Role of Trehalose during Recovery from Drought Stress in Micropropagated Banana (Musa spp.) Transplants.

Abstract

Micropropagated banana (Musa spp.) plants are widely accepted by growers as valuable, pathogen-free stock materials. Water stress is believed to adversely affect growth and yield of banana plants, as banana plants requires water in sufficient quantity for their normal metabolic activities. Trehalose is one of the organic substances currently known to be involved in osmotic adjustment, a significant strategy for plant drought tolerance. The current study was aimed to assess the role of trehalose as a presoaking treatment at 0, 20, 60 or 100 mM in improving tolerance of banana plantlets under in vitro drought stress conditions and following transitional period required in preparation for planting in the field. The pretreatment of 20 mM trehalose enhanced growth of banana plantlets under in vitro drought stress conditions in terms of root system and fresh weight. Non of in vitro stressed un-pretreated plantlets succeeded to continue grow during recovery stage in the green house. Results showed markedly higher indicators of growth recovery in banana transplants previously supplied with 20 mM trehalose. This growth improvement was accompanied with enhancement of chemical composition in terms of increasing pigments and reducing total free amino acids contents to reach almost normal levels in addition to higher total phenols content and overall antioxidant activity even more than control plants. Sodium Dodicyl Sulphate Polyacrylamide Gel Electrophoresis (SDS-PAGE) analysis showed over expressed protein band of 32 kDa molecular weight in recovered transplants pretreated with the highest trehalose concentration (100 mM). Recovered transplants pretreated with trehalose at the lowest concentration (20 mM) showed balanced up regulation of both trehalose-6-phosphate synthase (TPS) and trehalase genes over control, while recovered transplants pretreated with trehalose at the highest concentration (100 mM) showed also over expression of TPS gene but down regulation of trehalase gene under control.