Genotypic response of cowpea Vigna unguiculata (L.) to in vitro regeneration from cotyledon explants

A plant regeneration system applicable to 17 cowpea genotypes was developed . Cotyledons were initiated on 1/3 MS medium containing 15 to 35 mg N-6-ben zyladenine (BA) per l (66.6 to 155.3 mu M) for 5 to 15 d. For shoot regener ation, the explants were transferred to a medium containing 1 mg BA per l ( 4.4 mu M ). Within 1 wk, shoot formation was visible at the proximal end of the cotyledons. Regeneration percentages (1% to 11%) and the numbers of sh oots (4 to 12 per explant) were significantly influenced by genotype. Cultu re duration and BA concentration in the initiation stage significantly affe cted regeneration capacity. Explants initiated on media containing 15 mg BA per l for 5 d resulted in the highest percentage of explants capable of re generation. Conversely, the highest number of shoots was obtained from expl ants initiated on media supplemented with 35 mg BA per l. Whole plants were obtained on a plant growth regulator-free medium. To our knowledge, this i s the first report of plant regeneration from U.S. commercial cowpea cultiv ars and breeding lines. This system is adaptable to diverse cowpea genotype s and will facilitate cowpea genetic transformation.