HIGH-FREQUENCY PRODUCTION OF DOUBLED HAPLOID PLANTS OF BRASSICA-NAPUSCV TOPAS DERIVED FROM COLCHICINE-INDUCED MICROSPORE EMBRYOGENESIS WITHOUT HEAT-SHOCK

This report describes a very high genome doubling efficiency of Brassi ca napus cv. Topas plants, derived from microspores induced to undergo embryogenesis with a colchicine treatment, without the use of a heat treatment. The plants showed normal growth and development, and 90% we re fertile. In contrast, only 6% of the plants derived from heat-induc ed embryos were fertile diploids. All cytological analysis of the prog eny of fertile plants showed 2n=38 chromosomes. These results show tha t colchicine can simultaneously induce microspore embryogenesis and do uble the ploidy level to produce doubled haploid plants.