An improved protocol has been developed for somatic embryogenesis and plant regeneration of recalcitrant cottoncultivars. High callus frequencies and embryogenic tissue were developed in MSB medium supplemented with gradientconcentrations of KT and 2,4-D, their concentration decreasing from 0.1 to 0.01 mg L-1. Somatic embryos were successfullyincubated in 1/2 macronutrient MSB suspension supplemented with 0.5 g L-1 glutamine and 0.5 g L-1 asparagine. Decreasein macronutrient concentration of MSB significantly alleviated browning and was beneficial to suspension cells.Transformation of somatic embryos into plants was induced in MSB medium supplemented with 3% sucrose, 0.5 g L-1glutamine, 0.5 g L-1 asparagine, and 6.0 g L-1 agar. The effect of sucrose as carbohydrate was better than that of glucose forplant germination. Using this protocol, regenerated plantlets from the CCRI521 and Zhongzhi86-6 reached to as much as19.6 and 18.5% somatic embryos, respectively.
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