1a.Objectives (from AD-416)
To screen public spinach germplasm for new sources of resistance to downy mildew race 10.
1b.Approach (from AD-416)
The entire USDA spinach germplasm collection will be screened for downy mildew resistance in inoculated greenhouse tests. Documents Trust with California Leafy Greens Research Board.
This report documents research conducted under a cooperative agreement with California Leafy Greens Research Program. Downy mildew caused by Peronospora farinose f. sp. Spinaciae is the most important disease for California spinach growers. Along with the rapid increase of spinach consumption and production in recent years, many new downy mildew races have emerged including the latest Races 10, 11, 12, and 13. We increased pathogen isolates and identified their races through differential host tests. Screening 135 USDA spinach germplasm accessions and seven commercial cultivars for resistance to Race 10; and eight putative resistant accessions were identified for further testing. We are making crosses to develop near isogenic lines of different DM-resistant genes. Ten cultivars with different DM-resistant genes were intercrossed to combine their resistances.
Although Verticillium wilt has not been a problem for spinach production in California due to the late appearance of disease symptoms, spinach seeds may bring large amount of pathogen inoculums into fields, which poses a threat to other rotational crops in Salinas Valley such as lettuce and strawberry. No spinach cultivar resistant to Verticillium wilt is available on the market at present. In collaboration with a scientist's lab at the University of California-Davis, we screened 106 USDA spinach germplasm accessions for resistance in inoculated greenhouse tests. Six putative resistant accessions were identified for further testing. This project contributes directly to the Objective 3 of the in-house project, genetic improvement of spinach.