S-RNase-based genotyping of seven triploid cultivars of European pear (Pyrus communis L.)

Summary

Several cultivars of European pear (Pyrus communis L.) are triploid (2n = 51), produce little viable pollen, and exhibit S-RNase-based cross-incompatibility. In orchards where triploids are grown, two diploids (one to pollinate the triploids, and the other to pollinate the other diploid) must be inter-planted. In this study, seven European pear cultivars were confirmed to be triploid by flow cytometry analysis. An S-RNase-based, cleaved amplified polymorphic sequence (CAPS) marker system and S-RNase allele-specific PCR were used to genotype these triploids. A comparison of S-genotypes between the triploids and diploids of European pear identified those diploid(s) that could not be used to pollinate the triploids. Pollination tests confirmed the cross-incompatibility between a triploid and a diploid. The S-genotypes of the seven triploids will be useful for pollination management in orchards, and for breeding new cultivars using the triploids as seed parents. In addition, rapid amplification of cDNA ends was used to obtain the full-length sequences of the putative S₂₂- and S₂₃-RNase alleles amplified from the genomic DNA of three of the triploids.