Latex Harvesting Research Articles

Transcriptional and post-transcriptional regulation of the jasmonate signalling pathway in response to abiotic and harvesting stress in Hevea brasiliensis.

BackgroundLatex harvesting in Hevea brasiliensis amounts to strong abiotic stress that can cause a halt in production in the most susceptible clones. Although the role of jasmonic acid has been suggested in laticifer differentiation, its role in latex production and in the response to harvesting stress has received very little attention. Only a few key genes acting in the COI-JAZ-MYC module have been isolated and studied at transcriptional level.ResultsUse of a reference transcriptome obtained on rubber clone PB 260 covering a large number of tissues under different environmental conditions enabled us to identify 24 contigs implicated in the jasmonate signalling pathway in the rubber tree. An analysis of their expression profile by qPCR, combined with hierarchical clustering, suggested that the jasmonate signalling pathway is highly activated in laticifer cells and, more particularly, in the response to harvesting stress. By comparison with their genomic sequences, the existence of regulation by alternative splicing was discovered for JAZ transcripts in response to harvesting stress. Lastly, positive transcriptional regulation of the HbJAZ_1405 gene by MYC was demonstrated.ConclusionThis study led to the identification of all actors of jasmonate signalling pathway and revealed a specific gene expression pattern in latex cells. In-depth analysis of this regulation showed alternative splicing that has been previously shown in Arabidopsis. Interestingly, genotypic variation was observed in Hevea clones with contrasting latex metabolism. This result suggests an involvement of jasmonate signalling pathway in latex production. The data suggest that specific variability of the JA pathway may have some major consequences for resistance to stress. The data support the hypothesis that a better understanding of transcriptional regulations of jasmonate pathway during harvesting stress, along with the use of genotypic diversity in response to such stress, can be used to improve resistance to stress and rubber production in Hevea.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-014-0341-0) contains supplementary material, which is available to authorized users.

Root and rhizosphere processes-high time to dig deeper.

Root and rhizosphere processes-high time to dig deeper.

Regulation of MIR Genes in Response to Abiotic Stress in Hevea brasiliensis

Increasing demand for natural rubber (NR) calls for an increase in latex yield and also an extension of rubber plantations in marginal zones. Both harvesting and abiotic stresses lead to tapping panel dryness through the production of reactive oxygen species. Many microRNAs regulated during abiotic stress modulate growth and development. The objective of this paper was to study the regulation of microRNAs in response to different types of abiotic stress and hormone treatments in Hevea. Regulation of MIR genes differs depending on the tissue and abiotic stress applied. A negative co-regulation between HbMIR398b with its chloroplastic HbCuZnSOD target messenger is observed in response to salinity. The involvement of MIR gene regulation during latex harvesting and tapping panel dryness (TPD) occurrence is further discussed.

Ethnobotany, Traditional Knowledge, and Diachronic Changes in Non–Timber Forest Products Management: A Case Study of Himatanthus drasticus (Apocynaceae) in the Brazilian Savanna1

Ethnobotany, Traditional Knowledge, and Diachronic Changes in Non–Timber Forest Products Management: A Case Study of Himatanthus drasticus (Apocynaceae) in the Brazilian Savanna. The analysis of factors and processes that affect the traditional knowledge and the management practices deriving from it are essential for devising conservation strategies for non–timber forest products. The purpose of this study is to assess the traditional knowledge and analyze diachronic changes in management systems for non–timber forest products in a case study of an intensely exploited species from the Brazilian savanna, Himatanthus drasticus, commonly known as “janaguba.” Janaguba produces a latex of commercial value, widely used in popular medicine in Brazil. Recent pharmacological evidence of its medicinal properties has increased harvesting pressure on this resource. For this reason, we carried out an ethnobotanical characterization of the management systems used to harvest janaguba latex and of the traditional ecological knowledge associated with such practices. Three management systems were identified in latex harvesting, which may have varying ecological impacts on janaguba populations, depending on the amount of bark removed and the time interval between harvestings. Among the factors that can influence changes in the management systems over time are market pressure and growing demand for the product, loss of traditional knowledge, the system of land tenure, and the biological characteristics of the species, especially its high biomass regeneration capacity.

Impact of tapping and soil water status on fine root dynamics in a rubber tree plantation in Thailand.

Fine roots (FR) play a major role in the water and nutrient uptake of plants and contribute significantly to the carbon and nutrient cycles of ecosystems through their annual production and turnover. FR growth dynamics were studied to understand the endogenous and exogenous factors driving these processes in a 14-year-old plantation of rubber trees located in eastern Thailand. FR dynamics were observed using field rhizotrons from October 2007 to October 2009. This period covered two complete dry seasons (November to March) and two complete rainy seasons (April to October), allowing us to study the effect of rainfall seasonality on FR dynamics. Rainfall and its distribution during the two successive years showed strong differences with 1500 and 950 mm in 2008 and 2009, respectively. FR production (FRP) completely stopped during the dry seasons and resumed quickly after the first rains. During the rainy seasons, FRP and the daily root elongation rate (RER) were highly variable and exhibited strong annual variations with a total FRP of 139.8 and 40.4 mm-2 and an average RER of 0.16 and 0.12 cm day-1 in 2008 and 2009, respectively. The significant positive correlations found between FRP, RER, the appearance of new roots, and rainfall at monthly intervals revealed the impact of rainfall seasonality on FR dynamics. However, the rainfall patterns failed to explain the weekly variations of FR dynamics observed particularly during the rainy seasons. At this time step, FRP, RER, and the appearance of new FR were negatively correlated to the average soil matric potential measured at a depth of between 30 and 60 cm. In addition, our study revealed a significant negative correlation between FR dynamics and the monthly production of dry rubber. Consequently, latex harvesting might disturb carbon dynamics in the whole tree, far beyond the trunk where the tapping was performed. These results exhibit the impact of climatic conditions and tapping system in the carbon budget of rubber plantations.

Effectiveness of gaseous stimulation in low intensity latex harvesting in rubber plantations of Sri Lanka

Prevailing high price for rubber attracts growers to practise ethylene based gaseous stimulated harvesting as a method of efficient utilization of high panels and obtaining high yields at the last stage of the rubber tree. With no previous records, the present study was aimed to assess the effectiveness of gaseous stimulated harvesting systems in large scale application under Sri Lankan conditions. This system was found to be financially viable in terms of increased overall profitability and benefit cost ratio. Agronomically, it was effective with reduced bark consumption lengthening the harvesting period and increased worker use efficiency. Harvesters’ income increased with the application of the system motivating workers to be engaged in latex harvesting. In order to assure the full benefits, proper application and maintenance of the system and monitoring of tapping quality are essential. Potential reduction in the price of gas jacket and increase in tapping task size are also critical factors for the profitability of the system. Effect of the price of rubber and other commodities on the overall profitability is also discussed.

Harvesting the rubber tree once in four days; a solution to current issues in the rubber industry in Sri Lanka

Despite it’s importance, latex harvesting in rubber plantations poses significant problems demanding high level of skilled workers and cost of production. Low frequency harvesting (LFH) instead of traditional half spiral-once in two days system (S/2 d2), appears to be a practical solution to arrest these issues. Reduction of harvesting frequency has been limited only up to once in three days (S/2 d3) for Sri Lankan genotypes. Therefore based on some preliminary investigations, the present study was aimed at developing a suitable protocol for harvesting the rubber tree once in four days with the half spiral cut length (S/2 d4). In addition to the small scale genotypic comparison, the study comprised the commercial testing of S/2 d4 system. The overall yield given by the traditional S/2 d2 was used as the standard for the comparison and the stimulation protocol of this system was adjusted to obtain similar yields. The yield given by S/2 d4 under the stimulation protocol, applying 3.3% Ethephon (ET) once a month was comparable with that of the traditional S/2 d2 only in the wet areas of the country. Latex physiological parameters assured the sustainability of the stimulation protocol in all genotypes tested except in RRIC 102. At commercial level, S/2 d4 system has resulted in 19% reduction in the cost of production, 22% increase in overall profitability, 26% increase in harvesters’ income and 50% reduction in worker requirement in harvesting. Potential long-term impact of this system on latex yields and socio-economic sustainability, awareness programmes and limitations of LFH in dry climates are also discussed.

Tapping panel diagnosis, an innovative on-farm decision support system for rubber tree tapping

Latex is a key product for many tropical countries, of which 80% is produced by smallholders. Latex is produced by the rubber tree (Hevea brasiliensis). Given the 7-year immature unproductive period, establishing a rubber plantation requires considerable investment by smallholders, emphasizing the need for sustainable management. The difficulty of performing an agronomic diagnosis of a tree crop is to obtain an accurate picture of current and past cultivation practices, to be able to assess their impacts on the agro-ecosystem as well as on sustainability. Smallholders do not usually keep records of latex yield or of their technical practices, making it impossible to perform a diagnosis based on productivity. As latex harvesting involves tapping the bark, which leaves scars on the trunk, we hypothesised that these morphological traces would be good indicators of current and past practices and would thus enable a diagnosis based on the economic lifespan of plantation. To this end, we formalised a tapping panel diagnosis that involved reproducing the scars on tapping panel diagrams, and analysing them using two indicators: the amount of virgin bark consumed and the number of tapping years that remained. We validated this tapping panel diagnosis in a sample of 25 smallholder plantations in Cameroon, where we characterised eight tapping management systems reflecting different levels of tapping intensity. The assessment of the respective share of each tapping practice on virgin bark consumption revealed major effects of tapping frequency and of shaving thickness. We showed that the tapping panel diagnosis used as a decision support tool can increase remaining tapping years by 33% to 355%. To conclude, the tapping panel diagnosis formalised here for the first time will be a useful support for the participatory development of innovating tapping management schemes involving both technicians and smallholders.

Feasibility of rubber (Hevea brasiliensis Muell. Arg.) cultivation in Eastern province of Sri Lanka with the peasant community

Being a war torn area, Eastern province of Sri Lanka is relatively underdeveloped and a large extent of lands which were under chena cultivation is available. Rubber (Hevea brasiliensis Muell. Arg.) has proven to be a successful tree crop in the peasant community with its ability to provide continuous permanent income through latex harvesting. Therefore, a feasibility study of planting rubber in Eastern province was carried out. The area coming under the Intermediate zone was the target and rubber planting commenced in 2003 with the participation of three farmers in Komana village of the Padiyatalawa division in the Ampara district. Only two farmers were successful in the first attempt. However, this success led to plant rubber in over 100ha with 282 farmers in the region by 2008. Despite the dry spell, the survival and growth of rubber plants in most of sites were satisfactory and on average, the annual girth expansion rate was 7.35 cm. Rubber plants were expected to be harvested for latex by 7 years. Photosynthetic parameters under normal circumstances were rather healthy, however, under severe drought conditions they were affected indicating a drought induced photoinhibition or down regulation in photosynthesis. Potential of alleviating the adverse effects of droughts on plant growth using improved agro-management practices is discussed.

Gene expression pattern in response to wounding, methyl jasmonate and ethylene in the bark of Hevea brasiliensis

Natural rubber production in Hevea brasiliensis is determined by both tapping and ethephon frequencies. It is affected by a complex physiological disorder called tapping panel dryness. This syndrome is likely to be induced by environmental and latex harvesting stresses. Defence responses, including rubber biosynthesis, are dramatically mediated by wounding, jasmonate and ethylene (ET), among other factors. Using real-time RT-PCR, the effects of wounding, methyl jasmonate (MeJA) and ET on the relative transcript abundance of a set of 25 genes involved in their signalling and metabolic pathways were studied in the bark of 3-month-old epicormic shoots. Temporal regulation was found for 9 out of 25 genes. Wounding treatment regulated the transcript abundance of 10 genes. Wounding-specific regulation was noted for the HbMAPK, HbBTF3b, HbCAS1, HbLTPP and HbPLD genes. MeJA treatment regulated the transcript abundance of nine genes. Of these, the HbMYB, HbCAS2, HbCIPK and HbChi genes were shown to be specifically MeJA inducible. ET response was accompanied by regulation of the transcript abundance of eight genes, and six genes, HbETR2, HbEIN2, HbEIN3, HbCaM, HbPIP1 and HbQM, were specifically regulated by ET treatment. Additionally, the transcript level of the HbGP and HbACR genes was enhanced by all three treatments simultaneously. Overall, a large number of genes were found to be regulated 4 h after the treatments were applied. This study nevertheless revealed some jasmonic acid-independent wound signalling pathways in H. brasiliensis, provided a general characterization of signalling pathways and will serve as a new base from which to launch advanced studies of the network of pathways operating in H. brasiliensis.