DETECTING CROSS-INCOMPATIBILITY OF 3 NORTH-AMERICAN APRICOT CULTIVARSAND ESTABLISHING THE FIRST INCOMPATIBILITY GROUP IN APRICOT

Laboratory and orchard tests have shown that the apricot (Prunus armen iaca L.) cultivars 'Hargrand', 'Goldrich', and 'Lambertin-1' are cross -incompatible. All three cultivars are from North American breeding pr ograms and have 'Perfection' as a common ancestor. In orchard tests, c ompatible pollinations resulted in 19% to 74% fruit set, while incompa tible pollinations resulted in <2% fruit set. Microscopic examination showed that, in incompatible pollinations, pollen tube growth was arre sted in the style, most frequently in its third quarter, and that the ovary was never reached. It is proposed that self-incompatibility in a pricot is of the gametophytic type, controlled by one S-locus with mul tiple alleles, and that these three cultivars are S1S2.