DNA-Informed Strawberry Breeding in RosBREED

Providing breeders with DNA-based tools to combine disease resistance with excellent fruit quality in new rosaceous crop cultivars is the primary goal of the USDA-SCRI-funded RosBREED project. Here we present progress towards RosBREED objectives in the University of Florida (UF) strawberry breeding program. Large-effect QTLs for resistance to three strawberry diseases were identified: angular leaf spot caused by Xanthomonas fragariae (locus Xf1 on LG6D), crown and root rot caused by Phytophthora cactorum (Pc1 on LG7D), and crown rot caused by Colletotrichum gloeosporioides (Cg1 on LG6B). In addition, moderate-effect QTL were identified for soluble solids content (LG6A) and fruit weight (LG6C and LG4B). These five QTLs were discovered in UF germplasm totaling more than 1,100 individuals from 122 full-sib families and validated in sets of advanced selections totaling more than 600 individuals. These individuals were phenotyped for disease resistance and fruit quality over two years and genotyped with the Affymetrix IStraw90 Axiom^® SNP array. QTL discovery was conducted with FlexQTL™ software. Recombination patterns within QTL regions were analyzed and were used to inform SNP haplotype construction for QTL effect validations. Haplotype information was utilized in the selection of all parents and crosses in 2015. Marker-assisted seedling selection was performed on ~8000 seedlings using two previously developed DNA tests: a high-resolution melting assay for peach-like aroma (gamma-decalactone) and a SSR marker for perpetual flowering habit. Breeding gains realized with the use of DNA information and projected gains with the forthcoming DNA tests for Xf1 and Pc1 will be presented.