Fine Mapping and Candidate Gene Discovery for the Resistance to Angular Leaf Spot in Cultivated Octoploid Strawberry (Fragaria ×ananassa Duch.)

Abstract

Strawberry is one of the economically important fruit crops worldwide. Angular leaf spot (ALS) caused by Xanthomonas fragariae is the only bacterial disease in strawberry and is problematic in Florida strawberry production. Developing ALS-resistant cultivars is important as all commercial varieties are susceptible to ALS. In the previous study, a major quantitative trait locus (QTL) conferring resistance to ALS, FaRXf1, was identified, but the genomic region and genetic mechanisms for ALS resistance have not been characterized. We recently identified candidate genes for FaRXf1 by fine mapping and transcriptome analysis. For defining the FaRXf1 locus, seven newly developed molecular markers were used to genotype three populations (n = 663). The FaRXf1 region was delimited to a 330-kb interval on chromosome 6-2 in the ‘Camarosa’ reference genome. To identify candidate genes for FaRXf1, RNA sequencing was performed with five resistant or susceptible genotypes. We identified one candidate gene that is located within the genomic region of FaRXf1. This information will facilitate developing functional DNA markers and elucidating the genetic mechanism of FaRXf1 controlling resistance to ALS in cultivated octoploid strawberry.