Identification of pollen donors for the avocado cultivar Gwen in a mixed orchard by isozyme analysis

Abstract

SummaryIsozyme analysis of developing embryos of the avocado cultivar Gwen was conducted to determine the most likely pollen donors of trees in a mixed orchard including ‘Hass’, ‘Ryan’, ‘Reed’, ‘Bacon’, ‘Fuerte’, and ‘Ettinger’. A total of 130 embryos was collected from 12 ‘Gwen’ trees located adjacent to a range of different potential pollen donor cultivars. As some of the cultivars had identical zymograms at some loci, it was not always possible to identify positively a single male parent for a particular embryo. The most important pollen donor was ‘Ryan’ with a definite contribution of 53% and a possible contribution of 86%. Self-fertilization could not be excluded, with a possible frequency of about 5%, and a maximum of 17% pollination was possible with cultivars of flowering type A, the same as ‘Gwen’. Isozyme patterns for 9% of the embryos could not be accounted for by any of the cultivars in the orchard, and was attributed to pollen from nearby orchards. These results show that ‘Gwen’ is predominantly outcrossed by cultivars of the complementary flowering type, and that the major pollinator is ‘Ryan’.