Genomic characterization of self-incompatibility ribonucleases in the Central Asian pear germplasm and introgression of new alleles from other species of the genus Pyrus

The Pyrus species exhibit the so-called S-RNase based gametophytic self-incompatibility system, which is considered to be the most widespread self-incompatibility system among flowering plants. In this study, 57 Iranian pear (Pyrus communis L.) domestic cultivars and wild genotypes, plus 21 European pear cultivars used as references, were genotyped adopting a PCR-based genotyping assay using consensus and allele-specific primers. The results revealed traces of significant genetic contribution in the Iranian traditional varieties and genotypes from other Pyrus species; the genetic contribution of Japanese pear clearly emerged with the detection of some Pyrus pyrifolia S-RNase alleles. Moreover, our results highlighted the presence of three new S-RNase alleles (named S126, S127, and S128) that were not previously identified in P. communis, possibly introduced in the germplasm of cultivated pear through gene transfer from other cultivated or wild species.