Genetic architecture of cherry leaf spot () resistance in sour cherry ( L.) uncovered by QTL analyses in a biparental population genotyped with the 6 + 9 K SNP array.

Sour cherry ( L.) is an economically significant species in the Rosaceae family. Hitherto, there had been limited genetic and genomic resources to elucidate important horticultural traits in this species mainly because of the complex polyploid nature of its genome, a hybrid between and . An important trait that has not been well studied in sour cherry is resistance to cherry leaf spot (CLS), caused by the fungus . This work took advantage of the RosBREED 6 + 9 K SNP array to study the genetic basis of CLS resistance and inheritance in sour cherry. We established an F segregating population by crossing two cultivars, 'Schattenmorelle' and 'Pc 2' and genotyped both parents and the progeny with the cherry 6 + 9 K SNP array and SSR markers. We evaluated both parents and progeny for resistance and susceptibility to CLS under field conditions. The applied marker systems facilitated the development of parental genetic maps, and the identification of two stable QTLs associated with CLS resistance, in 'Pc 2' and susceptibility, , in 'Schattenmorelle' explaining 40.9% and 21.5%, respectively, of the phenotypic variation within the population. The mechanism of resistance in sour cherry appears to be independent of the CLS resistance QTL, , previously identified in as the -QTL and associated allele were not identified. Based on our findings, we propose a two-gene model for CLS resistance in sour cherry involving a susceptibility QTL, which might explain why some -resistant plants in previous studies were susceptible.