Evaluation of S-incompatibility locus, genetic diversity and structure of sweet cherry (<i>Prunus avium</i> L.) genetic resources by molecular methods and phenotypic characteristics

Sweet cherry is a vegetatively propagated, self-incompatible, perennial plant with a high level of heterozygosity and ancient breeding history. Maintenance and conservation of genetic resources are necessary for future breeding programmes, growers and fruit production stability. The knowledge about <i>S</i>-allele constitution of cultivars is very important for fruit growers and breeders. DNA molecular genetic methods were used for evaluation of genetic variability and <i>S</i>-genotyping within sweet cherry genetic resources. Totally, 13 different <i>S</i>-alleles in 29 <i>S</i>-locus combinations for 24 individual incompatibility groups within 153 sweet cherries accessions were detected. S₃ (88 cultivars), S₁ (60 cultivars) and S₄ (54 cultivars), followed by S₂ (34 cultivars) and S₆ (28 cultivars) were the most frequent <i>S</i>-alleles. <i>S</i>-alleles distribution linked to ripening time was also analysed. A total of 117 microsatellite SSR and EST-SSR polymorphic markers were used for molecular-genetic analyses. The hierarchical cluster analysis divided sweet cherry cultivars into seven clusters. Genetic relationships of individual cultivars corresponded with genealogical and geobotanical characteristics and known breeding history. Genetic population structure analyses in seven clusters (<i>K</i>= 7) supported hierarchical clustering results and involved ripening period, fruit colour and country of origin to genetic diversity evaluation of germplasm collection.