In Vitro Regeneration of Four Commercial Cotton Cultivars (Gossypium hirsutum L.) Grown in Xinjiang, China

Genetic improvement of cotton through biotechnology has been limited by lack of an efficient regeneration system. An efficient somatic embryo production and maturation procedure was thus developed to regenerate plantlets from hypocotyls of cotton cultivars Xinluzhong 20, Xinluzao 24, Xinluzao 33, and 03298 grown in Xinjiang. Calli were effectively produced by 0.01 to 0.10 mg L−1 kinetin (KT) and 0.10 mg L−1 2,4-dichlorophenoxyacetic acid (2,4-D), with a better result by 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 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 were further developed into plantlets in MSBF medium under the conditions of dehydration and ventilation, which were achieved using filter paper on medium and cotton tampon sealing flask. Using this protocol, normal plantlets with strong roots were developed from these cotton cultivars in 6 to 8 months. The successful regeneration protocol established in this study can be used to improve cotton cultivars by genetic engineering.