2019 ASHS Annual Conference

White rust, caused by Albugo occidentalis is a severe disease of economic importance that causes reduction in yield and quality in spinach (Spinacia oleracea L.). The use of resistant cultivars is economical and practical approach for white rust management. The objectives of this research are to evaluate white rust resistance in a panel of world-wide spinach germplasm, and to conduct genome-wide association study (GWAS) and genomic selection (GS) for white rust resistance in spinach. A total of 910 spinach genotypes were evaluated over 4 years at the Del Monte White Rust Nursery in Crystal City, TX. Over 100 spinach genotypes out of 910 were selected with levels of quantitative resistance to white rust pathogen. In our earlier research, GWAS and GS were analyzed in an association panel with 412 spinach genotypes using 3000 SNPs from ddRADseq and eight SNP markers were associated with white rust resistance. Based on RR-BLUP in rrBLUP, using 250 spinach genotypes as training set and 162 genotypes as validation set, the correlation coefficients (r) between genomic estimated breeding value (GEBV) and observed value of white rust resistance averaged 0.68 with the eight SNP markers. Currently GWAS is being conducted in 480 spinach genotypes including USDA spinach germplasm from over 30 countries, spinach commercial hybrids and Arkansas lines. Whole genome resequencing (WGR) is conducted with 10X genome coverage in BGI. It is expected that QTLs/genes and associated SNPs will be identified for white rust resistance in spinach and SNP markers could be used in spinach molecular breeding through MAS and GS.