Biochemical Evaluation of RRII 400 Series Clones of Hevea Brasiliensis for Drought Tolerance

Hevea brasiliensis is the most important commercial source of natural rubber (NR). Its cultivation is being extended to drought prone non-traditional areas to meet the increasing global demand in almost all the NR producing countries. To identify suitable drought tolerant clones for establishment in such areas, five modern Hevea brasiliensis clones (RRII 400 series) were evaluated along with the most popular clone in India, RRII 105 and a known drought tolerant check clone, RRIM 600. The drought tolerance potential of these clones were evaluated using physiological and biochemical parameters such as, leaf wax content, antioxidants, antioxidant enzyme activities and gas exchange parameters. Leaf epicuticular wax content, an important trait associated with drought and heat tolerance was found to be significantly higher in clone RRII 430 than in other 400 series clones and RRII 105. The clone RRII 430 also had significantly higher levels of ascorbic acid (antioxidant) content and super oxide dismutase (SOD) activity and those components play vital roles in defense against oxidative stress. When subjected to drought stress, this clone showed better net photosynthesis rate (P_N) and stomatal conductance (g_s) compared to other 400 series clones. The results indicated that the modern Hevea clone RRII 430 is the most potential drought tolerant clone among the 400 series clones.