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ARS Home » Pacific West Area » Salinas, California » Crop Improvement and Protection Research » Research » Research Project #436200

Research Project: Epidemiology of Spinach Downy Mildew Pathogen Peronospora effusa

Location: Crop Improvement and Protection Research

Project Number: 2038-22000-016-031-N
Project Type: Non-Funded Cooperative Agreement

Start Date: Mar 31, 2019
End Date: Nov 30, 2021

The objectives of this project include 1) Develop a standardized test to quantify inoculum in soil in the form of sporangia, mycelium, and oospores; 2) Develop a more thorough understanding of the epidemiological gaps addressing the relative importance of mycelium, sporangia, and oospores as primary inoculum and in generating genotypic (DNA fingerprinting) and phenotypic (virulence) diversity; and 3) examination of commercial fields and research field plots for (a) downy mildew presence; (b) determine if naturally occurring oospores are present in leaves; (c) examine potential mating type in bioassay crosses; (d) and, through a third party, do anonymous “trace-back” studies to determine if the pathogen can/was detected on seed, in seed-production fields, and determine spinach cropping history of fields with outbreaks.

A series of polymerase chain reaction (PCR)-based tests, filtering and gradient separation, and viability tests will be conducted to examine potential sources of primary inoculum. Lab, greenhouse, and field tests will be conducted to address the epidemiological gaps, and oospores will be analyzed following crosses in controlled greenhouse or growth chamber. The pathogen will be examined whether present or absent also in more isolated areas (in desert area away from main spinach production sites and in the isolation chambers).