Identification of (in)compatible S-genotypes and molecular characterisation of Italian sweet cherry cultivars

Italy is the first sweet cherry producer in Europe. Its rich germplasm of local cultivars has not been fully characterised or exploited in breeding programmes. Sweet cherry is a self-incompatible species; this trait is controlled by a gametophytically expressed multi-allelic (S) locus. The knowledge of sweet cherry S-alleles and cross-incompatibility groups is important for growers and breeders for choosing appropriate pollinators in the orchard and planning crosses. In this work, we analysed 94 sweet cherry cultivars native to the majority of sweet cherry growing regions in Italy. The microsatellite primer pair set and the reference cultivars agreed for cherry by the Prunus Working Group of the European Collaborative Programme for Genetic Resources (EPCGR) were used, as well as two consensus primer pairs for the incompatibility (S) locus. We assessed the genetic diversity and relatedness of this germplasm; identified a number of cases of duplicates, synonyms and homonyms; assigned each accession to known or new S-(in)compatibility group. Differences in the relative occurrence of S-alleles were found in comparison to international cultivars reported in various published works. The usefulness of local cultivars for both horticultural and breeding purpose is highlighted.