Molecular typing of the self-incompatibility locus of Turkish sweet cherry genotypes reflects phylogenetic relationships among cherries and other Prunus species

Self-incompatibility of sweet cherry (Prunus avium L.) is controlled by the multiallelic S-locus. While many cultivars and wild accessions have been S-genotyped, only limited data are available on accessions native to the center of origin of this species. Therefore, this study was carried out to determine the S-genotype of 11 landrace cultivars and 17 local genotypes selected from populations growing wild at the Black Sea coast. Eleven sweet cherries (S ₁–S ₇, S ₁₀, and S ₁₂–S ₁₄) and some wild cherries (S ₁₇–S ₁₉, S _21/25, and S ₃₁) S-RNase alleles were detected. The results indicate that Turkish cultivars represent a broader gene pool as compared with international cultivars. A new (S ₃₇) and a doubtful allele (provisionally labelled as S _7m) as well as the sour cherry S ₃₄-allele were identified in sweet cherry. These data and others (SSR variants within the S ₁₃-RNase introns) confirmed that allele pools of sweet and sour cherries in the Black Sea region are overlapping. A new cross-incompatibility group, XLV (S ₂ S ₁₈), was also proposed. Allele-specific primers were designed for S ₁₇–S ₁₉, S _21/25, S ₃₄, and S ₃₇. A phylogenetic analysis of the cherry S ₃₁-RNase and its trans-specific sister alleles reliably mirrored the assumed length of the time period after the divergence of species in the subgenera Cerasus and Prunophora. Most variations (insertions/deletions and single-nucleotide polymorphisms) in the S-RNase gene were silent and, hence, have not been exposed to natural selection. The results are discussed from the aspects of S-allele evolution and phylogenetic relationships among cherries and other Prunus species.