EFFICIENT PRODUCTION OF DOUBLED HAPLOID PLANTS THROUGH CHROMOSOME DOUBLING OF ISOLATED MICROSPORES IN BRASSICA-NAPUS

Three methods of chromosome doubling to produce doubled haploid plants from microspore cultures of Brassica napus were compared: colchicine treatment of microspore-derived plants, microspore-derived embryos, and isolated microspores. In the whole plant treatment, 53 % of the treated plants set seed, but the treatment delayed plant growth and reduced seed set. When microspore-derived embryos were treated with colchicine, the doubling frequency was 32 % (compared to 15 % for spontaneous doubling). Direct colchicine treatment of isolated microspores resulted in a doubling efficiency of 70 % of the whole plants. This treatment also stimulated embryogenesis in microspore culture, leading to increased plant regeneration. Thus, direct chromosome doubling of isolated microspores is efficient and more than 10 000 doubled haploid plants have been produced in this manner in the past three years in order to accelerate the plant-breeding process.