Distribution of S-alleles among Korean apples by PCR and cross-pollination.

To acquaint correct information about the fertilizability and analyze S-allele based genetic diversity among Korean apples, we investigated self-incompatibility genotypes by PCR and cross-pollination tests in field. As a consequence, S-genotypes of Korean apples were distributed within narrow genetic diversity as S1S3 for ‘Hongro’ and ‘Saenara’; S1S9 for ‘Gamhong’ and ‘Manbok’; S3S5 for ‘Seokwang’; S3S9 for ‘Sunhong’, ‘Seohong’, ‘Chukwang’, and ‘Hwahong’. Coupled with cross-pollination experiments in field, our results provide support for the view that apples are fully compatible when both of their S-loci differ and semi-compatible when they carry one different and one identical S-locus. Furthermore, the results of this study indicate that S-alleles have to be extended to various genotypes for Korean apple breeding.