Cloning of a new S-RNase and development of a PCR-RFLP system for the determination of the S-genotypes of Japanese pear

Abstract

Japanese pear exhibits gametophytic self-incompatibility that is controlled by the multiallelic S-locus. The S-locus encodes polymorphic S-RNase for the pistil-part S determinant in Japanese pear. Information about the S-genotypes is important for the selection of pollen donors for fruit production and breeding of Japanese pear cultivars. We determined the S-genotypes of three Japanese pear cultivars, 'Kinchaku' (S4Sk), 'Natsuhikari' (S 3S4) and 'Wakahikari' (S3S4), and an F1 hybrid cultivar between a Japanese pear cultivar and a European pear cultivar, 'Oharabeni' (S9Se), by PCR-RFLP analysis of S-RNase. A new Sk-RNase allele was identified in 'Kinchaku', and full length cDNA encoding Sk-RNase was sequenced. The S k-RNase was not effectively amplified by the previously published primers. We designed a new PCR primer combination for the amplification of the Sk-RNase allele in addition to the S1- to S 9-RNase alleles of Japanese pear, and developed a PCR-RFLP system for identifying the S1- to S9- and Sk-alleles.