The effect of TDZ on organogenesis and somatic embryogenesis in pigeonpea (Cajanus cajan L. Millsp)

The effect of TDZ was studied on seedlings of pigeonpea. Seedlings raised from decoated seeds on MS basal medium supplemented with a low concentration of TDZ (0.05-1.0 muM) induced multiple shoots, and an intermediary concentration (5.0 muM) produced clusters of leafy structures, and a higher concentration (10.0 or 20.0 muM) completely switched the regeneration pathway by inducing somatic embryos at the cotyledonary nodal region that developed into mature plants. Seedlings raised from seeds with intact seed coats, failed to produce multiple shoots or embryos under the same conditions. Multiple shoots were also induced from seeds exposed for short duration (24 h-14 days) on MS basal medium containing 10.0 muM TDZ and then transferred to MS basal medium. However, continuous exposer to TDZ is required for somatic embryogenesis. Histological examination revealed direct shoot organogenesis and somatic embryogenesis. All the shoots developed prolific roots at their basal ends on MS basal medium containing 2.5 muM 1BA. The well-developed plantlets were established in pots containing soil with 95% survival rate, and all the surviving plants were morphologically normal to plants raised from seeds. The present protocol is simple rapid (the initiation of tissue cultures to transplantation of regenerants to soil completed in 8 week) with high regeneration frequency (75%) and applicable to seven genotypes. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.