Two key genetic regions found to control leaf spot resistance in sour cherry
image: Gene model for CLS resistance and susceptibility in the sour cherry using a 'Schattenmorelle' × 'Pc 2′ biparental population. One half of the progeny have the dominant allele for CLS-resistance R1 for the QTL CLSR_1f. The other half have the dominant allele for CLS-high susceptibility S1 for the QTL CLSS_1f. The Punnett square shows the obtained allele combination for the progeny. Under each allele combination, the means of crown defoliation scorings are depicted and the number of individuals is shown in brackets. The first value represents the marker combination 1F_25143168 (R) with 1A_30613785 (S) and the second value the combination CPSCT027 (R) with 1A_30613785 (S). Resistant individuals carry the R1 allele and showed a mean defoliation score of 3.8/3.7 (blue). Highly susceptible individuals carry the S1 allele and showed a mean defoliation of 5.8/5.9 (red). Moderate individuals carrying both dominant alleles R1 and S1 are depicted in green. The recessive alleles are depicted in white. Chi-square test revealed that the observed segregation for R1 fit a the expected 1:1 ratio.
Credit: Horticulture Research
Cherry leaf spot is a destructive disease that causes premature defoliation, fruit yield loss, and long-term tree weakening in cherry orchards. Understanding how resistance is inherited in sour cherries can enable breeders to develop resilient cultivars and reduce chemical inputs. This study investigated the genetic basis of resistance by analyzing a biparental sour cherry population with high-density genetic markers. Researchers identified two major quantitative trait loci that determine resistance and susceptibility, offering a more refined view of how sour cherries respond to infection. These findings provide clear molecular targets that can be used to accelerate breeding strategies and improve disease management practices.
Cherry leaf spot, caused by Blumeriella jaapii, is one of the most widespread and economically damaging diseases of sour and sweet cherries. The disease leads to early leaf drop, reduces photosynthesis and yield, and compromises tree health over multiple growing seasons. Conventional management relies heavily on fungicide applications, which face increasing regulatory restrictions and environmental concerns. While partial resistance has been observed across some cherry varieties, the underlying genetic mechanisms have been poorly understood, largely due to the complex polyploid nature of the sour cherry genome. Based on these challenges, there is a need to conduct deeper research to clarify the genetic control of disease resistance.
Researchers from the Julius Kühn Institute have published (DOI: 10.1093/hr/uhaf035) new findings in Horticulture Research on May 1, 2025, revealing distinct genetic regions in sour cherry that control resistance and susceptibility to cherry leaf spot. Using a high-density SNP array and field disease evaluations in a biparental population, the team identified two key QTLs located on Chromosome 1 that influence response to infection. The study clarifies how resistance is inherited and provides breeders with molecular markers to support targeted selection of resistant cultivars.
The team established an F1 population from a cross between a highly susceptible cultivar (‘Schattenmorelle’) and a more tolerant cultivar (‘Pc 2’). Both parents and 202 progeny individuals were genotyped using the RosBREED 6+9K SNP array and SSR markers. Disease severity was then evaluated in both controlled inoculation trials and natural field infection across two growing seasons.
Two major QTLs located on the Prunus fruticosa subgenome of Chromosome 1 were consistently detected across years. The first QTL (named CLSR 1f) was associated with reduced disease severity and originated from the tolerant parent ‘Pc 2’. The second QTL (CLSS 1f) was linked to increased susceptibility and derived from ‘Schattenmorelle’. Together, the loci explained a substantial proportion of phenotypic variation, confirming a two-gene resistance model. Importantly, this resistance mechanism was found to be independent of the previously known QTL CLSR G4 derived from Prunus canescens, revealing that sour cherry carries its own distinct resistance source. Within the mapped regions, researchers also identified clusters of candidate genes encoding NLR and receptor-like proteins, indicating that immune signaling pathways may drive resistance.
“Our findings provide a clearer genetic explanation for why some sour cherry lines remain healthy while others suffer severe defoliation, even when they share similar ancestry,” the research team stated. “By distinguishing resistance and susceptibility loci, breeders now have precise molecular targets to guide parent selection and accelerate the development of new cultivars. Importantly, this research also broadens our understanding of plant immunity within polyploid fruit crops, where complex genome structures often mask key genetic mechanisms.”
This work will directly support breeding programs seeking to reduce reliance on fungicides and improve orchard sustainability. Molecular markers linked to CLSR 1f and CLSS 1f can now be used to screen seedlings at early stages, eliminating the need for multiyear field disease evaluations. Identifying resistance controlled by sour cherry’s own genetic background also offers strategic advantages, enabling breeders to avoid unwanted traits sometimes introduced through interspecies hybridization. Ultimately, these insights may lead to the release of new high-yielding, disease-resilient sour cherry cultivars that lower production costs and support environmentally responsible fruit production.
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References
DOI
Original Source URL
https://doi.org/10.1093/hr/uhaf035
About Horticulture Research
Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number one in the Horticulture category of the Journal Citation Reports ™ from Clarivate, 2023. The journal is committed to publishing original research articles, reviews, perspectives, comments, correspondence articles and letters to the editor related to all major horticultural plants and disciplines, including biotechnology, breeding, cellular and molecular biology, evolution, genetics, inter-species interactions, physiology, and the origination and domestication of crops.