Rubber Science

IDENTIFICATION OF SUPERIOR GENOTYPES AND PREPOTENT PARENT CLONES OF HEVEA IN NORTH EAST INDIA BY HALF-SIB PROGENY ANALYSIS
Pages 234-242
P. Deepthy Antony, S. K. Dey & Kavitha K. Mydin
- Abstract
- Keywords
Half-sib progeny analysis from selected clones has been successfully utilised for the identification of superior genotypes as well as prepotent parents for future breeding programmes in Hevea. The present study was conducted in Tripura in North East India utilising the half-sib progenies collected from nine Hevea clones and planted family-wise for seedling nursery evaluation. Girth, yield per unit girth and test tap yield were recorded two and a half year after field planting and analysed in comparison with reference clones for identification of superior genotypes and prepotent parents. Progenies of SCATC 93/114, PB 86 and Haiken 1 were superior in terms of vegetative vigour. Among the progeny families evaluated, RRIM 600 had the highest mean test tap yield (13.9 g t-110t-1) as well as yield per unit girth (0.78 g t-110t-1cm-1). Test tap yield of the half-sib progenies ranged from 0.52 g t-110t-1 to 79.62 g t-110t-1, with an overall mean yield of 12.23 g t-110t-1. Selection of top 20 per cent genotypes based on rank summation index revealed that mean yield of selections from family of PB 86 and SCATC 88/13 were better than the check clone, RRIM 600. Based on the study, 110 selections were made for further evaluation and an improvement of 32.9 per cent and 136 per cent were attained in girth and yield, respectively when compared to unselected population. Based on the superior performance of progenies and higher proportion of superior progenies, PB 86, RRIM 600 and Tjir 1 were identified as prepotent clones which can be utilised in future breeding programmes.

Genotypes, Half-sib progeny, Prepotency, Selection

AN EFFICIENCY INDEX FOR SELECTION OF BRUSH WEED CUTTER
Pages 243-247
Siju T
- Abstract
- Keywords
The brush weed cutters tested at Rubber Research Institute of India were ranked based on the comparative performance from a techno-economic perspective. The parameters used for evaluvating the brush weed cutters were assigned weights by expert judgement method and statistical method. The statistical method of assigning weights is preferred due to its unbiased nature. The final rankings of the weed cutters were influenced by the changes in weights given by the methods.

Weights, Statistical method, Efficiency index, Expert judgement, Ranks

EFFECT OF FERTILIZERS ON THE AVAILABILITY OF NUTRIENTS IN THE SOIL AND GROWTH AND YIELD OF MATURE RUBBER IN THE CENTRAL BRAHMAPUTRA VALLEY ZONE (CBVZ) OF ASSAM
Pages 248-253
R.P. Singh M. Choudhury & M. Joseph &N. Ashithraj
- Abstract
- Keywords
A field experiment in mature rubber was conducted in a grower’s field at Rampur village, Borgang, Sonitpur, Assam about 300 km away from Guwahati, the capital of Assam to study the response of mature rubber to inorganic fertilizers under the agro-climatic condition of Central Brahmaputra Valley Zone (CBVZ) of Assam using the clone RRIM 600. Girth and girth increment of rubber were significantly influenced by higher doses of fertilizers. Optimum levels of N, P and K for achieving the highest girth in mature rubber and improving the soil fertility was found to be 60:30:45 kg ha-1 yr-1. Similarly, application of N, P and K significantly improved the yield and dry rubber content (drc). The highest yield (g t-1t-1) and drc (%) was recorded with 60:30:45 kg ha-1 yr-1. Continuous application of fertilizers improved the soil fertility status.

North East India, Soil fertility, Leaf nutrient concentration, Girth, Fertilizer response, Dry rubber yield

QUALITY IMPROVEMENT OF RADIATION VULCANISED NATURAL RUBBER LATEX
Pages 254-262
Eldo K Abraham, Rosamma Alex, I. John Britto, Benny George, Sadeesh Babu P.S. & Lalit Varshney
- Abstract
- Keywords
An attempt was made to improve the green strength of fresh natural rubber latex by exposure to low doses of γ radiation followed by centrifuging to reduce the non-rubber ingredients. The centrifuged latex was then vulcanised by exposure to γ-radiation in presence of n-butyl acrylate as sensitizer. The non-rubber ingredients were further removed by suitable leaching operations. As a result of the chemical changes accompanied by exposure of latex to γ-radiation, the extractable protein content of the radiation vulcanised natural rubber latex (RVNRL) films decreased to acceptable levels (below 50 μg g-1). The mechanical properties of RVNRL also improved by using centrifuged natural rubber latex having high gel content or by blending with sulphur vulcanised natural rubber latex (SVNRL).

Prevulcanisation, Leachable protein, Radiation vulcanisation, Shrinkage

NITRILE RUBBER COMPOUNDS WITH IMPROVED FLEX-CRACK RESISTANCE
Pages 263-267
K.S. Mohanadas & Siby Varghese
- Abstract
- Keywords
Incorporation of reinforcing fillers is essential for enhancing of technologically important physical properties of elastomers. Various types of carbon black are highly efficient in reinforcing elastomers. Within the family of black fillers, reinforcing efficiency varies widely and this depends mainly on the particle size of the filler. For certain applications, along with reinforcement, resistance to flex-crack also has importance. In this study, conventionally used blacks namely HAF, FEF and GPF were compared for their flex-crack resistance in nitrile rubber vulcanizates. Nitrile rubber was selected since the study was aimed at developing a flex-crack resistant vulcanizate which can perform in hydrocarbon oil medium. By increasing the dosage of carbon black from 40 to 60 phr, flex-crack resistance improved up to 50 phr loading for the three fillers and this decreased thereafter. Among the fillers used, the one with the largest particle size produced the highest flex-crack resistance.

Particle size, Acrylonitrile rubber, Fatigue, Flex-crack resistance, Reinforcement

Digital library

Volume 27, Number 2, (December 2014) Articles 7 - 11