1a.Objectives (from AD-416):
The objectives of the proposed work are to identify target DNA sequences for differentiation of strains of the downy mildew pathogen, Peronospora effusa, and to deploy spore traps to the field for specific detection of the pathogen. The work also entails examination of other potential pathogen inoculum sources, including seed and soil.
1b.Approach (from AD-416):
Isolates of Peronospora effusa will be collected from the field and collaborators. DNA will be extracted and alignments of specific DNA sequences will be performed. Spore traps will be deployed near spinach fields for detection of the pathogen, and DNA extracted from spore trap samples also will be analyzed.
This work supports objective 2 of the parent project, to develop molecular diagnostic tools for the identification of emerging diseases of vegetables and strawberries. Isolates of Peronospora effusa, or Deoxyribonucleic acid (DNA) from Peronospora-infected plants were collected from the field and from collaborators. Target DNA sequences were identified in this isolate or DNA sample collection for the differentiation of species of the spinach downy mildew pathogen, Peronospora effusa, from related species. Spore traps were deployed in the Salinas Valley, California, for specific detection of the pathogen. Analyses of spore trap samples revealed detection of Peronospora effusa, and detection of the pathogen at higher levels near an infected spinach field. The results suggest that a DNA based assay coupled with spore trapping may be useful for studying optimal conditions for downy mildew disease outbreaks, and disease prediction. Work was also initiated to identify and examine other potential pathogen inoculum sources, including seed and soil. Oospores, which can survive between growing seasons in the soil, were identified in leaf samples of spinach in California.