Effect of culture conditions on the plant regeneration via organogenesis from cotyledonary node of cowpea (Vigna unguiculata L. Walp)

Abstract

A rapid and efficient regeneration system via organogenesis from cotyledonary node explants of cowpea (Vigna unguiculata L. Walp) has been established. The cotyledonary node explants excised from 4 days old seedlings, placed in vitro on medium containing salts of Murashige and Skoog and vitamins of Gamborg’s media (MSB₅). Adventitious shoots occurred at the basal end of the initiated axillary buds that preexisted at the node regions. BAP at 1.25 mg/l was the optimum for shoot induction. The combination of BAP with IBA had worthless effect on shoots proliferation. The number of adventitious buds was promoted when the seeds were preconditioned with appropriate concentrations of BAP (2 to 3 mg/l), whereas was depressed with higher concentrations of BAP (5 to 15 mg/l). The regeneration system was further optimized due to the presence of cotyledons attaching to the cotyledonary node explants. Explants with two entire cotyledons from 4 days old seedlings produced the greater number of shoots (7.83) after 3 weeks on MSB5 medium supplemented with 1.25 mg/l BAP. Regenerated shoots could well elongate on regulator-free basal medium and well root with 100% of success on the half strength medium supplemented with various concentrations of IBA (0, 0.1, 0.3, and 0.5 mg/l). The regenerated plantlets were cultured on the pots containing sterilized vermiculite and soil (1:1) with 27% of survival.

Key words: Cowpea, plant regeneration, cotyledonary node, organogenesis.