Abstract
Stylar proteins were analyzed to establish the self-incompatibility genotype (S-genotype) of several Japanese pear cultivars. The predicted genotypes established by gel electrophoresis were confirmed with pollination experiments. By comparing protein banding patterns of a cultivar with an unknown S-genotype with those of a known one, the genotypes of 'Kisui', 'Aikansui', 'Chikusui', 'Hohsui', and 'Choju' were estimated as S4S5, S4S5, S3S4, S3Sx, and S1Sx, respectively. The first 2 genotypes were confirmed by pollination experiments in the orchards, but the last 3 cultivars were not. 'Chikusui' has a relatively low fruit set when crossed with 'Shinseiki' (S3S4) and 'Seigyoku' (S3S4) over 4 years tested, but, at present, we can not conclude that the combinations are incompatible. Banding patterns of 'Hohsui' indicate that its genotype may be S2S3, S3S4 or S3S5, but at the same time, it is clearly compatible with cultivars possessing the same S-genotypes. A reciprocal cross of 'Hohsui' with the tester cultivar possessing S3-allele was also fertile, indicating that 'Hohsui' is not homozygous for S3-allele. An apparent S1-protein band and a faint S4- or S5-band were observed in 'Choju' style by gel electrophoresis. A detailed discussion including genealogical backgrounds of S-genotypes of 'Hohsui' and 'Choju' is included in this text.
