Evaluating drought stress tolerance in different Camellia sinensis L. cultivars and effect of melatonin on strengthening antioxidant system

Drought stress really restring the growth and development of tea plant and affecting quality and yield. In tea growing areas of Iran, drought stress is a serious problem that affects the yield and quality of green leaves, therefore introducing cultivars that tolerate drought stress is one of the breeding purpose. To distinguish the variations in four tea cultivars response to drought stress and the role of melatonin in reducing the destructive effects of drought stress, an experiment was done at Tea Research Center of Iran, using the factorial based on completely randomized design with three replicates. The first experimental factor was the cultivar at 4 levels (DG39, DG7, DN and Kashef) and the second factor was irrigation interruption treatment at 5 levels, including control (full irrigation), irrigation interruption for 7 days with 100 mu m melatonin foliar application, irrigation interruption for 7 days without melatonin foliar application, irrigation interruption for 14 days with melatonin foliar application and irrigation interruption for 14 days without melatonin foliar application. The study indicated that the physiological and biochemical traits were significantly different among the cultivars and treatments. Based on some traits such as malondialdehyde, the activities of antioxidant enzymes (CAT, POD), carotenoid and polyphenol content, DG 39 and based on traits such as proline, total sugar and chlorophyll content, DN are introduced as the cultivars that showed better tolerance to drought stress and these cultivars can be used in future breeding programs. Also melatonin treatment significantly enhanced the drought tolerance of tea seedlings, as demonstrated by decreased membrane damage, raised the concentration of proline, total protein, and total sugar and enhanced the activities of catalase and peroxidase during drought stress.