Effects of Auxin/Cytokinin Combinations on Shoot Proliferation in Banana Cultivars

African Crop Science Journal, Vol. 7. No. 4, pp. 605-611, 1999 Effects of Auxin/Cytokinin Combinations on Shoot Proliferation in Banana Cultivars Code Number: CS99052 ABSTRACT: The effects of cytokinin/auxin interactions on in vitro shoot proliferation of bananas were investigated. Shoot-tips (3 mm), excised from in vitro-plantlets of Kibuzi (AAA-EA), Bwara (AAA-EA) and Ndiziwemiti (ABB) cultivars, were cultured on basal Murashige and Skoog modified medium (Talengera et al., 1994) to determine the cytokinin/auxin combination and concentration that gives high shoot proliferation in the three cultivars. The modified medium was supplemented variously by equimolar concentrations of Benzylaminopurine (BAP)/Indolebutyric acid (IBA): 16.8/1.0, 20.8/1.0, 24.8/1.0, 28.8/1.0, 16.8/1.2, 20.8/1.2, 24.8/1.2 and 28.8/1.2 M. The above concentrations were also used in: Kinetin (KN)/ Napthalene acetic acid (NAA), Thidiazuron (TDZ)/NAA, TDZ/IBA, Zeatin (ZN)/NAA and ZN/IBA. ZN/NAA and TDZ/NAA supplemented medium suppressed shoot proliferation rates in the three cultivars at all concentrations while BAP/IBA combinations induced more shoot prolifration in cultivar Ndiziwemiti than was previously observed on 20.8 M BAP modified MS medium. Cultivars reacted differently to different BAP/IBA concentrations: Ndiziwemiti had its best proliferation rate of 4.6 at 16.8/1.2 M; Bwara, 8.5 at 24.8/1.0 M; and Kibuzi, 4.5 at 24.8/1.2 M. Other proliferation rates, for Ndiziwemiti, included 2.8 at 24.8 M BAP/1.0 M NAA and 4 at 28.8 M / 1.0 M IBA. In most cases higher proliferation rates were observed in cytokinin/auxin combinations in which a weak auxin (IBA) was included. KEYWORDS: Auxins, cytokinins, Musa sp., shoot induction Copyright 1999, African Crop Science Societ