S-RNase allele identification and incompatibility group assignment in sweet cherry (Prunus avium L.) indigenous genotypes

Abstract

Sweet cherry (Prunus avium L.) is one of the economically most important members of the Rosaceae family. In this fruit species, most genotypes are self-incompatible and certain pairs of genotypes are cross-incompatible. This incompatibility is genetically determined by the multiallelic two linked genes of S-locus (S-RNase and SFB genes), with gametophytic action. Therefore, determination of S-alleles of new sweet cherry genotypes is highly valuable tool for growers to design orchards, and for breeders to choose parents in breeding programmes. This work was undertaken primarily to identify the S-alleles and incompatibility groups in 15 indigenous sweet cherry genotypes collected in orchards of individual growers in the Republic of Serbia, i.e. 11 genotypes in the region of Čačak (ʻGТ-1ʼ, ʻGТ-2ʼ and ʻGТ-4ʼ to ʻGТ-12ʼ) and four genotypes in the region of Belgrade (ʻGТ-13ʼ to ʻGТ-16ʼ). The S-alleles of each genotype were determined by PCR amplification of the S-RNase gene, with consensus primers for the first and second introns, as well as with allele-specific primers. The obtained results revealed eight alleles (S1, S2, S3, S4, S5, S6, S9 and S12), that generated the following eight S-genotypes: S1S5 (ʻGТ-1ʼ), S2S3 (ʻGТ-7ʼ, ʻGТ-14ʼ, ʻGТ-15ʼ and ʻGТ-16ʼ), S3S4 (ʻGТ-10ʼ and ʻGТ-12ʼ), S3S6 (ʻGТ-4ʼ and ʻGТ-13ʼ), S3S9 (ʻGТ-8ʼ), S3S12 (ʻGТ-5ʼ and ʻGТ-6ʼ), S6S9 (ʻGТ-2ʼ and ʻGТ-11ʼ) and S5Sx (ʻGТ-9ʼ). S2S3 was the most frequent allelic combination (27%), which was observed in four assessed genotypes. The S-allelic constitutions allowed assignment of the genotypes to their corresponding incompatibility groups as follows: III (ʻGТ-10ʼ and ʻGТ-12ʼ), IV (ʻGТ-7ʼ, ʻGТ-14ʼ, ʻGТ-15ʼ and ʻGТ-16ʼ), VI (ʻGТ-4ʼ and ʻGТ-13ʼ), X (ʻGТ-2ʼ and ʻGТ- 11ʼ), XIV (ʻGТ-1ʼ), XVI (ʻGТ-8ʼ) and XXII (ʻGТ-5ʼ and ʻGТ-6ʼ). S-genotyping results represent important information on cross-compatibility in these local genotypes and also reveal the S-locus diversity of sweet cherry indigenous material.