Rachilla: An additional source for embryogenic callus induction and transformation in Oryza sativa L.

Rachilla, the portion joining sterile glumes to palea and lemma, in the rice spikelet has been found to be an additional source of embryogenic callus and transformation, Induction of callus from rachilla was distinct in inflorescences of size 3cm or above, Inflorescence length ranging between 3 and 5 cm was found to be ideal for induction of callus from rachilla, The response was optimum when the florets were of 2-5 mm, The callus induced from rachilla is lustrous, friable and embryogenic, and facilitated much faster establishment of uniform embryogenic suspension cultures (3-4 weeks) compared to seed-derived calli (6-8 weeks). Though the frequency of callus induction from rachilla is low compared to mature seed-derived calli, the regeneration potential of the former is higher. The rachilla callus could be used for bombardment either directly or after establishment of suspension cultures. The calli derived from rachilla did show advantage over seed-derived calli by hastening the process of establishing suspension cultures or for genetic transformation.