DIRECT SOMATIC EMBRYOGENESIS AND PLANTLET REGENERATION FROM SEEDLING LEAVES OF WINGED-BEAN, PSOPHOCARPUS-TETRAGONOLOBUS (L) DC

Excised seedling leaf segments of winged bean [Psophocarpus tetragonol obus (L.) DC.] underwent direct somatic embryogenesis under appropriat e incubation conditions. Initiation and development of the somatic emb ryos occulted using a two-step culture method. The culture procedure i nvolved incubation for 28 days on MS basal medium supplemented with 0. 1-0.5 mg/l NAA and 1.0-2.0 mg/l BA (induction medium) before transfer to MS medium supplemented with 0.1 mg/l IAA and 2.0 mg/l BA (embryo de velopment medium). The initial exposure to low levels of NAA coinciden t with high levels of BA in the induction medium was essential for emb ryogenic induction. Maximum embryogenesis (43.3%) was obtained with 0. 2 mg/l NAA and 2.0 mg/l BA, and at least 14 days on induction medium w ere required prior to transfer to the embryo development medium. The c onversion frequency of cotyledonary embryos was 53.3% upon culture on MS medium containing 0.1 mg/l ABA for 7 days followed by transfer to M S medium supplemented with 0.1 mg/l IBA and 0.2 mg/l BA. Following con version, the regenerated plantlets were transferred to soil and showed normal morphological characteristics.