In vitro shoot tip multiplication of cowpea Vigna Unguiculata (L.) Walp

Shoot multiplication was induced in cowpea, cv. Georgia-21, from shoot tip explants. Shoot tips, 5 mm long, were isolated from in vitro-grown seedlings and cultured on MS medium containing$N^6-benzyladenine$(BA) at 1, 2.5, or 5 mg/liter ($4.4, 11.1, or 22.2 \mu M$) or 6-furfurylaminopurine (kinetin) at 1, 2.5, or 5 mg/liter ($4.6, 11.6, or 23.2 \mu M$) combined with 2,4-dichlorophenoxyacetic acid (2,4-D) at 0.01, 0.1, or 0.5 mg/liter ($0.05, 0.5, or 2.3 \mu M$) or naphthaleneacetic acid (NAA) at 0.01, 0.1, or 0.5 mg/liter ($0.05, 0.5, or 2.7 \mu M$). Cultures were maintained at a 12-h photoperiod ($40 \mu mol \cdot m^{-2} \cdot s^{-1}$) and$23 \pm 2\textdegree C$. Treatments with BA induced greater shoot proliferation than those with kinetin. The highest number of shoots was produced on 5 mg ($22.2 muM$) BA per liter in combination with NAA or 2,4-D at 0.01 mg/liter (0.05 μ M). Callus proliferated from the basal ends of shoot pieces in all treatments. The cultures also formed roots in the presence of kinetin, but not on BA-containing medium. To produce whole plants, the shoots were separated and rooted on 0.1 mg ($0.5 \mu M$) NAA per liter. Resulting plants grew normally under greenhouse conditions. Shoot tips provide an excellent explant source for cowpea micropropagation and can be used for callus induction.