Twelve clones of Hevea brasiliensis including three clones of the RRIM 700 series introduced from Malaysiain 1993 were planted at the Central Experiment Station of the Rubber Research Institute of India in 1994.Yield of the clones in different tapping panels such as BO-1, BO-2, BI-1 and the pooled yield were analyzed for clonal and seasonal yield performance and stability. Stability of yield of clones over the years and different tapping panels were computed. Yield of the clones in low and high yielding seasons were calculated. Monthly yield contribution and yield trend were also recorded. In the BO-1 panel highest yield was recorded in the hybrid clone 86/44 followed by RRIM 722, 86/120, RRII 105 and RRIM 712. In the BO-2 panel, the top yielders were RRII 105, RRIM 722, 86/44 and 86/120 and their yields were on par. When the pooled yields of the BO-1 and BO-2 panels were analyzed, it was found that clones 86/44, RRII 105, 86/120 and RRIM 722 were the most promising clones in the trial. In the BI-1 panel, RRIM 722 recorded the highest yield. Clone 86/120 was the most stable clone in the high yielding and low yielding environments. Monthly yield contribution varied from four per cent (March and April) to eleven per cent in July, August and November. During the rest of the high yielding months, monthly yield contribution was ten per cent (September, October and December) and nine per cent (January and June). Monthly yield contribution varied from four to six per cent in the low yielding environment. There was a sharp decline in yield contribution in February (4%) from that of January (9%) and significant increase in June (9%) from that of May (6%). The high yielding season represented 81 per cent of the total annual yield and the low yielding season represented 19 per cent. Ranking based on yield and girth showed the hybrid clone 86/120 in rank one position followed by 86/44,RRII 105 and RRIM 722.

A field experiment was conducted at Pathalia, Sepahijala district of Tripura during 2007 to 2013 to study the effect of integrating organic manures with chemical fertilizers on soil properties, growth and uptake of nutrients by young rubber. Treatments were standard recommended dose of chemical fertilizers (RDF), farm yard manure (FYM) @ 20 kg plant-1 + 50 per cent of RDF and control (no fertilizer and no manures). The field experiment was conducted in farmer’s field in blocks of 125 plants in each block. Significant increase in girth and height were observed in plants that received FYM @ 20 kg plant-1 + 50 per cent of RDF and its influence was more pronounced in the initial years. At the end of six years, mean girth and tappability of the plants receiving FYM @ 20 kg plant-1 with 50 per cent of RDF, were 48.3 cm and 68.3 per cent,respectively. The corresponding mean girth for plants receiving 100 per cent recommended dose of chemical fertilizers and control plot were 44.7 cm and 35.8 cm, respectively. Tappable plants under these two treatments were 57.6 and zero per cent, respectively. Integrating FYM with chemical fertilizers increased the available N significantly compared to application of chemical fertilizers alone or control. Significant increase in leaf nutrient content of plants was also observed due to combined application of FYM and chemical fertilizers (RDF) indicating higher uptake of applied nutrients. DTPA extractable Zn and Mn were also significantly increased due to combined application of FYM and chemical fertilizers. Results from the experiment revealed that application of FYM @ 20 kg plant-1 with 50 per cent RDF could reduce the gestation period of rubber plants by six months to one year, besides improving soil health, when grown in the denuded lands in Tripura.

A full-length genomic DNA encoding the light harvesting chlorophyll a/b binding protein (CAB), expressed mainly in green leaves, for which the expression is reported to be directly related to the juvenility of the plant tissues, was cloned and sequenced. Initially CAB gene was amplified through PCR from the genomic as well as cDNA of Hevea brasiliensis using primers designed from the conserved regions of the CAB gene reported earlier from related plant species. The PCR amplified fragment (0.5 kb) was eluted, cloned and sequenced. The sequence revealed the presence of 525 bps that showed 91 per cent homology with CAB mRNA from Ricinus communis. Further, full length CAB gene (0.8 kb) was amplified from genomic DNA using Ricinus communis specific primers. The sequence revealed the presence of a fragment of 802 bp which showed 90 per cent sequence homology with the reported cDNA sequence of CAB gene from Ricinus communis. The region amplified in the present study contains the full protein coding sequence with no introns. The phylogenetic tree showed the close relationship of the CAB gene of Hevea with Ricinus communis and Populus trichocarpa apart from the other eukaryotic plants. The amino acid sequence deduced spans an open reading frame of 265 amino acids with predicted molecular weight of 28 kDa and iso-electric point (pI) as 5.45. A protein model was also predicted for the amino acid sequence. This is the first report on isolation and characterization of a full length CAB gene from Hevea brasiliensis.

As the cultivation of Hevea in India is extended to non-traditional regions, it is necessary to identify high yielding clones for each agro-climatic zone. For this purpose, three sets of ortets found promising from holdings in Kerala were planted in South Karnataka region and their performance was evaluated. This report discusses about the performance of one set of 14 ortets in comparison with the performance of check clones RRII 105, GT1 and RRIM 600. In terms of girth, tappability, annual yield, yield stability and summer yield stability, the ortets Tly 55, Tly 56, CES 140, Kly 30, Pal 39A and Kly 26 were superior among the ortets studied they were on par with the control clone GT1 in terms of yield in the agro-climatic conditions of the DK district of Karnataka. Among the above promising ortets, Kly 30 has an additional advantage of being tolerant to abnormal leaf fall disease. These clones need to be further subjected to large scale participatory on - farm trials to validate and confirm their superiority in this agro-climatic region.

Soil urease and phosphatase enzymes play a major role in the mineralization process of organic substrates and their activities were influenced by numerous factors of which soil properties play a key role. The influence of litter from cover crops (Pueraria phaseoloides and Mucuna bracteata) and rubber (Hevea brasiliensis) on the dynamics of urease and acid phosphatase enzymes in the plantation floor of rubber in the traditional region of cultivation was monitored continuously for three years through a field experiment. Pre-calculated quantities of different litter were subjected to natural decomposition in soil and the soil samples were retrieved and activities of urease and phosphatase were monitored twice in a year. The results indicated that both enzyme activities were higher in plots with Pueraria than Mucuna or rubber. The urease enzyme activity ranged from 77.4 to 179.5 ppm of urea hydrolyzed g-1 of soil hr-1 and the phosphatase enzyme activity ranged from 230.5 to 482.0 μg of p-nitrophenol released g-1 of soil hr-1. Urease maintained significant negative correlations with pH in all the treatments. Positive significant correlations were recorded for urease and acid phosphatase activity with total N in the case of leguminous cover crops

This paper examines the seasonality in the production of natural rubber (NR) and whether it has changed in the major producing countries like Thailand, Indonesia, Malaysia and India in the context of fall in the production and productivity of NR. Using the monthly data on production of NR and the technique of change-point analysis, the trends in seasonality at aggregate level (over period) and disaggregate level (within months) was examined for the 23 years period from 1991 to 2013. At aggregate level,seasonality in NR production remained the same in these countries over the period. At disaggregate level also the pattern remained the same in Thailand and Malaysia when it displayed significant changes in India and Indonesia since 1998. Changes in production at disaggregate level are indicative of impending changes in the seasonality of NR production in India and Indonesia. Hence, it is imperative to initiate a multidisciplinary investigation to explore the underlying factors for ensuring the sustainability of commercial cultivation of NR in these countries