Identification of S-genotypes in local pear cultivars from the Yellow River area

There are many endemic pear germplasm resources distributed in the ancient Yellow River area. Identification of pear S-genotype is an important basis for pear breeding and production. Using a pair of consensus primers specific to pear S-RNase, PCR amplification from genomic DNA of 17 local cultivars were carried out. Then the PCR products were purified and sequenced. The PCR amplification results showed that all cultivars contained two S-RNase fragment bands. Dangshansuli, Dangshanxinsu, Dangshanfusu, Dangshanxisu, Zipicao, Qingpicao, Fusu, Hanli, Xiangmianli, Heli, Wanli No.2, Wanli No.5 and Wanli No.6, these 13 cultivars all contained two common bands, one identified as S₃₄-RNase (DQ269500), another fragment sequence have 100% homology with S₇-RNase (AB002143) and S₂₇-RNase (EF643640) sequences in GenBank. Based on the analysis of the S-gene, it was confirmed that S₇-RNase and S₂₇-RNase exon amino acid sequences are identical. Therefore, the S-genotypes of Dangshansuli, Hanli, Xiangmianli, Dangshanfusu, Qingpicao, Jizaosu, Heli, Lianglizaosu, Dangshanxinsu, Wanli 4, Wanli 6 and Dangshanxisu, were identified as S₇ S₃₄ or S₂₇ S₃₄. The other five pear cultivars were identified as, Shuihulu (S₁₉S₃₄), Waiweibacao (S₁S₁₉), Jizhuahuang (S₁S₃₄), Wanli 5 (S₃S₃₄), Zisu (S₁₉S₃₄), Jizhuahuang (S₁S₃₄). Through the identification of the S-genotypes, out of 17 cultivars, there are 16 cultivars tested contained S₃₄-RNase. This implies that S₃₄-RNase is the dominant S-RNase of pears in the ancient Yellow River region.