THE SELF-INCOMPATIBILITY LOCUS OF APRICOT HELPS TO CLARIFY SEVERAL EVOLUTIONARY ASPECTS

Self-incompatibility of apricot (Prunus armeniaca) is governed by the multi-allelic S-locus, in which the pistil S-ribonuclease (S-RNase) and the pollen expressed S-haplotype specific F-box (SFB) genes reside. In apricot, self-compatibility (SC) is due to a loss-of-function mutation within the pollen gene of the S C -haplotype. Apricot S 8 -, S 9 - and S C -haplotypes were analysed using fruit set evaluation, genomic PCRs, RT-PCRs and DNA sequencing of the S-RNase and SFB alleles. Controlled pollinations revealed that the cross 'Cegledi orias' (S 8 S 9 ) × 'Cegledi arany' (S C S 9 ) set well, but the reciprocal cross did not. Sequence analysis revealed that SFB 8 is the first known progenitor allele of a naturally occurring SC allele in Prunus. A phylogenetic analysis suggests that S C -haplotype could have evolved in a cultivar with S 8 S i genotype, where S i is an unidentified incompatibility allele. The S C S 8 Magyarkajszi cultivars might have developed from such a mating. Several single nucleotide polymorphisms were identified in the S C -RNase and could be used for monitoring apricot dissemination routes between Eastern and Western Europe. The apricot S C -RNase was subjected to an intron phase analysis revealing some protein evolutionary aspects. Our results have notable implications for the elucidation of the evolutionary history of present day apricot cultivars and, in general, for the understanding of the transition from self-incompatibility (SI) to self-compatibility.