MODIFICATION OF CELL-DEVELOPMENT IN-VITRO - THE EFFECT OF COLCHICINE ON ANTHER AND ISOLATED MICROSPORE CULTURE IN BRASSICA-NAPUS

In an attempt to discover the biological basis of microspore derived embryogenesis, the effect of the antimicrotubule agent colchicine on anther and free microspore embryogenesis was investigated. The microtubule inhibitor colchicine promoted embryogenesis from cultured anthers, both with regard to the number of anthers responding and the number of embryos being produced per anther. A similar promotional response was also observed with cultured microspores, Although the parameters for cultured anthers and free microspores differed, administration of the drug for a short period immediately prior to pollen mitosis I seems to exert the maximum promotional effect. Of the five cultivars of Brassica napus studied, all responded to colchicine treatment. However, the drug did release more embryogenic potential in poor-responding varieties (i.e. Lirawell and Optima) than in the highest responding variety (Topas), Colchicine also resulted in increased embryogenic response in microspores cultured at lower temperatures. These results are considered in terms of models proposed to explain the switch in microspore development from a gametophytic to a sporophytic pathway. The use of colchicine as agent to promote embryogenesis in previously recalcitrant species other than Brassica is also discussed.