Water Relations and Osmolite Accumulation Related to Sugarcane Yield Under Drought Stress in a Tropical Climate

The number of areas subject to drought is likely to increase in response to climate change and will affect the yields of globally important crops such as sugarcane. In this respect, the aim of the present study was to assess the drought tolerance of sugarcane varieties in different phenophases and identify the physiological and biochemical characteristics associated with the lowest yield loss under drought conditions. Six of the most widely cultivated varieties in the region were studied, namely SP79-1011, RB855113, RB92579, RB867515, RB72454 and RB855536. Plant physiological characteristics were assessed during the dry season in the tillering, intense growth and ripening stages, and yield was quantified after 12 months of cultivation. This study shows that different sugarcane varieties are more affected by drought in the intense growth phenophase, since plants showed a greater decline in water and osmotic potential at midday during this period. The varieties most affected by drought in this phenophase were RB855536 and RB855113, which exhibited greater reductions in water and osmotic potential. They also had larger osmoregulator accumulation as a response to drought, but not enough to prevent dehydration, which likely contributed to the lower yield. The RB867515 and RB92579 varieties underwent no significant change in osmotic potential at midday during drought stress in the intense growth phase, despite of low leaf water potential, and little variation in the osmoregulators contents. For these reasons, these two varieties showed greater drought acclimation potentials and were more productive as submitted to drought conditions.