Location: Crop Improvement and Protection ResearchTitle: Transmission of spinach downy mildew via seed and infested leaf debris
|MCGRATH, MARGARET - Cornell University
|CORRELL, JIM - University Of Arkansas
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/1/2023
Publication Date: 5/1/2023
Citation: Klosterman, S.J., Clark, K.J., Anchieta, A.G., Kandel, S.L., Mou, B., McGrath, M.T., Correll, J., Shishkoff, N. 2023. Transmission of spinach downy mildew via seed and infested leaf debris. International Spinach Conference, May 1-2, 2023, Melbourne, Australia (virtual).
Technical Abstract: Spinach downy mildew, caused by the oomycete pathogen Peronospora effusa, is a worldwide constraint on spinach production. The role of airborne sporangia in the disease cycle of P. effusa is well established, but the role of the sexual oospores of P. effusa is less clear. Surveys of modern spinach seed lot samples since 2014 have revealed the presence of oospores in 19% of the lots. To evaluate seed transmission of spinach downy mildew via oospores in this study, we used glass isolator chambers to grow out oospore-infested spinach seed and non-infested seeds mixed with oospore-infested crop debris in two independent experiments. Downy mildew diseased spinach plants were found 37 days after planting in the chambers that contained one of two oospore-infested seed lots in the first experiment, and 34 days after planting in the second experiment. Isolator chambers with seeds coated with oospore-infested leaf debri also gave rise to downy mildew diseased spinach plants in both experiments. Spinach plants in glass chambers initiated from seeds without oospores did not show downy mildew symptoms. Similar findings were obtained using the same seed lot samples in a third experiment conducted in a growth chamber. Grow out tests with seed of two oospore-infested cultivars revealed the characteristic Peronospora sporangiophores growing from one seedling of each cultivar. The results provide evidence that oospore-infested plant debri in soil can cause downy mildew and further evidence of seed transmission of downy mildew in spinach via oospores.