Improved plant regeneration in cowpea through shoot meristem

Abstract: Cowpea is a highly recalcitrant nutrient-rich leguminous vegetable crop. Efforts to genetically transform cowpea with insect-resistant genes remains a challenging task due to lack of an efficient regeneration system. We have established an efficient regeneration system in cowpea through shoot meristem. Shoot meristems were isolated from embryos that were precultured for 3-5 days on Murashige and Skoog (MS) medium containing 8.9 uM benzylaminopurine (BA). The isolated shoot meristems were cultured on MS medium containing 0.89 uM BA. After 3-4 weeks, multiple shoots were separated from the explant and cultured on half-strength MS medium for elongation and rooting. More than 90% of the regenerants formed roots. The rooted plantlets were transferred first to peat pellets and subsequently to the greenhouse. The plants were allowed to flower and set seed. The efficiency of regeneration in all four cultivars ranged from 76-87%, demonstrating a significant improvement over the published protocols (1-32%). At least six to seven plantlets were obtained from each meristem. The protocol using shoot meristems is simple, efficient, rapid and genotype-independent and may be amenable for transformation through particle bombardment.