RUBBER YIELD OF CERTAIN CLONES OFHEVEA BRASILIENSIS AND ITS RELATIONSHIPWITH CLIMATE VARIABLES

摘要

The relationship between long term yield of seven Hevea clones and climatic parameters such as minimum temperature (T_(min)), maximum temperature (T_(max)), sunshine hours (s), rainfall (R) and relative humidity [RH1 (morning) and RH2 (afternoon)] was studied under a typical tropical humid climatic regime. Of the seven genotypes, RRII 105 was significantly high yielding (68.0 g/t/t), while Gi 1 (40.5 g/t/t) and RRIM 600 (43.8 g/t/t) registered relatively low yields. Climatic parameters were regressed on yield. T_(max) was found to be the most important influencing factor with a negative relationship in each clone (slopes from -7.299 to -3.353). T_(max) showed less monthly variability when compared to RH in the corresponding period. RH was seen to be low during the winter and pre-monsoon seasons. Yield was found to be the most important function of T_(max) (R~2= 0.21). Most of the clones showed an increase in yield with time mainly during the monsoon season (slopes from 4.94 to 2.56 per year). The R~2 ranged from 0.30 (RRII 105) to 0.76 (RRII 203) during the monsoon season. The clone RRII 208 did not show any increase in yield, while RRIM 600 showed a varied response of yield with time over different seasons. The study indicated the moderate level of decrease in yield with increasing T_(max). However, rising temperature in the long-term climate change scenario,the yield decline in rubber clones need to be evaluated further in large scale.