Observations on Inheritance of Male Sterility in Apricot

Male sterility is defined as the deviant condition in normally bisexual plants when no viable pollen is formed (Frankel and Galun, 1977). Male sterility has been exploited as an effective tool to aid hybrid seed production in many crops. Using this trait, seed producers can transform one inbred from a planned hybridization into a “female” line, thereby ensuring seed of hybrid origin on the male-sterile parent (Janick, 1972). However, male sterility is an undesirable characteristic in scion cultivars of Prunus to be used for fruit production because this trait would restrict yield in large monocultural production blocks. From the viewpoint of an apricot breeding program, male sterility is a characteristic to be avoided (Scott and Weinberger, 1944). A review of apricot (Prunus armeniaca L.) pollen fertility (Burgos, 1991) indicated that only two cases of male-sterile apricot cultivars (‘Arrogance’ and ‘Colorao’) have been described (García et al., 1988). In this paper we show where several male-sterile trees were observed in progenies from controlled hybridizations in P. armeniaca, and we propose a preliminary inheritance model of the trait. Nine different crosses with a total of 378 trees were scored for the male sterility trait. Male-sterile anthers can be distinguished visually from normal fertile anthers during the bloom period. Shrunken, discolored anthers are indicative of male-sterile pollen and provide a sharp contrast to the swollen, yellow appearance of normal pollen-fertile anthers (Connors, 1927). Several samples of shrunken, discolored anthers were chosen randomly to