High frequency androgenesis from isolated microspores of maize.

Anthers from a highly androgenic genotype of maize (139/39-02), when cultured in a modified, liquid YP medium, dehisced within 2-7 days resulting in a stationary suspension of microspores. After 12-15 days, the microspore suspension was found to contain multicellular masses which went on to produce macroscopic embryo-like structures within 20-25 days of culture initiation. Embryogenic callus could be obtained by transferring microspore-derived embryos onto a modified N6 medium supplemented with 2.5 mg/l dicamba and 0.1 mg/l 2,4-D. Subculture onto hormone-free medium resulted in plant regeneration. Over 400 embryo-like structures per 100 anthers cultured have been obtained from liquid induction medium as compared to 55 embryos per 100 anthers cultured on an agar-solidified medium. Approximately 5-25% of these embryo-like structures went on to produce callus from which plants could be recovered. Mechanical isolation of microspores from anthers precultured for 0, 3, and 7 days also resulted in embryo production and plant regeneration. This represents the first report of plant recovery from isolated maize microspores. The use of a liquid induction medium applied to a highly androgenic genotype allows for the production of large numbers of microspore-derived plants and provides a single, haploid cell regeneration system for maize.