PCR-based identification of all 13 known self-incompatibility (S) alleles of sweet cherry is reported. Two pairs of consensus primers were designed from our previously published cDNA sequences of S(1) to S(6) S-RNases, the stylar components of self-incompatibility, to reveal length variation of the first and the second introns. With the exception of the first intron of S(13), these also amplified S(7) to S(14) and an allele previously referred to as S(x), which we now label S(16). The genomic PCR products were cloned and sequenced. The partial sequence of S(11) matched that of S(7) and the alleles were shown to have the same functional specificity. Allele-specific primers were designed for S(7) to S(16), so that allele-specific primers are now available for all 13 S alleles of cherry (S(8), S(11) and S(15) are duplicates). These can be used to distinguish between S alleles with introns of similar size and to confirm genotypes determined with consensus primers. The reliability of the PCR with allele-specific primers was improved by the inclusion of an internal control. The use of the consensus and allele-specific primers was demonstrated by resolving conflicting genotypes that have been published recently and by determining genotypes of 18 new cherry cultivars. Two new groups are proposed, Group XXIII (S(3) S(16)), comprising 'Rodmersham Seedling' and 'Strawberry Heart', and Group XXIV (S(6) S(12)), comprising 'Aida' and 'Flamentiner'. Four new self-compatibility genotypes, S(3) S(3)', S(4)' S(6), S(4)' S(9) and S(4)' S(13), were found. The potential use of the consensus primers to reveal incompatibility alleles in other cherry species is also demonstrated.
Recently, an S haplotype-specific F-box (SFB) gene has been proposed as a candidate for the pollen-S specificity gene of RNase-mediated gametophytic self-incompatibility in Prunus (Rosaceae). We have examined two pollen-part mutant haplotypes of sweet cherry (Prunus avium). Both were found to retain the S-RNase, which determines stylar specificity, but one (S 3 9 in JI 2434) has a deletion including the haplotype-specific SFB gene, and the other (S 4 9 in JI 2420) has a frame-shift mutation of the haplotype-specific SFB gene, causing amino acid substitutions and premature termination of the protein.The loss or significant alteration of this highly polymorphic gene and the concomitant loss of pollen self-incompatibility function provides compelling evidence that the SFB gene encodes the pollen specificity component of self-incompatibility in Prunus. These loss-of-function mutations are inconsistent with SFB being the inactivator of non-self S-RNases and indicate the presence of a general inactivation mechanism, with SFB conferring specificity by protecting self S-RNases from inactivation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.