查看更多>>摘要：The successful release of RRII 105, the first high yielding Indian hybrid clone in 1980 was a game changer in the Indian rubber plantation sector. Until then the Malaysian clone RRIM 600 has been the ruling clone in India. RRII 105 could yield 369 kgha~(-1)yr~(-1) more than RRIM 600. Large scale expansion of rubber cultivation in India during the 1980s using RRII 105 made India a significant rubber producing country, productivity ranking the highest in the world and meeting almost the entire demand for rubber from domestic production for several years. The production-consumption gap started to widen with the current price decline from the beginning of this decade. The present analyses show that during the period between 1991 and 2017, the total economic value of the incremental yield produced by RRII 105 (over RRIM 600) in India was to the tune of USD 6635 million. This translated into maximum incremental revenue of Rs. 28,000 per grower per year in 2011-12 when the number of growers was as high as 1.2 million. Bringing such a substantial economic benefit to a large number of farmers as a result of just one innovation, namely RRII 105 has no parallel in Indian agriculture. To avoid the risk of extensive monoclonal planting more number of high yielding, climate-resilient "smart clones" with fast growth rate, high timber yield and pest/disease tolerance should be released in quick succession. The present rubber breeding cycle of 25 years is too long. Towards achieving the objective of shorter breeding cycle, advanced breeding tools such as molecular breeding, marker assisted selection and genetic engineering should be adopted.
查看更多>>摘要：Tropical cyclone Ockhi that came close to Kanyakumari district in Tamil Nadu state of India on 30 November 2017 destroyed close to half a millioin rubber trees in the district even though the eye of the storm did not make a landfall there. The scale of the destruction was unpercedented in the nealy 120 year history of rubber cultivation in India. More than 900 smallholdings lost about 1,78,000 trees and the large estates in the district lost another 2,83,000 rubber trees. The affected smallholdings lost an average of 61 per cent of the trees. A few medium sized estates also lost more than 50 per cent of the trees. More than 95 per cent of the loss was due to uprooting. Mature and yielding trees and trees planted in lowlying fields were more vulnerable to uprooting. No loss of trees was reported from adjacent Kerala, except for some loss in Punalur region, about 100 kms North of the most affecetd areas in Kanyakumari district. Potential threats to rubber cultivation in India and other countries from severe tropical cyclones in the context of global warming are also discussed.
查看更多>>摘要：Plant nuclear DNA is an inherently unstable molecule and can be damaged metabolically or by a number of stress factors like extreme temperatures, drought and pathogen attack. In the present study, excised leaf discs harvested from two Hevea clones, RRII 430 (relatively drought tolerant) and RRII 414 (relatively drought susceptible) were subjected to water deficit stress in vitro using PEG under low and high light conditions in a plant growth chamber and another set of leaf discs kept under sunlight in open field. The integrity of genomic DNA from the leaf discs subjected to the stress conditions indicated a fair degree of DNA fragmentation in drought susceptible clone under high light alone as well as in the combination of high light and PEG stresses. In the drought tolerant clone, DNA was comparatively intact with no visible signs of fragmentation. On the other hand, under very high light conditions in the open field, significant level of DNA fragmentation was observed in both the clones indicating that high light can inflict serious damages to DNA in both drought tolerant and susceptible clones.
查看更多>>摘要：Quality of the produce is crucial in ensuring fair price to the farmers. Farmers' practices followed in harvesting and post harvesting affects the quality of rubber produced. The present study identified the practices most commonly adopted by cup coagulum producers in different regions of Thailand and its possible effect on quality of the produce. Data were collected through individual interviews with 771 farmers distributed in the historical and new rubber-producing areas. The classification of farmers based on the combination of three practices with a potential adverse impact on rubber quality viz. non-rubber contaminants, latex coagulation process and coagulum maturation, identified the diversity of harvesting and post-harvest practices. Practices were not uniform within regions. However, regional specificities could be highlighted. The main risks for rubber quality were systematic coagulation with sulfuric acid in the Centre-east and North-east and the presence of non-rubber contaminants in the South. Farmers were unaware of the good practices for quality production, the kind of acid that they used, and the impact of their practices on quality. Significant gap exists between the processors' concerns and the farmers' perception of rubber quality. Since the sustainability of smallholders' production largely depends on their ability to meet the quality requirements, interactions between the stakeholders is highly warranted.
查看更多>>摘要：Open pollinated seeds of Hevea brasiliensis were collected from polyclonal seed gardens and multi-clone trials situated in both traditional and non-traditional rubber growing zones in India and evaluated in three agro-climatically different zones viz. traditional region (Kerala), drought (Maharashtra) and cold (West Bengal) conditions. Evaluation of these polycross progeny populations resulted in the selection of 146 superior progenies. The minimum dry rubber yield of selections in Kerala was 20 g t~(-1)10t~(-1), West Bengal was 15 g t~(-1)10t~(-1) and Maharashtra was 5 g t~(-1)10t~(-1). Mean dry rubber yield of the selections from each population was significantly different from the mean of each population. The highest number of selections was obtained from the progeny population of Tura followed by Kanyakumari, Nagrakata and Agartala. The final selections were 64, 39, 43 which was 7, 4 and 6 per cent, respectively from Kerala, Maharashtra and West Bengal. Progeny populations originated from the traditional regions outperformed the populations from the non-traditional regions of Maharashtra and West Bengal even when screened in their respective non-traditional climates. Meanwhile, when the progeny populations originated from the non-traditional regions were planted in the ideal traditional climate, they performed better than in their native climates. A clear distinction was obtained between the yield of the progenies with girth below the population mean and the yield of the progenies with girth above the population mean. From a total of 6126 progenies evaluated, a total of 2685 progenies were test-tapped and out of the 146 selections, only two of the selections fell in the below mean girth group while 144 selections (99% of the selected progenies) were in the above mean girth group. A strong association of 49 per cent (R~2) dependence of the population yield on girth was observed. Progenies originated from the drought region showed a high dependence of yield on girth (56%) suggesting vigorous girth as a requirement for economic yield in the drought regions. Rubber plants grown in cool climate was superior in yield and girth than that observed under hot climate. Severe reduction in girth and rubber yield was found under the dry climate while reduction in height of plants was noticed under the cool climate. This study also suggests establishment of new PSGs to obtain recombinants with higher levels of yield and girth growth.
查看更多>>摘要：Present study utilized multi-resolution satellite images of Indian remote sensing (IRS) satellites for identification and estimation of spatial extent of NR and wastelands suitable for NR cultivation in the state of Assam in India. Temporal and multi-resolution satellite images of IRS R I and II L-3, L-4, Cartosat PAN were used for the study. We used Cartosat PAN merged L-4 data for mapping of areas under NR and wastelands suitable for its cultivation. Spectral signature, phenological characteristics and ground truth information were used to identify rubber holdings. Wastelands suitable for rubber cultivation were estimated from the high resolution satellite data using terrain conditions, land cover types etc. Mapping of the wastelands suitable for NR cultivation was carried out excluding the areas under food crops, forests, steep valleys and lands which are more suitable for food crop cultivation. Spatial extent of rubber plantation in Assam was 16,872 ha and about 24,783 ha of wastelands suitable for NR cultivation were estimated during 2011-2012. Karimkhanj district of Assam has the highest extent of wastelands (6,969 ha) followed by Karbi Anglong (6,052 ha), Kamrup (4,525 ha) and Goalpara (2,988 ha) districts. These four districts accounted for about 69.8 per cent of total rubber cultivation and 82.8 per cent of total wastelands estimated in the state. Other fairly suitable districts for NR cultivation are Dima Hasao, Hailakandi, Dhubri, Kokrajhar and Jorhat. These districts have 13 per cent of total wastelands suitable for NR. In general, spread and occurrences of NR and wastelands suitable for its cultivation are more in south-western and north-southern districts than in the north-eastern districts of the state. Estimated wastelands can be prioritized hierarchically for further analyses of suitability in terms of soil and climate variables. This study also serves as a GIS based decision support system for planners in NR sector.
查看更多>>摘要：Twenty-two potential wild Hevea accessions along with three modern clones viz. RRII 105, RRIM 600 and RRII 208 were evaluated in the seventh to eleventh years of growth in the traditional rubber growing region of Kerala, India. Highly significant clonal differences were observed for yield and growth traits, except bole height. RO 2629 had the highest yield of 29.4 g t~(-1)t~(-1) followed by AC 716 (24.9 g t~(-1) t~(-1)) and AC 4149 (23.6 g t~(-1) t~(-1)), respectively. RO 2629 also had the highest girth, girth increment per year over four years and bole volume. The girth in the seventh year ranged from 26.9 cm (RO 287) to 47.8 cm (RO 2629); girth increment from 3.6 cm (RO 3804) to 6.7 cm (RO 2629); branching height from 2.2 m (RO 3804) to 3.1 m (MT 2233); wood quantity from 0.03 m~3 (RO 3804) to 0.10 m~3 (RO 2629). PCV was higher than the GCV for all the characters and the highest PCV was recorded for mean yield over two years. Heritability was also high for mean yield. Girth was significantly correlated with girth increment and wood quantity. RO 2629, MT 2233, AC 4149 and AC 626 ranked top with the maximum number of desirable traits. Having a different genetic background from the traditional Wickham clones, these accessions will serve to broaden the genetic base of present-day cultivated Hevea by introgression into the elite cultivars.
查看更多>>摘要：Twenty five phosphofungal isolates from rubber (Hevea brasiliensis) plantations were evaluated for solubilization of ferric phosphate, aluminium phosphate, tricalcium phosphate fertilizer grade rock phosphate and acid phosphatase activity. Among the twenty five, seven isolates showed solubilization of phosphates and fertilizer grade rock phosphate and belonged to Aspergillus spp. and Penicillium spp. and was selected for further studies. These selected isolates were further evaluated for its beneficial effect on growth of rubber seedlings raised in root trainer cups. Among the seven, one isolate, Penicillium spp. (Pf 11) was further evaluated for growth improvement in root trainer plants in combination with 25,50 and 100 per cent of the recommended dose of fertilizer and compared with uninoculated plants with 25,50 and 100 per cent of fertilizer. The plants inoculated with Pf 11 at 50 per cent fertilizer showed higher girth, height and root development followed by inoculation with Pf 11 at 25 per cent fertilizer level. Girth of plants in treatment with Pf 11 at full fertilizer was lower than the treatment with 25 and 50 per cent fertilizer application in combination with inoculation. Highest population of inoculated phospho fungi was at 25 per cent fertilizer application and was reduced as the fertilizer levels increased. An efficient phosphofungus (Pencillium spp.) could be isolated from the rubber plantations and upon inoculation in rubber seedlings recorded better growth at 50 per cent of the recommended level of fertiliser.
查看更多>>摘要：Yield components like total volume and dry rubber content (DRC) of latex were analyzed in summer and peak yielding seasons in the renewed bark to assess the performance of RRII 400 series clones. Significant variations were observed among the clones under evaluation with regard to the parameters. RRII 414 and RRII 430 showed the highest total latex volume as well as dry rubber yield both in summer and peak yielding seasons when tapped in the renewed bark. Total latex volume was less irrespective of the clone during summer compared to peak season. Clones responded differently to summer stress. The drop in total latex volume during summer ranged from 39.5 to 64 per cent and 36.6 to 60.9 per cent in LST I and LST II, respectively. The highest drop in summer latex volume was recorded in clone RRII 430. When virgin and renewed panels were compared, the total volume of latex was less in renewed panel compared to virgin panel in both the LST's barring very few exceptions. Status of clones with regard to latex volume, DRC and dry rubber yield in virgin panel (BO-1) and renewed panel (BI-1) were comparable in majority of the clones. The present study proved the superiority of RRII 430, RRII 417 and RRII 414 in the long run as well.
查看更多>>摘要：Devulcanisation of filled rubber vulcanisates through mechanical/ mechano-chemical processes in a two-roll mill is a well-established technique. The general mechanism of mechano-chemical devulcanisation suggests blocking of possible reunion of free radicals produced via crosslink scission. Hence the efficiency of shear induced devulcanisation processes can be improved significantly by the effective utilization of a chemical /process that can instantaneously block the reunion of the radicals formed by bond scission. A new concept of blocking the reunion free radicals formed by shear breaking of crosslinks using a stable free radical and thereby increasing the efficiency of devulcanisation is presented. A cyclic nitroxide stable free radical viz. 4-hydroxy 2, 2, 6, 6-tetramethylpiperidine 1-oxyl free radical (4-Hydroxy TEMPO abbreviated as 4HT) assisted mechanical devulcanisation of carbon black filled NR vulcanisates (un-aged and aged) in which 4HT was used to block the recombination of the radicals formed by bond scission. Stable free radical increased the per cent devulcanisation and revulcanisate properties of devulcanised rubber in all cases under consideration. The recombining capacity of different type of cleaved crosslinks (mono-, di- and poly- sulphidic) were found to decisively influence the per cent devulcanisation of samples under shear induced devulcanisation. The influence of factors like cure system, crosslink density, the extent of ageing etc. of the original sample on the devulcanisation efficiency and the subsequent revulcanisate properties are discussed in detail.
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