Date and Time
Location
112 Buckhout Laboratory
Phytophthora blight, caused by the soilborne oomycete pathogen Phytophthora capsici, is a devastating disease of squash and pepper. Options for host resistance in these two crops vary drastically. In squash, no cultivars are commercially available with resistance to Phytophthora blight, although research at Cornell has led to the development of breeding lines with reduced root and crown rot symptoms compared to commercial checks. To identify loci involved in resistance, we crossed a Cornell breeding line to a susceptible zucchini variety and performed bulk segregant analysis in the F2 generation. Whole genome resequencing of pooled DNA samples revealed four genomic regions with significant allele frequency differences between susceptible and resistant progeny. In a population of 187 F2:3 families, markers in these four regions alone could predict Phytophthora root and crown rot resistance with a median fivefold cross-validation accuracy of 0.45, compared to 0.50 from a genomic prediction model using genome-wide markers, showing their potential for use in marker-assisted selection. In pepper, plant breeders have developed cultivars with high resistance to Phytophthora root and crown rot. However, some pathogen isolates are able to overcome deployed resistance genes and cause disease on these varieties. We employed association mapping in a panel of 118 genetically distinct P. capsici isolates to map loci associated with the ability to cause disease on different pepper varieties. Preliminary analyses resulted in the identification of several SNPs associated with virulence, including one located inside a putative effector gene.