Factors promoting efficient in vitro regeneration from de-embryonated cotyledon explants of Arachis hypogaea L.

Highly efficient (>90%) protocols were developed for in vitro regeneration from de-embryonated cotyledon explants of peanut (Arachis hypogaea L.). Phytohormone combinations and concentrations, explant source and orientation, period of incubation and the response of genotypes were examined for optimization of the regeneration efficiency. Adventitious shoot primordia could be induced from de-embryonated cotyledon explants when (1) the proximal end of the explant was kept in contact with the shoot induction medium-I supplemented with 5 mg l−1 BAP + 2 mg l−1 2,4-D for 4 weeks, or (2) the distal end was kept in contact with shoot induction medium-II supplemented with only BAP at 20 mg l−1 for the first 2 weeks, followed by subculture in the same medium containing 15 mg l−1 BAP for the next 2 weeks. Orientation of placing the explant on the above media was critical for in vitro regeneration. The factors affecting the morphogenic responses like, repetitive organogenesis, shoot elongation, in vitro flowering and rhizogenesis were examined. Shoot bud formation was genotype independent. Histological studies showed multicellular origin of adventitious shoot primordia. The protocols gave healthy and fertile plants within 4 months