Ethanol treatment enhances drought stress avoidance in cassava (Manihot esculenta Crantz)

The external application of ethanol has been reported to enhance salinity, drought and heat stress tolerance in various plant species (Nguyen et al. 2017 ; Bashir et al. in prep.; Matsui et al. in prep). However, the effects of ethanol application on increased drought tolerance in cassava, an important tropical starch crop used for food security and industrial application by a billion people world-wide, remain unknown. In the present study, morphological, physiological, and molecular responses to drought were analyzed in cassava after the treatment with ethanol. The present study showed that the ethanol treatment increased drought avoidance in cassava than the water treatment. Ethanol treatment induced stomatal closure, resulting in the increase of leaf temperature. The decrease in water content of the leaves during drought stress treatment was reduced in ethanol-treated plants compared with control plants. Transcriptome analysis revealed that the expression of drought stress response-related genes and ABA response-related genes was lower in ethanol-treated plants compared with control plants on 12 days after drought treatment. The first to third leaves from the top of stems from 1.0% ethanol-treated or water treated plant for 5 days, drought-treated plant treated drought stress for 6 days after 1.0% ethanol or water pretreatment and drought-treated plant treated drought stress for 12 days after 1.0% ethanol or water pretreatment were collected for transcriptome analysis.