High frequency somatic embryogenesis and plant regeneration of an elite Chinese cotton variety

An elite Chinese cotton (Gossypium hirsutum L.) cultivar Simian-3 was chose n for tissue culture. Callus with a high frequency of somatic embryogenesis , somatic embryos, and regenerative plants was obtained. Callus was induced from three types of explants on MSB (MS salts with B-5 vitamins) medium su pplemented with zeatin (ZT) only, but the percentage of callus induction an d growth of callus varied. It appeared that it was much easier to induce ca llus from hypocotyl than cotyledon or root explants. The concentrations of ZT were critical to the induction and proliferation of callus. The optimum ZT concentration for callus induction was 3.0 similar to5.0 mg/L. Two kinds of callus could be identified after 70 days of culture: embryogenic and no nembryogenic callus. Embryogenic callus developed into somatic embryos at v arious stages after 20 days of subculture. The capability of embryogenesis depended on the explant types. The root was the most responsive explant for production of somatic embryos, the hypocotyl was the next, and the cotyled on was the last. Moreover, a low concentration of ZT was advantageous to th e induction of embryogenic callus. 2,4-dichlorophenoxyacetic acid (2,4-D) p romoted the proliferation of embryogenic callus, but had a negative effect on the differentiation and germination of somatic embryos. Addition of acti vated charcoal or a proper combination of ZT and 3-indoleacetic acid (IAA) could promote the production, maturation and germination of somatic embryos . The best medium for the proliferation of embryogenic callus was ZH medium (Zhang et al., 1996) with 1.0 mg/L 2,4-D, 0.5 mg/L kinetin (KT) and 0.5 mg /L ZT. The best medium for the differentiation and germination of somatic e mbryos was MSB with 0.1 mg/L ZT and 2 g/L activated charcoal. An efficient protocol for the production of high frequency somatic embryogenesis and pla nt regeneration of an elite cotton variety Simian-3 has been developed. Com plete plants could be regenerated through somatic embryogenesis from hypoco tyl, cotyledon and root explants in 3-4 months.