Latex Harvesting Research Articles

Can fertilization be a driver of rubber plantation intensification?

Improving the productivity of existing rubber plantations is necessary to cope with the growing demand for natural rubber (NR) while limiting the environmental and social impacts linked to the expansion of rubber cultivation at the expense of natural ecosystems and food crops. The effect of fertilization on NR yield is still unclear and is poorly documented particularly in Thailand, the world leader in NR production. Hence, the main objective of this study was to re-assess the possible effects of fertilization on the yield of intensively managed rubber plantations in Thailand. Our main hypothesis was that the effect of fertilization would be higher with intensive latex harvesting practices (high tapping frequency with ethylene stimulation). To test this hypothesis, we set-up a split-plot experiment with four fertilization doses (T1, no fertilization, T2, T3, T4, respectively low, medium and high doses of NPK fertilizer) and two tapping systems (S/2 d2 with and without ethylene stimulation). Here, we present the results of the first three years on dry rubber yield, latex metabolism assessed with the latex diagnosis method, and latex and rubber properties related to their technological properties. Our results showed a positive effect of fertilization on yield from the first year, but the effect was only statistically significant (p < 0.05) in the third year. The maximum effect of fertilization (+13%) compared to the control treatment (T1) was obtained with the highest dose of fertilizer (T4). Cumulatively over the 3-year period, the increase in yield was +5% with the T2 dose, and +8% with the T3 and T4 dose. Contrary to our main assumption, we observed no interaction between fertilization and ethylene stimulation. Latex diagnosis revealed that the effect of fertilization on yield was linked with a direct effect on latex metabolism mainly through an increase in inorganic phosphorus content (Pi). Finally, we observed no detrimental effect of the fertilizer treatments on latex and rubber quality. We can thus conclude that increasing latex yield through fertilization combined with intensive tapping does not involve any identified risks for the quality of rubber. Taken together, our results demonstrate that fertilization can help increase the yield of rubber plantations where intensive latex harvesting is practised. However, in a context of low NR prices for rubber farmers, the economic return of a +8% increase in yield is questionable. Our trial is continuing to assess the long term effects of the fertilization on yield as well as on the growth and nutritional status of the trees, and the nutrient balance of the plantation.

Navigation of autonomous vehicle for rubber tree orchard

This research has studied the navigation of autonomous vehicles in rubber tree orchards. It was emphasised on the rubber tree plantation in Thailand. Due to the high labour costs in the rubber industry and the demand for natural rubber has continued to decline over the past several years. The farmer were struggled to reduce the labour costs in production. The development of autonomous vehicle technology in rubber plantation can be a way to ease the production costs, such as reducing the amount of labour in fresh latex harvesting. This work was aimed to develop algorithm of a vision system for replacement of expensive sensors used in typical autonomous vehicles. The vision system model was implemented using only one camera installed on the vehicle to search for calibrated targets which were put on the rubber tree trunk. There were two important parameters, tree row offset and target distance, which were concerned when determining the performance of the autonomous vehicle in the rubber tree orchards. In order to evaluate the accuracy of the system, a set of experiments was conducted at a distance of 1-5 meters between the target and the camera. The results were compared between the controlled environment in the laboratory and the uncontrollable environment in the real rubber plantation.

Effect of different preceding crops and land preparation methods on the agrophysiological and health parameters of Hevea brasiliensis Muell. Arg clone GT 1 in southwestern Côte d'Ivoire

Land preparation method and preceding crops affect the evolution of rubber trees. Its ignorance and/or poor execution do not allow the efficient development of the agronomic and economic potentialities of plantations. In order to remove this constraint, a study was undertaken in southwestern Côte d'Ivoire. The rubber trees were planted at 510 trees/ha according to a Fisherblock experimental design, of six preceding crop treatments with three repetitions. Only one latex harvesting system was applied (S/2 d/4 6d/7 ET 2.5% Pa 1 (1) 6/y). The parameters measured were rubber yield, annual average girth increment, physiological profile, sensitivity to tapping panel dryness and sensitivity to root rot caused by the genus Fomes. The results showed that the rate of rubber trees found in the plots was good (90.73± 0.47 %) and had varied with land preparation method depending on the preceding crops. Vegetative growth at tapping (2.05±1.36 cm.year -1 ), and average rubber yield (2053±179 kg.ha-1 .year -1 ) and the rate of tree loss due to the genus Fomes (8.33±0.42%) were influenced by land preparation method. The good productivity, the good physiological state of the rubber trees were characterized by a well balanced physiological profile and a tapping panel dryness rate (3.60 ± 1.74%), independently of treatments. The Agroeconomic results showed that mechanically prepared fallow (813641 FCFA.ha-1 .year -1 ) was the best preceding crop and land preparation method. This technical result has two main interests for the national rubber-growing industry, since it actively participates in the national policy for fighting against deforestation but also contributes to the establishment of a secondary forest by the attributes of the rubber-growing plant cover.

Bark and latex harvesting short-term impact on native tree species reproduction.

The bark and the latex of plants constitute non-timber forest products (NTFPs) of medicinal and economic value that are widely harvested throughout the world. Bark and latex harvesting impacts on plant reproduction are controversial in the literature. Some species are negatively impacted, some do not show any response, and others may exhibit higher flower and fruit production after harvesting. In areas of rainforests and cerrado (tropical savanna) in northeastern Brazil, local people intensely remove the bark of Himatanthus drasticus (for latex collection) and Stryphnodendron rotundifolium for medicinal purposes. We aimed to investigate the short-term impact of harvesting upon reproductive effort of tree species, using those species as models. We assumed that bark harvesting negatively interferes in the reproductive capacity of plant species. Individuals of both species were harvested 2months before blooming (treated) and the production of reproductive structures, physical characteristics of fruits and seeds, and the pre-emergent reproductive success were compared between treated and control (intact) individuals. All parameters of H. drasticus declined after bark removal, except pollen and ovule production. The only reproductive parameters of S. rotundifolium that were negatively affected were pollen and ovule production, and the pre-emergent reproductive success was higher in treatment individuals. We discuss the differences found between the species regarding responses to harvesting. Our results show that harvesting have short-term effects upon reproduction and may impair gene flow by affecting pollination and seed dispersal of tree species.

Production Systems to Minimize the Latex Harvesting Cost of Rubber (Hevea brasiliensis)

Latex harvesting is the most costly activity in natural rubber production and the shortage of available skill and unstable latex harvester are the main factor affecting in Rubber cultivation and its lead to increase cost of production. Low frequency system (LFT) with the hormonal stimulation is a solution to solve this problem that minimize the cost of latex harvesting. Therefore, a study was conducted for nine years on production systems that minimize the cost of latex harvesting in southwestern Côte d'Ivoire with clones IRCA 130, GT 1 and PB 217 of Hevea brasiliensis. These production systems differ from each other by an increase in tapping frequency, in comparison with the standard tapping (d3) on the above clones in southwestern Côte d'Ivoire. The results indicated that production systems that minimize the cost of latex harvesting admittedly resulted in losses of rubber yield per hectare per year from 1 to 37%, but improved the yield per tree per tapping as well as the productivity of the tapper from 20 to 46%, in year. Moreover, these systems contributed to the improvement of the vegetative growth of trees and kept the rate of dry trees in low level (less than 7%). Furthermore, these systems also helped to reduce the cost of tapping labor from 1 to 50%, as well as operating costs from 2 to 47%, in comparison with European Scientific Journal October 2018 edition Vol.14, No.30 ISSN: 1857 – 7881 (Print) e - ISSN 1857- 7431 191 the standard tapping (d3). Finally, in the context of a shortage of tapping labor, these systems help increase the farmer’s profit margin from 26% to 113%, as well as the tapper’s income from 26% to 89%. Therefore, it appears that the use of low frequency harvesting system with the appropriate stimulants appears as a solution to minimize latex harvesting cost and unavailability of harvesters in rubber cultivation.

Incidence Des Fortes Fréquences De Stimulation Hormonale Sur Deux Régimes de Saignée Descendante Du Clone PB 215 : Faible (d6) et Modéré (d4), Au Sud-Est De La Côte D’Ivoire

The clone PB 235 of Hevea brasiliensis is characterized by a rapid growth, homogeneity, and a virgin bark which is suitable for tapping. However, it is sensitive to the very intense latex systems harvesting technologies. This paper focuses on determining the incidence of strong frequencies of stimulation on two downward tapping systems of clone PB 215: low (d6) or moderate (d4). Rubber trees were planted with the density of 510 trees/ha (7 m x 2.8 m) in accordance with a randomized complete block design. Tapping at d6 frequency with 8 and 12 hormonal stimulations and the d4 stimulated 0 and 8 times per year were evaluated. The intensification of hormonal stimulation with the d6 did not have any worthy beneficial effect on the dry rubber yield of the rubber trees. In d4, the stimulation involved a reduction in the sucrose content which led to a significant increase of the dry rubber yield. However, it contributed to an increase in the tapping panel dryness. At moderate tapping, the application of hormonalstimulation allowed us to distinguish between the two latex harvesting technologies. At d6, the two treatments were similar regardless of the stimulation level. Tapping at d6 supports a reduction of tapping workforce and a longer economical durability of the trees, compared to tapping at d4. The intensification of hormonal stimulation applied to lower tapping frequencies (d6) did not have any negative incidence on the clone PB 235. However, it has promoted tapping panel dryness in tapping at d4 frequency.

Transcriptome analysis in Hevea brasiliensis latex revealed changes in hormone signalling pathways during ethephon stimulation and consequent Tapping Panel Dryness

Tapping Panel Dryness (TPD) affects latex production in Hevea brasiliensis. This physiological syndrome involves the agglutination of rubber particles, which leads to partial or complete cessation of latex flow. Latex harvesting consists in tapping soft bark. Ethephon can be applied to stimulate latex flow and its regeneration in laticifers. Several studies have reported transcriptome changes in bark tissues. This study is the first report on deep RNA sequencing of latex to compare the effect of ethephon stimulation and TPD severity. Trees were carefully selected for paired-end sequencing using an Illumina HiSeq 2000. In all, 43 to 60 million reads were sequenced for each treatment in three biological replicates (slight TPD trees without ethephon stimulation, and slight and severe TPD trees with ethephon treatment). Differentially expressed genes were identified and annotated, giving 8,111 and 728 in response to ethephon in slight TPD trees and in ethephon-induced severe TPD trees, respectively. A biological network of responses to ethephon and TPD highlighted the major influence of metabolic processes and the response to stimulus, especially wounding and jasmonate depression in TPD-affected trees induced by ethephon stimulation.

Contribution of Latex Micro Diagnosis to Modern Management of Rubber Plantations: Case of Clones With Low or Slow Metabolism PB 217 and PR 107

The cultivated rubber clones are sensitive to latex harvesting regimes according to their laticiferous metabolism. Thus, in order to determine the best latex harvesting systems of clones with low or slow metabolism, six latex harvesting technologies are applied to them in a bulk statistical device from Fisher to four rehearsals. The rubber is tapped in downward half spiral stimulated or not for nine years after the opening of the tapping panel. The agronomic parameters (production, vegetative growth), the tapping panel dryness and those of the latex micro diagnosis were evaluated. The results indicate that these clones independently of the latex harvesting system have good rubber productivity (2310 kg.ha -1 .y-1 ) with good radial vegetative growth (2.9 cm.y -1 ). Their trees show a well-balanced physiological profile and an acceptable sensitivity to the tapping panel dryness (4.9%). However, the physiological index, the bark consumption and the sensitivity to the tapping panel dryness lead to retain the latex harvesting technologies "S/2 d3 6d/7 Pa1(1) ET2.5% 4/y, S/2 d4 6d/7 Pa1(1) ET2.5% 4/y and S/2 d4 6d/7 Pa1(1) ET2.5% 8/y” for the best. This index, favorably influencing the choice of technologies adapted to clones with active metabolism, contributes to the modern and efficient management of a rubber plantation.

Latex micro diagnosis, modern management tool of rubber plantations of clones with moderate metabolism GT 1, RRIC 100 and BPM 24

Objective : The cultivated rubber clones are sensitive to latex harvesting regimes according to their laticiferous metabolism. This study was done to determine the best latex harvesting system (s) of clones with moderate metabolism (GT 1, RRIC 100 and BPM 24). Methodology and Results : Six latex harvesting technologies were applied to these clones in a bulk statistical device from Fisher to four rehearsals. The rubber trees were tapped in downward half spiral stimulated or not, for nine years after the opening of the tapping panel. The agronomic parameters (latex production, vegetative growth), the tapping panel dryness and those of the latex micro diagnosis were evaluated. The results indicate that these clones independently of the latex harvesting system have good rubber productivity (2234 kg.ha -1 .y -1 ) with good radial vegetative growth (2.4 cm.y -1 ). Their trees showed a well-balanced physiological profile and an acceptable sensitivity to the tapping panel dryness (3.2 %). However, the physiological index, the bark consumption and the sensitivity to the tapping panel dryness lead to retain the latex harvesting technology S/2 d4 6d/7 Pa1 (1) ET2.5% 4/y” for the best. Conclusion and application of results : This index, favourably influencing the choice of technologies adapted to clones with active metabolism, contributes to the modern and efficient management of a rubber plantation. Key words : latex-harvesting technology, rubber clones, moderate metabolism, tapping panel dryness, physiological parameters

Peeling of small diameter rubber log using spindleless lathe technology: evaluation of veneer properties from outer to inner radial section of log at different veneer thicknesses

Rubber forest plantation (RFP) in Malaysia was currently governed by small holders who provided lower diameter logs as they managed plantation using higher planting density, higher frequency tapping practice and young-tapping systems to enhance latex harvesting yield and fulfil demand for rubber timber. Nevertheless, these new planting systems will affect the growth of rubber tree and result in the production of smaller diameter (< 20 cm) rubber logs compared to conventional planting systems. Hence, this raises the question of the small diameter log with respect to its impact on veneer quality. The aim of this study is to determine the properties of rubberwood veneers manufactured from outer to inner radial section of log at different veneer thicknesses. The rubber logs with diameter less than 20 cm were peeled up to 3 cm of peeler core to produce 1, 2 and 3 mm veneer thickness using spindleless lathe. Veneer properties such as thickness variation, lathe checks, surface roughness and contact angle were evaluated from outer to the inner radial section of log at three different veneer thicknesses. Results showed that rubber trees are suitable for peeling due to its consistent density ranging from 650 to 706 kg/m3. Better visual grades recovery can be obtained when peeling thinner rubberwood veneers. The thickness variation, lathe check depth, length and surface roughness of rubberwood veneers increased with increasing veneer thickness, whereas lathe check frequency decreased with increasing veneer thickness. In general, veneer thickness has more prominent effects on the properties of rubberwood veneer compared to the effect of log radial section.

Latex Micro Diagnosis, Modern Management Tool of Rubber Plantations of Clones With Active or Rapid Metabolism IRCA 18, IRCA 130, PB 235, PB 260 and PB 330

The cultivated rubber clones are sensitive to latex harvesting regimes according to their laticiferous metabolism. Thus, in order to determine the best latex harvesting systems of clones with active or rapid metabolism (IRCA 18, IRCA 130, PB 235, PB 260 and PB 330), six latex harvesting technologies are applied to them in a bulk statistical device from Fisher to four rehearsals. The rubber is tapped in downward half spiral stimulated or not for nine years after the opening of the tapping panel. The agronomic parameters (production, vegetative growth), the tapping panel dryness and those of the latex micro diagnosis were evaluated. The results indicate that these clones independently of the latex harvesting system have good rubber productivity (2310 kg.ha -1.y1) with good radial vegetative growth (2.9 cm.y-1). Their trees show a wellbalanced physiological profile and an acceptable sensitivity to the tapping panel dryness (4.9%). However, the physiological index, the bark consumption and the sensitivity to the tapping panel dryness lead to retain the latex harvesting technologies “ S/2 d3 6d/7 Pa1(1) ET2.5% 4/y and S/2 d4 6d/7 Pa1(1) ET2.5% 4/y ” for the best. This index, favorably influencing the choice of technologies adapted to clones with active metabolism, contributes to the modern and efficient management of a rubber plantation.

Incidence of latex harvesting technologies on agronomic and physiological parameters and profitability of some rapid metabolic class clones of rubber tree (&lt;i&gt;Hevea brasiliensis&lt;/i&gt;) in southwestern Côte d’Ivoire

Rubber tree rapid-metabolism clones generally have interesting agronomic and physiological characteristics. However, they are mostly sensitive to tapping panel dryness and breakage due to wind. This could be probably due to overexploitation caused by high tapping frequencies and/or high hormonal stimulation systems. To try solving this problem, a study was carried out over nine years using clones PB 260, PB 280 and PB 330 planted at a density of 510 plants/ha in southwestern Cote d’Ivoire. The experimental design was a randomized complete blocks with different latex harvesting technologies. The estimated parameters were rubber yield, radial vegetative growth, physiological profile and the profitability of applied latex harvesting technologies. Results indicated that non-stimulated combined with high tapping frequency latex harvesting system (d2 0/y) showed a level of rubber yield comparable to that of tapping frequencies d3 and d4 in all studied clones irrespective of the level of hormonal stimulation applied. Furthermore, the absence of hormonal stimulation had no negative influence on the vegetative growth and the physiological profile of rubber trees. Every two days (d2) tapping system without stimulation generated a profit margin statistically identical to that of low tapping frequencies (d4, d5 and d6) irrespective of the level of hormonal stimulation. © 2017 International Formulae Group. All rights reserved. Keywords: Rapid-metabolism clones, Cote d’Ivoire, tapping frequency, Hevea brasiliensis , rubber yield, physiological profile

Effects of Different Tapping Rest Periods during Wintering and Summer Months on Dry Rubber Yield of Hevea Brasiliensis in Thailand

In Thailand, the farmers tend to tap rubber trees as often as possible during the shortened favourable periods due to the erratic rainfall pattern and the long tapping rest during wintering/summer season, lasting for three months. Wintering pattern is well known having an impact on yield. This impact is related to relationship between long term yield, climatic parameters and to the physiology of the rubber tree itself. In Thailand, the long rest from tapping was questioned as it concerns the duration and the months. The purpose of this study was to compare the effect of different durations of tapping rest during wintering season on the latex's yield. Combinations of duration and months of tapping rest were tested on yield over a six-year period of latex harvesting. Decreasing the duration of the tapping rest from three months to zero did not induce any significant higher yield per tree over the six years of tapping. (Resume d'auteur)

The Hevea brasiliensis AP2/ERF superfamily: from ethylene signalling to latex harvesting and physiological disease response

Ethylene is a hormone known for its involvement in the process of latex harvesting in Hevea brasiliensis. It facilitates latex flow by activation of endogenous metabolism in the anastomosed latex cells called laticifers. In regard to its ambivalent role, ethylene is both favourable to the latex production and unfavourable, to a certain level, to the apparition of a physiological disease termed as tapping panel dryness (TPD). Comprehensive researches have been carried out to reveal the molecular actors in ethylene biosynthesis and signalling pathways in Hevea brasiliensis. One of the most important superfamily implicated as the last transcription factor known in plant ethylene signalling is the APETALA2/ETHYLENE RESPONSE FACTOR (AP2/ERF). Currently, 114 unique sequences related to the Hevea AP2/ERF gene superfamily have been identified and characterized. Specific characterizations under the condition of harvesting stress and the occurrence of TPD have identified 36 gene expression markers (GEMs). Eighteen of these GEMs were predicted as ortholog with 19 Arabidopsis AP2/ERF genes. The characterization was mainly focused on transcriptional regulation, whilst potential post-transcriptional and post-translational regulations of HbAP2/ERF genes were formerly predicted. Three HbERF groups (HbERF-VII, HbERF-VIII and HbERF-IX) were hypothesized to have an important role in Hevea tolerance during latex production as they highly accumulated in laticifers and in response to multiple abiotic stresses. Further functional analysis of several key genes is suggested in order to fully understand the regulation of HbAP2/ERFs. Finally, the molecular markers for future Hevea breeding could be possibly developed from this superfamily.

The Hevea brasiliensis AP2/ERF superfamily: from ethylene signalling to latex harvesting and physiological disease response

Ethylene is a hormone known for its involvement in the process of latex harvesting in Hevea brasiliensis. It facilitates latex flow by activation of endogenous metabolism in the anastomosed latex cells called laticifers. In regard to its ambivalent role, ethylene is both favourable to the latex production and unfavourable, to a certain level, to the apparition of a physiological disease termed as tapping panel dryness (TPD). Comprehensive researches have been carried out to reveal the molecular actors in ethylene biosynthesis and signalling pathways in Hevea brasiliensis. One of the most important superfamily implicated as the last transcription factor known in plant ethylene signalling is the APETALA2/ETHYLENE RESPONSE FACTOR (AP2/ERF). Currently, 114 unique sequences related to the Hevea AP2/ERF gene superfamily have been identified and characterized. Specific characterizations under the condition of harvesting stress and the occurrence of TPD have identified 36 gene expression markers (GEMs). Eighteen of these GEMs were predicted as ortholog with 19 Arabidopsis AP2/ERF genes. The characterization was mainly focused on transcriptional regulation, whilst potential post-transcriptional and post-translational regulations of HbAP2/ERF genes were formerly predicted. Three HbERF groups (HbERF-VII, HbERF-VIII and HbERF-IX) were hypothesized to have an important role in Hevea tolerance during latex production as they highly accumulated in laticifers and in response to multiple abiotic stresses. Further functional analysis of several key genes is suggested in order to fully understand the regulation of HbAP2/ERFs. Finally, the molecular markers for future Hevea breeding could be possibly developed from this superfamily.

Role of lutoid membrane transport and protein synthesis in the regeneration mechanism of latex in different Hevea clones

Natural rubber (cis-1,4 polyisoprene) is synthesised in the milky cytoplasm, the latex, of specialized cells called laticifers in the bark tissues of the rubber tree (Hevea brasiliensis). Regeneration mechanism of latex after each tapping (controlled wounding of the bark) was studied in relation to lutoid membrane enzymes and protein synthesis in twelve rubber clones with varying yield potentials during the peak rubber yielding season. High activity of membrane enzymes and better availability of biochemical energy [ATP] were observed in clones viz; RRII 105, RRIM 600, PB 260, RRII 422 and RRII 430. The highest protein biosynthetic capacity was noticed in clone PB 260 and RRIM 600. However, high ATP content, increased invertase activity and protein biosynthesis were observed in the medium yielding clone GT1 compared to clones with low rubber yield potential. Very low sugar content and increased invertase activity in the latex of clone PB 260 indicated intense latex metabolism with high protein turnover that implies fast recouping of the cellular metabolites lost during latex harvesting. Clone PB 217 was characterized by very high sucrose and low ATP concentration and ATPase activity in latex indicating slow metabolism and hence be suitable for inducing latex metabolism using ethylene stimulant. Low rubber yielding clones such as RRII 33 and RRII 38 were consistently recorded a high sucrose content but very low activity of membrane enzymes, reduced ATP concentration and low protein biosynthesis in latex. Among the recently released modern clones (RRII 400 series), latex regeneration capacity was higher in RRII 422 and RRII 430. The significance of lutoid membrane transport and protein synthesis is discussed in relation to general latex metabolism of these rubber clones. The outcome of this study would be helpful to design suitable latex harvesting systems and yield stimulation methods for optimizing latex production in each clone based on metabolic profiling.

The Hevea brasiliensis XIP aquaporin subfamily: genomic, structural and functional characterizations with relevance to intensive latex harvesting.

X-Intrinsic Proteins (XIP) were recently identified in a narrow range of plants as a full clade within the aquaporins. These channels reportedly facilitate the transport of a wide range of hydrophobic solutes. The functional roles of XIP in planta remain poorly identified. In this study, we found three XIP genes (HbXIP1;1, HbXIP2;1 and HbXIP3;1) in the Hevea brasiliensis genome. Comprehensive bioinformatics, biochemical and structural analyses were used to acquire a better understanding of this AQP subfamily. Phylogenetic analysis revealed that HbXIPs clustered into two major groups, each distributed in a specific lineage of the order Malpighiales. Tissue-specific expression profiles showed that only HbXIP2;1 was expressed in all the vegetative tissues tested (leaves, stem, bark, xylem and latex), suggesting that HbXIP2;1 could take part in a wide range of cellular processes. This is particularly relevant to the rubber-producing laticiferous system, where this isoform was found to be up-regulated during tapping and ethylene treatments. Furthermore, the XIP transcriptional pattern is significantly correlated to latex production level. Structural comparison with SoPIP2;1 from Spinacia oleracea species provides new insights into the possible role of structural checkpoints by which HbXIP2;1 ensures glycerol transfer across the membrane. From these results, we discuss the physiological involvement of glycerol and HbXIP2;1 in water homeostasis and carbon stream of challenged laticifers. The characterization of HbXIP2;1 during rubber tree tapping lends new insights into molecular and physiological response processes of laticifer metabolism in the context of latex exploitation.

Latex Harvesting Technologies Adapted to Clones IRCA18, IRCA 111, IRCA 130, PB 235 and PB 260 of Hevea brasiliensis (Rubber Tree) of the Class to Active Metabolism in South-Western Côte d’Ivoire

Latex Harvesting Technologies Adapted to Clones IRCA18, IRCA 111, IRCA 130, PB 235 and PB 260 of Hevea brasiliensis (Rubber Tree) of the Class to Active Metabolism in South-Western Côte d’Ivoire

Time Course Variation of Some Latex Physiological Parameters Associated with Yield of Rubber (Hevea brasiliensis) Grown in Eastern Province of Sri Lanka

Rubber cultivation in Eastern Province, is predominantly in the intermediate zone of which climatic conditions are considered to be sub-optimal for growing rubber. Due to low level of atmospheric RH%, latex flow tends to cease early after tapping in these areas. Turgidity of latex vessels associated with the water content of latex vessels decreases with the sunrise when evapotranspiration increases. Hence, time of commencing tapping greatly influences on the latex yield. Therefore, the present study was aimed to identify the best time of the day for latex harvesting through an assessment on latex physiological parameters. In order to identify the best time for tapping, variations in several physiological parameters together with latex yield were assessed at different time intervals, i.e., 04:00, 05:00, 06:00, 07:00 and 08:00 in two smallholder sites in the eastern Province. Latex volume, dry rubber content (DRC%), initial flow rate (IFR) and plugging index (PI) were analysed along with the environmental factors at the time of tapping. Latex volume per day (LVPD) was highly associated with the overall latex yield hence had become the prime factor concerned. The highest LVPD was recorded between 05:00 to 06:00 hrs. Dry rubber content of latex had increased after 06:00 h and that could be attributed to the water status of the trees which was governed by evapotranspiration. During 05:00-06:00 hrs time period, RH% was almost 100% and temperature was around 23° C. When tapping commenced after 06:00 h, the overall yield declined. There was a tendency of increasing the plugging index (PI) with the delay of tapping. Therefore, the study concluded that high yields could be obtained in this agro-ecological region if tapping is performed before 06:00 h. Keywords: Hevea , Intermediate zone, Rubber, Sub-optimal climatic conditions, Tapping time

Ethylene Response Factors Are Controlled by Multiple Harvesting Stresses in Hevea brasiliensis

Tolerance of recurrent mechanical wounding and exogenous ethylene is a feature of the rubber tree. Latex harvesting involves tapping of the tree bark and ethephon is applied to increase latex flow. Ethylene is an essential element in controlling latex production. The ethylene signalling pathway leads to the activation of Ethylene Response Factor (ERF) transcription factors. This family has been identified in Hevea brasiliensis. This study set out to understand the regulation of ERF genes during latex harvesting in relation to abiotic stress and hormonal treatments. Analyses of the relative transcript abundance were carried out for 35 HbERF genes in latex, in bark from mature trees and in leaves from juvenile plants under multiple abiotic stresses. Twenty-one HbERF genes were regulated by harvesting stress in laticifers, revealing an overrepresentation of genes in group IX. Transcripts of three HbERF-IX genes from HbERF-IXc4, HbERF-IXc5 and HbERF-IXc6 were dramatically accumulated by combining wounding, methyl jasmonate and ethylene treatments. When an ethylene inhibitor was used, the transcript accumulation for these three genes was halted, showing ethylene-dependent induction. Subcellular localization and transactivation experiments confirmed that several members of HbERF-IX are activator-type transcription factors. This study suggested that latex harvesting induces mechanisms developed for the response to abiotic stress. These mechanisms probably depend on various hormonal signalling pathways. Several members of HbERF-IX could be essential integrators of complex hormonal signalling pathways in Hevea.