Twenty six clones from India, China, Malaysia, Indonesia and Sri Lanka, cultivated under the agroclimate of Sub-Himalayan West Bengal were evaluated for girth (over 24 years) and yield (over 19 years). A wide range of variability in terms of girth, timber volume, annual yield, yield in different panels and monthly yield was observed. The Chinese clone SCATC 88/13 ranked first with significantly high timber volume, biomass and high yield over different years and months compared to RRIM 600, the widely planted clone in the region SCATC 88/13 can be considered as a suitable clone for this region. 

Possibility of using of endosymbionts in the management of Corynespora leaf disease of young rubber (Hevea brasiliensis) was studied through in vitro assay and field evaluation. Endophytic bacteria isolated from different parts of the rubber tree were screened for the in vitro antagonistic activity against Corynespora. A Bacillus isolate (8LK) showed 3.3 cm inhibition zone on the growth of the Corynespora in dual culture and this was selected for bioassay and nursery evaluation. Bioassay using the detached leaves of endophyte treated plants showed reduction in lesion size upon inoculation with pathogen. Compatibility study of the endophytic bacteria with recommended fungicide (Carbendazim) was conducted under in vitro condition and found compatible and was evaluated in susceptible clone in the nursery stage. The results showed that the integrated treatments were on par with the general fungicide recommendation in controlling the Corynespora leaf disease in nursery. 

Spatial variability in soil properties arises due to parent materials, climate, landscape attributes and anthropogenic factors. Geo-statistical methods are effectively used for preparing geographical distribution maps of soil properties based on limited number of samples collected in soil surveys. Geo-referenced soil samples were collected from rubber growing regions of South India, analysed following standard analytical protocol and available Ca and Mg status were mapped geostatistically using kriging interpolation technique.  The study showed that rubber growing soils of south and central Kerala were low in available Ca status, and medium in available Mg status. From Trissur district onwards, available Ca and Mg status showed a gradual increase towards north. In the northern districts, except in Kozhikode, available Ca and Mg status were in the high range in majority of the area. In Wayanad and Kasaragod districts, 100 per cent of the area showed high Mg status. In Karnataka, except in some areas of Dakshin Kannada district, Ca status was high. Almost entire rubber area in Karnataka, Goa and Maharashtra showed high Mg status. The study delineated areas low in Ca and Mg availability which need intervention with respect to Ca and Mg nutrition of rubber plants. 

Retaining natural flora in the interspace instead of cover crops/intercrops is one of the options to meet the challenges of biodiversity conservation in monoculture rubber plantations. A field experiment was initiated during 2012 at the Central Experiment Station of Rubber Research Institute of India to study the possibility of retaining natural flora in rubber plantations as a means for promoting biodiversity. The effect of natural flora and legume covers on growth of rubber, soil moisture and fertility status and biomass turnover were studied. The treatments comprised four weed management options viz. rubber + Pueraria, rubber + Mucuna, rubber + natural cover (maintaining 1 m2 around the plant basin weed free) and rubber + natural cover (maintaining rubber with life-saving weeding). Growth of rubber plants was significantly reduced by allowing natural flora with life- saving weeding and the reduction in girth over a period of four years was to the tune of 27 per cent compared to rubber with cover crops whereas there was only a slight reduction (7%) in the growth of rubber plants with 1m2 weeding. Biomass turnover was significantly higher for Mucuna followed by natural cover. A stable pH was maintained throughout the immaturity period for rubber with natural flora while slight acidification was noticed in the early years of immaturity in plots with legume covers. Comparable organic carbon, available P, K, Ca and Mg were maintained by Mucuna and natural flora. The soil moisture status under natural flora and Mucuna during summer was also positively influenced.  The results indicated that promotion and maintenance of natural understory vegetation in rubber monoculture plantations with minimum weeding around the plant basin was an agronomicaly and economically feasible and ecologically viable strategy to improve biodiversity and maintain soil fertility in rubber plantations. 

Breeding for natural disease resistance is a viable eco-friendly and long-term strategy for sustainable integrated disease management in Hevea. Many clones and germplasm accessions show variable levels of resistance. Being a repository of resistance genes acquired from its parents viz. Hevea benthamiana and AVROS 363, clone Fx 516 was used for hybridization with high-yielding but susceptible RRII clones to recover high-yielding recombinants with enhanced resistance. In addition, open pollinated half-sibs of Fx 516 were also collected and evaluated to rapidly recover high-yielders with disease tolerance. Another high-yielding Wickham x Amazonian hybrid (HP 90/21) was also used in the breeding programme. In the first phase, the above segregating population comprising of hybrids and half-sibs were evaluated for juvenile growth and yield. Wide range of growth and yield performance among the hybrids and half-sibs was recorded. Highest range in yield was exhibited by progenies from RRII 414 x Fx 516 (6-212 g t-115t-1).   Specifically, cross combination of RRII 414 x Fx 516 yielded a selection with very high juvenile yield (212 g t-115t-1) followed by those of RRII 430 x Fx 516 (158 g t-115t-1), RRII 414 x HP 90/21 (152 g t-115t-1) and RRII 429 x Fx 516 (111 g t-115t-1). Similarly, the top selection from half-sib family of disease resistant clone Fx 516 possessed very high-yield (172 g t-115t-1). A large number of selections which are vigorous and very high-yielding has been identified offering wide scope for further screening for disease-resistance and large-scale evaluation for high-yield with potential for commercial deployment to enable sustainable rubber cultivation. 

Among the root diseases of rubber (Hevea brasiliensis), brown root disease is predominant in the traditional rubber growing regions of South India. In vitro sensitivity of fifteen new fungicides was evaluated using poisoned food technique, which identified five fungicides viz. Tebuconazole; Hexaconazole; Epoxyconazole+Pyraclostrobin; Tebuconazole+Trifloxystrobin and Metiram+Pyraclostrobin on par with the standard recommended fungicides Tridemorph and Propiconazole which are currently banned from the market. These fungicides are being taken for field testing in order to confirm their efficiency in the field.