Analysis of S-alleles by PCR for determination of compatibility in the 'red delicious' apple orchard

In a previous study, the apple 'Jonathan' was shown to be semi-compatible with the 'Topred' sport of 'Red Delicious', the main cultivar in Israel. This incompatibility led to reduced pollination potency, explaining the low yield obtained from 'Topred' rows adjacent to 'Jonathan'. Hence, the importance of identifying the level of compatibility for all 'Topred' pollinators became apparent. By analysing S-allele by PCR with primers for the various S-alleles of the cultivars in the 'Topred' orchard, including S10 and S28, which were cloned in this study, it was evident that apart from 'Jonathan', the common pollinators for 'Topred' are fully compatible with it. The ability to identify all S-alleles in the 'Topred' orchard was also utilized to resolve the observation that, although 'Topred' is considered self-incompatible, self-pollinated, net-caged, 'Topred' flowers set some fruit. Applying PCR-analysis of S-alleles to the progeny of the suspected self-pollinated 'Topred' fruit revealed that the fruit-set was the outcome of cross-pollination, perhaps the consequence of fertilization by wind carried pollen. Hence, the notion that 'Topred' is totally selfincompatible was confirmed and the efficiency of progeny PCR S-allele analysis for the determination of the pollen donor was exhibited.