2018 ASHS Annual Conference

Spinach (Spinacia oleracea L., 2n=2x=12) is an economically important vegetable crop worldwide. The objectives of this spinach project are: (1) genetic mapping and SNP marker identification for downy mildew and white rust resistance; (2) QTL and association mapping and SNP marker identification for Fusarium wilt resistance; (3) introgression of downy mildew and white rust resistance into spinach lines with diverse leaf quality characteristics to satisfy market demand; and (4) construction of high density SNP consensus genetic maps of the six chromosomes in spinach using whole genome resequencing. The project is a collaborative effort with the University of Arkansas, USDA-ARS at Salinas, Texas A&M AgriLife, and Washington State University. A total of 480 spinach genotypes are being evaluated for downy mildew, white rust, and Fusarium wilt disease resistance. Downy mildew resistance is being evaluated under both field and greenhouse/growth chamber conditions; white rust resistance is being evaluated at the Del Monte White Rust Nursery in Crystal City, TX and at the White Rust Nursery in Weslaco, TX; and Fusarium wilt resistance is being evaluated in the greenhouse at the Washington State University Mount Vernon NWREC in Mount Vernon, WA and at the University of Arkansas, Fayetteville, AR. Genotyping is being conducted at BGI and Novogene using genotyping by sequencing (GBS) and whole genome resequencing (WGR). Approximately 500,000 SNPs have been identified in in spinach genotypes thus far. Both QTL and association mappings are being used to identify QTLs and SNP markers for disease resistance to the three diseases. The WinQTLCart, Q-gene, and QTLNetwork are being used for QTL mapping, and the general linear model (GLM) and mixed linear model (MLM) from TASSEL, GAPIT, and FarmCPU will be used for genome wide association studies (GWAS). So far, numerous SNP markers linked to downy mildew resistance locus RPF1 have been identified, and SNP markers strongly associated with white rust resistance have been identified. The QTLs and SNP markers will provide breeders with robust tools to improve resistance selection for resistance to these economically important diseases through marker-assisted selection (MAS) and genomic selection (GS).