Microspore Developmental Stage and Anther Length Influence the Induction of Tomato Anther Callus

Anthers of L-680A', 'Licato', and 'Ailsa Craig' tomato (Lycopersicon es- culentum Mill.) were plated on Doy's basal medium 1 to determine whether microspore developmental stage and anther length influence anther callus production. Although calli were induced at all stages of anther development, anthers containing prophase I- stage microspores produced the highest frequency of calli. Fewer calli were produced as microspores approached the uninucleate and binucleate pollen stage. Callus diameter also decreased as anther development progressed. Significantly larger calli were pro- duced from prophase I than later-stage anthers. Time of anther harvest (morning vs. afternoon) did not significantly affect callus number or diameter. Anther and flower bud length both were significantly correlated with anther developmental stage, the number of anthers producing calli, and mean calli diameter. In each case, anther length exhibited a significantly better correlation than bud length. Efficient production of haploid or dihap- loid tomato plants from microspores could provide plant breeders with the ability to produce large numbers of homozygous lines from an F 1 plant in just one generation. Al- though the development of haploid or dihap- loid plants from cultured anthers have been demonstrated in several plant species, these techniques have not been widely adapted in tomato, because, until recently, callus pro- duction and plantlet formation rates were <0.7% (Zamir et al., 1980). However, se- lection of either an optimum medium or so- lidification agent can increase the frequency