2017 ASHS Annual Conference

Brown rot, caused by Monilinia spp., is one of the most important diseases of stone fruits. The fungus mainly affects the blossoms and fruit, and the resulting disease can lead to significant pre- and postharvest yield losses. Estimated annual cost to the U.S. stakeholders for disease management can reach $170 million. Although some degree of tolerance has been detected in peach landraces (‘Bolinha’) and interspecific material (almond x peach), most of the commercial cultivars are susceptible. In commercial peach production, the disease can only be controlled by routine fungicide applications, which may cause both environmental and human health concerns. The Clemson University peach breeding program within the RosBREED project aims to understand the genetics behind the peach fruit response to brown rot; with the goal of combining disease tolerance with high fruit quality via DNA-informed breeding. To this end we have phenotyped 26 cultivars/advanced selections and 140 progeny in 10 breeding families using ‘Bolinha’ as source of tolerance. Fruit response to brown rot was assessed in wounded and non-wounded disease assays in 2015 and 2016. Genotypic data, obtained by using newly developed 16K peach SNP array, and previously reported QTLs [QTL1.1, QTL1.2 on linkage group (LG) 1, SK_if_2009 on LG2, and FL_rd_2009 on LG3] associated with brown rot response in peach fruit, were used to evaluate allelic variability in brown rot associated genomic regions. We found 9 and 3 haploblocks in two QTLs on LG1, respectively; 2 haploblocks in QTL region on LG 2, and 3 haploblocks in QTL region on LG3, with number of haplotypes/alleles ranging from 3-7. Phenotypic performance or trait values of these alleles/haplotypes will be discussed. The data presented here provide a foundation for the development of predictive DNA information that has a potential for an immediate application in U.S. peach breeding.