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ARS Home » Pacific West Area » Pullman, Washington » Grain Legume Genetics Physiology Research » Research » Publications at this Location » Publication #329299

Research Project: Genetic Improvement of Cool Season Food Legumes

Location: Grain Legume Genetics Physiology Research

Title: Chickpea damping-off due to metalaxyl-resistant Pythium: An emerging disease in the Palouse

Author
item Chen, Weidong
item Van Vleet, Stephen - Washington State University

Submitted to: WSU Extension Bulletin
Publication Type: Experiment Station
Publication Acceptance Date: 2/10/2016
Publication Date: 4/18/2016
Citation: Chen, W., Van Vleet, S. 2016. Chickpea damping-off due to metalaxyl-resistant Pythium: An emerging disease in the Palouse. WSU Extension Bulletin. FS211E.

Interpretive Summary: Pythium species are a group of ubiquitous plant pathogens, existing in almost all agricultural soils. They can persist in soil for many years, and can affect a wide range of crops including legumes, cereals, and Brassica crops. In cold spring conditions that favors Phythium damping off, the only currently reliable control is seed treatment with metalaxyl. Legumes and large-seeded (Kabuli-type) chickpeas are highly vulnerable to Pythium damping-off when planted in cold, wet soil in the spring, due to their thin seed coat and copious seed exudates during germination. For decades, the preferred and only available seed treatment for reliable control of damping-off was metalaxyl. Seed treatments including metalaxyl have been the silver bullet for protecting chickpea seed from Pythium damping off. Recently in some notable cases, metalaxyl is losing its effectiveness because Pythium species in Palouse soils are developing resistance to metalaxyl. In the field, Pythium isolates obtained from ungerminated seeds or from soil adjacent to rotten chickpea seeds consistently show high levels of resistance to metalaxyl. In the greenhouse, metalaxyl treatments failed to protect chickpea seeds inoculated with metalaxyl-resistant Pythium isolates from damping-off. All evidence shows that the poor germination of Kabuli chickpea is due to the presence of metalaxyl-resistant Pythium populations. Current research is searching for alternative fungicide for managing the metalaxyl-resistant Pythium.

Technical Abstract: Legumes and large-seeded (Kabuli-type) chickpeas are highly vulnerable to Pythium damping-off when planted in cold, wet soil in the spring, due to their thin seed coat and copious seed exudates during germination. For decades, the preferred and only available seed treatment for reliable control of damping-off was metalaxyl. Seed treatments including metalaxyl have been the silver bullet for protecting chickpea seed from Pythium damping off. Recently in some notable cases, metalaxyl is losing its effectiveness because Pythium species in Palouse soils are developing resistance to metalaxyl. In May, 2014, we observed germination failure of large-seeded chickpeas in fields near Colton, Washington. In addition, soil samples were collected within (infected) and outside (uninfected) the chickpea damping-off area. These soil samples were used to determine the incidence of resistance in the problem soils. Pythium isolates from within and outside the area where damping-off occurred were then used to test for resistance on media containing metalaxyl. Soils sampled from the areas where there was poor germination consistently had Pythium isolates with high levels of resistance to metalaxyl. Under controlled conditions, metalaxyl treatments failed to protect chickpea seeds from damping-off inoculated with metalaxyl-resistant Pythium isolates. All evidence shows that the poor germination of Kabuli chickpea is due to the presence of metalaxyl-resistant Pythium populations. Current research is searching for alternative fungicide for managing the metalaxyl-resistant Pythium.