Induction of multiple shoots and plant regeneration from apical tips of diploid cotton, Gossypium arboreum L.

Protocol ensuring high frequency plant regeneration and induction of multiple shoots from apical tips in diploid cotton, Gossypium arboreum L has been developed. Apical tips (0.5 cm) from two G. arboreum genotypes, LD694 (commercial cultivar) and DS-5 (GMS line), were analyzed for plant regeneration on different media compositions (MS, DKW, N₆, B₅) supplemented with various concentrations of growth regulators (BAP, Kin, IBA). Maximum plant regeneration (87% in LD 694 and B3% in DS-5) was obtained on ½ strength MS medium containing 0.2% (w/v) activated charcoal. Regenerated plants were subjected to multiple shoot induction by transferring on media supplemented with different concentrations of BAP ranging from (1 mg l⁻¹ to 5 mg l⁻¹). The number of shoots formed per shoot apex ranged from 2 to 18, and 65% of the shoot apices induced multiple shoots on DKW medium supplemented with 1 mg l⁻¹ BAP. Rapid and vigorous shoot growth was obtained on liquid DKW medium supplemented with 560 mg l⁻¹ proline, 500 mg l⁻¹ casein hydrolysate and 10 ppm GA₃. Ultimately, 35% of the shoots induced roots upon transfer to ½ strength MS solid medium supplemented with 0.2% (w/v) activated charcoal. The developed protocol can be used for maintenance and multiplication of elite material such as male sterile and transgenic lines as it allows formation of multiple shoots.