To meet its rising demand natural rubber cultivation is being extended to the North Eastern (NE) regions of India where low temperature is a major growth limiting factor.  Among the non-traditional areas, there is greater focus on expanding rubber cultivation in the NE region. In the present study, low temperature responses were evaluated in five clones of Hevea brasiliensis. Young plants (six to eight-month-old) were grown under ambient tropical conditions successively exposed to low temperature for 14 days by a gradual reduction of temperature from 30oC/22oC to 15oC/7oC and allowing a stress recovery period of five days at 30oC/22oC under controlled condition. Cold stress treatment significantly affected growth in the experimental clones. However, three clones under stress condition viz. SCATC 88/13, RRII 208 and RRIM 600 showed better leaf and stem dry weight (DW). Leaf mass fraction (LMF), stem mass fraction (SMF) and leaf thiol content levels were higher in SCATC 88/13, RRIM 600 and RRII 208.  When exposed to low temperature there was a reduction in the content of photosynthetic pigments, maximum photochemical efficiency (Fv/ Fm) and effective quantum yield of PSII (FPSII) in all the genotypes; however, reduction was the least in SCATC 88/13 and RRIM 600.  During stress recovery the rate of PSII repairing was better in three clones viz. SCATC 88/13, RRII 208 and RRIM 600.  Although most of the clones showed sensitivity to low temperature stress, there was variations in cold response and recovery capabilities of the clones in terms of growth and photosynthetic parameters. Overall, clone SCATC 88/13 followed by RRIM 600 and RRII 208 had better tolerance to cold stress.

The Hevea breeding programme in Sri Lanka aims to produce high yielding and vigorous rubber clones with good secondary characteristics for adoption by the rubber sector. The full-sib population produced by the 1982 hybridization programme was evaluated at various stages viz., nursery, small scale clone trial and estate collaborative large scale trials in different agro-climatic regions. Subsequently, RRISL 2006 (HP 82-140) was identified as a very promising clone with good latex and timber properties.  Based on the evaluation, clone RRISL 2006 was recommended as a Group III clone for small scale planting in plantation sector.  This paper discusses about various aspects of the clone in terms of its morphological characteristics, biochemical aspects of latex and disease resistance traits.

The present study was undertaken at the Ganolgre Research Farm under the Regional Research Station, Rubber Research Institute of India, Tura, Meghalaya.  Ten clones were included in this study. Three trees per clone were selected randomly and the pattern of defoliation and refoliation was recorded. Maturity of new flushes, date of onset of flowering, fruiting, maturity of the fruits and seed germination of individual clones were also recorded. Data showed that the wintering characters were mainly influenced by the prevailing climatic conditions of the region. The clones showed varying trends in wintering, refoliation, maturity of new flushes, flowering and fruit maturity characteristics over the years.  In general, the RRII clones showed early wintering followed by RRIM 600 and RRIM 605; whereas Gl 1 and GT 1 showed late wintering, refoliation, maturity of new leaves, flowering, fruiting and fruit maturity characteristics. 

Evolving climate-resilient and high-yielding clones of Para rubber tree (Hevea brasiliensis) is one of the top priorities in natural rubber research. In view of the above, transgenic plants of clone RRII 105 integrated with HbMnSOD gene for imparting abiotic stress tolerance, were developed via Agrobacterium-mediated genetic transformation. The transgenic plants possessed better drought tolerant traits as evidenced from various physiological and molecular studies conducted in the contained facility.  In continuation, a small scale confined field trial of the transgenic plants was initiated at the Regional Research Station, Guwahati, Assam following the biosafety regulations. The transgenic plants are being assessed for their ability to withstand cold stress, disease incidence and latex yield. The commercial release of transgenic plants can be carried out only after assessment of the performance in the confined field trial.

Hevea brasiliensis is the primary source of natural rubber and its seeds are being used as an important source of stock seedlings for propagation and potential raw material for non-edible oil production. The present study deals with assessment of seed trait variability in seeds of RRII 400 series clones of H. brasiliensis viz., RRII 414, RRII 417, RRII 422, RRII 429 and RRII 430. The results demonstrated that seeds of RRII 414 had the highest dry weight (4.5 g), followed by  RRII 417 (3.3 g), RRII 429 (3.3 g), RRII 430 (3.3 g) and RRII 422 (3.0 g). The highest kernel dry weight was recorded by the seeds of clone RRII 414 (2.4 g). Positive correlation was found between total seed weight and kernel weight of seeds. RRII 429 registered the highest percentage of germination (72 %) followed by RRII 422 (59 %) and RRII 414 (58 %). The study showed that the seed weight could be used as an indicator of kernel biomass in sorting seeds for commercial oil production and stock seedling generation.

This paper presents the potential of blending ground tyre rubber (GTR) with natural rubber (NR) as a strategy to address the management of end-of-life tyres. The present work also investigated the possibility of improvements with respect to vulcanizate properties of NR/GTR blends through two protocols viz. mechanical devulcanization of GTR before blending and incorporation of carbon black filler in the blends. The cure characteristics, crosslink density and vulcanizate properties of blends were determined and compared. Results showed that incorporating mechanically devulcanized GTR (DGTR) led to better vulcanizate properties compared to vulcanizates containing an equivalent amount of GTR. Additionally, low loading of carbon black filler improved the properties for both types of blends. The study suggests that the vulcanizate properties of virgin NR/GTR blends can be tailored to meet specific requirements by modifying the incorporation protocols. For meeting high tensile properties, the incorporation of mechanically devulcanized GTR is recommended, while for lower property requirements, GTR with a small amount of carbon black is recommended.