Abstract: Cotton grown in Xinjiang is critical to successful cotton production in China. Genetic improvement in cotton via biotechnology is limited due to lack of an efficient regeneration system. Here, an efficient somatic embryo procedure was developed to regenerate plantlets from hypocotyls of cotton cultivars Xinluzhong 20, Xinluzao 24, Xinluzao 33 and 03298 grown in Xinjiang. Calli were effectively produced on the medium with 0.01–0.10 mg L^-1 Kinetin (KT) and 0.10 mg L^-1 2,4-Dichlorophenoxyacetic acid (2,4-D), especially with 0.02 or 0.10 mg L^-1 KT and 0.10 mg L^-1 2,4-D. Split hypocotyl segments and double amounts of KNO₃ in the medium during induction of calli were beneficial to the emerge of embryogenic calli. Embryogenic calli and globular-stage somatic embryos were effectively initiated with high concentration of KT and low concentration of 2,4-D in ECM media (0.05 or 0.10 mg L^-1 KT and 0.01 mg L^-1 2,4-D). Embryos further developed into plantlets in MSBF medium under conditions of dehydration and ventilization achieved respectively by filter paper on medium and cotton tampon sealing flask. Using this proto-col, normal plantlets with strong roots well developed from these cotton cultivars for 6 to 8 months, increasing the range of cotton genotypes that can be regenerated. The successful regeneration protocol established in this study can be used to improve cotton cultivars by genetic engineering.

Key words: Gossypium hirsutum L., Regeneration, Somatic embryogenesis