Determination of S-allele combination in an italian apple (Malus × domestica Borkh.) germplasm core collection

An S-RNase-based gametophytic self-incompatibility (GSI) system, a mechanism that forces outbreeding by preventing self-fertilization, characterizes the genus Malus. Knowledge of the self-incompatibility (S) genotypes of apple cultivars is crucial for choosing pollen donors for fruit production and breeding. Even though the S-allele of most commercial apple cultivars has already been identified, limited information is available about the S-allele diversity within local germplasm collections. In this study, 67 S-allele combinations of local apple accessions were identified. The allele S3 was the most common among local apple accessions followed by S1 and S7. The main aim of this study is to provide new information on cultivar compatibility, and these results will be used to set up new parent selection in apple breeding programmes as well as pollinator selection for the commercial orchard.