In vitro adventitious shoot bud differentiation and plantlet regeneration in Feronia limonia L. (Swingle)

In vitro adventitious shoot bud regeneration systems are considered most suitable for Agrobacterium- and biolistics-mediated genetic transformation to obtain transgenic plants. In the present investigation, multiple adventitious shoot buds could be induced directly from Feronia limonia hypocotyl explants inoculated on Murashige and Skoog (MS) medium containing different growth regulators. During the initial phase, the hypocotyl segments nearer to the cotyledons responded quickly compared to those closer to the root. The response, however, was comparable in both the segments in subsequent subculture. Of the various cytokinins, 2.22 mu M 6-benzylaminopurine (BA) proved to be more effective compared to kinetin (Kn). The two-way interaction of BA and Kn significantly influenced shoot regeneration and contributed the most among the interactions studied. The best response, however, was obtained when 2.22 mu M BA and 2.32 mu M Kn were combined. Although the effect of auxins like alpha-naphthaleneacetic acid (NAA) combined with cytokinins evoked a significant response in terms of number of shoot buds, this response did not supersede the effect of combined cytokinins. None of the polyamines tested induced shoot buds on hypocotyl segments. Adventitious shoots were multiplied on MS medium containing 2.22 mu M BA, 6.96 mu M Kn, and 0.05 mu M NAA. More than 60% of the shoots produced roots when cultured on medium containing one-quarter strength MS salts, 1.0% sucrose, 0.6% agar, and 7.36 mu M indole-3-butyric acid. The adventitious origin of shoot buds showing continuous vascular connections was confirmed through histological investigations.