In vitro plantlet regeneration from cotyledons of the tree-legume Leucaena leucocephala

摘要

Two plant regeneration methods applicable to Leucaena leucocephala were developed. In the first method, involving organogenesis via callus formation, cotyledon, hypocotyl and root segments were initiated on MS medium containing different concentrations of N-6-benzyladenine (BA), 2,4-dichlorophenoxyacetic acid (2,4-D), and naphthaleneacetic acid (NAA). Both compact (type I) and friable (type II) calli were obtained from the cotyledon and hypocotyl explants treated with different concentrations of the growth regulators. Shoots were generated only from the friable calli formed from the cotyledon explants. The calli formed from the hypocotyl explants did not generate shoots and the root explants died without forming callus. Cotyledon explants from 3-4 day old seedlings showed maximum callus induction compared to those from older seedlings. In a second method involving direct organogenesis, excised cotyledons were cultured on 1/2 MS medium containing 10-35 mg l(-1) N-6-benzy-ladenine (BA) for 7-14 days. Transfer of the cotyledons to regeneration medium containing low BA resulted in callus formation and subsequent shoot regeneration from the base of the excised cotyledon explants, with up to 100% frequency. Regenerated shoots rooted best on a basal medium containing no growth regulators.