S-RNase based S-genotyping of Japanese plum (Prunus salicina Lindl.) and its implication on the assortment of cultivar-couples in the orchard

Determination of the genetic compatibility between self-incompatible cultivars is crucial in agriculture. The Rosaceae family carries the S-RNase-mediated gametophytic self-incompatibility (GSI) system. Each haplotype is conferred by an S-locus. The S-locus contains two highly polymorphic genes, S-RNase and SFB, which are characteristic of each haplotype and therefore these genes are ideal markers for molecular S-genotyping. In this study 43 Japanese plum cultivars grown in Israel were S-genotyped based on their S-RNase gene sequences. Four alleles, S^b, S^c, S^e and S^h are widespread and together are responsible for 87% of the S-haplotypes therefore many of the cultivar combinations are semi-compatible. In Israel semi-compatibility was shown to correlate with low yield. However, two cultivars, 'Wickson' S^fS^k and 'Shiro' S^fS^g carry rare S-haplotypes and, therefore, are fully compatible with most of the analyzed cultivars.