars resistant to S. vesicarium, and growers rely on fungicide applications at 10–14 day intervals to manage the disease. Fungicide resistance in S. vesicarium was documented in New York State and Ontario in 2017. Studies were conducted in 2020 to investigate changes in fungicide resistance. Thirty isolates of S. vesicarium from onions in southern Ontario were collected and assessed for resistance to azoxystrobin (FRAC 11) and fluopyram (FRAC 7), which are active ingredients of commonly used fungicides in the region. Two isolates collected from oats in Saskatchewan in 1995 were used as a historical baseline and were sensitive to both active ingredients when tested in 2017. Using a conidial germination assay, 97% (n = 29) of isolates were resistant to 5 ppm azoxystrobin, 70% (n = 21) were resistant to 100 ppm azoxystrobin and 100% (n = 30) of the isolates were resistant to 10 ppm fluopyram. A mycelial growth assay showed that most isolates (95%) were resistant to azoxystrobin and only 20% (n = 6) of isolates were resistant to fluopyram. Information from this study revealed an overall increase in fungicide resistance compared to 2017. These fungicides have been extensively used in Ontario for control of S. vesicarium in the Holland Marsh but should be avoided as they will be ineffective in suppressing SLB. Additional studies examining S. vesicarium insensitivity to other fungicides and efficacy of alternative control methods are recommended.
Investigations on the timing of fruit infection by Colletotrichum fioriniae causing bitter rot of apple
A. MUNAWAR1, V. ADAM1, S. REYNOLDS1, C. BAKKER1, K. G. MCGUFFIN1,2, M. R. MCDONALD1 AND K. S. JORDAN1
1Department of Plant Agriculture, Simcoe Research Station, University of Guelph, Simcoe, ON N3Y 4N5, Canada2Ontario Ministry of Agriculture, Food and Rural Affairs, Simcoe Research Station, Ontario, N3Y 4N5, Canada
Colletotrichum fioriniae is the prevalent pathogen causing bitter rot of apple in Ontario. The pathogen can cause latent infection before inducing visible symptoms, making it challenging to control. The timing of fruit infection is not known in Ontario. Two experiments were conducted in 2020 to investigate timing of infection of apple fruit. In experiment-1, twenty-five asymptomatic fruits were inoculated weekly from fruit size 5–58 mm along with twenty-five non-inoculated controls. Symptom appearance on the fruits were recorded biweekly and after storage. In experiment-2, fifty asymptomatic fruits were collected weekly from fruit size 5–58 mm. Half of these fruits were plated on PDA medium for fungal detection and the remaining half were stored at 4°C for 5 months and assessed for symptoms after 2 weeks at 22°C. In experiment-1, the disease incidence was 12% at 5-mm fruit size, 8% at 20 mm, 36% at 28 mm, 16% at 32 mm, 12% at 33, 42, and 50 mm, 24% at 54 mm, and 4% at 55 and 58 mm in the field. There were no symptoms on the control fruit. Post-harvest disease incidence was lower on control fruit (4–36%) than inoculated fruit (74–100%). These observations were consistent with inoculum presence in rain traps and weather data collected during the season. In experiment-2, the fungus was detected in 2% fruit at 17 mm and 4% fruit at 28 mm and symptoms were observed on fruit at 28 mm (4%) and 42–58 mm (2–24%). The results indicated that apple fruit can become infected at any stage of fruit development. These experiments are being repeated in 2021.