Colchicine, an efficient genome-doubling agent for maize (Zea mays L.) microspores cultured in anthero

The construction of maize genotypes with high haploid induction capacity ma de it possible to study the effect of colchicine on maize androgenesis in v itro. Anther cultures of three hybrids were treated with 0.02% and 0.03% co lchicine for 3 days at the beginning of microspore induction. Colchicine ad ded to the induction medium had no negative influence on the androgenic res ponses (anther induction, induction of structures of microspore origin and their regeneration ability) of the genotypes examined. However, significant ly higher fertility was observed in plants originating from colchicine-trea ted microspores, especially at 0.03%. Cytological examinations showed that colchicine treatment before the first microspore division efficiently arres ted mitosis and resulted in homozygous doubled-haploid microspores. Under t he experimental conditions, the antimitotic drug had no later effect on the division symmetry of the microspore nucleus, and unequal divisions remaine d dominant. Callus formation from the induced microspores seemed to be more typical (ranging between 60-70%)! but embryo frequency was increased by ap proximately 10%, especially at the higher colchicine concentration. These r esults suggest that the mechanism of colchicine action in premitotic maize microspores may differ from that previously observed in wheat.