The pear (Pyrus pyrifolia) has gametophytic self-incompatibility (GSI). To elucidate the S-genotypes of Korean-bred pear cultivars, whose parents are het-erozygotes, the PCR amplification using S-RNase primers that are specific for each S-genotype was car-ried out in 15 Korean-bred pear cultivars and 5 Japa-nese-bred pear cultivars. The difference of the frag-ment length was shown in the following order: S6 (355 bp) < S7 (360 bp) < S1 (375 bp) < S4 (376 bp) < S3 and S5 (384 bp) < S8 (442 bp) < S9 (1,323 bp) < S2 (1,355 bp). We analyzed the sequence of the S-RNase gene, which had introns of various sizes in the hypervariable (HV) region between the adjacent exons with a fairly high homology. The sizes of the introns were as follows: S1 = 167 bp, S2 = 1,153 bp, S3 = 179 bp, S4 = 168 bp, S5 = 179 bp, S6 = 147 bp, S7 = 152 bp, S8 = 234 bp, S9 = 1,115 bp. There were five conservative and five hypervariable regions in the introns of S1, S3, S4, S5, S6 and S7-RNases. A pairwise comparison of these introns of S-RNases revealed homologies as follows: 93.7% between S1- and S4-RNases, 93.3% between S3- and S5-RNases and 78.9% between S6- and S7-RNases. PCR-RFLP and S-RNases sequencing determined the S-genotypes of the pear cultivars. The S-genotypes were S4S9 for Shinkou, S3S9 for Niitaka, S3S5 for Housui, S1S5 for Kimizuka-wase, S1S8 for Ichiharawase, S3S5 for Mansoo, S3S4 for Shinil, S3S4 for Whangkeumbae, S3S5 for Sunhwang, S3S5 for Whasan, S3S5 for Mihwang, S5S? for Cheng-silri, S3S5 for Gamro, S3S4 for Yeongsanbae, S3S4 for Wonhwang, S3S5 for Gamcheonbae, S3S5 for Danbae, S3S4 for Manpoong, S3S4 for Soowhangbae and S4S6 for Chuwhangbae. The information on the S-genotypes of pear cultivars will be used for the pollinizer selec-tion and breeding program.

Keywords: Gametophytic Self-Incompatibility (GSI), PCR-RFLP