In Vitro Morphogenesis in cultivated varieties of Sorghum bicolor (L.) Moench

In vitro plant regeneration is achieved in cultivated varieties of Sorghum bicolor from immature inflorescence explants through embryogenic callus induction and also organogenesis. Explants were cultured on modified Murashige and Skoog's medium, supplemented with 2% sucrose and 0.8% agar and 1.5 mg/l 2,4-D for callus induction. Two types of calli were identified in the second week. One was white, compact, nodular, embryogenic callus (e.callus) and another one was unorganized, pale yellow coloured and non-embryogenic. Embryogenic callus induction ranged from 44% to 84%. Variety IS 3477 exhibited high frequency of embryogenic callus (e. callus) (84%) while IS 27703 displayed low callusing frequency (44%). Embryogenic callus upon transferring onto regeneration medium containing 1 mg/l 6-benzylaminopurine exhibited shoot initiation within 4 days after transfer of the calli. Shoot induction was maximum at 1 mg/l of BAP. Maximum number of shoots (13) were observed per culture in IS 2898. Root induction was noticed after transferring the shoots onto medium containing 1 mg/l indoleacetic acid. In addition to maximum induction of e.callus and highest number of shoot induction, long term maintenance of e.callus was another remarkable feature of the above varieties and hence it is advantageous to use them in plant breeding programmes aimed at improvement of this crop.