Identification of inconsistent S-genotypes in 15 Chinese pear (Pyrus L.) cultivars

Most pear (Pyrus L.) cultivars exhibit gametophytic self-incompatibility (GSI), controlled by a single S-locus. Cross-compatible cultivars with different S-genotypes must be inter-planted in an orchard for efficient fruit production. Thus, it is essential to identify S-genotypes in order to choose pollinators for fruit production. The S-genotypes of many Chinese pear cultivars have been identified, but some results remain inconsistent. In this study, 15 Chinese pear cultivars with inconsistent S-genotypes were selected for further identification using 37 leaf samples collected from six different regions in China. The S-genotypes of all 15 pear cultivars were determined by polymerase chain reaction (PCR), cloning, and sequencing of the PCR products. The S-genotypes were as follows: 'Baozhuli' (S22S42), 'Cangxixueli' (S5S15), 'Hanxiang' (S12S31), 'Hangqing' (S1S4), 'Jinqiuli' (S3S9), 'Jinfeng' (S17S19), 'Longxiang' (S16S42), 'Nanguoli' (S11S17), 'Pingxiangli' (S(31)Sd), 'Qingkui' (S1S3), 'Qingxiang' (S4S7), 'Qiubai' (S17S19), 'Yaqing' (S4S17), 'Yanbiandaxiangshui' (S12S16), and 'Zaoli18' (S4S28). S-12-RNase (EU117115) and S36-RNase (DQ417607) were identified as the same S-RNase gene by comparing and analysing S-RNase gene sequences in GenBank. Moreover, S-17-RNase (AY249432) and S-34-RNase (DQ269500) contained the same coding regions and an intron, which indicated that they were also the same S-RNase gene. These data should be useful for choosing suitable orchard pollinators and in pear breeding programmes.