Self-incompatibility alleles of apple cultivars and advanced selections

The S-alleles of 55 apple (Malus xdomestica Borkh,) cultivars and selection s were determined using an allele-specific polymerase chain reaction (PCR) amplification system for 11 different S-alleles (S2, S3, S4, S5, S7, S9, S2 4, S26, S27, Sd, Sf), Four cultivars had S-alleles different than those pre dicted by their parentage. Three commercial cultivars of unknown pedigrees had S-genotypes that suggested 'Delicious' and 'Golden Delicious' were the parents. S-genotyping results supported controlled pollination test results . The genotypes of the five triploid cultivars examined were consistent wit h the unreduced gamete being contributed by the female parent. Although a l arge number of S-genotypes is available in apple, artificial selection or r epeated use of the same cultivars as parents appears to have significantly restricted the number of compatibility groups associated with commercial cl ones. In controlled reciprocal crosses between two cultivars of known S-gen otypes, the segregation of S-genotypes and S-alleles was 1:1:1:1, the ratio expected for random pairing of alleles.