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’ (S⁴S^k), ‘Natsuhikari’ (S³S⁴) and ‘Wakahikari’ (S³S⁴), and an F₁ hybrid cultivar between a Japanese pear cultivar and a European pear cultivar, ‘Oharabeni’ (S⁹S^e), by PCR-RFLP analysis of S-RNase. A new S^k-RNase allele was identified in ‘Kinchaku’, and full length cDNA encoding S^k-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 S^k-RNase allele in addition to the S¹- to S⁹-RNase alleles of Japanese pear, and developed a PCR-RFLP system for identifying the S¹- to S⁹- and S^k-alleles.