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.