IN-VITRO REGENERATION OF THE TROPICAL MULTIPURPOSE LEGUMINOUS TREE SESBANIA-GRANDIFLORA FROM COTYLEDON EXPLANTS

A system using cotyledon pieces as explants and a BAP/NAA containing m edium was developed for in vitro mass propagation of Sesbania grandifl ora, a tropical nitrogen-fixing leguminous tree. The age and the light ing conditions of seedlings providing the explants were shown to be cr itical factors for both bud induction and bud elongation. Optimal choi ce for an efficient and reproducible bud induction process consisted o f dark-grown seedlings, 24/36 h-old-post-imbibition, that yielded up t o 96% of explants producing more than 30 buds each, after one week in culture. Bud development occurred throughout a direct organogenesis pa thway, from the proximal and adaxial cut surface of the explants as pr oved by histological studies. Additional sites of regeneration were al so obtained after wounding on the epidermal surface of explants, sugge sting a large distribution of regenerative cells all along the explant s. Bud elongation, i.e. stem differentiation and leaf growth, was impr oved by bud isolation from cotyledon explants and their further subcul ture in liquid bud elongation media for one week. Rooting was obtained on an auxin medium after 3 weeks and plants were established in soil with 92% success.