Physiological basis of drought tolerance in potato grown under long-term water deficiency

Coping with water shortages without compromising tuber yield is a major challenge for potato (Solanum tuberosum L.) production in northern China. In this study, we used three potato cultivars with different sensitivities to drought to evaluate the effect of long-term drought stress on morphological and physiological characteristics under field conditions during three growing seasons (2009-2011). Our aim was to identify the specific drought tolerance traits of the potato cultivars to enable their cultivation in arid and semi-arid regions. Our results show that the drought-tolerant cultivars had higher tuber yields under conditions of drought due an increased number of tubers per hill and increased individual tuber weight. Compared with the drought-sensitive cultivar Neishu no. 7, the drought-tolerant cultivars Kexin no. 1 and Konyu no. 3 had stronger root systems and a higher capacity for water absorption at later developmental stages and a higher leaf relative water content, which conferred enhanced water retention under drought conditions. Moreover, the levels of superoxide radical and hydrogen peroxide were lower and the activities of antioxidative enzymes, including superoxide dismutase, peroxidase and catalase, were higher in the drought-tolerant cultivars under drought stress conditions. These combined characteristics allowed the cultivars to exhibit different levels of water deficiency. The above agro-morphological and physiological parameters could be used as a basis for breeding potato varieties with enhanced drought tolerance.