Latex Yield Research Articles

Study toward the Development of Relationship between Ref Gene Expression and Yield Potential of Hevea Clones

Rubber is the third largest plantation crop in Sri Lanka. In 2018, Rubber production was declined from 83.1 million kilograms to 82.6 million kilograms. Development of high yielding clones to the rubber industry is a prime objective of Hevea breeding and selection. Rubber Elongation Factor (Ref) protein mainly helps for the biosynthesis of natural rubber in Hevea brasiliensis. Rubber particles are tightly bound to this Ref protein. Genomic sequence of Ref gene is 1367 bp long. Previous studies found that the positive correlation between Ref gene expression pattern and latex yield. The clones in the group III clone recommendation are needed to upgrade in to group II gradually with their performance. Selected three clones in the group III as RRISL 2006, RRISL Centennial 3 and RRISL Centennial 4 were undertaken to study their Ref gene expression and promoter analysis with latex yield to verify their performance. Quantitative gene expression of Ref gene was done to identify the expression pattern of Ref gene and promoter. Livak method (2-∆∆CT) used to analyze the quantitative gene expression and paired t test was used to identify significant difference between control and treatments. Compared to the control clone RRISL 203, the yields of all other three clones were significantly higher as well as their Ref gene expression was up-regulated differently with 2 to 7 fold difference. Up-regulation of Ref gene in the clone RRISL 2006 is significantly higher with seven fold compared to the control clone RRISL 203. The average yield of RRISL 2006 in the year 2019 was 27.3 g/t/t and average yield of RRISL Centennial 3 was 28.3 g/t/t. But the difference was not significant. In January 2020, where samples were collected, the RRISL 2006 recorded highest 55.77 g/t/t. RRISL Centennial 4 was showed around four fold up-regulation compared to the clone RRISL 203 as well as yield also higher to RRISL 203. The clone RRISL Centennial 3 also followed the same pattern but the fold difference was around 2.5 over the control clone RRISL 203. The results we reproved the positive correlation between Ref gene expression and the high yield. However this relationship was not observed between RRISL Centennial 3 and RRISL Centennial 4, as the clone RRISL Centennial 4 showed higher fold difference over to RRISL Centennial 3 but yield was low. Therefore this relationship is needed to be further analyzed. The copy number of Ref promoter also important to understand the clear relationship between Ref gene expression and yield potential of Hevea clones.

Effect of Two Fungicides on Mycelial Growth of Fungi Causing Leaf Blight and Wilt of the Rubber Plant (Hevea brasiliensis Muell Arg.) in Cameroon

Rubber (Hevea brasiliensis Muell. Arg., Euphorbiaceae) is a tropical tree crop mainly grown for the industrial production of latex. The rubber sector in Cameroon is faced with the effects of global economic crisis and a drop in the yield of latex due to several pests and diseases. This study focused on leaf diseases caused by Fusarium oxysporum and Pestalotiopsis microspora. The fungi were isolated from the leaves of the rubber plant and cultured for characterization on two media (Potato Dextrose Agar (PDA) and Potato Carrot Dextrose Agar (PCDA)) at various temperature and pH levels. Using the poison food technique, an in vitro assay was done to assess the effect of two fungicides (Synthetic Fungicide 1 (SF1) and Synthetic Fungicide 2 (SF2)) at the respective doses of 0.006, 0.013 and 0.025 g.L-1, and 0.005, 0.01 and 0.02 g.L-1 on the growth of the two fungi. Results obtained show that PDA is most favourable for the growth of both fungi compared to PCDA. Both fungi attained optimal growth at pH 7 and at an incubation temperature of 25 oC. Neither F. oxysporum nor P. microspora grew on SF1-amended PDA and PCDA at all doses of the fungicide. SF2 significantly (P>0.05) inhibited the growth of P. microspora by 53.3% at the dose of 0.025 g.L-1 while F. oxysporum was less sensitive to the fungicide at all doses. In vitro pathogenicity test revealed similar disease symptoms as those observed in the field. This study shows that SF1 is the best fungicide against F. oxysporum and P. microspora as it gave 100% inhibition on the growth of both fungi.

On-farm effect of bamboo intercropping on soil water content and root distribution in rubber tree plantation

ABSTRACT Introducing permanently an associated crop in rubber plantations may improve biodiversity and soil cover, optimize resource use, and diversify farmer’s income. However, the associated crop may also compete with the rubber trees for resources such as space and water. The case of bamboo-rubber agroforestry system is peculiar, as bamboos present features common to both grasses and trees, they grow fast and are considered strong competitors for water. Soil organic matter and water content, bulk density, root distribution, canopy cover, and rain interception were studied on farm to understand the effects of bamboo intercropped in rubber tree plantation, compared with rubber monoculture in southern Thailand. In the rubber-bamboo association, soil water content was lower in shallow depth, whereas it increased in deeper horizons. There was no significant difference in fine root distribution of rubber trees with or without bamboo; therefore, the total root density (rubber + bamboo) was higher in the association. Canopy cover and rain interception were also higher in association with bamboo. Further studies are required to better understand in this system, the balance between higher superficial water use and increased water retention in lower soil depth, together with more specific studies on soil properties, tree development, and latex yield.

Produksi Lateks Pekat Melalui Proses Pendadihan Dengan Pengaturan Waktu Dan Kecepatan Penggetaran

Increasing concentrated latex production is the important things to supply rubber industries, and reduce imports. The quality of latex is evidently altered by shock during transportation, thus providing important information in improving creaming processes. The study aimed to find the duration and speed shaking in accelerating the formation of concentrated latex with creaming technique. The study was arranged factorialin Randomized Block Design with duration (24, 48, and 72 hours) and speed shaker (0, 150, 200, and 250 rpm). The observed wereprocessing time separation between latex and serum (hour), concentrated latex yield (%), total soluble content (%), dry rubber content, pH, colour, and the smell of latex. The results showed that the duration of vibration did not affect time separation between latex and serum, concentrated latex yield, total soluble content, and dry rubber content. The speed of vibration speeds up the processing time separation between latex and serum, affecting the yield and dry rubber content of concentrated latex. The combination of duration and speed of vibration affects the processing time separation between latex and serum. The fastest processing time separation is 32 hours on 48 hours of duration with 150 and 200 rpm speed vibration of orbital shaker. Keyword: concentrated latex, creaming, duration and speed vibration, orbital shaking

The impact of ridge direction and latex on the yield of potato (Solanum tuberosum l.) in typic hapludands, Pengalengan, West Java

The objective of this experiment was to find out the effect of ridge direction and latex soil conditioner on potatoes yields on Typic Hapludands from Pangalengan. The experiment was conducted in Pangalengan, with elevation 1,600 meters above sea level and 30% of slope steepness. The experiment used a split plot design with 12 treatments and three replications. The main plot ridge direction consists of: in line with slope direction, in line with contour, and diagonal. The sub plot was latex concentration level as follow: 0%, 0.6%, 1.2% and 1.8%. The result of the experiment showed that there was no interaction effect between ridge direction and latex soil conditioner. The independent effect of latex just influenced potatoes yields. Potatoes yield of latex 0%, 0.6%,1.2% and 1.8% was 72.97 kg was 74.47 kg, 75.14 kg and 76.48 kg, respectively.

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.

Latex quality and yield parameters of Hevea brasiliensis (Willd. ex A. Juss.) Müll. Arg. clone PB 260 for different tapping and stimulant application frequencies

Tapping and stimulant applications are an attempt to increase latex yield. A combination of stimulants with low intensity tapping systems was expected to reduce tapping costs. In addition, it was necessary to regulate the stimulant application frequency based on type and potential clone production. The objective was to determine the effect on physiological parameters and latex yield of Hevea brasiliensis (Willd. ex A. Juss.) Müll. Arg. clone PB 260 for different tapping and stimulant application frequencies. The study design was split block in randomized complete block plots with three replicates and two factors. The main plot was the tapping system consisting of four levels: quarter-spiral downward tapping (S/4 d3), quarter-spiral upward tapping (S/4U d3), half-spiral downward tapping (S/2 d3), and half-spiral upward tapping (S/2U d3). The subplots were four stimulant application frequencies consisting of ethephon 2.5% applied once every 15 d (ET 15d) and gas stimulant (equal to ± 100% ethylene) applied once every 9 d (ETG 9d), once every 18 d (ETG 18d), and once every 27 d (ETG 27d). The highest sucrose levels (3.62 mM) were obtained in S/2 d3 and ET/15d combination. The highest inorganic P content (27.68 mM) was in S/2 d3 and ETG/18d. The highest yield (2418.53 kg ha-1 yr-1) was in S/4d3 and ETG/18d. The tapping system S/4d3 and ETG/18d combination was able to increase production by 102.26% compared with the conventional tapping system (S/2 d3 and ET/15d). After the 1-yr trial, all treatments showed 0.47 to 0.54 mM thiol content, which indicated that plants did not experience over-exploitation stress

Study of Plasma Electrolysis Method on Starch-Based Hybrid Latex Synthesis

The plasma electrolysis is a rich source of free radicals, it commonly induces unusual chemical reaction. This paper focus to study plasma electrolysis induces grafting reaction between latex and starch to prepare a functional material – ether bond – with radicals as the initiator to produce hybrid latex which presume has acoustic property. By the method of plasma electrolysis, the reaction can take place and the difference of polarity between the reactants can be overcome. The synthesis – both by using anodic and cathodic plasma – is said to work qualitatively when the characterization results by using Fourier Transformation Infrared Spectroscopy (FTIR) arises a new ether bond waves at around 1560 cm-1. The synthesis processes – both by using anodic and cathodic plasma – were investigated more specifically by looking at the effect of electrolyte, Na2SO4 concentration used with variations of 0.02; 0.03; 0.04 M to the efficiency of synthesis. The applied operating voltage of the process are 567.5 and 340.5 volt for anodic and cathodic, respectively. The reaction time is 10 minutes, and the efficiency of synthesis is represented by % yield of hybrid latex per kJ of electric energy consumption. The obtained efficiencies – from anodic and cathodic – were 0.04; 0.02; 0.01 and 0.18; 0.13; 0.12, for each of electrolyte concentrations, respectively.

Study of Plasma Electrolysis Method on Starch-Based Hybrid Latex Synthesis

The plasma electrolysis is a rich source of free radicals, it commonly induces unusual chemical reaction. This paper focus to study plasma electrolysis induces grafting reaction between latex and starch to prepare a functional material – ether bond – with radicals as the initiator to produce hybrid latex which presume has acoustic property. By the method of plasma electrolysis, the reaction can take place and the difference of polarity between the reactants can be overcome. The synthesis – both by using anodic and cathodic plasma – is said to work qualitatively when the characterization results by using Fourier Transformation Infrared Spectroscopy (FTIR) arises a new ether bond waves at around 1560 cm-1. The synthesis processes – both by using anodic and cathodic plasma – were investigated more specifically by looking at the effect of electrolyte, Na2SO4 concentration used with variations of 0.02; 0.03; 0.04 M to the efficiency of synthesis. The applied operating voltage of the process are 567.5 and 340.5 volt for anodic and cathodic, respectively. The reaction time is 10 minutes, and the efficiency of synthesis is represented by % yield of hybrid latex per kJ of electric energy consumption. The obtained efficiencies – from anodic and cathodic – were 0.04; 0.02; 0.01 and 0.18; 0.13; 0.12, for each of electrolyte concentrations, respectively.

PERBANDINGAN HASIL GETAH ANTARA JELUTUNG KAPUR (Dyera lowii Hook.F) DAN JELUTUNG SANAMAN (Dyera costulata) DI HUTAN RAWA GAMBUT KALAMPANGAN (Comparison the Latex Yields Between Jelutung Kapur (Dyera lowii Hook.F) and Jelutung Sanaman (Dyera costulata)

ABSTRACT Jelutung kapur (Dyera lowii Hock) and jelutung sanaman (Dyera costulata) are species that grow well at the peat swamp forest in Canal of Taruna, Kalampangan, Palangka Raya City. Aim of this research was to compare the latex yield between jelutung kapur (Dyera lowii Hock) and jelutung sanaman (Dyera costulata) at the peat swamp forest in Kalampangan. The research was done using factorial design with two factors, i.e. peat thickness (4 m and 5 m) and diameter class of the trees. Variables of the research were diameter (dbh) and height of 24 jelutung kapur and 18 jelutung sanaman. Data were collected each month as long as 11 months with considering the weather condition, i.e. precipitation and temperature. Research result show that there is irreversibility between precipitation vs temperature to latex yield. The more of precipitation so the higher of temperature that cause the reduction of latex yield. According BNT test, the highest latex yield is gotten from jelutung kapur with diameter class of &gt;24 cm that grow at the site with the thickness of 4 m, meanwhile the lowest latex yield is gotten from jelutung sanaman with diameter class of &lt; 24 cm that grow at the site with the thickness of 5 m. Average latex yield of jelutung kapur is 363,63 ml/extract/tree/month.&#x0D; Keywords: Diameter class, latex yield, peat thickness, precipitation, temperature.

Particleboard Manufactured from Rubberwood RRIM 2002 Clone Planted with Different Fertilizer Treatment

This work focus on the effects of SRF (Slow Release Fertilizer) + NPK fertilizer rates on the properties of rubberwood particleboards produced. The particleboards were fabricated using rubber tree trial clone RRIM 2002. RRIM 2002 clone still in trial plot with age of 4-year old and classified as Latex Timber Clone which estimated to produce large wood volume and also better latex yield. The properties of particleboard were categorized and evaluated based on fertilizer treatment applied on RRIM 2002 clone tree: T1 (SRF + NPK at normal rate), T2 (SRF + 1.5 x NPK at normal rate), T3 (SRF + 2.0 x NPK at normal rate) and T4 (SRF + 2.5 x NPK at normal rate, control (NPK at normal rate). The resin used for particleboard fabrication was urea formaldehyde (UF) (63.9% solid) type E1. The resin content is 10%. The thickness of board is 10 mm with density 700 kgm-3 . The particleboards were fabricated and assessed in accordance to Japanese Industrial Standard for Particleboard (JIS A 5908-2003). The properties that been assessed were on modulus of elasticity (MOE), modulus of rupture (MOR), internal bonding (IB), thickness swelling (TS) and water absorption (WA). From this study, it is found that fertilizer treatment influences the particle recovery and performance of particleboard especially on dimensional stability and internal bonding properties which significantly affected. The MOR and MOE of particleboard made from rubber trees that treated with SRF-NPK fertilizer showed better performance compared to that of with NPK fertilizer alone (control), however, the differences were not significant. In term of IB, no specific trend was observed. Lastly, for dimensional stability (TS and WA), particleboard produced from SRF-NPK fertilizer reduced the board stability when subjected to cold water soak.

Opposite physiological effects upon jasmonic acid and brassinosteroid treatment on laticifer proliferation and co-occurrence of differential expression of genes involved in vascular development in rubber tree.

During growth of woody plant-trunk, the secondary meristem functions in giving rise the xylem and phloem. Rubber tree (Hevea brasiliensis Muell. Arg.), in addition, contains laticifers (latex producing vessels) in the vicinity of phloem. Insights into regulatory mechanisms of gene networks underlying laticifer proliferation in rubber tree has remained very limited. The candidate vascular development-related genes were selected to investigate for expression profile in phloem and xylem tissues of high latex yield- and high wood yield-clones of rubber tree. The differential gene expression between the mature branch-xylem and -phloem tissues was clearly observed. The cis-regulatory motif analysis revealed the existent of putative jasmonic acid (JA)- and brassinosteroid (BR)-responsive regulatory motifs in promoter regions of these genes, and consequently the effect of exogenous application of JA, BR or their respective signaling inhibitors, on the formation of laticifers in rubber tree was demonstrated. Interestingly, the laticifer numbers were significantly increased in JA-treatment, correlated with up-regulation of phloem development-related genes in both rubber tree clones. On the contrary, the laticifers were decreased in BR-treatment accompanying by up-regulation of xylem development-related genes, especially in high wood yield-rubber tree clone. BR-inhibitor treatment also enhanced laticifer numbers, while JA-inhibitor suppressed laticifer differentiation. Taken together, this study unveils the molecular interplay between JA/BR on vascular development in rubber tree and how this impacts the appearance of laticifers in this plant. This process isvital for a better understanding on laticifer differentiation and its impact in the manipulation of wood and latex yield in rubber tree improvement program.

Unraveling vascular development-related genes in laticifer-containing tissue of rubber tree by high-throughput transcriptome sequencing

About 90% of natural rubber is obtained from tapping of the rubber tree (Hevea brasiliensis) for latex, which is circulated in the laticifers. Nowadays, the world supply of natural rubber is not sufficient for global demand, thus the increased latex yield was significantly underlined. In addition, the demand for wood (as a xylem part) from rubber tree was also increased as renewable resource for various applications. Laticifers are found in the secondary phloem containing tissue of rubber tree trunk-inner soft bark. The number of laticifers varies in consistent with latex yield and in responses to jasmonic acid level. This present study was committed to comparative transcriptome analysis in laticifers containing mature phloem, mature xylem and newly developed stem tissues of high latex-yield clone (RRIT251, with more laticifers) and high wood-yield clone (RRIT402, with less laticifers) of rubber tree to classify the genes and pathways involved with phloem (with laticifers) and xylem cell differentiation. There were 49, 54, 46 and 50 of vascular development-related genes in primary and secondary tissues of phloem and xylem, respectively. Differentially expressed genes in jasmonic acid signaling pathway was established with their highest expression in phloem tissue with laticifer cells of RRIT251, while genes in auxin signaling and secondary cell wall biosynthetic pathways were up-regulated in xylem tissue of RRIT402 for high wood yield. Promoter analysis of candidate-differentially expressed genes suggested the related pathway and putative regulatory elements for gene regulation. This genome-wide exploration of vascular development-related genes unraveled a largely unknown gap of this special vascular development containing laticifers in rubber tree.

Production and Physiology Characteristics of Some Rubber Clones in Early Tapping with Growth Regulator

The study was aimed to study latex production and physiology character of some rubber clones in early tapping with the use of Plant Growth Regulators (PGR) and the relationship between production and latex yield characters. The research was conducted in KarangInong Farm, PTP-N I Kso PTP-N III, East Aceh. The research was prepared using two factors Nested Design, namely 5 clone factors and 7 hormone factors. The treatment was repeated twice, but nested in the clone factor, so the number of experimental units was 7 x 5 x 2 = 70. Each experimental unit consists of 4 plants with the total is 280 plants. The results showed that response of each clone and hormone was different for production parameters and latex yield character. Treatment of clone PB 340 and hormone H6 (600 ppm IAA + Kinetin 60 ppm) yield the highest production (g/p/s). The best Interaction of clone and hormone treatment is K4H4 (IRR 107 clone with IAA 500 ppm + Kinetin 60 ppm) as indicated by production parameters (38.04 g/p/s), sucrose content (9.14 mM, phosphoric acid (6.84 mM), Thiol (0.50 mM) and plugging index (16.34%)

A high-density genetic map and QTL mapping on growth and latex yield-related traits in Hevea brasiliensis Müll.Arg

Hevea brasiliensis Müll.Arg., the rubber tree, is an important industrial crop, which is the major source of nature rubber. Recently, Simple Sequence Repeat (SSR)- and Single Nucleotide Polymorphism (SNP)-based genetic maps have been reported, however further trait-related markers are needed for efficient molecular breeding in rubber tree. In this study, a total of 206 F1 progeny derived from a cross of CATAS 8–79 × MT/C/11 9/67 were sequenced and genotyped by specific–locus amplified fragment sequencing (SLAF-seq) technology. Based on 268,592 SNPs obtained from SLAF-seq, a high-density genetic map with 4,543 SNPs was constructed, covering 2,670.27 cM of the whole rubber tree genome. This map has an average marker distance of 0.59 cM.Based on the high-density genetic map, dynamic quantitative trait loci (QTL) analysis of latex yield and stem growth was carried out by conditional and unconditional QTL mapping. To our knowledge, it is the first time to perform conditional QTL mapping of rubber tree for exploring QTLs expressed selectively at different growth stages. In total, eleven QTLs for stem growth and 12 QTLs for latex yield, distributing in 15 linkage groups (LGs), were detected, explaining 3.1%–18.4% of the phenotypic variance. Two QTLs, qSG-8-2 for stem growth and qLD-8-3 for latex yield, were mapped within the same marker interval of LG 8 with a genetic distance of 3.0 cM. Herein the high-density genetic map and trait-related QTLs in rubber tree were reported, which will facilitate the genetic research of rubber tree and enhance rubber tree molecular breeding.

Climbing the mountain fast but smart: Modelling rubber tree growth and latex yield under climate change

Pará rubber (Hevea brasiliensis Müll. Arg) plantations have expanded into regions with sub-optimal growth conditions: distinct dry seasons and temperatures cooler than in humid tropics. The impact of these new marginal environments and future climate change on rubber tree development and latex yield is largely unknown. This hampers reliable prediction of farmers’ revenues and extent of carbon sequestration at landscape level. To improve our understanding of rubber trees response to planting at high altitudes and associated increase in planting densities, we applied the process-based Land Use Change Impact Assessment tool (LUCIA). It was calibrated with detailed ground survey data from Xishuangbanna, southwest China to model tree biomass development and latex yield in rubber plantations at the tree, plot and landscape level. Plantations were analyzed at <900 m above sea level (a.s.l., lowland rubber) and ≧900 m a.s.l. (highland rubber) in order to characterize the effect of elevation on rubber trees. Three planting densities: low (<495 trees ha−1), medium (495–600 trees ha−1) and high (>600 trees ha−1) were tested. Four greenhouse gas emission scenarios, with Representative Concentration Pathways (RCP) ranging from the lowest RCP 2.6 to the highest emission scenario RCP 8.5, were used to test rubber tree response to climate change. During a 40-year rotation under current climate, lowland rubber plantations grew faster and had larger latex yields than highland rubber. The average biomass of lowland rubber was 9% and 18% higher than those of highland rubber for aboveground and belowground biomass, respectively. High planting density rubber plantations showed 5% and 4% higher above ground biomass than those at low- and medium-planting density, but simulations suggest that the cumulative latex production decreased strongly by 26% and 14% respectively. The results of the RCP 8.5 climate change scenario suggested that during 40 years simulation mean total biomass and cumulative latex yield of highland rubber (per tree) increased by 28% and 48%, while lowland rubber increased by 8% and 10% respectively when compared to the baseline. Other rubber cultivation regions could also benefit from this modelling approach that helps in optimization of carbon stock and latex production in rubber-based system. The results could help in development of future climate change adaption and mitigation strategies.

Modification of Rubber (Hevea brasiliensis Muell. Arg.) Spacing for Long-term Intercropping

Low prices of rubber has been a serious problem to rubber growers in Indonesia. Rubber-based intercropping systems offers a practical solution to this issue and increasing overall productivity, for example by growing upland rice and maize between the rubber tree rows. This study was aimed to determine the suitable spacing in rubber planting to facilitate long-term rubber-based intercropping systems. A field experiment was established in a smallholder rubber plantation in the Tanah Laut Regency, South Kalimantan with area of 50 ha. Two planting patterns of rubber clone PB260 were tested: (1) single row planting pattern (SR) by 6 m x 3 m, and (2) double row planting pattern (DR) by 18 m x 2 m x 2.5 m. The experiment showed that the girth of the rubber trees with the SR system at the 1st tapping year was slightly larger than that in the DR system, even though statistically it was not signifi cant. The latex yield per tree of SR and DR systems were similar, however, latex yield per hectare of SR system was higher than the DR system due to a higher tree population in the SR system. The DR system was technically suitable for long term intercropping, because when the rubber tree reached 8 to 9-year-old, the light penetration was &gt; 80% at distance of about 4 m from the rubber tree rows. Economically, DR system can increase the added values for rubber farmers because it allows long term intercropping. Rubber-based intercropping with DR system is suitable to be applied, especially by smallholders, with a marginal benefi t cost ratio of around 2.07. Keywords: Hevea, intercropping system, rubber planting pattern, spatial arrangement

Efektifitas Pemberian Stimulant Better dan Waktu Sadap Terhadap Produksi Lateks Tanaman Karet (Hevea brasiliensis Muell Arg

The factors that influence rubber production are planted clones, plant care and tapping techniques. With the right tapping technique, both tapping time, tapping method and mature tapping age, the production potential of a superior clone of rubber plants that has been well maintained can be maintained. The technique of rubber tapping is closely related to the expected level of production, even very determining the age of the tree economy. The research objective was to determine the effect of stimulant better and tapping time on latex production. The method used was a randomized block design with two-factor split plot design. The first factor (main plot) is the time of tapping consists of 3 levels, namely; w1: 05 in the morning, w2: 06 in the morning, w3: 07 in the morning. The second factor (sub-plot), namely the stimulant dosage better consists of 4 levels, namely; b0: control, b1; 0.5 g, b2; : 1 g, b3; 1.5 g. The results showed that stimulate better treatment had a significant effect on latex volume, wet weight and latex dry weight, but was not significant for latex dryness levels. Tapping time was not significant for latex yield, latex volume, wet weight, latex dry weight and highest dry rubber content at 7am. Stimulant Better treatment has a significant effect on latex volume, wet weight, and latex dry weight, but if given at high doses it will reduce the dry content of rubber. The interaction of treatment when tapping and stimulant is better not significant for latex production. The stimulant application better does not exceed the dose of 0.5 g / principal. Doses&gt; 0.5 g / staple will have an impact on the dry tapping field.

Genomic technologies for Hevea breeding.

The commercial production of high quality natural rubber (NR) solely depends on Hevea brasiliensis Muell. Arg, (Para rubber tree) and accounts for >98% of total production worldwide. NR with its unique properties is an essential commodity for the automobile industry and its synthetic counterparts are in no way substitute to it. The rubber tree genome is very complex and plays an important role in delivering the unique properties of Hevea. But a lack of knowledge on the molecular mechanisms of rubber biosynthesis, disease resistance, etc., in elite clones of rubber still persists. Marker-assisted selection and transgenic techniques were proved to be advantageous in improving the breeding efficiency for latex yield, disease resistance, etc. The suppression subtractive hybridization (SSH), in the form of subtracted cDNA libraries and microarrays, can assist in searching the functions of expressed genes (candidate gene approach). Expressed sequence tags (ESTs) related to various metabolic aspects are well utilized to create EST banks that broadly represent the genes expressed in one tissue, such as latex cells, that assists in the study of gene function and regulation. Transcriptome analysis and gene mapping have been accomplished in Hevea at various stages. However, a selection criterion to delineate high yielding genotypes at the juvenile stage has not been accomplished so far. This is the main pit fall for rubber breeding apart from stock-scion interactions leading to yield differences among a clonally multiplied population. At least four draft genome sequences have been published on Hevea rubber, and all give different genome size and contig lengths-a comprehensive and acceptable genomic map remains unfulfilled. The progress made in molecular markers, latex biosynthesis genes, transcriptome analysis, chloroplast and mitochondrial DNA diversity, paternity identification through Breeding without Breeding (BwB), stimulated latex production and its molecular intricacies, molecular biology of tapping panel dryness, genomics for changed climates and genome mapping are discussed in this review. These information can be utilized to improvise the molecular breeding programs of Hevea in future.

Involvement of HbMC1-mediated cell death in tapping panel dryness of rubber tree (Hevea brasiliensis).

Tapping panel dryness (TPD) causes a significant reduction in the latex yield of rubber tree (Hevea brasiliensis Muell. Arg.). It is reported that TPD is a typical programmed cell death (PCD) process. Although PCD plays a vital role in TPD occurrence, there is a lack of detailed and systematic study. Metacaspases are key regulators of diverse PCD in plants. Based on our previous result that HbMC1 was associated with TPD, we further elucidate the roles of HbMC1 on rubber tree TPD in this study. HbMC1 was up-regulated by TPD-inducing factors including wounding, ethephon and H2O2. Moreover, the expression level of HbMC1 was increased along with TPD severity in rubber tree, suggesting a positive correlation between HbMC1 expression and TPD severity. To investigate its biological function, HbMC1 was overexpressed in yeast (Saccharomyces cerevisiae) and tobacco (Nicotiana benthamiana). Transgenic yeast and tobacco overexpressing HbMC1 showed growth retardation compared with controls under H2O2-induced oxidative stress. In addition, overexpression of HbMC1 in yeast and tobacco reduced cell survival after high-concentration H2O2 treatment and resulted in enhanced H2O2-induced leaf cell death, respectively. A total of 11 proteins, rbcL, TM9SF2-like, COX3, ATP9, DRP, HbREF/Hevb1, MSSP2-like, SRC2, GATL8, CIPK14-like and STK, were identified and confirmed to interact with HbMC1 by yeast two-hybrid screening and co-transformation in yeast. The 11 proteins mentioned above are associated with many biological processes, including rubber biosynthesis, stress response, autophagy, carbohydrate metabolism, signal transduction, etc. Taken together, our results suggest that HbMC1-mediated PCD plays an important role in rubber tree TPD, and the identified HbMC1-interacting proteins provide valuable information for further understanding the molecular mechanism of HbMC1-mediated TPD in rubber tree.