Abstract

Amala O. Arinze, Dilara Afroz Shathi and Ogunesan B. A

The identification of drought tolerant banana varieties under natural environment is complicated by difficulties in field management, variation in phenotype and unexpected rainfall events. A study to develop an alternative and rapid technique to screen for drought tolerant banana varieties by an in vitro technique was carried out. Effects of 0.09 M sucrose, 0.09 M sorbitol and 0.0 M sugar on growth of banana plantlets were compared under in vitro conditions. Results from this experiment proved that sorbitol is not a source of energy for in vitro banana plantlets and it could be used as a neutral osmotic inducer. Exploration of different levels of osmotic stress induced by 0.1 to 0.5 M sorbitol in the media and their effects on the growth of banana plantlets proved that the concentration of 0.2 M sorbitol is the highest concentration to reveal different growth parameters. The application of this concentration on banana varieties of Williams, Popoulou, Obino l'Ewai, Lep Chang Kut, Mbwazirume (negative control: drought sensitive), and Cachaco (positive control: drought tolerant) showed that all varieties were affected by sorbitol osmotic stress but the degree of sensitivity is different. Significant differences in reduction of gain of fresh and dry weight, new roots and leaves, and leaf area were observed between Cachaco and Mbwazirume. For most growth parameters, Cachaco showed the lowest reduction and Mbwazirume presented the highest reduction due to osmotic stress. The varieties Williams and Lep Chang Kut showed a level of drought tolerance after Cachaco. Lep Chang Kut had the lowest reduction of gain of new root and fresh weight, and water content; whereas, Williams occupied the second position of low reduction of gain of leaf area, number of leaves, and the third position in low reduction of gain of new root and dry weight. After, Obino l'Ewai occupied the fourth position and Popoulou came as the fifth position. Mbwazirume was the last in the tolerance of sorbitol induced osmotic stress with high reduction in many growth parameters evaluated. From this study, an in vitro technique to screen drought tolerant banana varieties was developed, and the drought tolerance of Cachaco and Lep Chang Kut and drought sensitivity of Mbwazirume were proved. The total gain of fresh and dry weight, number of new leaves and leaf area were identified to be appropriate growth parameters for identifying drought tolerant banana varieties under in vitro condition.