Cultivated Hevea brasiliensis clones of the South East Asian rubber growing countries have their origin from ‘Wickham clones’.  Since the cultivated clones are characterized with a low genetic variability, it is difficult to identify them based on their morphological characteristics. Therefore, DNA-based markers were used for accurate identification through genotyping of H. brasiliensis clones, which is essential for maintaining genetic purity of cultivated clones. We developed microsatellite markers that could discriminate H. brasiliensis clones, used for cultivation or maintained for breeding purposes in India.  Thirty-eight popular clones could successfully be identified using only three polymorphic microsatellites. In order to identify the clones, microsatellites hev-glu (intronic TC repeats of ß-1,3 glucanase gene), hmct19 and hmac14 (generated from Hevea genomic library) were used sequentially in descending order of their powers of discrimination. These three microsatellite markers could independently discriminate 10 clones based on their unique allelic profiles. Among these three markers, hev-glu with its high discriminatory power (0.916) could identify six clones based on their characteristic allelic combinations. Similarly, hmct19 and hmac14 uniquely discriminated two clones each originating from Sri Lanka and Malaysia. Using the marker hev-glu, rest of the 32 clones were grouped into 10 clusters/ genotypes. When these individual groups comprising 32 clones were assessed for the locus hmct19, 21 clones could be identified and 11 clones remained unidentified. Following application of the marker hmac14, all remaining 11 unidentified genotypes could clearly be differentiated. Thus, the above markers can be used effectively to resolve any dispute concerning clonal identity in rubber. 

Hevea brasiliensis is the major source of latex for the commercial production of natural rubber (NR). Corynespora leaf fall disease caused by Corynespora cassiicola is one of the major diseases affecting both nursery and mature rubber trees. Next-generation sequence based transcriptome assembly of tolerant (GT 1) and susceptible (RRII 105) clones in control (healthy) and pathogen challenge inoculated (treated) conditions elucidated the role of several transcripts in subduing the infection of C. cassiicola in H. brasiliensis. Classical defense-related genes involved in systemic acquired resistance, cell wall reinforcement, NBS-LRR proteins and phytoalexin biosynthesis were highly upregulated in GT 1 under healthy (unchallenged) condition. Expression of genes encoding leucine-rich repeat proteins, serine/threonine protein kinase and phytoalexins in the tolerant clone GT 1 were remarkably increased but were almost suppressed or downregulated in the susceptible clone RRII 105 under pathogen inoculated conditions, demonstrating importance of these genes in imparting disease resistance against C. cassiicola. Significant upregulation of negative hypersensitive response and antioxidant defense in inoculated tolerant clone GT 1 revealed their role in suppression of necrotic symptoms induced by 
C. cassiicola. Downstream analysis of selected differentially regulated genes would assist in development of marker-based selection tools to rapidly identify tolerant clones of Hevea at an early stage of screening.

The wild germplasm of the Para rubber tree (Hevea brasiliensis) was introduced to India primarily to expand the genetic base vital for enhancing crop improvement. Genetic diversity of 110 wild rubber germplasm (Hevea brasiliensis) accessions was assessed using random amplified polymorphic DNA (RAPD) markers. The polymorphism information content (PIC) ranged from 0.31 to 0.49 indicating their efficiency in revealing the polymorphism among wild accessions. A total of 126 loci were amplified using 16 primers, which revealed an overall polymorphism of 98 per cent. The accessions possessed a high variability as indicated by the wide range of similarity coefficients ranging from 0.16 to 0.81. Cluster analysis following unweighted pair-group method analysis (UPGMA) broadly classified the 110 wild accessions into nine distinct clusters. The clusters showed geographical distinctiveness to the three states of Brazil from where the accessions were originally collected. A few accessions, which were distinctly divergent in the clusters, were also identified. This finding can contribute to the conservation of wild Hevea germplasms and its utilization in future breeding programs

In order to meet rising global demand for natural rubber, rubber cultivation is increasingly being expanded to non-traditional regions which are prone to abiotic stresses like drought and cold. Thus, breeding climate-resilient clones has become an important priority for Para rubber tree (Hevea brasiliensis). One such hybridization for drought tolerance carried out in 1993 yielded fifteen hybrid selections which were consequently evaluated for their long-term growth and yield in a small scale trial (1998) at Central Experimental Station of Rubber Research Institute of India, Kerala State, India. Clone 93/105, followed by 93/112, 93/216, 93/214 and check clone RRIC 52 attained more than 70 per cent tappability in opening year (2005). Other check clones PB 260 (50%), PB 217 (48%), RRII 105 (24%) and RRIM 600 (23%) had lesser tappability.  Based on growth assessed in the 15th year, check clone RRIC 52 had highest girth (84 cm) followed by clones 93/112 (80 cm), 93/216 (80 cm) and 93/184 (79 cm). Comparatively, check clone RRII 105 attained a girth of 61 cm.  Based on annual mean dry rubber yield over 10 years of tapping, clone 93/214 had highest yield (71 g t-1 t-1) followed by PB 260 (60 g t-1 t-1), PB 217 (53 g t-1 t-1) and 93/80 (52 g t-1 t-1). Clone 93/88 (50 g t-1 t-1) and 93/ 216 (50 g t-1 t-1) gave on par yield with check clone RRII 105 (49 g t-1 t-1). Clone 93/216 gave highest summer yield (41 g t-1 t-1) followed by 93/214 (37 g t-1 t-1) and 93/145 (36 g t-1 t-1). Summer yield of 93/80 (33 g t-1 t-1) was on par with that of PB 217 (33 g t-1 t-1). In comparison, check clone RRII 105 along with RRIM 600 gave a summer yield of 26 g t-1 t-1. Regarding genetic parameters, tappability in opening year showed low heritability (H2=0.36). In contrast, long-term rubber yield showed high heritability (H2=0.60) while summer yield showed moderate heritability (H2=0.40). Top selection 93/214 (RRII 105 x RRIC 52), possessing highest annual rubber yield and appreciable summer yield, was elevated as pipeline clone (P 218) for further long-term evaluation in large scale trial at Chethackal and multi-locational on-farm trials under Phase 5 (2016) of Participatory Clone Evaluation Programme. After assessment of its overall performance, the above pipeline clone will be recommended as a region-specific clone for commercial planting, particularly in drought prone non-traditional regions. 

The state of Meghalaya in northeast India is suitable for rubber cultivation outside the traditional rubber belt although the climate of the region is sub-tropical. A monoclonal plantation of rubber clone RRIM 600 planted in 1987 in Garo Hills of Meghalaya was evaluated for growth and yield performance. The initial tree stand of the plantation was 1800 trees and over a period of 38 years the plantation lost 803 trees at an estimated rate of 21 trees per year. Assuming that the present annual tree loss rate would continue beyond the present age of the plantation, an estimate of the progress, peak and decline of the plantation as a managed sink of atmospheric CO2, source of carbon, biomass and oxygen production were worked out.  Accordingly, it was assumed that the plantation would reach its peak in the 59th year and then begin to decline its potential as a carbon sink till the plantation comes to extinction in the 87th year due to natural loss of trees. The total biomass accumulated in the area was 1748 tons and per tree average was 1.76 tons. The plantation sequestered 848 tons of carbon and the average of a tree was 0.83 ton. An estimated 46.3 kg carbon was sequestered annually in a tree, of which 36 kg was in the shoot, 6 kg in the root and 4.3 kg as dry rubber.  The plantation removed 3112 tons of atmospheric CO2. A single tree in the plantation removed 3.04 tons CO2 over the years.  Annually, 83.0 kg CO2 was removed by a tree. The plantation released an estimated amount of 2264 tons of oxygen and a single tree released around 
2.22 tons O2 over the years. The study also estimated that a hectare of plantation in its 18th year with a tree stand of 400 trees accumulated around 182.8 ton ha-1 of biomass and a corresponding carbon sequestration of 88.0 ton ha-1. The total CO2 removal and the O2 release were 323.6 ton ha-1 and 235 ton ha-1, respectively. The annual biomass accumulation and carbon sequestration were 11.1 ton ha-1 and 5.7 ton ha-1, respectively.  An estimated 21.1 ton ha-1 atmospheric CO2 was removed and 15.2 ton ha-1 oxygen was released annually from a hectare. Rubber plantation provides not only livelihood to the farming community but also acts as a managed sink of atmospheric carbon dioxide helpful to mitigate the effects of carbon emission in the atmosphere. 

Rubber cultivation is a critical component of Tripura’s agrarian economy. This study investigated the extent,
determinants and constraints of adoption of recommended agricultural practices among 250 rubber growers
across six major rubber-producing districts using a stratified random sampling approach. The findings revealed
notable disparities in adoption rates. While the use of improved clones (98.0%) and polybag plants (96.8%) was
nearly universal, other practices such as mechanization and root trainer planting remained entirely unadopted,
indicating significant gaps in the integration of scientific recommendations. Low adoption rates of intercropping
(6.8%) and rain guarding (8.4%) further highlighted systemic barriers, including financial limitations, inadequate
awareness and limited access to extension services. Chi-square analysis revealed significant associations
between socio-economic variables and adoption: education positively influenced rain guarding (χ² = 18.75, p
p≤ 0.05), farm size was linked to intercropping (χ² = 15.32, p≤ 0.05), and credit access was a key factor for
mechanization (χ² = 22.91, p≤ 0.05). Regression models confirmed these trends, with credit access (β = 0.72,
p≤ 0.01) emerging as the strongest predictor of mechanization adoption, followed by education (β = 0.58, p ≤
0.01) and farm size (β = 0.41, p≤ 0.05). Thematic analysis of farmer perceptions underscored key challenges,
including high cost (59.6%), poor awareness (34.8%), limited extension penetration (30%) and credit constraints
faced by 72.8 per cent of respondents. These findings emphasized the critical need for integrated interventions
ranging from subsidized inputs and targeted credit programs to expanded extension services and farmer
education to close adoption gaps and promote sustainable rubber cultivation in Tripura.