Identification of new self-incompatibility alleles in sweet cherry (Prunus avium L.) and clarification of incompatibility groups by PCR and sequencing analysis

Correct assignment of sweet cherry cultivars to cross-compatibility groups is important for the efficient production of cherry fruit. Despite considerable confusion in the literature, these groups continue to be an effective tool for predicting pollination effectiveness for breeders and growers. PCR fragments generated from cherry S-RNase sequences coincided with specific S-allele phenotypes. Twenty five genomic DNA fragments, representing the six most common alleles, were cloned and sequenced. In addition, fragments were characterized from four new S-alleles. These genomic and cDNA sequences were invariant among cultivars with the same S-allele. Using the sequence data, PCR and restriction enzyme-based methodology was developed for rapid analysis of S-genotypes. Analysis and description of fragmentation patterns for S-allele determination are discussed. The method was utilized to characterize the S-allele composition of 70 sweet cherry cultivars obtained from collections in North America, including many of the named releases from the Canadian breeding programs at Agriculture and Agri-Food Canada in Summerland, B.C., and Vineland, Ontario. A number of differences between published S-allele assignments and PCR data were discovered and a new listing of cultivar S-allele assignments is presented.