HORMONAL REGULATION OF ROOT MORPHOGENESIS IN CALLUS CULTURE OF COWPEA (Vigna unguiculata L. WALP)

Morphogenesis in high plants is controlled by manipulating the balance of auxins and cytokinins. In cowpea however, morphogenesis is not fully understood and very difficult to regulate. This study established a routine system for callus induction and root regeneration from primary leaves of cowpea (Vigna unguiculata L. Walp). Embryonic axes were used to establish seedling under in vitro condition and primary leaves from the in vitro seedlings were used are explants for the establishment of callus culture using different concentrations of 2, 4-dichlorophenoxyacetic acid (2, 4-D). To regenerate root, calli were subcultured on hormone free media or media fortified with 2.22µM N6-Benzylaminopurine (BAP). Callus induction was efficient (85.03%) on Murashige and Skoog (MS) basal salts with B5 vitamins (MSB5) fortified with 6.78μM 2, 4-Dichlorophenoxyacetic acid (2, 4-D) and induction frequency gradually decreases with reduction in the concentration of 2, 4-D. When calli were subcultured on MSB5 in the presence of N6-Benzylaminopurine (BAP), roots developed in 85% of the calli, with mean number of roots per callus ranging from 1 – 7. The presence of BAP was essential for roots development, as calli subcultured on hormone free media failed to develop roots, indicating the significance of hormonal balance in plant morphogenesis. The use of callus culture as experimental materials could help in understanding the processes of shoots and roots morphogenesis in cowpea. Root cultures could also be used in the production of secondary metabolites of pharmaceutical and other industrial values from genetically engineered callus.