Development of Subgenome-Specific Markers for FaRXf1 Conferring Resistance to Bacterial Angular Leaf Spot in Allo-Octoploid Strawberry

Bacterial angular leaf spot (ALS) caused by Xanthomonas fragariae has become increasingly problematic to strawberry producers and nurseries. The use of genetic resistance is the most effective way to manage ALS. In our previous study, the major locus, FaRXf1, was identified for resistance to ALS in the linkage group 6D (LG6D). In this study, we developed subgenome-specific markers tightly associated with FaRXf1 and tested for their accuracy for high-throughput marker-assisted selection (HTP-MAS). Using the recently published octoploid reference genome sequence, we identified the location of FaRXf1 on chromosome Fvb6–2. The sequences of IStraw90 Axiom® SNP markers for FaRXf1 were used to design subgenome-specific high-resolution melting (HRM) markers. Two newly developed subgenome-specific HRM markers (Xf1HRM-8263 and Xf1HRM-8073) were consistent in their ability to correctly determine resistance and susceptibility of a total of 56 tested accessions. To validate the effectiveness of markers in HTP-MAS, we tested both CTAB purified DNA and NaOH crude extracts. The newly developed subgenome-specific marker Xf1HRM-8073 can be effectively used for the breeding of ALS resistance in cultivated strawberry.