Effects of Medium Renovation and Colchicine Treatment on Embryogenesis of Isolated Microspores in Brassica rapa ssp. chinensis

Using Brassica rapa syn B campestris ssp chinensis cv Maoshan (a local variety) which had good response to microspore culture as donor plant, the experiment was carried out to evaluate the effects of medium renovation and direct colchicine application on the embryogenesis of isolated microspores The chromosome ploidy level in regenerated plants derived from direct colchicine treatment of microspores was also analyzed in the present experiment The results indicated that the change of liquid NLN 10 medium with 10 % sucrose after 2 d initiation showed a significant increase in embryogenesis (by a 1 5 fold), compared to non medium renovation control In addition, the quality of embryos was greatly improved through medium change Direct colchicine treatment of isolated microspores with the concentration of 0 8 mg/L for 2 d produced the most embryos, and the highest doubling efficiency of 74 3% was obtained Whereas higher colchicine concentrations of 4～20 mg/L were unable to improve embryogenesis, and the adverse effects on embryo germination and plant regeneration were also observed