Long term changes in climate of major natural rubber (NR) growing tracts of India were quantified and their impact on NR productivity was estimated using multiple linear regression models. Day-to-day variations in productivity in terms of dry rubber yield per tree per tap (g/t/t) could be best explained based on the variations in daily maximum temperature (Tmax) and daily minimum temperature (Tmin) and variations in other weather variables did not contribute much to the variations in daily productivity. For unit rise in Tmax and Tmin, NR productivity was affected differently in different agro-climatic regions. If both Tmax and Tmin rose by 1 ⁰C, NR productivity will reduce by 9-16% in the agroclimatic conditions of Kerala and by 11% in the hot and drought-prone North Konkan region. On the other hand, in the cold- prone North Eastern India, there is hardly any reduction in NR productivity if both Tmax and Tmin went up by 1 ⁰C. Our analysis show that if the present warming trend continues, NR productivity in Kerala could be reduced by 4-7% and that in North East India could go up by as much as 11% in the next decade. North Konkan region may also register about 4% reduction in NR productivity in the next decade if the present warming trend continues; however, absolute yields will continue to remain high in Kerala.

Long-term temporal changes were analyzed with respect to important climatic factors influencing rubber cultivation in the traditional rubber growing regions of India. Rainfall, temperature and sunshine hours, being the major climatic factors influencing rubber growth and yield, were analyzed at four rubber research stations in the traditional rubber growing regions of Tamil Nadu, Kerala and Karnataka having daily datasets ranging from 11 to 53 years. No significant trend was noted in the annual rainfall amount and total number of rainy days over 53 years at Kottayam. Annual maximum and minimum temperature trends were not significant for stations other than Kottayam. Increase in maximum temperature was observed in Kottayam while minimum temperature decreased in Parliar and Nettana. The daily bright sunshine hours showed a decreasing trend in Kottayam. Extreme rainfall events increased in Padiyoor. Long-term decadal means in maximum temperature showed an increase of 2 ⁰C over 53 years in Kottayam while it was 0.5 _⁰C in Parliar. Increase in temperature, decrease in bright sunshine hours and skewed rainfall were observed at some of the traditional rubber growing locations.

Two transgenic plants (L1 and L2) of Hevea brasiliensis (clone RRII 105) integrated with the manganese superoxide dismutase (MnSOD) gene were developed from two independent Agrobacterium mediated genetic transformation events. Six month old bud grafted plants of clone RRII 105 (control), non-transgenic somatic plants (control) and transgenic plants (L1 & L2), growing in polybags were subjected to water stress and their drought tolerance traits were evaluated through molecular, physiological and biochemical tools. MnSOD transcript abundance, leaf water potential, PS II activity, photosynthetic oxygen evolution and respiratory oxygen uptake rates, H₂O₂ content and superoxide dismutase and peroxidase enzyme activities were studied. Northern analysis indicated a higher MnSOD transcript level in the stressed transgenic plants. The maximum potential photochemical efficiency of PS II was not altered under drought stress. On the contrary, the effective quantum yield of PS II and mid-day leaf water potential were reduced in all the plants, however, the extent of reduction was small in L1 plants. Similarly, the drought mediated reduction in photosynthetic oxygen evolution rate was smaller in the SOD transgenic L1 plants than in the other plants. The SOD activity was 35 and 31 per cent higher under normal and drought conditions, respectively in the transgenic plant L1 than the bud grafted plants of clone RRII 105. Though there was an increase in SOD activity and H₂O₂ content in L1 plants, corresponding changes were not observed in the case of peroxidase activity. The results indicated that the transgenic plant L1 is superior to all other plants in terms of drought tolerance. Development of transgenic plants for abiotic stress tolerance, integrated with genes like MnSOD is a significant step in extending rubber cultivation to marginally suitable areas in the present scenario of changing climate.

Perennial trees like natural rubber plants sequester large quantities of atmospheric CO₂ into biomass and therefore, mitigate the increase in greenhouse gas (GHG) emission. In the present study measurements of CO₂ and water vapour flux of a natural rubber ecosystem were attempted for one continuous year. An eddy covariance (EC) flux measurement system was installed on an 18 meter tower inside a rubber plantation (4-5 years old) at the Central Experimental Station of the Rubber Research Institute of India (RRII) which is situated in the traditional rubber growing region of Kerala. The daily net ecosystem exchange (NEE) of CO₂ by the rubber ecosystem was in the range of 1-25 g/m2/day during the study period. Most of the days recorded a net CO₂ sequestration. However, a few days recorded a net CO₂ efflux (R_eco) from the plantation to atmosphere. The mean annual NEE of the 4-5 years old rubber plantation was 11 g CO₂ /m²/day which works out to 33.5 tons CO₂/ha/year indicating that rubber plantation is a potential sink for atmospheric CO₂. The amount of carbon sequestered by the plantation as calculated from the EC data was compared with carbon sequestration of the trees calculated from biomass inventory method. The annual mean evapotranspiration was 3.5 mm/day as calculated from the EC data indicating the high efficiency of sequestering carbon per unit amount of water consumed.

Climate change studies involve interaction of many factors and for meaningful interpretations, integrated analysis is essential. GIS is an ideal platform for this. In the uncertain scenario of climate change, our decisions need to be prioritized and for this multi-criteria decision analysis provides a very good tool. An attempt has been made to assess the vulnerability of rubber plantations to soil erosion as a result of heavy rainfall and runoff in Kozhenchery taluk of Pathanamthitta district of Kerala, India. Analysis has indicated that the major portion of rubber plantation (81%) is distributed on locations that have medium adaptability to rainfall variability and least (0.9%) on areas showing low adaptability. Spatial analysis of rubber distribution map with soil erodibility map has indicated that 60.5 per cent of rubber area is distributed on land with highly erodible soil with moderate slope followed by 37 per cent on less erodible soil with moderate slope. Maps highlighting the areas vulnerable to rainfall variability and soil erosion will serve as an ideal tool for planners, researchers and extension people to develop suitable strategies for enhancing NR production in India.

A total of 12 promising clones, including the newly released RRII 400 series clones were evaluated in three geographically diverse locations across the traditional and non traditional rubber growing tracts in India. The present paper reports the yield performance of these clones for the 4^th to 6^th year of tapping. The response of the clones to changes in meteorological variables in different locations in the same period was also examined. In Kanyakumari, RRII 105, RRII 430 and RRII 203 were on par. In Agartala, RRII 422 and RRII 429 were the top yielders and registered significantly superior yield to both the controls, RRII 105 and RRIM 600. In Nagrakata, RRII 429 was the highest yielder and RRII 417 and RRII 422 also recorded significantly superior yield than the controls. Genotype Environment Interactions (GEI) for rubber yield was analysed from the trials with a view to identify clones with wide adaptability as well as specific adaptation. AMMI model was selected to quantify GEI and the analysis revealed that environment (E) and GEI together contributed to the major proportion (72.8%) of the variations in rubber yield. Twenty seven percent of the total variation was attributed to genotypes (G). Genotype means ranged from 35.31 g/t/t to 56.24 g/t/t. Clones RRII 429, RRII 422, RRII 417, RRII 430 and RRII 105 were high yielding ones across environments. RRIM 600 was found to be the widely adapted clone. RRII 429 showed the highest interaction. Weather parameters viz., maximum and minimum temperatures, RH, sunshine hours and rainfall were studied in relation to rubber yield in the three locations. Maximum temperature was negatively correlated with yield in Kanyakumari, irrespective of clones. In Agartala and Nagrakata the results were however inconclusive.