Survey of diseases and pests of rubber (Hevea brasiliensis) in Tripura was carried out in 18 locations covering 47 sites of West and South Tripura districts during 2008-10. The survey revealed prevalence of four leaf diseases (viz. powdery mildew, Colletotrichum and Corynespora leaf diseases and Periconia leaf blight), pink disease and brown root in varying intensities. However, powdery mildew, Colletotrichum leaf disease and brown root disease were found to be more common. Among insect pests, minor incidence of scale insects (in association with sooty mold), mealy bugs, termites, borer beetles and mooply beetles were observed. The plantations were also damaged by other animals like spotted dear and rats. The trend of disease and pest occurrence over three years was more or less consistent.

Tolerance to extreme climatic conditions being experienced in non-traditional rubber growing regions in India involves genes/regulatory factors associated with this trait in Hevea brasiliensis. Identification of such genes/factors is necessary for evolving suitable clones for such regions. For this purpose, gene expression analysis was carried out on leaf samples of Hevea clones with varying tolerance levels viz. RRII 105 and RRIM 600 (relatively cold susceptible and tolerant respectively) exposed to low temperature stress. Among the 21 Hevea specific genes analyzed, expression of LEA 5 protein, ETR1, NAC transcription factor, annexin, ABC transporter protein, WRKY transcription factor, GPX, ACO2, HbDRT50 and peroxidase responded to low temperature stress. Among these genes, LEA 5 protein, peroxidase, ETR1, ETR2 and NAC transcription factor were found associated with tolerance. Genes such as NAC transcription factor, LEA 5 protein and peroxidase showed high magnitude level of expression under cold conditions indicating its stronger association with cold tolerance. This need to be further validated with more such tolerant clones to identify the best candidate genes/regulatory factors associated with cold tolerance.

The effect of three arbuscular mycorrhizal fungi (AMF) on growth of rubber seedlings in polybags was studied. Among these the seedlings treated with Glomus fasciculatum had attained the highest growth rate in terms of girth and height followed by those treated with Glomus mosseae and Gigaspora margarita. The dual inoculation with G. fasciculatum and G. mosseae exhibited a synergistic effect on growth of plants. The high percentage of mycorrhizal root colonization, spore numbers and maximum plant biomass increase were recorded in the combined inoculation of G. fasciculutum and G. mosseae over the control. An increase in the total plant biomass over control was also observed in singly treated plants with G. fasciculatum, G. mosseae and G. margarita. In nursery, the girth and height of plants in combined inoculation with AMF and Phosphate solubilizing microorganisms (PSM) was significantly superior to rest of the treatments. The dual inoculation of seedlings with AMF + Azotobacter sp. also attained higher girth and height over the uninoculated plants. In single inoculation, plants with AMF attained the highest girth and height followed by PSM and Azotobacter. The present study shows the potential of AM fungi along with PSM or Azotobacter to improve the growth of rubber seedlings in the seedling nursery.

A comparison of two tapping practices (continuous tapping throughout the year and with annual tapping rest during February to April) with respect to 18 Hevea clones (viz. RRII 105, RRII118, RRII 203, RRIM 600, RRIM 605, PB 86, PB 235, PB 5/51, GT 1, Gl 1, RRIC 102, RRIC 105, RRII 208, RRII 5, PB 260, PB 310, PB 311 and PR 255) of varying yield potential was evaluated in Assam. The performance of these clones with respect to rubber yield, girth, dry rubber content (DRC) and tapping panel dryness (TPD) under two tapping practices during Regime I (non-cold season) and Regime II (cold season) were evaluated. Trend in yield was always higher in annual tapping rest (ATR) than in continuous tapping (CT) except in 3 clones (PB 260, PB 5/51 and PB 311). Among the clones evaluated, RRIM 600, RRII 203, RRII 208, PB 235, PB 310, RRII 118 and GT 1 yielded above average under both tapping practices indicating these clones were more efficient in yield potential under sub-tropical humid conditions of Assam.

Sequestering atmospheric CO2 through tree cultivation is an environmentally acceptable option. Recently the Rubber Research Institute of India released several high yielding clones of Hevea (RRII 400 series) and the present study was taken up to determine the carbon sequestration potential of these clones by two methods viz. conventional tree felling and allometric equation without tree felling. The trees planted in a clone evaluation trial in RBD design with three replication at RRII, Kottayam were used for the study. The clones selected were RRII 414, RRII 417, RRII 422, RRII 429 and RRII 430 and RRII 105. In the first method, carbon stock per tree was determined using the carbon content of plant parts viz. trunk, branches, leaf and root and the carbon sequestration potential of clones at the plantation level was estimated. In the second approach, the biomass accumulation at different growth stages was estimated using allometric equation based on girth of the trees for a period of 17 years the carbon accumulated at each growth stage was estimated assuming the carbon content as 42 per cent of the biomass. The study showed that the clones varied in growth pattern, biomass accumulation and carbon sequestration potential. The carbon sequestration potential of RRII 429 was 113.73 t/ha and it was significantly superior to that of all the other clones. The clones RRII 414 and RRII 417 also had a significantly higher carbon sequestration potential than RRII 105.

Nanotechnology is recognized as one of the highly promising areas for technological development in the 21st century. Polymer nanocomposite is a rapidly emerging multidisciplinary research activity whose results could broaden the applications of polymers for the benefit of many industries. This article reviews different types of nanomaterials used for the preparation of polymer nanocomposites with special reference to rubber nanocomposites. The role of nanotechnology and its global outlook has been summarized. Different types of nanomaterials and their physical and chemical properties have been discussed in detail. It focuses on the general properties of the nanocomposites, their classification and routes of synthesis. Preparation of polymer nanocomposites derived from various nanomaterials, especially nanoclays; their morphological analysis, filler dispersion have been described. The techniques used for the characterization of polymer nanocomposites and their physical properties have been discussed categorically. The major challenges in nanotechnology research have been categorized in terms of the structures from nano to micro levels. Recent developments in natural rubber latex based nanocomposites and their blends with synthetic latices have been discussed. The application of polymer nanocomposites, especially in the packaging and automobile industries have been summarized.