Determination of the S-allele composition of sweet cherry (Prunus avium L.) cultivars grown in the southeast of Spain by PCR analysis

The Alicante Mountain area is one of the main sweet cherry (Prunus avium L.) production zones of Spain, located in the southeast of the country. An extensive range of local and foreign cherry cultivars are grown in this area, but the incompatibility S-allele composition of most of them is unknown. Correct assignment of cultivars to cross-incompatibility groups is essential for the efficient design of new orchards, and for planning future breeding crosses. In this work, a total of 19 local and 15 foreign cherry cultivars grown in the Alicante Mountain area were analysed by PCR, using conserved primers for the S-RNase gene and restriction analysis to determine their S-genotypes. A new S-genotype, assigned to the universal donor (0) group, has been found in 'Primulat' (S2S9). In addition, a new incompatibility group is proposed, Group XLI (S12S22), consisting of 'Cherovina Primerenca' and 'Nadal Tendre'. Two S-alleles were amplified for each cultivar, except for 'Endiabla' and 'Runar' (S3S3) which are proposed to be homozygous for the S-3-allele. On the basis of this hypothesis, they have been tentatively assigned to the self-compatible (SC) group. Interestingly, the S-22-allele was present in 26% of the 19 local cultivars, but completely absent from the 15 foreign cherry cultivars. Cloning and genomic DNA sequence analysis of the S-22-RNase gene is reported, and its occurrence in other populations discussed.