Identification of S-genotypes of six pear cultivars and sequence analyses of S45-RNase.

Pear is a typical fruit tree of gametophytic self-incompatibility(GSI).This characteristic results in low yield under the condition of natural pollination,so it is necessary to arrange varieties for pollination or to perform artificial pollination to increase the yield.Classifying pear S-genotypes is useful for breeding programs and help to the selection of suitable pollina-tors.Using a pair of primers specific to pear S-RNases,PCR amplification from genomic DNAs of six Chinese pear cultivars was carried out.Then the PCR products were extracted,cloned and sequenced.The amplified fragments were assigned to their respective S-RNases by Blast analysis.The S-genotypes of the six tested self-incompatible cultivars were identified as follows: Baozhu(S22S42),Banjinsu(S5S21),Zhangyechangba(S19S22),Guidechangba(S19S22),and Shuidonggua(S15S45).S45-RNase was deposited in GenBank under the accession number of EF643634.S45 showed the highest similar to S26 in the amino acid sequence.But there was five-amino-acid differenec in the hyper variable regions(HV) between S45 and S26.