Efficient regeneration from hypocotyl explants in three cotton cultivars

A high frequency in vitro shoot bud differentiation and multiple shoot production protocol from hypocotyl segments of 8 to 10-d-old seedlings of cotton has been developed. Murashige and Skoog (MS) basal medium with Nitsch and Nitsch vitamins was found to be optimal in shoot regeneration. A combination of 2 mg dm⁻³ thidiazuron and 0.05 mg dm⁻³ naphthaleneacetic acid was the most effective for shoot regeneration (76 %) and an average of 10.6 shoots per responding explant. Combination of the cytokinins benzylaminopurine and kinetin induced better regeneration response than their individual treatments. Supplementation of the culture medium with ethylene inhibitor silver nitrate and activated charcoal showed beneficial effects. Optimal rooting was obtained on half-strength MS medium supplemented with 1 mg dm⁻³ indolebutyric acid and activated charcoal. Scanning electron micrographs of in vitro cultured explants revealed that shoot primordia were formed de novo.