Microspore mutagenesis and in vitro selection for resistance to soft rot disease in Chinese cabbage (Brassica campestris L-ssp pekinensis)

Plants resistant to soft rot disease were produced by in vitro-mutagenesis and -selection using a microspore culture system in Chinese cabbage. The ef fect of ultraviolet (UV) irradiation on microspore embryogenesis was invest igated. Embryo production decreased with increasing duration of UV-irradiat ion and the LD50 was estimated to correspond to an exposure of 12 s. Cultur e filtrate of soft rot bacteria caused a reduction of embryo formation from microspores and plant regeneration from microspore-derived embryos, sugges ting that the culture filtrate is phytotoxic. After 6,657 embryos derived f rom UV-irradiated microspores were selected on a medium containing a soft r ot culture filtrate, 250 plantlets were regenerated. When their progenies w ere assessed for resistance to soft rot disease, three lines showing a mark edly increased resistance to the disease were obtained. The resistant plant s are considered to be mutants produced by in vitro-mutagenesis.