In vitro somatic embryogenesis in callus cultures of Azadirachta indica A. Juss. -: a multipurpose tree

Plant regeneration via somatic embryogenesis was achieved in embryogenic callus cultures derived from immature zygotic embryos 40 days after anthesis of Azadirachta indica A. Juss. on semisolid basal Murashige and Skoog (MS) salts and vitamins supplemented with 1.11 mu M 6-benzylaminopurine (BA) and 4.52-6.78 mu M 2,4-dichlorophenoxyacetic acid (2,4-D). The globular-stage embryos were induced when the callus was transferred to medium with 1.11 mu M BA and 0.45 mu M 2,4-D. The highest average number of somatic embryos per 200 mg of callus was 152.8 after 8 weeks of culture on the medium. Maturation and germination of the somatic embryos were achieved on half-strength MS salts and vitamins supplemented 0.38-0.94 mu M abscisic acid (ABA) and 2% (w/v) sucrose. The maximum percentage (64.2%) of germination was obtained with 0.94 mu M ABA within 2 weeks of culture. Somatic embryo-derived plantlets were acclimatized in a greenhouse and subsequently showed normal growth. This efficient protocol will be helpful for propagating elite clones on a mass scale and will also be useful for genetic transformation study.