Proliferation rate effects of cytokinins on banana (Musa spp.) cultivars

Shoot-tips (3 mm) of banana (Musa spp.) cultivars Kibuzi (AAA-EA), Bwara (AAA-EA) and Ndiziwemiti (ABB) were cultured on modified Murashige and Skoog nutrient salts. The modified medium was supplemented with various equimolar concentrations (16.8, 20.8, 24.8 and 28.8 mM) of BAP, TDZ, ZN, 2-iP and KN to determine suitable concentration ranges of the cytokinins for micropropagation of banana cultivars. Three sub-culture cycles were used and after each sub-culture, the shoots per explant were counted. To select a suitable and cost effective cytokinin, the optimum concentration, its cost in US $ and its corresponding proliferation rate were determined. The results showed that shoot proliferation was significantly ( p0.001) dependent on cytokinin type, its concentration and the banana cultivar. The responses of cultivars to BAP were significantly ( p0.05) better than other adenine-based cytokinins (ZN, KN and 2-iP). The TDZ showed high cytokinin activity and its diluted concentration of 0.045, 0.23, 1.14, 5.68, 6.81 and 9.1 mM showed, in case of Ndiziwemiti, progressively increased proliferation with increasing concentrations up to 9.5 shoots per explant. Ndiziwemiti was recalcitrant to the protocol of Talengera et al. (Talengera, D., Magambo, M.J.S., Rubaihayo, P.R., 1994. African Crop Sci. J. 2, 17–21). In the case of Kibuzi the proliferation rate increased from 2 to 5.4 for 0.045 to 5.68 before suddenly falling to 1.2 shoots per explant. The results demonstrated that cultivars differed significantly ( p0.05) in their shoot proliferation responses to different TDZ concentrations and that TDZ is more economical tha