Abstract:

Many restrict factors still remain in cotton genetic transformation, which requires appropriate tissue followed by regeneration. Long tissue culture duration, unpredictability of tissue culture, and a high degree of genotype dependence are more troublesome in plant regeneration of cotton. The objectives of this study were to examine some factors (including hormone combination, salts of ammonium, Fe²⁺ content and genotypes) significantly affect the efficiency of regeneration and transformation in cotton and optimize the somatic embryogenesis of upland cotton using 22 cultivars including 10 cultivars from Yellow River valley, 10 cultivars from Yangtze River valley, and two highly responsible genotypes Coker 201 and YZ^-1. Most of the genotypes showed high regenerability under the IBA/KT hormone regime. NH4+ was necessary during the callus induction and subculture, but it should be omitted and replaced by NO3+ during somatic embryogenesis. The content of Fe²⁺ was the key factor for callus induction and differentiation. The differentiation medium could significantly improve the conversion from the fast growing callus to embryogenic callus with the FeSO₄ concentration of 56 mg L^-1. Under the optimized culture procedure, most of the genotypes collected from the two valleys showed the similar regeneable abilities, except a relative longer time taken during the somatic embryogenesis of cultivars from the Yangtze River valley. The somatic embryogenesis and plant regenerations of eight genotypes(i.e. Ek3, Ek5, Em20, Em23, Ym9, Ym12, Yz73, and Ym1221) firstly obtained.

Key words: Cotton (Gossypium hirsutum L.), Genotype, Somatic embryogenesis, Regenerability