2018 ASHS Annual Conference

Brown rot, caused by Monilinia spp., is one of the most important diseases for stone fruit worldwide. The fungi affect peach in both pre and post-harvest stages and can cause severe yield loss. Although some degree of tolerance has been reported in stone fruits (peach and almond), the genetic resistance in peach cultivars is still lacking. To date, few genomic regions in peach associated with brown rot response in fruit skin and flesh have been detected. Limited knowledge suggested brown rot tolerance in peach is a quantitative trait controlled by multiple genes with small effect. To further understand the genetics behind brown rot tolerance in peach, we phenotyped 26 cultivars and 138 progeny from 9 crosses across two seasons (2015 and 2016) for skin and flesh response to brown rot infection, and genotyped using newly developed 16K peach SNP array. Association mapping, using GModel2, revealed a total of 32 SNPs (P<1E-07) significantly associated with brown rot response in either peach fruit skin (21) and/or flesh (12) across the whole genome. Candidate gene analyses within the haplotype regions of the detected markers identified 23 predicted genes associated with pathogen infection response/resistance. Two candidate genes, Prupe.7G072600 and Prupe.7G072700, in haploblock (Hap) 7_2, shared high identity with polygalacturonase-inhibiting protein (PGIP), a highly conserved antifungal gene in Rosaceae family. Detailed analysis of the brown rot response associated with the haplotypes (H) in Hap7_2, suggested that absence of H5 significantly reduced brown rot disease severity index in skin and flesh. The information presented here provides an important foundation for further dissection of the genetics behind brown rot tolerance in peach.