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The rubber tree Hevea brasiliensis (Willd. Ex Adr. De Juss.) Müell Arg.] is an important source of latex for the production natural rubber. Natural rubber is an important biopolymer used in various industries, but aspects related to hormonal regulation in biosynthesis are still unknown, which would allow optimizing its production. We review the molecular and physiological mechanisms of increases latex regeneration and flow by the stimulation of rubber trees with exogenous applications of ethylene and jasmonate. We found that the increase in latex regeneration by ethylene is due to the increase in gene level expression and enzymatic activity of key photosynthesis and glycolysis enzymes for the generation of precursors in the first phase of rubber biosynthesis. Latex flow is supported by up-regulated genes in sucrose metabolism such as invertases, induction of sucrose transporters (SUT), and aquaporins (PIP) to maintain flow and turgor pressure in laticifers. Meanwhile, the increase in latex yield mediated by jasmonate may be due to the induction of laticifer differentiation in the long term and in the short term be mediated by the induction of small rubber particles (SRPP) as non-enzymatic cofactors in the production of latex. This information contributes to the knowledge of latex biosynthesis, which allows for a greater support for the exogenous application of jasmonates and ethylene to regulate its production. [ABSTRACT FROM AUTHOR]

The increase in demand for natural rubber has led to the search for alternative sources. Lactuca serriola is emerging as a promising candidate, as the quality of the natural rubber it produces is comparable to that of the Pará Rubber Plant, Hevea brasiliensis. This study examines the effect of methyl jasmonate (MeJA), a known elicitor, on the expression of key rubber biosynthesis pathway genes (HMGR1, HMGS1, CPT2, and SRPP1) in the latex of L. serriola plants. The expression levels of these genes increased significantly after the foliar application of 200 and 400 µM MeJA. The highest relative expression level for HMGR1, HMGS1, CPT2 and SRPP1 was 3.74, 18.56, 11.91and 16.59 fold respectively. Furthermore, the rubber content in L. serriola showed a significant rise post-treatment compared to the control with increasing the level of MeJA (6.19%, 7.24% and 7.85% which correspond to 0, 200 and 400 µM). Gel permeation chromatography revealed an augmentation in the molecular weight of extracted natural rubber from treated plants. Samples treated with 400 µM of MeJA had the highest molecular weight (1570 kg mol−1) compared to control (1186 kg mol−1). This study has demonstrated that MeJA, through the regulation of rubber biosynthesis genes, is capable of enhancing the quality and quantity of natural rubber extracted from alternative sources, such as L. serriola. [ABSTRACT FROM AUTHOR]

The basic helix-loop-helix (bHLH) transcription factors play crucial roles in plant growth, development, and stress responses. However, their identification and insights into the understanding of their role in rubber trees remain largely uncovered. In this study, the bHLH gene family was explored and characterized in rubber trees using systematic bioinformatics approaches. In total, 180 bHLH genes were identified in the rubber tree genome, distributed unevenly across 18 chromosomes, and phylogenetic analysis classified these genes into 23 distinct subfamilies. Promoter regions revealed a high density of cis-elements responsive to light and hormones. Enrichment analysis indicated involvement in numerous biological processes, including growth, development, hormone responses, abiotic stress resistance, and secondary metabolite biosynthesis. Protein interaction network analysis identified extensive interactions between HbbHLH genes and other functional genes, forming key clusters related to iron homeostasis, plant growth, and stomatal development. Expression profiling of HbbHLH genes have demonstrated varied responses to endogenous and environmental changes. RT-qPCR of eleven HbbHLH genes in different tissues and under ethylene, jasmonic acid, and cold treatments revealed tissue-specific expression patterns and significant responses to these stimuli, highlighting the roles of these genes in hormone and cold stress responses. These findings establish a framework for exploring the molecular functions of bHLH transcription factors in rubber trees. [ABSTRACT FROM AUTHOR]

Powdery mildew and anthracnose are the main diseases of rubber trees. In recent years, there have been large outbreaks in the rubber-planting areas of Asia, seriously affecting the yield and quality of rubber latex. ZAR1 is a conserved and distinctive coiled-coil nucleotide-binding leucine-rich (CNL) repeat in the plant kingdom, playing a crucial role in disease-resistance processes. To elucidate the function of the HbZAR1 gene in rubber trees (Hevea brasiliensis), three candidate HbZAR1 genes were identified using bioinformatics methods and comprehensively analyzed. The results indicate that the HbZAR1 protein is conserved in different plant species. Examination of cis-regulatory element sequences of HbZAR1genes reveals that the HbZAR1 gene promoter exhibits a remarkable enrichment of stress, light, and hormone elements. An expression analysis shows that the expression levels of the three HbZAR1 genes are highest in the bark and lowest in latex. Three HbZAR1 genes can respond to both rubber tree Erysiphe quercicola and Colletotrichum siamense infection; especially, HbZAR1.1 and HbZAR1.2 show significant upregulation in expression levels during the early stages of infection. These findings suggest that the three HbZAR1 genes may be involved in rubber tree susceptibility to E. quercicola and C. siamense through different immune mechanisms. Subcellular localization results indicate that the HbZAR1 genes are expressed in the nucleus and plasma membrane. This study also shows that the three HbZAR1 genes and activated mutant HbZAR1.1D481V do not induce stable ROS production and cell death, suggesting possible gene degradation, functional redundancy, or acting as minor genes in disease resistance. This research provides valuable insights for further studying the function of HbZAR1 genes in rubber trees and the mechanisms of immune molecules. [ABSTRACT FROM AUTHOR]

Hevea brasiliensis is an evergreen woody tree widely used in industrial production in tropical rain forest. However, rubber trees are extremely vulnerable to low temperature stress, which seriously limits the cultivation and use of rubber trees in low temperature areas. NAC transcription factor gene family is common to many plant species, and can participate in a variety of behaviors that are crucial for plants to cope with the challenges from the environment. However, little is known about the evolution history, function and expression patterns of NAC family in rubber trees. Here, 51 HbNAC genes were identified in rubber tree by genome search, and they were divided into 11 subclasses according to phylogenetic relationship. The members of a subfamily share a similar number of introns and exons. We conducted transcriptome analyses to obtain cold-responsive HbNACs, and the transcriptome data showed the expression of HbNAC26 and HbNAC11 was significantly induced by cold stress, suggesting a potential role of these genes in cold stress. The expression pattern of HbNACs in different tissues and different developmental stages was studied by real-time PCR. In addition, the complementary effect of defective yeast mutants indicated that the HbNAC11 gene could be a positive regulator of cold stress in rubber trees. The results of this study can lay a foundation for studying the biological function of NAC and improving cold resistance breeding of rubber trees. [ABSTRACT FROM AUTHOR]

Hevea brasiliensis, or the Para rubber tree, is a major commercial source of natural rubber (NR). The rubber tree is susceptible to various fungal attacks, which affect NR production and Corynespora cassiicola is one of the major pathogens affecting young and mature rubber trees. Corynespora leaf fall disease (CLFD) outbreaks often cause serious loss in latex productivity by adversely affecting tree health. Since fungicidal chemical control is uneconomical and unsustainable, improving host resistance is the most effective strategy for the long-term management of this disease. In this context, 78 Hevea genotypes were screened against two virulent isolates of two races of C. cassiicola (Race 1 and Race 2). The level of host resistance was determined in vitro using detached leaf bioassay and those genotypes that were found to be highly resistant were subjected to further evaluation under greenhouse conditions. Seven genotypes were classified as highly resistant against both races of C. cassicola in vitro, with less than 20% disease intensity. Subsequent assessment under greenhouse conditions identified three genotypes with less than 40% disease severity and corresponding rAUDPC value of less than 0.4 when challenged with both races of C. cassiicola. These resistant genotypes are suitable candidates to be included in breeding programmes aimed at the development of superior clones with durable resistance against Corynespora leaf fall disease. [ABSTRACT FROM AUTHOR]

Rubber seed shell (Hevea brasiliensis) was used as a low-cost substrate to produce lactic acid via Lactobacillus plantarum LB2. The medium components were initially screened by two-level full factorial design. Three variables (pH, moisture, and polyoxyethylene sorbitan monooleate (PSM)) were used in the central composite design and response surface methodology. The amount of PSM was found to be a significant variable in lactic acid production. Lactic acid was purified and used for the chemical fabrication of a polylactic acid-chitosan composite film. Compared with the polylactic acid, the composite film improved the tensile strength, elongation strength, and tearing strength. The film prepared with 1% chitosan-polylactic acid exhibited the maximum antibacterial activity against Bacillus cereus (21 ± 1 mm) and the lowest activity against Escherichia coli (10 ± 1 mm). The polylactic acid-chitosan film prepared with 1% chitosan was used as a packing material to store the fish fillets and presented reduced mesophilic (4.3 ± 0.1 Log CFU/g) and psychrotropic (3.2 ± 0.2 Log CFU/g) bacterial populations compared with those of the control (4.9 ± 0.2 Log CFU/g and 3.7 Log CFU/g). Rubber seed shells can be used as an alternative culture medium for lactic acid production, to reduce the production cost of polylactic acid. [ABSTRACT FROM AUTHOR]

The Oomycetes fungus Phytophthora spp. which causes Abnormal leaf fall (ALF) disease poses a significant threat as one of the most devastating diseases affecting rubber trees in India. A total of 30 Phytophthora isolates were obtained from ALF-affected samples collected during the Southwest monsoon season of Kerala. The colony morphology of Phytophthora isolates revealed eight different types of growth patterns, with stellate, stellate striated, and petaloid patterns growing rapidly, whereas chrysanthemum pattern grew slowly. Sporangia were papillate to non-papillate in various shapes, and sporangiophores exhibited simple, simple sympodial, or irregularly branching patterns. Highly virulent isolates exhibited petaloid morphology and rapid growth rates. Regardless of their virulence, all isolates showed susceptibility to the fungicide metalaxyl. Under in vitro conditions, the highly virulent isolate (R17) from rubber caused severe infections in chili, brinjal, and tomato with brown water-soaked lesions. Sequence analysis and multi-locus phylogeny of Internal transcribed spacer (ITS), cCytochrome c oxidase 1 (COX 1), Heat shock protein 90 (HSP 90), and Ribosomal protein L10 (RPL 10) confirmed the pathogen as Phytophthora meadii. A comprehensive understanding of both morphological and molecular traits of P. meadii is crucial for precise identification and future genetic variability studies. • P. meadii isolates exhibited varied morphology and susceptibility to the metalaxyl. • Hevea clones RRII 414 and 417 showed tolerance to P. meadii. • Solanaceae species like brinjal, chili, and tomato are susceptible to cross-infection by P. meadii from rubber trees. • Multi-locus phylogeny with ITS, COX1, HSP90, and RPL 10 genes confirmed the identity of P. meadii. [ABSTRACT FROM AUTHOR]

Agroforestry ecosystems are an efficient strategy for enhancing soil nutrient conditions and sustainable agricultural development. Soil extracellular enzymes (EEAs) are important drivers of biogeochemical processes. However, changes in EEAs and chemometrics in rubber-based agroforestry systems and their mechanisms of action are still not fully understood. Distribution of EEAs, enzymatic stoichiometry, and microbial nutrient limitation characteristics of rubber plantations under seven planting patterns (RM, rubber monoculture system; AOM, Hevea brasiliensis-Alpinia oxyphylla Miq; PAR, Hevea brasiliensis-Pandanus amaryllifolius Roxb; AKH, Hevea brasiliensis-Alpinia katsumadai Hayata; CAA, Hevea brasiliensis-Coffea Arabica; CCA, Hevea brasiliensis-Cinnamomum cassia (L.) D. Don, and TCA, Hevea brasiliensis-Theobroma Cacao) were analyzed to investigate the metabolic limitations of microorganisms and to identify the primary determinants that restrict nutrient limitation. Compared with rubber monoculture systems, agroforestry ecosystems show increased carbon (C)-acquiring enzyme (EEAC), nitrogen (N)-acquiring enzyme (EEAN), and phosphorus (P)-acquiring enzyme (EEAP) activities. The ecoenzymatic stoichiometry model demonstrated that all seven plantation patterns experienced C and N limitation. Compared to the rubber monoculture system, all agroforestry systems exacerbated the microbial limitations of C and N by reducing the vector angle and increasing vector length. P limitation was not detected in any plantation pattern. In agroforestry systems, progression from herbs to shrubs to trees through intercropping results in a reduction in soil microbial nutrient constraints. This is primarily because of the accumulation of litter and root biomass in tree-based systems, which enhances the soil nutrient content (e.g., soil organic carbon, total nitrogen, total phosphorus, and ammonium nitrogen) and accessibility. Conversely, as soil depth increased, microbial nutrient limitations tended to become more pronounced. Partial least squares path modelling (PLS-PM) indicated that nutrient ratios and soil total nutrient content were the most important factors influencing microbial C limitation (−0.46 and 0.40) and N limitation (−0.30 and −0.42). This study presented novel evidence regarding the constraints and drivers of soil microbial metabolism in rubber agroforestry systems. Considering the constraints of soil nutrients and microbial metabolism, intercropping of rubber trees with arboreal species is recommended over that of herbaceous species to better suit the soil environment of rubber plantation areas on Hainan Island. [ABSTRACT FROM AUTHOR]

Natural rubber is a crucial industrial material, and it is primarily harvested from the latex of the rubber tree Hevea brasiliensis by tapping the tree trunk. During the regular tapping process, mechanical damage seriously affects latex reproduction and rubber yield, but the molecular mechanisms on tapping stimulation remain unclear. In this study, we firstly determined the changed physiological markers on latex regeneration, overall latex yield, and latex flow time during the tapping process. Then, we combined proteomics and transcriptomics analyses of latex during tapping and identified 3940 differentially expressed genes (DEGs) and 193 differentially expressed proteins (DEPs). Among them, 773 DEGs and 120 DEPs displayed a persistent upregulation trend upon tapping. It is interesting that, in the detected transcription factors, basic helix-loop-helix (bHLH) family members occupied the highest proportion among all DEGs, and this trend was similarly observed in DEPs. Notably, 48 genes and 34 proteins related to natural rubber biosynthesis were identified, and most members of small rubber particle protein (SRPP) and rubber elongation factor (REF) showed a positive response to tapping stimulation. Among them, SRPP6 and REF5 showed significant and sustained upregulation at the gene and protein levels following tapping, indicating their pivotal roles for post-tapping rubber biosynthesis. Our results deepen the comprehension of the regulation mechanism underlying tapping and provide candidate genes and proteins for improving latex production in the Hevea rubber tree in future. [ABSTRACT FROM AUTHOR]

Drought conditions can severely impact rubber (Hevea brasiliensis) plantations, leading to economic loss in Malaysia. The study aimed to assess the impact of varying soil moisture levels on the physiological characteristics of five latex timber clones (LTCs) of rubber, with the goal of identifying the most suitable clone for specific soil moisture conditions. These conditions include (1) field capacity, (2) 75% available water (AW), (3) 50% AW, (4) 25% AW, and (5) wilting point, with the ultimate objective of optimizing cultivation methods and fostering sustainable rubber production in Malaysia. The five clones under investigation include RRIM3001, RRIM2025, RRIM2001, RRIM928, and PB350. Leaf chlorophyll content, stomatal conductance, and net photosynthesis were measured 4 and 8 months after treatment (MAT). The findings indicated significant effects of moisture stress on various physiological attributes, including total chlorophyll content, relative chlorophyll content, stomatal conductance, and net photosynthesis rate. At 4 and 8 MATs, the clones subjected to field capacity exhibited the highest values for these physiological characteristics, followed by those exposed to 75% available water, with the lowest values observed at the wilting point. RRIM3001 consistently exhibited the highest total chlorophyll content, stomatal conductance, and net photosynthesis among the clones at both sampling dates. The highest net photosynthesis was observed in the RRIM3001 clone under field capacity conditions. Furthermore, a significant positive correlation was identified between total chlorophyll and relative chlorophyll contents, as well as between net photosynthesis and stomatal conductance. These findings carry practical implications for water management during the initial growth phase of rubber seedlings and for replanting initiatives in rubber plantations. [ABSTRACT FROM AUTHOR]

Biodiesel predominantly originates from edible oil. Exploring non-edible oil resources is crucial to biodiesel manufacturing's commercial viability and food security. This study examines four non-edible seed oils Hevea brasiliensis, Madhuca longifolia, Azadirachta indica, and Gossypium hirsutum as biofuel feedstocks. This study optimized reaction parameters to improve base-catalyzed transesterification, oil extraction and biodiesel synthesis. The produced esters were identified by nuclear magnetic resonance, Fourier transform infrared, and gas chromatography mass spectrometry. Elements composition was determined using inductively coupled plasma-optical emission spectrometry and elemental analyzer. The biofuel's physicochemical properties met American Society for Testing and Materials and European standards. The maximum amount of crude oil was seen in Hevea brasiliensis using the soxhlet extraction process, ranging from 52-63%. This was followed by Madhuca longifolia 38-55%, Azadirachta indica 24-33%, and Gossypium hirsutum with 19-27%. The density of the plant sources exhibited a range of 0.88-0.90 g/cm3 @ 15 °C, while the kinematic viscosity showed a range of 3.2-4.1 mm2/s. The elemental composition of biodiesel, expressed as percentages of carbon, hydrogen, nitrogen, and oxygen, varied between the ranges of 70.52-76.30, 11.25-14.02, 1.18-2.75, and 9.11-13%, respectively. Since they may be grown in infertile and unproductive settings, these non-consumable seeds are cost-effective for renewable energy. They also help solve the energy situation by boosting biodiesel production.. [ABSTRACT FROM AUTHOR]

Hevea brasiliensis is an important cash crop with the product named natural rubber (NR) for markets. Ethylene (ET) is the most effective yield stimulant in NR production but the molecular mechanism remains incomplete. Here, latex properties analysis, transcriptome analysis, and metabolic profiling were performed to investigate the mechanism of NR yield increase in four consecutive tappings after ET stimulation. The results revealed that sucrose and inorganic phosphate content correlated positively with dry-rubber yield and were induced upon ET stimulation. Stimulation with ET also led to significant changes in gene expression and metabolite content. Genes involved in phytohormone biosynthesis and general signal transduction as well as 51 transcription factors potentially involved in the ET response were also identified. Additionally, KEGG annotation of differentially accumulated metabolites suggested that metabolites involved in secondary metabolites, amino-acid biosynthesis, ABC transporters, and galactose metabolism were accumulated in response to ET. Integrative analysis of the data collected by transcriptomics and metabolomics identified those differentially expressed genes and differentially accumulated metabolites are mainly involved in amino-acid biosynthesis and carbohydrate metabolism. Correlation analysis of genes and metabolites showed a strong correlation between amino-acid biosynthesis during ET stimulation. These findings provide new insights into the molecular mechanism underlying the ET-induced increase in rubber yield and further our understanding of the regulatory mechanism of ethylene signaling in rubber biosynthesis. [ABSTRACT FROM AUTHOR]

This study evaluated the foliar antioxidant activity in nine Hevea brasiliensis genotypes from the ECC-1 (Élite Caquetá Colombia) selection and IAN 873 cultivar (control) in trees in the growth stage in two large-scale clonal trials in response to different climatic (semi-humid warm and humid warm sites) and seasonal (dry and rainy periods) conditions in the Colombian Amazon. The results indicated that Reactive Oxygen Species (ROS) production increased under conditions of lower water availability (dry period), leading to lipid peroxidation, high defense of photosynthetic pigments, and development of better osmotic adjustment capacity in the ECC 64, IAN 873, ECC 90, and ECC 35 genotypes due to high concentrations of carotenoids (0.40 mg g-1), reducing sugars (65.83 μg mg-1), and malondialdehyde (MDA) (2.44 nmol ml-1). In contrast, during the rainy period, a post-stress action was observed due to high contents of proline and total sugars (39.43 μg g-1 and 173.03 μg g-1, respectively). At the site level, with high Photosynthetically Active Radiation (PAR) values (1143 moles photons m-2 s-1), temperature (32.11°C), and lower precipitation (135 mm), higher antioxidant activity (chlorophylls a, b and total, carotenoids, and proline) was recorded at the humid warm site, demonstrating that the ECC 90, ECC 64, and ECC 66 genotypes are tolerant to water deficit compared to IAN 873. The ECC 64 genotype, independent of seasonal changes and site conditions, presented the highest contents in Chl a, total Chl, reducing sugars, total sugars, and MDA, showing a tendency to adapt to fluctuating conditions. This study showed that water fluctuations do not cause the same metabolic responses, these vary within the same species, depending on their developmental stage and the climatic and seasonal variations characteristic of the Colombian Amazon. [ABSTRACT FROM AUTHOR]

The Latex Diagnosis (LD) is performed through the determination of dry rubber (DRC), sucrose (Suc), inorganic phosphorus (Pi) and thiol (RSH) contents. It is carried out through the colorimetric method using a single cuvette spectrophotometer, which is time-consuming and requires a high volume of chemicals. It also needs to be executed as soon as the samples are collected so that limits the adoption of LD. The adaptation of the protocol to a multiplate reader and suitable conservation aimed to overcome the limitations. The experiments were carried out at the Indonesian Rubber Research Institute, Sembawa, Palembang, and Research Center for Biotechnology, Universitas Gadjah Mada, Yogyakarta. Various combinations of solution volumes, adapted from standard protocol, were tested. The closest slope of the standard curve to control was then applied to 7 randomly selected trees. The result showed that for Suc, the composition of 10 µL samples, 30 µL of 2.5 % TCA and 210 µL anthrone reagent was suitable for determination using a multiplate reader. The combination of 40 µL of sample, 85 µL of 2.5 % TCA and 125 µL mL FeSO4 solution was suitable for Pi determination, while 100 µL samples, 5 µL DNTB and 100 µL Tris is recommended for RSH. The measurement using a multiplate reader resulted in comparable contents (average deviations were 1.83, 2.69 and 3.51 % for Suc, Pi, and RSH, respectively), lower time and chemicals consumptions, and a larger number of sample handling compared to single cuvette method. This study also tested the effect of freeze-drying for sample conservation. The result indicated that freezedrying was able to maintain the Pi level (deviation 0.93 %). However, it increased Suc (deviation 19.43 %) and decreased ascorbate (AsA) significantly (deviation 43.60 %); therefore, freeze-drying might not be suitable for conserving serum samples in the LD method. [ABSTRACT FROM AUTHOR]

The possible utilization of Bagalunga (Melia azedarach L.) was determined based on its physical and mechanical properties. Tests were done following the ASTM D143-2019 standard. Tree samples were collected from two municipalities of Quezon province, the Philippines-namely Sariaya and Unisan. The results showed that compared to the trees from Sariaya, the trees collected from Unisan had 13.48 and 14.24% higher green moisture content (MC) and basic relative density (RD), respectively. However, their tangential (TS), radial (RS), longitudinal (LS), and volumetric shrinkage (VS) were 12.21, 4.42, 28.94, and 7.83% lower than those of the former. Furthermore, the RD of M. azedarach was similar to that of Gmelina arborea, and Acacia mangium and higher than that of Falcataria falcata. As for VS, it was comparable and in some cases even higher than those of commercially used timber species with medium to low VS. For the strength properties, in both green and 12% MC conditions, the strength of trees from Unisan was significantly higher than trees from Sariaya. However, both remained within the medium strength classification-similar to Swietenia macrophylla, G. arborea, and A. mangium but higher than Eucalyptus deglupta, Hevea brasiliensis, and F. falcata. The significant effect of axial height was observed in MC, RD, LS, and VS, and minimal variation was found in the mechanical properties. Industrial tree plantation developers may consider using M. azedarach as an alternative species, with careful consideration of the axial height and location, as these factors can influence tree properties. [ABSTRACT FROM AUTHOR]

The occurrence of black crust, a disease previously considered secondary, has become a cause for concern due to early leaf fall in rubber trees (Hevea brasiliensis). This study aimed to identify sources of resistance to black crust in 21 clones of rubber trees in a clonal garden. To achieve this, the disease severity was evaluated through eight assessments conducted over a 2‐year period. In each evaluation, 15 leaflets from three different parts of the plant (bottom, middle third and crown) were randomly collected, resulting in a total of 45 leaflets per plant. These leaflets were then taken to the laboratory, and the software Leaf Doctor was used to measure the percentage of leaf area exhibiting symptoms of black crust. The results were analysed using the Scott‐Knott test at a 5% probability level. The clones with the highest infected leaf area observed during the evaluations were IAC300, IAC418, IAC503, PB311 and RRIM600. Clone IAC511 did not show any symptoms of the disease in any of the evaluations. Clones IAC301, IAC411, IAC501, IAC507 and IRCA111 exhibited low percentages of affected leaf areas. Additionally, this study revealed the progression of the disease over the evaluation period. The infection initially starts on the youngest leaves (crown) in March and subsequently intensifies in the middle third of the plant, corresponding to the youngest leaf previously infected in the crown. Furthermore, environmental data collected in the experimental area over the 2‐year evaluation period indicated that the disease manifests with greater severity when the average temperatures fall below 25°C after periods of heavy rainfall, followed by dry periods with low relative humidity. The data presented in this study significantly contribute to the management of this disease in the field by identifying clones where the disease manifests with lower severity. [ABSTRACT FROM AUTHOR]

Areas identified as escape zones for Pseudocercospora ulei, the causal agent of South American Leaf Blight (SALB), are being sought for the development of profitable rubber growing, as high-yielding Asian clones can be grown there without suffering repeated defoliation caused by epidemics of the disease. A performance trial with 10 clones was set up in 2006 in such an escape zone in Ecuador with non-American clones whose high production potential is acknowledged elsewhere in the world, some of which are recommended on a commercial scale. Production results over seven years, between 2013 and 2019, indicated a very high potential for this material in this new region, reaching average yields of 2.5 t/ha/year for clones PB 280, PB 312 and PB 314, and 1.85 t/ha/year for the control clone RRIM 600, despite a very pronounced 5-month dry season. However, the risks of wind damage and tapping panel dryness were found to be very high for PB 312 and PB 314. Clone PB 280 proved to perform best overall, with 93% of trees in production and one of the lowest Tapping Panel Dryness (TPD) rates. This clone, distinguished by its medium high latex metabolism and a high sucrose reserve, presents a highly promising alternative for the cultivation of rubber trees in escape zones. This is particularly relevant in situations where the phytosanitary risk associated with P. ulei is constrained. [ABSTRACT FROM AUTHOR]

Pestalotiopsis leaf fall disease (PLFD) has been on the increase in recent years, resulting in diminished latex yield in many rubber producing countries. Thus far, some reports have pointed to the presence of fungal pathogen(s) other than Pestalotiopsis sp. in the diseased leaves. To decipher the diversity of fungal pathogens, a total of 110 early-stage and another 110 late-stage symptomatic leaves were sampled from 12 Hevea clones in seven different areas in Malaysia during wintering and wet seasons at different times of the year. A total of 487 fungal isolates were obtained; 241 were from the early-stage and 246 from the late-stage symptomatic leaves. These isolates were clustered into 11 morphotypes based on colony appearance and microscopic observation of the spore. The diversity analysis revealed significant differences in morphotype richness and evenness when comparing different rubber clones, seasonal effects, and locations by which the fungal isolates were sampled. Five isolates representative of the five predominant morphotypes associated with PLFD were analysed using the Internal Transcribed Spacer (ITS) markers and BLAST analysis. Their closest relative species were identified as Colletotrichum conoides, Neopestalotiopsis surinamensis, Lasiodiplodia theobromae, Phyllosticta fallopiae and Letendraea cordylinicola. This study enhanced our understanding of PLFD, particularly the diversity and distribution of fungal communities associated with the disease across different rubber clones, seasons, and locations in Malaysia. The identification of these fungal isolates associated with PLFD symptoms paves the way for further research into their pathogenicity and the development of targeted management strategies to mitigate the disease. [ABSTRACT FROM AUTHOR]

The rubber tree (Hevea brasiliensis) is vulnerable to infections by various fungal pathogens. White root disease infection is one of the most prevalent diseases of rubber in Malaysia. This disease is caused by the fungus Rigidoporus microporus. Delayed management of this disease can cause considerable reduction in total tree stand and ultimately decreased land productivity. The utilisation of elicitor proteins to heighten host plant resistance represents a sustainable approach to disease control by reducing the use of chemical fungicides. The cerato-platanin protein family is the most widely reported class of elicitor proteins. This study isolated a member of the cerato-platanin family from R. microporus and evaluated its expression during H. brasiliensis infection. Total RNA was extracted from the mycelial sample of R. microporus followed by cDNA synthesis, isolation and cloning of the cerato-platanin transcript referred to as rmcp. In silico characterisation of the obtained sequence was then conducted and the relative expression of the gene was evaluated using RT-qPCR. A transcript of 438 bp encoding 145 amino acids protein, denoted as RmCP, was isolated and cloned. RmCP is composed of a cerato-platanin domain and a predicted N-terminal signal peptide. Phylogenetic analysis grouped RmCP into a cluster together with cerato-platanin proteins originating from basidiomycetes. The expression of rmcp gene was consistent throughout the study period and was not significantly different from axenic culture. This suggests the gene to have a fundamental function in the life cycle of R. microporus. [ABSTRACT FROM AUTHOR]

Natural rubber latex (NRL) collected from various Hevea brasiliensis clones, namely RRIM600, RRIT251, and PB235, was used to prepare vulcanized natural rubber. The influence of protein content in various natural rubber clones on storage hardening, tensile properties, and thermal properties was investigated. It was found that the RRIM600 clone exhibited the highest protein content. The increased storage hardening is related to the higher protein content in the latex. The cure characteristic of vulcanized natural rubber depends on the proteins in NRL and acts as an activator in vulcanization system. Moreover, the RRIM600 clone exhibited the maximum of 300% modulus, 500% modulus, tensile strength, and thermal stability. This is attributed to the chemical interaction (H-bonding interaction), physical crosslink (entanglement), and also the presence of strain-induced crystallization in natural latex molecules. Thus, this study is aimed to understand the key role of non-rubber components from different clones on the networking structure. The concept utilized in this study holds great potential for a wide range of applications, leveraging the properties of natural rubber latex collected from diverse clones. [ABSTRACT FROM AUTHOR]

The rubber tree (Hevea brasiliensis) is one of the major domesticated crops planted commercially for the production of natural rubber (NR) worldwide. In recent years, rubber trees in the Southern states of India and other rubber-producing countries have experienced a severe leaf spot disease, characterized by the appearance of several brown circular spots in the initial stage, which later spread all over the lamina of fully matured leaves, leading to yellowing and defoliation. The causal organism of this Circular Leaf Spot (CLS) disease has not been conclusively identified in any previous studies. In this study, we collected infected leaf samples from various locations in the South Indian states. We aimed to identify the actual fungal pathogen that causes the CLS disease on rubber trees. Based on the morphological and molecular analysis of the most frequently isolated fungi from infected leaf samples were identified as Colletotrichum siamense and Colletotrichum fructicola. Pathogenicity tests also confirmed the involvement of isolated Colletotrichum spp. in the development of CLS disease. These findings provide valuable insights into understanding the CLS disease and its impact on rubber cultivation. To our knowledge, it is the first report of C. siamense and C. fructicola associated with CLS disease of rubber trees in India. [ABSTRACT FROM AUTHOR]

Ecosystem level carbon loss and the resultant loss of CO2 mitigating capacity of rubber (Hevea brasiliensis) plantations of 23 and 30 years in a hilly urbanized terrain dominated by development and construction activities was investigated. The total carbon loss of the rubber ecosystem due to the destruction of a surface area of 10, 25, and 50 hectares of rubber plantation was derived from published data of destructive tree felling based on the biomass and carbon sequestration potential of one hectare of rubber plantation. The popularly cultivated clone RRII 105 since 1980 occupying 85% of the total rubber area in India was chosen for the study. The data was analyzed using ANOVA and Standard Error (SE) Means for the base data and extrapolated to ecosystem-level calculation. Results revealed a total ecosystem carbon loss of 2142, 5355, 10710 tons for 23 years and 3415, 8538, 17075 tons for 30 years under deforested area of 10, 25, and 50 hectares, respectively. The carbon loss (tons) from tree biomass (tons) removal was 570, 1425, 2850, litter fall was 575, 1438, 2875 and sheet rubber was 432, 1080, 2160 for 23 year plantation. In 30 years plantation, carbon loss from tree biomass was 1480, 3700, 740, litter fall was 750, 1875, 3750, and sheet rubber was 621, 1553, 3105 tons. Total soil carbon stock loss (tons) was 565, 1413 and 2825 for both 23 and 30 years, since the soil carbon stock was calculated similarly with one value for both plantation years. Other studied clones such as RRII 414, RRII 429, and RRII 417 recorded 44-50 percent higher carbon loss compared to RRII 105. The highest carbon loss was recorded in the central part and lowest in the area with severe drought. The study clearly depicts the importance of rubber plantations in mitigating climate change due to massive removal of rubber plantations, an important economically and environmentally sustainable agro ecosystem. The study recommends for putting in place appropriate policies and regulations to restrict the removal of economic tree plantations for ecosystem sustainability. [ABSTRACT FROM AUTHOR]

Background: Plants allocate resources to growth, defense, and stress resistance, and resource availability can affect the balance between these allocations. Allocation patterns are well-known to differ among species, but what controls possible intra-specific trade-offs and if variation in growth vs. defense potentially evolves in adaptation to resource availability. Methods: We measured growth and defense in a provenance trial of rubber trees (Hevea brasiliensis) with clones originating from the Amazon basin. To test hypotheses on the allocation to growth vs. defense, we relate biomass growth and latex production to wood and leaf traits, to climate and soil variables from the location of origin, and to the genetic relatedness of the Hevea clones. Results: Contrary to expectations, there was no trade-off between growth and defense, but latex yield and biomass growth were positively correlated, and both increased with tree size. The absence of a trade-off may be attributed to the high resource availability in a plantation, allowing trees to allocate resources to both growth and defense. Growth was weakly correlated with leaf traits, such as leaf mass per area, intrinsic water use efficiency, and leaf nitrogen content, but the relative investment in growth vs. defense was not associated with specific traits or environmental variables. Wood and leaf traits showed clinal correlations to the rainfall and soil variables of the places of origin. These traits exhibited strong phylogenetic signals, highlighting the role of genetic factors in trait variation and adaptation. The study provides insights into the interplay between resource allocation, environmental adaptations, and genetic factors in trees. However, the underlying drivers for the high variation of latex production in one of the commercially most important tree species remains unexplained. [ABSTRACT FROM AUTHOR]

Rubber trees (Hevea brasiliensis) serve as the primary source of natural rubber. Their native habitat is characterized by warm and humid conditions, so they are particularly sensitive to low temperatures. Under such stress, latex burst can cause severe damage to rubber trees, which is due to the uniqueness of their economically productive parts. In order to establish a correlation between young and mature rubber trees and provide a novel prospective for investigating the mechanisms of latex burst and chilling resistance in rubber trees, the chlorophyll contents, photosynthesis, and chlorophyll fluorescence parameters in four varieties of one-year-old rubber tree seedlings were analyzed under artificially simulated chilling stress. The latex burst characteristics were subsequently recorded. A comprehensive statistical analysis of the chilling-resistance rank was conducted using the membership function method and the combination weighting method. Meanwhile, chemical compositions and tensile properties of barks from two-year-old twigs of mature rubber trees were ascertained. A correlation analysis between chilling resistance, chemical compositions, and tensile properties was performed to identify any interrelationships among them. The results showed that the number and the total area of latex-burst positions in variety Reken628 seedlings were greater than those in other varieties, and the lowest number and total area of latex-burst positions were observed in variety RRIM600 and variety PR107, respectively. With the exception of variety GT1, nectar secretion was noted in all other varieties of rubber tree seedlings under chilling stress. The chilling resistance of the four varieties decreased in the following order: variety GT1 > variety RRIM600 > variety PR107 > variety Reken628. The chilling resistance was strongly (p < 0.001) negatively correlated with cellulose content and acid-insoluble lignin content, respectively. The total area of latex burst was significantly (p < 0.001) and positively correlated with holocellulose content and maximum load, respectively. Furthermore, this study also provides new insights into the mechanism of nectar secretion induced by low temperatures and its association with the chilling resistance of rubber trees. [ABSTRACT FROM AUTHOR]

Natural rubber (NR) films with different natural networks—concentrated NR (CNR), deproteinized NR (DPNR), and small rubber particles (SRP)—are investigated to explore the relationship between network structure and film properties using atomic force microscopy (AFM) in PeakForce Quantitative Nanomechanics (QNM) mode. Nitrogen content, gel content, and particle size distribution analyses reveal distinct network topologies in each latex type. Mechanical testing shows variations in tensile strength and crosslink density. AFM analysis provides insights into the crosslink network structures within the pre‐vulcanized latex film. It is found that DPNR and CNR films have a uniform distribution of crosslink networks, with DPNR exhibiting higher Young's modulus values. In contrast, SRP shows varying Young's modulus values, suggesting poor coalescence arising from a harder particle surface and a softer rubber core in an inhomogeneous network structure intrinsic to the non‐rubber components (NRCs) make‐up of SRP latex. This study highlights the pivotal role of natural network structures formed by NRCs in determining the ultimate properties of latex films, which has significant implications for the rubber industry, particularly in the production of latex‐dipped products, medical devices, and bioengineering applications. [ABSTRACT FROM AUTHOR]

Rubber tree (Hevea brasiliensis) is reproduced by bud grafting for commercial planting, but significant intraclonal variations exist in bud-grafted clones. DNA methylation changes related to grafting may be partly responsible for intraclonal variations. In the current study, whole-genome DNA methylation profiles of grafted rubber tree plants (GPs) and their donor plants (DPs) were evaluated by whole-genome bisulfite sequencing. Data showed that DNA methylation was downregulated and DNA methylations in CG, CHG, and CHH sequences were reprogrammed in GPs, suggesting that grafting induced the reprogramming of DNA methylation. A total of 5,939 differentially methylated genes (DMGs) were identified by comparing fractional methylation levels between GPs and DPs. Transcriptional analysis revealed that there were 9,798 differentially expressed genes (DEGs) in the DP and GP comparison. A total of 1,698 overlapping genes between DEGs and DMGs were identified. These overlapping genes were markedly enriched in the metabolic pathway and biosynthesis of secondary metabolites by Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis. Global DNA methylation and transcriptional analyses revealed that reprogramming of DNA methylation is correlated with gene expression in grafted rubber trees. The study provides a whole-genome methylome of rubber trees and an insight into the molecular mechanisms underlying the intraclonal variations existing in the commercial planting of grafted rubber trees. [ABSTRACT FROM AUTHOR]

T-shaped mortise and tenon members are the main structure of traditional Chinese furniture. In this paper, the double-dovetail joint used for face-toface joint of rubber wood (Hevea brasiliensis Muell. Arg) is transformed into a new type of double-dovetail joint and rounded double-dovetail joint for T-shaped members of point joint structure. The ultimate pull-out test and bending strength test were carried out on the two structures and three structures of oval mortise, round rod mortise and right angle mortise. The results show that the ultimate pull-out force of the round double-dovetail joint is 39% higher than that of the double-dovetail joint, and the bending resistance capacity is 8.9% higher, and the strength and stability are better than those of other split mortises and tenons, which proves that this structure can be used in actual production, and also proves that the mortise and tenon connected by the surface has the possibility of transforming into a point connection structure. The concave structure of the rounded double-dovetail joint makes the mortise and tenon fit well, the tenon squeezed tight, and a good bonding effect was achieved. This structure can also provide greater friction and resistance, delay rubber adhesive failure and improve the stability. [ABSTRACT FROM AUTHOR]

The study was carried out to determine the effectiveness of Hartindo AF21 as a wood preservative against subterranean termites, specifically Coptotermes curvignathus Homgren (Rhinotermitidae) in Malaysian conditions. The aim was to examine the performance of Hartindo AF21 in preventing termite attacks on Koompassia malaccensis and Hevea brasiliensis. The tests involved using various concentrations of Hartindo AF21 in both single choice (no-choice) (ASTM D3345) and aboveground (IHM/WEL/1) scenarios. The findings from the laboratory and above-ground tests revealed that concentrations of Hartindo AF21 above 20% created a sufficient chemical barrier or resulted in high mortality rates for C. curvignathus after 15 days. Additionally, both wood species treated with Hartindo AF21 displayed typical repellent wood preservative behavior, with reduced feeding and mass loss as the concentr ation of preservative increased. [ABSTRACT FROM AUTHOR]

A new, simple, and selective colorimetric method of determining formaldehyde in Hevea brasiliensis latex was developed by using a casein/ferric chloride/polyvinyl alcohol hydrogel composite (casein/FeCl3/PVA) in a modified Leach test. Under heating, formaldehyde reacted with 8% casein in the presence of 0.1% FeCl3 and 4.3% HCl (v/v) entrapped in a 30% PVA hydrogel packed in a syringe. A purple-colored product was formed with a maximum absorbance of 525 nm. The color change was evaluated at the color detection zone indicated on the the syringe. The %magenta values were easily evaluated by using a mobile phone application and employed to determine formaldehyde content. The casein/FeCl3/PVA composite gave a readable response in a formaldehyde detection range from 0.04 to 0.80% with a linear response between %magenta and formaldehyde concentration (R2 = 0.9955). The detection limit was 0.032%, and precisions were in the range 0.67–4.94%. The casein/FeCl3/PVA composite was applied to the analysis of ammonia-preserved latex samples, and recoveries of formaldehyde from samples spiked at 0.1, 0.3, and 0.5% ranged from 81.55 to 99.51% (RSDs ≤ 5.41%). The recoveries and precision of the proposed method were comparable with those of high-performance liquid chromatography (HPLC). The developed method was also selective, showing no interference from other latex preservatives, i.e., phenol, ammonia, or tetramethylthiuram disulfide. [ABSTRACT FROM AUTHOR]

Utilizing conventional wood preservatives poses potential risks to ecosystems and human health. Therefore, the wood protection industry must develop alternatives that are both efficient and environmentally friendly. In this paper, industrial tobacco waste extracts were used as eco-friendly wood preservatives against wood decay fungi. Three major constituents in the extracts were identified via gas chromatography-mass spectrometry (GC-MS) and included nicotine, neophytadiene, and 2,7,11-cembratriene-4,6-diol. The antifungal activities of waste tobacco extracts and these three major constituents against wood decay fungi were tested. At a concentration of 40 mg/mL, the tobacco waste extract treated with 50% ethanol significantly inhibited the activity of wood decay fungi. This was because the extract contained nicotine as the primary active component and neophytadiene as a synergistic active component. Wood decay resistance tests were conducted on Pinus yunnanensis and Hevea brasiliensis treated with a 50% ethanol extract of tobacco waste at a concentration of 40 mg/mL. The mass losses of Pinus yunnanensis exposed to G. trabeum and T. versicolor were 4.11% and 5.03%, respectively, while the mass losses in Hevea brasiliensis exposed to G. trabeum and T. versicolor were 7.85% and 9.85%, respectively, which were classified as highly resistant. The acute ecotoxicity of the tobacco waste extract was assessed using a kinetic luminescent bacteria test with Aliivibrio fischeri, which revealed significantly lower acute toxicity than a commercial copper-based wood preservative. This study offers insights into high-value utilization of tobacco waste and advancement of natural wood preservatives. [ABSTRACT FROM AUTHOR]

The objective of this work was to evaluate the development of Davidiella sp. and its asexual form, Cladosporium sp., under different environmental conditions in the rubber tree (Hevea brasiliensis). Rubber tree leaves were inoculated with a spore suspension and kept in a humid chamber under different temperatures and wetness periods. The behavior of the fungi was evaluated using a scanning electron microscope (SEM) and an ultraviolet light microscope (UV). In the images obtained in SEM, four hours after inoculation of the fungus, it was possible to verify the germination and penetration of conidia at temperatures of 10 to 20 °C. The formation of conidiophores was verified from six hours after inoculation, indicating that it is in the reproductive period. In the sexual phase, in SEM, from four hours after inoculation, it was possible to verify the formation of small protuberances at temperatures between 10 and 20 °C. These black dots evolve into circular, protruding black spots, like the symptoms of black crust, with apparent spore formation on them. The data obtained from the UV analyses corroborate those from SEM, showing that the fungus has good development in its two phases between temperatures of 20 and 25 °C and that the period of wetness on the leaf can contribute to the initial development of the pathogen. [ABSTRACT FROM AUTHOR]

In this research, activated carbon was obtained from rubber fruit shells (ACRPs). The obtained activated carbon (ACRPs) was modified by magnetite particle coating and silanization with triethoxyiphenylsilane (TEPS) to produce a new magnetic adsorbent (ACRPs-MS). The affinity of as-prepared adsorbent (ACRPs-MS) toward methylene blue (MB) and crystal violet (CV) dyes was tested in mono-component and bi-component solutions. Structural characterization proves the success of the magnetite coating process and the silanization of ACRPs. In the infrared (IR) spectroscopy spectrum of ACRPs-MS, Si–O-Fe and Si–O-Si bonds were identified, which indicated the presence of magnetite and silane. This is also supported by the elemental composition contained in the energy-dispersive X-ray (EDX) diffractogram. In addition, the presence of the porous structure of the surface of the material and the increase in the specific surface area increase the accessibility of contaminants such as MB and CV dyes to be adsorbed to the ACRPs-MS adsorption site effectively. The experimental results showed that the adsorption of mono-component MB and CV dyes by ACRPs-MS was optimum at pH 8 and an interaction time of 60 min. The adsorption kinetics of mono-component MB and CV dyes by ACRPs-MS tended to follow pseudo-second-order kinetics (PSO) models with PSO rate constant (k2) values of 0.198 and 0.993 g mg−1 min−1, respectively. The adsorption of MB and CV dyes by ACRPs-MS in a bi-component mixture tends to follow the Langmuir isotherm model with adsorption capacity (qm) values of 85.060 and 90.504 mg g−1, respectively. Analysis of adsorption data on the bi-component mixture between MB and CV by ACRPs-MS with the Langmuir isotherm equation for a binary mixture resulted in qm of 22.645 × 10–3 mmol equiv g−1. ACRPs-MS material can be used repeatedly five times with adsorption ability > 80%. Desorption of MB and CV dyes was carried out using 0.05 M HCl solution. ACRPs-MS material was able to adsorb MB and CV dyes with a large adsorption capacity and could be used in repeated adsorption. Thus, it can be stated that ACRPs-MS can be used as an effective adsorbent for MB and CV dyes, either singly or in a bi-component mixture. [ABSTRACT FROM AUTHOR]

Natural rubber (NR) is utilized in more than 40,000 products, and the demand for NR is projected to reach $68.5 billion by 2026. The primary commercial source of NR is the latex of Hevea brasiliensis. NR is produced by the sequential cis-condensation of isopentenyl diphosphate (IPP) through a complex known as the rubber transferase (RTase) complex. This complex is associated with rubber particles, specialized organelles for NR synthesis. Despite numerous attempts to isolate, characterize, and study the RTase complex, definitive results have not yet been achieved. This review proposes an innovative approach to overcome this longstanding challenge. The suggested method involves isolating the RTase complex without using detergents, instead utilizing the native membrane lipids, referred to as "natural nanodiscs", and subsequently reconstituting the complex on liposomes. Additionally, we recommend the adaptation of large nanodiscs for the incorporation and reconstitution of the RTase complex, whether it is in vitro transcribed or present within the natural nanodiscs. These techniques show promise as a viable solution to the current obstacles. Based on our experimental experience and insights from published literature, we believe these refined methodologies can significantly enhance our understanding of the RTase complex and its role in in vitro NR synthesis. [ABSTRACT FROM AUTHOR]

Scientific manuring, by adopting balanced nutrition in perennial plantations is the need of hour for increased productivity and addressing global warming by adopting 4 R nutrient stewardship. Continuous use of NPK in perennial crops can lead to deficiency of micronutrients. Therefore, a study was carried out to understand nutrient status of major rubber growing tracts and to formulate a customized nutrient mixture for rubber. A detailed soil fertility assessment and leaf tissue analysis of mature rubber plantations of age group 11-15 years in five agro ecological units (AEU) in Thiruvananthapuram were conducted during the study. Based on this, a multi micronutrient mixture was formulated for rubber and the composition of the mixture was Zn -3.64 %, B -8.04 %, Fe- 2.01 %, Cu- 2.55 % and Mn-3.25 %. For accessing the effect of the mixture, a field experiment was conducted in existing rubber plantation of RRII 105 replanted in 2005 at Aryanad (AEU 14) in randomized block design with seven treatments and three replications, namely general recommendation of NPK at 30:30:30 kg ha-1year-1, soil test based recommendation of NPK at 22:8:21 kg ha-1 year-1, application of multi micronutrient mixture along with soil test based recommendation of NPK at varying levels from 5 to 15 kg ha-1year-1. The treatments had a significant effect on dry rubber content (DRC). For the post monsoon, summer, and annual period, the highest DRC was noticed in 15 kg ha-1 of the mixture applied plot which was on par with 7.5 kg ha-1 applied plot. Application of micronutrient mixture resulted in enhancement of different micronutrient pools and enriched nutrient storehouse. It was also observed that available micronutrients were within sufficiency level even after application of the mixture. Multi micronutrient mixture application at 7.5 kg ha-1 along with soil test based recommendation of NPK can be considered for future studies. [ABSTRACT FROM AUTHOR]

Trees contribute to combating global warming by absorbing CO2, thus enhancing the quality of the environment. Sri Lanka maintains about 112,000 ha of Hevea brasiliensis (rubber) plantations, where 85.7% is in the wet zone. When rubber trees decline in latex production, after 30–33 years of planting, they are harvested to regenerate the next cycle. Rubber timber in Sri Lanka is used mainly for manufacturing interior parts of furniture, tool handles, and toys, leaving minimal chances for the emission of CO2 by combustion. Therefore, rubber is a good source of carbon sequestration, which can be used to earn additional benefits for the farmers. Estimating tree biomass helps to assess the carbon sequestration of those trees. Therefore this study aimed to build allometric models to predict the biomass using diameter at breast height (dbh) and total tree height (h). Since uprooting rubber trees is not allowed till maturity, whole‐tree, above‐ground, and stem biomass prediction models were built by uprooting ten 30‐ and 31‐year‐old trees from two rubber estates of the low country wet zone of Sri Lanka. For the rest of the ages, dbh and h prediction models were built by age using data collected from six age classes of rubber trees from the same two estates so those variables could be used as inputs to the biomass prediction models. For dbh and h models, Michaelis–Menten functions performed better than power‐law functions. Biomass was estimated for the stem and large branches by converting respective volumes to weights. Weight measurements were taken directly for biomass assessment for small branches, foliage, and roots. The quality of models was determined based on both qualitative and quantitative evaluations. The finding proved that the biomass of rubber plantations could effectively be estimated by dbh and h over time. [ABSTRACT FROM AUTHOR]

The cultivation of Hevea brasiliensis (rubber) is promoted as a productive and ecological alternative, especially in agroforestry systems, although research is still required to address its impact on soil chemical conditions. This study aimed evaluate the possible effects of five types of land use on the chemical properties of horizons A and B in soils of the Colombian Amazon: agroforestry system of H. brasiliensis with timber and fruit trees, agroforestry system of H. brasiliensis associated with stubble, H. brasiliensis monoculture, secondary forest as positive control and native grass as negative control. The conditions of pH, exchangeable aluminum, organic carbon, potassium, phosphorus, calcium, magnesium, base saturation and cationic exchange capacity were evaluated. Similarities in soil chemical properties were found between secondary forest, agroforestry systems with fruit trees and agroforestry systems associated with stubble. The H. brasiliensis monoculture did not present significant differences with the native pasture. The pH was the only variable affected by soil use, while the percentage of organic carbon and the contents of phosphorus, calcium, magnesium and potassium changed depending on the A and B horizons, demonstrating that the variability of the chemical fertility of the clay soils of the Amazon are more related to the characteristics of their horizons than to the type of land use. [ABSTRACT FROM AUTHOR]

• First report of RNA- seq analysis of Hevea clones in response to abnormal leaf fall (ALF) disease caused by Phytophthora. • A comparative transcriptome analysis of resistant and susceptible clone performed to gain insights into its resistance mechanism against ALF. • Compared to a susceptible clone, several differentially expressed genes were found in the resistant clone. • Several signalling pathways and transcription factors were also expressed during infection. Rubber is an important industrial commodity and Hevea brasiliensis is the commercial source of natural rubber (NR). Abnormal Leaf Fall (ALF) disease caused by Phytophthora meadii is one of the major diseases affecting yield of NR. Understanding Hevea-Phytophthora interaction mechanism is essential to manage this devastating disease. Transcriptome analysis was employed to gain an understanding on the molecular mechanisms that confer resistance to Phytophthora that would facilitate development of disease-tolerant Hevea clones. As our current understanding of Hevea-Phytophthora interaction is limited, an attempt was made to analyze and compare the transcriptomes of tolerant and susceptible clones of H. brasiliensis in response to P. meadii infection (in healthy and Phytophthora challenge-inoculated condition) during early, middle and late phases of infection by using the RNA-Seq technology. The transcriptome sequencing generated an average of 19,000 differentially expressed genes (DEGs) in both clones. When comparing the tolerant clone to the susceptible clone, there was an overall increase in the number of DEGs and a progression in the number of DEGs, indicating a more active engagement of transcriptional activity in the tolerant clone. Functional annotation, KEGG analysis and enrichment analysis revealed that the major pathways enriched for the DEGs were involved in plant hormone signal transduction and plant-pathogen interaction. An analysis of DEGs during each phase showed that the most active transcripts involved in defense mechanisms were activated during mid-phase and in the case of susceptible clone least transcripts were induced during mid-phase than in any other phase in both the clones. Many DEGs belonging to the MYB, NAC, WRKY and AP2/ERF transcription factor families were observed in both clones. Comparative studies revealed their differential involvement in tolerant and susceptible clones against Phytophthora infection. These findings may facilitate further exploration of Hevea-Phytophthora interaction and in cloning for defense related genes. [ABSTRACT FROM AUTHOR]

Corynespora leaf fall disease caused by the fungus Corynespora cassiicola is a major leaf disease of Hevea brasiliensis, the commercial source of natural rubber. Different clones of H. brasiliensis show varying levels of sensitivity towards different strains of C. cassiicola. The genetic mechanism behind the differential sensitivity of H. brasiliensis clones has to be identified in order to develop clones resistant to wider range of C. cassiicola strains. The available information on the sensitivity of H. brasiliensis clones is based on the observation of natural infection or infection of detached leaves. In the present study, the sensitivity of seven H. brasiliensis clones towards two strains of C. cassiicola belonging to two different races was determined using a more precise method by artificial infection of the plants under controlled conditions. Strain CLN 16 was found to be more virulent compared with CSB 16, as it induced more severe symptoms in a shorter period. Among the four different stages of leaves, Stage II leaves with copper brown to apple green colour showed higher sensitivity to both strains followed by Stage III leaves with apple green appearance. Among the clones, RRIM 600 had a higher susceptibility towards CSB 16; however, it was the most resistant clone towards CLN 16. Clone PB 350 showed the highest susceptibility towards CLN 16 whereas RRIM 928 showed the highest resistance towards CSB 16. The present study provides a platform for further studies leading to the development of H. brasiliensis clones with resistance towards wider range of C. cassiicola strains. [ABSTRACT FROM AUTHOR]

The majority of the world's natural rubber comes from the rubber tree (Hevea brasiliensis). As a key enzyme for synthesizing phenylpropanoid compounds, phenylalanine ammonia-lyase (PAL) has a critical role in plant satisfactory growth and environmental adaptation. To clarify the characteristics of rubber tree PAL family genes, a genome-wide characterization of rubber tree PALs was conducted in this study. Eight PAL genes (HbPAL1-HbPAL8), which spread over chromosomes 3, 7, 8, 10, 12, 13, 14, 16, and 18, were found to be present in the genome of H. brasiliensis. Phylogenetic analysis classified HbPALs into groups I and II, and the group I HbPALs (HbPAL1-HbPAL6) displayed similar conserved motif compositions and gene architectures. Tissue expression patterns of HbPALs quantified by quantitative real-time PCR (qPCR) proved that distinct HbPALs exhibited varying tissue expression patterns. The HbPAL promoters contained a plethora of cis-acting elements that responded to hormones and stress, and the qPCR analysis demonstrated that abiotic stressors like cold, drought, salt, and H2O2-induced oxidative stress, as well as hormones like salicylic acid, abscisic acid, ethylene, and methyl jasmonate, controlled the expression of HbPALs. The majority of HbPALs were also regulated by powdery mildew, anthracnose, and Corynespora leaf fall disease infection. In addition, HbPAL1, HbPAL4, and HbPAL7 were significantly up-regulated in the bark of tapping panel dryness rubber trees relative to that of healthy trees. Our results provide a thorough comprehension of the characteristics of HbPAL genes and set the groundwork for further investigation of the biological functions of HbPALs in rubber trees. [ABSTRACT FROM AUTHOR]

Hevea brasiliensis (Para rubber tree) is a commercially cultivated crop for latex production worldwide. Rubber trees from Southern states of India have been affected by Circular Leaf Spot (CLS) disease caused by Colletotrichum fructicola and Colletotrichum siamense causing yellowing and severe defoliation in rubber plantations in recent years. In this study, we collected infected leaf samples of CLS disease from different locations in the South Indian states of Kerala, Tamil Nadu, and Karnataka. Colletotrichum fructicola and C. siamense were identified as the causative agents of CLS disease and the isolate, C. fructicola was used for genomics analysis. We performed whole-genome sequencing (WGS) of, C. fructicola and carried out gene content analysis by comparing it with other reported Colletotrichum species. In silico analysis revealed a rich repertoire of pathogenicity genes and CAZymes in C. fructicola encoding secreted proteins, effectors, plant cell wall degrading enzymes, and secondary metabolism-associated proteins with possible roles in the host-specific interaction and pathogenicity. Our dataset provides a rich resource for understanding the pathogenicity-related genes that are involved in CLS disease progression and gives a basis for subsequent functional genomics research in C. fructicola. [ABSTRACT FROM AUTHOR]

Among the Hevea species, rubber tree (Hevea brasiliensis) is the most important source of natural rubber. In previous studies, we sequenced the complete nuclear and chloroplast genomes of Hevea species, providing an invaluable resource for studying their phylogeny, disease resistance, and breeding. However, given that plant mitochondrial genomes are more complex and more difficult to assemble than that of the other organelles, little is known about theirmitochondrial genome, which limits the comprehensive understanding of Hevea genomic evolution. In this study, we sequenced and assembled the mitochondrial genomes of four Hevea species. The four mitochondrial genomes had consistent GC contents, codon usages and AT skews. However, there were significant differences in the genome lengths and sequence repeats. Specifically, the circular mitochondrial genomes of the four Hevea species ranged from 935,732 to 1,402,206 bp, with 34-35 unique protein-coding genes, 35-38 tRNA genes, and 6-13 rRNA genes. In addition, there were 17,294-46,552 bp intergenomic transfer fragments between the chloroplast and mitochondrial genomes, consisting of eight intact genes (psaA, rrn16S, tRNAVal, rrn5S, rrn4.5S, tRNA-Arg, tRNA-Asp, and tRNA-Asn), intergenic spacer regions and partial gene sequences. The evolutionary position of Hevea species, crucial for understanding its adaptive strategies and relation to other species, was verified by phylogenetic analysis based on the protein-coding genes in the mitochondrial genomes of 21 Malpighiales species. The findings from this study not only provide valuable insights into the structure and evolution of the Hevea mitochondrial genomebut also lay the foundation for furthermolecular, evolutionary studies, and genomic breeding studies on rubber tree and other Hevea species, thereby potentially informing conservation and utilization strategies. [ABSTRACT FROM AUTHOR]

Natural rubber is an important industrial material derived from caoutchouc trees (Hevea Brasiliensis). By chemical composition, it is a polymer material that is mostly cis-1,4-polyisoprene. It falls into the category of elastomers, which enables its wide usage due to its specific characteristics. Polymer materials include plastic, rubber, and glue and are the most important technical materials. Rubbers are used in the production of conveyor belts, shock absorbers, coatings, fenders, engines, and device parts. They are also used in composite materials such as threads, particles, and matrix materials. By analyzing the properties of natural rubber, the subject of the research is defined, i.e., the characterization of natural rubber samples and their connection with macroscopic properties. In accordance with the subject of the research, in this paper, tests are carried out on samples of natural rubber, which are obtained in the form of thin films from latex and cross-linked by gamma radiation. A total dose of 300 kGy is applied to the samples in the state of uniaxial deformation. In this sense, a hypothesis is put forward that involves examining the influence of radiation dose on the morphology of natural rubber samples using scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometry (EDX). The investigation aims to emphasize the importance of the method in acquiring a comprehensive characterization of the material samples, which are used both in maritime areas and in other fields of application. [ABSTRACT FROM AUTHOR]

Taraxacum kok-saghyz (TKS), a rubber-producing plant with excellent potential, emerges as a viable substitute for rubber tree (Hevea brasiliensis). While natural rubber is a desirable material, conventional techniques for assessing rubber content have faced challenges in meeting practical production requirements. To address this issue, we have developed a pyrolysis–mass spectrometry (PY-MS) instrument for the quantitative evaluation of natural rubber (NR) content in rubber-producing plants. The derived standard curve equation, established for the detection of TKS dry weight through external standard calibration, demonstrates a correlation coefficient (R2) surpassing 0.99. The method exhibits commendable recovery rates (93.27–107.83%), relative standard deviations (RSD ≤ 3.93%), and a swift analysis time of merely 10 min per sample, thereby enabling accurate and efficient quantification of NR dry weight. Additionally, the PY-MS system we designed can be modified for vehicular use, enabling on-site, in situ analysis, and it provides substantial support for TKS breeding and propagation efforts. This approach possesses significant potential for extensive utilization in the assessment of rubber content in rubber-producing plants other than TKS. The integration of pyrolysis–mass spectrometry for the identification of polymers with high molecular weight offers a valuable pathway for the examination of diverse polymers. [ABSTRACT FROM AUTHOR]

Belonging to the Euphorbiaceae family, the Para rubber tree is formally referred to as Hevea brasiliensis in scientific terms. It is commonly known as an important economic commodity in Thailand because the natural rubber primarily originates from the milky latex obtained from the tree. However, the available research on the phytochemicals found in different parts of the rubber tree and their biological effects is quite restricted. This study aimed to determine the phytochemical constituents, antioxidant and antibacterial activity studies on the crude dry leaf extracts of H. brasiliensis. The results indicated the presence of alkaloids, anthraquinones, cardiac glycosides, coumarin, flavonoids, saponin, steroids, tannins, and terpenoids. The total phenolic content was 63.95±4.31 mgGAE/g in the ethanolic leaf extract. The ethanolic extract displayed notable effectiveness in scavenging free radicals (71.2±0.17%) at 500 μg/ml concentration and antioxidant capacity (the lowest IC50 value 42.57±0.91 μg/ml). The ethanol extract of the leaf of H. brasiliensis showed inhibition zone on all of the selected bacteria (gram-positive; Bacillus subtilis, Staphylococcus aureus, Staphylococcus epidermidis, and gram-negative; Escherichia coli, Pseudomonas aeruginosa) at 200 mg/ml. In conclusion, the dried leaves of H. brasiliensis compose phytochemicals that exhibit antioxidant and antibacterial activities and possesses the potential to act as a reservoir of plant-derived antibiotics and natural antioxidants. [ABSTRACT FROM AUTHOR]

Land surface temperature is predicted to increase by 0.2 °C per decade due to climate change, although with considerable regional variability, and heatwaves are predicted to increase markedly in the future. These changes will affect where crops can be grown in the future. Understanding the thermal limits of plant physiological functioning and how flexible such limits are is thus important. Here, we report on the measurements of a core foliar thermotolerance trait, T 50, defined as the temperature at which the maximum quantum yield (Fv / Fm) of photosystem II declines by 50%, across nine different Malaysian Hevea brasiliensis clones. We explore the relative importance of interclonal versus intraclonal variation in T 50 as well as its association with leaf and hydraulic traits. We find very low variation in T 50 within individual clones (mean intraclonal coefficient of variation (CoV) of 1.26%) and little variation across clones (interclonal CoV of 2.1%). The interclonal variation in T 50 was lower than for all other functional traits considered. The T 50 was negatively related to leaf mass per area and leaf dry matter content, but it was not related to hydraulic traits such as embolism resistance (P 50) or hydraulic safety margins (HSM 50). The range of T 50 observed (42.9–46.2 °C) is well above the current maximum air temperatures T max,obs (T 50 − T max,obs >5.8 °C), suggesting that H. brasiliensis is likely thermally safe in this south-east Asian region of Malaysia. [ABSTRACT FROM AUTHOR]

Key message: Unreduced megagametophytes via second-division restitution were confirmed through heterozygosity analysis, and four candidate physical centromeres of rubber were located for the first time. The evaluation of maternal heterozygosity restitution (MHR) is vital in identifying the mechanism of 2n gametogenesis and assessing the utilization value of 2n gametes. In this study, three full-sib triploid populations were employed to evaluate the MHR of 2n female gametes of rubber tree clone GT1 and to confirm their genetic derivation. The 2n female gametes of GT1 were derived from second-division restitution (SDR) and transmitted more than half of the parental heterozygosity. In addition, low recombination frequency markers were developed, and four candidate physical centromeres of rubber tree were located for the first time. The confirmation that 2n female gametes of rubber tree clone GT1 are derived from SDR provides insights into the molecular mechanisms of 2n gametogenesis. In addition, the identified centromere location will aid in the development of centromeric markers for the rapid identification of the 2n gametogenesis mechanism. [ABSTRACT FROM AUTHOR]