Abstract: To identify S-genotypes of pear cultivars or a few types of wild species native to China，S-RNase specific PCRs were used. After cloning and sequencing of PCR products , the S-genotypes of 20 pear cultivars or wild species individuals were determined. Subsequent sequence analysis showed that 'Aolian' (S_pS₃₂) from Pyrus. sinkiangensis Yü, 'Diaodan'(S_dS_e) from P. phaeocarpa Rehd, 'Shageda'(S₃₆S_d) from P. xerophila Yü and one type of Xingyeli(S₂₂S_c) originated from China shared some S-RNases with species from P. communis , which provided with evidence that S-RNase alleles occurred before the divergence of oriental and occidental pear. Two novel S-RNases were also discovered in 'Maili' and 'Neimenggushanli' in P. ussuriensis, and deposited as S40-, S41-RNase under the accession numbers of DQ903313 and DQ988687, respectively, whose deduced amino acid sequences showed high similarities to S₁₁-RNase(100% ) and S₆-RNase (94.4%) in Malus, respectively. The high similar score between S-RNase in Pyrus and Malus indicated that S-RNase existence predated the speciation between Pyrus and Malus.

Key words: Pyrus, Self-incompatibility, S-genotype, S-RNase gene