Determination of self-incompatible genotypes in 21 cultivated sweet cherry cultivars in Greece and implications for orchard cultivation

Summary

Sweet cherry is self-incompatible due to having a gametophytic self-incompatibility system. S alleles in the style and pollen determine possible crossing relationships. Knowledge of the S allele constitution of cultivars is important for sweet cherry growers and breeders. Recently, molecular methods have been developed to distinguish between S alleles in sweet cherry.The S allele genotypes of 21 sweet cherry cultivars widely grown in Greece, including 19 not previously genotyped, were determined based on their S-RNase gene sequences using PCR analysis. Eight different S alleles in ten combinations were distinguished and two new S-genotypes (S₁S₁₃ and S₄S₃₀) were documented. Four alleles, S₁, S₃, S₄, and S₉ were widespread and together were responsible for 85% of the S-haplotypes. Therefore many of the cultivar combinations were semi-compatible. In Greece, semi-compatibility was shown to correlate with low yields. However, the cultivar ‘Hybrid Tragana Edessis x Unknown’ (S₃S₁₃) and the cultivar ‘Kapsiotika’ (S₂S₅) carry rare S-haplotypes and are therefore fully cross-compatible with most of the cultivars analysed.