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-grow n 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-furfurylamin opurine (kinetin) at 1, 2.5, or 5 mg/liter (4.6, 11.6, or 23.2 mu M) c ombined 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) a t 0.01, 0.1: or 0.5 mg/liter (0.05, 0.5, or 2.7 mu M). Cultures were m aintained at a 12-h photoperiod (40 mu mol.m(-2).s(-1)) and 23 +/- 2 d egrees C. Treatments with BA induced greater shoot proliferation than those with kinetin. The highest number of shoots was produced on 5 mg (22.2 mu M) BA per liter in combination with NAA or 2,4-D at 0.01 mg/l iter (0.05 mu M). Callus proliferated from the basal ends of shoot pie ces 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 lit er. Resulting plants grew normally under greenhouse conditions. Shoot tips provide an excellent explant source for cowpea micropropagation a nd can be used for callus induction.