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

## TL;DR

This study identifies genetic regions in sour cherry linked to resistance and susceptibility to cherry leaf spot, using a new SNP array and a cross between two cultivars.

## Contribution

The study uncovers two stable QTLs for CLS resistance and susceptibility in sour cherry, offering a new two-gene model for resistance.

## Key findings

- Two QTLs, CLSR_1f and CLSS_1f, explained 40.9% and 21.5% of CLS resistance and susceptibility variation.
- The CLSR_G4 QTL from P. canescens was not found in sour cherry, suggesting a different resistance mechanism.
- A two-gene model is proposed to explain CLS resistance, including a susceptibility QTL.

## Abstract

Sour cherry (Prunus cerasus 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 Prunus avium and Prunus fruticosa. An important trait that has not been well studied in sour cherry is resistance to cherry leaf spot (CLS), caused by the fungus Blumeriella jaapii. 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 F1 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, CLSR_1f in ‘Pc 2’ and susceptibility, CLSS_1f, 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, CLSR_G4, previously identified in P. canescens, as the CLSR_G4-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 CLSR_G4-resistant plants in previous studies were susceptible.