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 w ith the 'Topred' sport of 'Red Delicious', the main cultivar in Israel. Thi s incompatibility led to reduced pollination potency, explaining the low yi eld obtained from 'Topred' rows adjacent to 'Jonathan'. Hence, the importan ce of identifying the level of compatibility for all 'Topred' pollinators b ecame 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, w hich were cloned in this study, it was evident that apart from 'Jonathan', the common pollinators for 'Topred' are fully compatible with it. The abili ty to identify all S-alleles in the 'Topred' orchard was also utilized to r esolve the observation that, although 'Topred' is considered self-incompati ble, 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-pollinat ion, perhaps the consequence of fertilization by wind carried pollen. Hence , the notion that 'Topred' is totally self-incompatible was confirmed and t he efficiency of progeny PCR S-allele analysis for the determination of the pollen donor was exhibited.