S-allele determination of Pillnitzer apple cultivars

Apple (Malus sp.) has an S-RNase-based gametophytic self-incompatible system ruled by a multi-allelic S-locus. Self-pollination of apple cultivars is hindered and pollinators with at least one different S-allele are required for successful fertilization. To determine the S-allele combination in cultivars and advanced breeding clones bred in Dresden-Pillnitz, 69 genotypes from Pillnitz and 65 cultivars, clones, and wild apple species accessions were analyzed. Cultivars with known S-alleles were selected for comparison of the data. The alleles S2, S3, S5, S16b, and S24 were present in 64 of the genotypes bred in Pillnitz. The most abundant alleles in the other genotypes were S2, S3, S5, and S9. Only one S-allele could be determined for the wild species accessions M. ×arnoldiana MAL0004, M. floribunda 821, and ‘Russian Seedling’, and the determination of S-alleles for M. fusca MAL0045 failed. A new S-allele, tentatively designated SRegia, was detected in 'Regia'. The analyzed S-allele combination of some cultivars differed from those published, e.g. S2S16b genotype was here determined for 'Pinova' in contrast to S2S9 genotype assigned in the literature. Knowledge about the S-allele status of the cultivars helps in the selection of a suitable pollinator.