S-RNase genotypes of apple cultivars grown in Japan and development of a PCR-RFLP method to identify the S6- and S21-RNase alleles

Accurate knowledge of the S-genotypes of apple cultivars is important for use in a breeding programme. We analysed the S-RNase genotypes of 65 apple (Malus X domestica Borkh.) cultivars grown in Japan that had 'Cox's Orange Pippin', 'Jonathan', or 'Delicious' as their progenitors, using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analyses. In this process, we developed a PCR-RFLP method to identify the S-6- and S-21-RNase alleles that may be present in 'Cox's Pomona'. We showed that one of the alleged parents of 'Allington Pippin','Cox's Pomona', 'Merton Worcester', and 'Webster' might be wrong. We also showed that the S-16a- and S-16b-RNase alleles were functionally identical, and that 'Komitsu' was produced by a cross between 'Jonathan' X 'Starking Delicious'.