Post-fumigation survival of soilborne pathogens of strawberry and lettuce

Authors: Matson, Michael; Kane, Saben; ZEPEDA, SASCHA - Former ARS Employee; CROUCH, UMA - Pennsylvania State University; Martin, Frank

Submitted to: American Phytopathological Society Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 3/25/2022
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Strawberry and leafy greens are the most common rotation crops in the Salinas Valley of California. While the soil fungal pathogens Macrophomina phaseolina and Fusarium oxysporum f. sp. fragariae occupy specific lineages that govern their specificity to one particular crop, Verticillium dahliae can infect both strawberry and lettuce, depending on the cultivar. All three of these pathogens are primarily controlled with fumigation and following the phase out of methyl bromide, diseases caused by these pathogens are trending upwards due to the replacement fumigants not being as effective as methyl bromide. Here, we investigate the detection and post-fumigation DNA survival of these three soilborne fungal pathogens using molecular techniques. Relic DNA from non-viable propagules can introduce significant issues when determining pathogen pressure via molecular soil assays, since amplification of pathogen DNA from viable and non-viable spores cannot be differentiated. Thus a certain window of time must pass following fumigation before it is possible to evaluate the effectiveness of said fumigation; the length of this window is currently under evaluation. All pathogens can be reduced following fumigation to levels near the limit of detection using standard DNA extraction techniques for qPCR assays, though in some cases significant disease may be observed at the end of the season. A recently developed lager-soil-volume DNA extraction assay can extend the detection limit beyond previous techniques, and can thus further clarify pathogen populations and how it relates to disease incidence.