A study was carried out to screen Hevea clones for cold stress tolerance in a high elevation region. A polybag nursery comprising of 31 Hevea clones along with other popular clones was established in a cold stress prone/high elevation region at Mattupetty, Munnar, Kerala while another set grown at Rubber Research Institute of India, Kottayam served as control. Growth parameters (sprouting, survival rate, stem height, number of leaves emerged and leaf length), leaf chlorophyll content and gas exchange parameters such as net CO2 assimilation rate (A), stomatal conductance (gs), transpiration rate (E) and instantaneous Water Use Efficiency (WUEi) were recorded during the cold stress period at Munnar and control conditions at Kottayam. The clones viz. P 202, P 48, P 89, P 68, P 47 and P 201 had better survival and vigorous growth under cold stress conditions. In terms of net CO2 assimilation rate (A), pipeline clone P 68 was the best performer followed by P 48, P 94, P 180 and P 181 along with check clone RRIM 600. Rank sum analysis revealed the potential inherent cold stress tolerance in clones P 48, P 68, P 168, P 116, P 202 and P 181 during juvenile growth phase. These clones which were superior in terms of better growth and physiological parameters can be evaluated in field to affirm their inherent cold stress tolerance, yield potential and suitability for cultivation in cold stress prone regions. 

Para rubber (Hevea brasiliensis), naturally growing in the Amazon forests of South America, was widely distributed to South East Asian countries, including India and China in the early 19th Century. The potential distribution range of natural rubber (NR) in India was modelled for 2050 and 2070 under different Representative Concentration Pathways (RCP 2.6, 4.5, 6.0, 8.5) scenarios of changing climate using ecological niche modeling (Maxent) to study the impact of climate change on NR cultivation. The current emissions are tracking close to the RCP 8.5 pathway and if it continues the average increase of temperature in 20812100 will be 3.7oC relative to increase during 1986-2005. Under various future emission scenarios, the potential niche for growing NR in India will expand to sub-optimal regions as many colder regions will be warmer and many traditional regions will become less suitable for this species. Our studies indicate that the  most significant bioclimatic variable contributing to future distribution patterns of rubber plantations in India is  temperature, particularly the maximum temperature during the warmest month/season, followed by annual precipitation. 

Many hectares of land in northern parts of West Bengal have become unsuitable for cultivation of tea due to the rise in soil alkalinity following deposition of dolomite rich silts. In order to study the feasibility of growing rubber in such highly alkaline soils, six Hevea clones viz. RRII 208, RRII 417, RRII 422, RRII 429, RRIM 600 and RRII 605 were planted during 2011 at two sites viz. (i) Sarugaon Tea Estate (Falakata, West Bengal) where the soil pH is alkaline (pH 7.43) and (ii) Regional Research Station, RRII, Nagrakata where the soil pH is acidic (pH 4.40). In the alkaline soil at Sarugaon TE, RRII 417 recorded the highest tree girth (62.50 cm) followed by RRII 208 (60.51 cm) in the twelfth year of growth. In the year of opening of trees, the percentage of tappable trees was the highest in RRII 429 in acidic soil as compared to alkaline soil.  The annual mean yield was also highest in RRII 429 in acidic soil. RRII 208 performed better than all other clones in terms of plant girth, bark thickness and annual yield in alkaline soil. 

Rubber elongation factor (REF) is a 14.6 kDa stress related family protein, which plays a major role in the chain elongation process of natural rubber biosynthesis pathway in Hevea. Due to its significance in rubber biosynthesis, molecular markers developed from REF gene will be ideal for genetic analysis and association studies related to yield and rubber quality in Hevea. Attempts were made to characterise REF gene in different genotypes to identify sequence polymorphisms like SNPs and indels. Phylogenetic analysis was performed to understand their similarity/dissimilarity with homologs in other plant species as well.  Genomic region of REF gene was amplified and sequenced from five different genotypes to identify nucleotide variations among them and haplotype blocks were constructed using the Single Nucleotide Polymorphisms (SNPs) identified. A total number of 32 novel SNPs were identified with a frequency of 1 in every 53 bases. Five haplotypes were constructed from the SNP data and their impact at the functional level was estimated by gene expression studies. The SNP and generated haplotype data from the study has wide applications in different areas of Hevea crop improvement like assessment of genetic diversity, characterisation of cultivated clones and wild accessions, yield related marker development etc. Additionally results from this study further ascertain distinctive nature of REF gene in Hevea which may be partly responsible for its high rubber producing capability.

The rubber tree (Hevea brasiliensis) is one of the most important domesticated crops planted commercially for the production of natural rubber (NR) worldwide. However, one of the biggest constraints of rubber cultivation is foliar diseases, which cause stunted growth of young rubber plants and reduced yield in mature rubber trees. Among the leaf diseases, Colletotrichum Leaf Disease (CLD) is one of the most common diseases causing economic loss. Two species of Colletotrichum viz. C. acutatum and C. gloeosporioides are the causative agents of Colletotrichum leaf disease. In addition to these, two other species were also isolated from infected leaf samples and included in this study. Colletotrichum spp. on rubber trees i.e. C. acutatum and C. gloeosporioides infect immature leaves and persist even in the mature leaves, but C. siamense and C. fructicola infect mature leaves and cause different kinds of symptoms. The present study was focused on the different Colletotrichum spp. infecting rubber trees and analysis of their phenotypic, genotypic and pathogenicity variations. 

Progenies collected from nine clones growing in a polyclonal seed garden (Karnataka, India) of Hevea brasiliensis were evaluated for their long-term growth and yield performance along with RRII 105 as check clone. Polycross progenies recorded high tappable girth (71%) in the opening year and it was sustained in later years. After 15 years of planting, the progenies attained very high girth than RRII 105 with high range and CV. Family of PB 217 had the highest CV (23%) indicating good scope for selection. Progenies of Ch 26 recorded the highest girth (mean, 92 cm) followed by AVT 73 (mean, 89 cm).  Dry rubber yield of progenies ranged from 11 to 99 g t-1 t-1 (mean yield, 40 g t-1 t-1; CV, 42%). Families of PB 242, PB 217 and PB 215 (mean yield, 43 g t-1 t-1) followed by Ch 26 (mean yield, 42 g t-1 t-1) recorded high yield. Families of PB 242 and PB 217 with high CV (>40%) also comprised of very high yielding progenies (>90 g t-1 t-1) indicating a good scope for selection. Clone RRII 105 exhibited high variability for yield (range, 12 to 71 g t-1 t-1; CV, 27%). There was no correlation between girth and yield in the polycross and clonal population. Initially, selection based on population mean yield identified 69 progenies. After applying a more rigorous criterion, 23 selections with more than 60 g t-1 t-1 were identified. Top yielders of each family having 70 g t-1 t-1 and above yield, based on yield of the top performing ramete of clone RRII 105, were identified as priority selections for further clone evaluation studies. These six top polycross selections had maximum yield potential of 99 g t-1 t-1 and maximum girth of 127 cm, based on long-term data, which offer good scope for inclusion in Category 3 of planting recommendations and for further long term clonal evaluation and selection.