Natural Rubber Production Research Articles

Effect of Limonene on the Tensile Properties and Chemical Changes of Natural Rubber Products

Effect of Limonene on the Tensile Properties and Chemical Changes of Natural Rubber Products

Genome-Wide Identification and Expression Analysis of the REF Genes in 17 Species

Natural rubber production currently relies heavily on a single species, Hevea brasiliensis, underscoring the urgent need to identify alternative sources to alleviate the strain on natural rubber production. The rubber elongation factor (REF) and small rubber particle protein (SRPP), both members of the REF/SRPP gene family, are crucial for natural rubber biosynthesis. However, research on the REF gene has predominantly focused on H. brasiliensis and Taraxacum kok-saghyz. We conducted a comprehensive genome-wide identification and characterization of the REF gene, identifying 87 REF protein sequences across 17 plants species. We observed a significant increase in the copy numbers and expression of REF genes in rubber-producing plants. Notably, in H. brasiliensis, T. kok-saghyz, Eucommia ulmoides, Lactuca sativa, and other rubber-yielding species, the number of REF genes has markedly increased. Furthermore, some REF genes in H. brasiliensis form a distinct clade in phylogenetic analyses and exhibit differences in conserved motif arrangements and tertiary protein structures compared to other REF genes. These findings suggest that REF genes in rubber-producing plants may have undergone independent evolution, leading to changes in copy number and structure. These alterations could contribute to the production of natural rubber in these species. The results of this study provide a scientific basis for further research into the mechanisms of rubber production in plants and for identifying potential rubber-producing species.

Effect of Proteins on the Vulcanized Natural Rubber Crosslinking Network Structure and Mechanical Properties

Proteins are important factors affecting the properties of natural rubber. Therefore, investigating the effect of free and bonded proteins on the structure and mechanical properties of the vulcanized crosslinking network of natural rubber would provide a theoretical basis for the production of high mechanical resistance natural rubber. Herein, natural rubbers with different protein contents and types were prepared by high-speed centrifugation. And, the effects on their network structure, vulcanization, tensile strength, tearing strength and dynamic mechanical properties were investigated. The results showed that the reduction in protein content led to the decrement in the entanglement networks, crosslinking density and tensile and tear strengths of the vulcanized natural rubber. Moreover, the bonded proteins had an obvious influence on the vulcanization process, while free proteins played an important role in the crosslink densities. These results reveal that both bonded and free proteins are involved in the vulcanization process and the construction of the vulcanized crosslinking network structure of natural rubber, which enhances the mechanical properties such as the modulus and tensile strength of vulcanized natural rubber.

Posisi Pasar Karet Indonesia Di Pasar Internasional

Indonesia's position as the largest rubber producing country in the world allows them to become the main exporter of natural rubber. Indonesia exports the majority of its natural rubber production to countries like Japan, India, Brazil, the United States, South Korea, China, Turkey, and others. The competition between Indonesia and other producing countries in exporting rubbers to international markets is relatively tight. The aim of this research is to analyze the position of Indonesia’s technically specified natural rubbers (TSNR) in the international market compared to other exporting countries. The analytical method used is the Almost Ideal Demand System (AIDS) Model. The data used in this research is secondary data from Indonesia, Thailand, Malaysia, Ivory Coast, Vietnam, Belgium, and Nigeria over the last 10 years (2012 – 2022). The results show that there is a tight competition between Indonesia and Thailand, Ivory Coast, Belgium, Nigeria and the Rest of the World in competing for market share of natural rubber in the international market because the relationship between Indonesia's natural rubber and these countries are substitutional. Meanwhile, Indonesia's natural rubber relationship with Malaysia is complementary. Indonesian natural rubber is a normal good, so if there is an increase in prices it will cause a decrease in demand. If there is an increase in demand for rubber exports in the international market, then the country that will benefit the most is Vietnam. Meanwhile, Indonesia is the fourth ranked country that will benefit the most if it happens.

In silico analysis of secreted effectorome of the rubber tree pathogen Rigidoporus microporus highlights its potential virulence proteins.

Rigidoporus microporus, the causative agent of the white root rot disease of rubber trees, poses a significant threat to natural rubber production worldwide. Understanding the molecular mechanisms facilitating its pathogenicity would be crucial for developing effective disease management strategies. The pathogen secretes effector proteins, which play pivotal roles in modulating host immune responses and infection. In this study, in silico analyses identified 357 putative secreted effector proteins from the R. microporus genome. These were then integrated into previous RNA-seq data obtained in response to rubber tree latex exposure. Annotation of putative effectors suggested the abundance of proteins in several families associated with the virulence of R. microporus, especially hydrophobin proteins and glycoside hydrolase (GH) proteins. The contribution of secreted effectors to fungal pathogenicity was discussed, particularly in response to rubber tree latex exposure. Some unknown highly expressed effectors were predicted for the protein structures, revealing their similarity to aminopeptidase, ubiquitin ligase, spherulin, and thaumatin protein. This integrative study further elucidates the molecular mechanism of R. microporus pathogenesis and offers alternative targets for developing control strategies for managing white root rot disease in rubber plantations.

Genome-wide identification of oxidosqualene cyclase genes regulating natural rubber in Taraxacum kok-saghyz.

Nine TkOSC genes have been identified by genome-wide screening. Among them, TkOSC4-6 might be more crucial for natural rubber biosynthesis in Taraxacum kok-saghyz roots. Taraxacum kok-saghyz Rodin (TKS) roots contain large amounts of natural rubber, inulin, and valuable metabolites. Oxidosqualene cyclase (OSC) is a key member for regulating natural rubber biosynthesis (NRB) via the triterpenoid biosynthesis pathway. To explore the functions of OSC on natural rubber producing in TKS, its gene family members were identified in TKS genome via genome-wide screening. Nine TkOSCs were identified, which were mainly distributed in the cytoplasm. Their family genes experienced a neutral selection during the evolution process. Overall sequence homology analysis OSC proteins revealed 80.23% similarity, indicating a highly degree of conservation. Pairwise comparisons showed a multiple sequence similarity ranging from 57% to 100%. Protein interaction prediction revealed that TkOSCs may interact with baruol synthase, sterol 1,4-demethylase, lupeol synthase and squalene epoxidase. Phylogenetic analysis showed that OSC family proteins belong to two branches. TkOSC promoter regions contain cis-acting elements related to plant growth, stress response, hormones response and light response. Protein accumulation analysis demonstrated that TkOSC4, TkOSC5 and TkOSC6 proteins had strong expression levels in the root, latex and plumular axis. Comparison of gene expression patterns showed TkOSC1, TkOSC4, TkOSC5, TkOSC6, TkOSC7, TkOSC8 and TkOSC9 might be important in regulating NRB. Combination of gene and protein results revealed TkOSC4-6 might be more crucial, and the data might contribute to a more profound understanding of the roles of OSCs for NRB in TKS roots.

Enhanced Rubber Yield Prediction in High-Density Plantation Areas Using a GIS and Machine Learning-Based Forest Classification and Regression Model

Rubber is a perennial plant grown for natural rubber production, which is used in various global products. Ensuring the sustainability of rubber cultivation is crucial for smallholder farmers and economic development. Accurately predicting rubber yields is necessary to maintain price stability. Remote sensing technology is a valuable tool for collecting spatial data on a large scale. However, for smaller plots of land owned by smallholder farmers, it is necessary to process productivity estimates from high-resolution satellite data that are accurate and reliable. This study examines the impact of spatial factors on rubber yield and evaluates the technical suitability of using grouping analysis with the forest classification and regression (FCR) method. We developed a high-density variable using spatial data from rubber plots in close proximity to each other. Our approach incorporates eight environmental variables (proximity to streamlines, proximity to main river, soil drainage, slope, aspect, NDWI, NDVI, and precipitation) using an FCR model and GIS. We obtained a dataset of 1951 rubber yield locations, which we split into a training set (60%) for model development and a validation set (40%) for assessment using area under the curve (AUC) analysis. The results of the alternative FCR models indicate that Model 1 performs the best. It achieved the lowest root mean square error (RMSE) value of 19.15 kg/ha, the highest R-squared (R2) value (FCR) of 0.787, and also the highest R2 (OLS) value of 0.642. The AUC scores for Model 1, Model 2, and Model 3 were 0.792, 0.764, and 0.732, respectively. Overall, Model 4 exhibited the highest performance according to the AUC scores, while Model 3 performed the poorest with the lowest AUC score. Based on these findings, it can be concluded that Model 1 is the most effective in predicting FCR compared to the other alternative models.

Synergistic effects of chitosan and gamma irradiation on enhanced fungal growth inhibition and biodegradability of natural rubber latex film

Developing novel formulations and processes to improve the fungal growth inhibition and biodegradability of NR products has become a major challenge for the scientific community, given the health risks associated with fungi in natural rubber (NR) products and the environmental concerns regarding NR waste. Consequently, this study comprehensively investigated the synergistic effects of chitosan and gamma irradiation on enhancing fungal growth inhibition and biodegradability in natural rubber latex (NRL) films. The research involved incorporating varying chitosan contents (0, 3, 6, or 9 phr) into NRL composites and exposing them to different gamma doses (0, 5, 10, or 15 kGy). The results showed that increasing the chitosan content and the gamma dose improved the ability of the NRL samples to inhibit fungal growth on their surfaces. This was evidenced by the absence of fungal colonies after 7 days of incubation on potato dextrose agar (PDA) plates for NRL samples irradiated at 5–15 kGy with 9 phr of chitosan. This determination was based on isolating fungi from the film surfaces, followed by serial dilution and a viable plate count. The biodegradability tests also revealed that the NRL films irradiated at 15 kGy with 9 phr of chitosan had the highest weight loss, reaching as high as 10.42 ± 0.62 % after soil burial for 8 weeks. However, the results indicated that gamma irradiation on the pristine NRL and chitosan/NRL films did not substantially alter the thermal stabilities, density, morphology, and functional groups of the samples. Lastly, by comparing the tensile properties of all the NRL films to the ASTM D3578-01a standard for examination gloves, the optimum conditions for the NRL films were 5 kGy of gamma irradiation with 9 phr of chitosan. This combination resulted in gloves with sufficient tensile strength and complete fungal growth inhibition.

Trend TSR 20 rubber prices between producing countries in Southeast Asia

Natural Rubber is one of the world's largest commodities used for industrial needs. The price of TSR 20 rubber continues to fluctuate, which has a significant impact on some farmers in various countries. This study analyzes the price trend of TSR 20 rubber in Southeast Asia. The purpose of this study is to analyze trends and fluctuations in STR 20 rubber prices in Southeast Asia, such as Standar Thailand Rubber (STR 20), Standar Indonesia Rubber (SIR 20), Standar Vietnam Rubber (SVR 20), and Standar Malaysia Rubber (SMR 20) for 72 months from January 2017 - December 2022. This research uses trend analysis with simple linear regression method. This research uses the historical method by conducting research on a source which is then critically analyzed. Data collection techniques are obtained by tracing data and documents that have been stored by agencies including the Ministry of Agriculture, Ministry of Trade, International Rubber Study Group (IRSG), Singapore Commodity Exchange (SICOM), Association of Natural Rubber Producing Countries (ANRPC), Food and Agriculture Organization (FAO), The World Bank, and Gapkindo as well as existing literature and sites. The results obtained are positive trends where each development between countries has experienced a positive price increase, such as, STR 20 has a polynomial line equation Y = 0.0331x2 – 95,28x + 68596, then SIR 20 Y = 0.0231x2 -66,443 + 47966, SVR 20 Y = 0,0301x2 – 86,824x+ 62648, and SMR 20 Y = 0,0279x2 – 80,411x + 58010.

TkJAZs-TkMYC2-TkSRPP/REF Regulates the Biosynthesis of Natural Rubber in Taraxacum kok-saghyz.

Taraxacum kok-saghyz (TKS) is a natural rubber (NR)-producing plant and a model plant for studying the biosynthesis of NR. Analyzing and studying the biosynthetic mechanism of NR is an important way to cultivate high-yield rubber TKS varieties. JAZ proteins, which belong to the Jasmonate ZIM domain family, function as negative regulators in the jasmonic acid (JA) signal transduction pathway. MYC2 is typically regarded as a regulatory factor for the target genes of JAZ proteins; JAZ proteins indirectly influence the gene expression regulated by MYC2 by modulating its activity. Theoretically, JAZ is expected to participate in growth, development, and responses to environmental cues related to rubber and biomass accumulation in TKS, all of which rely on the interaction between JAZ and MYC2. In this study, we identified 11 TkJAZs through homology searching of the TKS genomes and bioinformatics analyses. Subcellular localization, Y2H, and BiFC analysis demonstrate that TkJAZs and TkMYC2 are localized in the nucleus, with all TkJAZs and TkMYC2 showing nuclear colocalization interactions. Overexpression of TkMYC2 in TKS inhibited leaf development, promoted root growth, and simultaneously increased NR production. RNA-seq and qRT-PCR analysis revealed that the TkSRPP/REF genes exhibit varying degrees of upregulation compared to the wild type, upregulating the TkREF1 gene by 3.7-fold, suggesting that TkMYC2 regulates the synthesis of NR by modulating the TkSRPP/REF genes.

Utilizing color analysis and image processing for the assessment of the color of block para rubber

This research explores the use of image processing and color analysis as a reliable approach for evaluating para rubber color quality. An automated color comparator prototype, based on the CIELAB color method and employing various image processing algorithms, is introduced. The research aims to enhance the precision of color analysis for block para rubbers (BPRs), a critical raw material in the rubber industry, impacted by environmental conditions during the sun-drying process. The study follows international standards for BPR specimen preparation and employs an image acquisition system, threshold techniques, and algorithms for color analysis. The proposed method aligns with Rubber Research Institute standards. The outcomes demonstrate the effectiveness of the automated system in accurately assessing the color values of BPRs, providing valuable insights for the rubber industry. This image processing technique offers advantages in natural rubber production for products requiring specific color characteristics.

Analysis of Factors Affecting Indonesian Natural Rubber Exports

The aim of this research is to determine and analyze the short-term and long-term influence of Indonesian natural rubber production variables, international consumption, and international natural rubber prices on Indonesian natural rubber exports. This research was carried out using Time series data for the period 1989-2022 using numerical calculations of research variables using the Error Correction Model (ECM) analysis method assisted by EViews12 software. The population used in this research is information on Indonesian Natural Rubber Exports for 1989-2022. As a result of the analysis and discussion that has been carried out, it can be concluded that: Indonesian Natural Rubber Production has a positive influence in both the long and short term on Indonesian Natural Rubber Exports. International Natural Rubber Consumption in the long term has an insignificant influence with a negative correlation on the volume of Indonesian Natural Rubber Exports. International Natural Rubber Prices in both the long and short term have an insignificant influence with a positive correlation on Indonesian Natural Rubber Exports.

Response of N, P, and metal ions in deep soil layers to long-term cultivation of rubber and rubber-based agroforestry systems

The growing demand for natural rubber products has driven the expansion of rubber plantations in recent decades. While much attention has been given to studying the long-term effects of rubber and rubber-based agroforestry systems on surface soil properties, there has been a tendency to overlook changes in soil properties in deeper layers. Our study addresses this gap by examining alterations in nitrogen (N), phosphorus (P), and metal ion levels in deep soil layers resulting from the prolonged cultivation of rubber and rubber-based agroforestry systems. We found notable shifts in soil NH4+ and NO3− concentrations within the 0–30 cm soil layer across different-aged rubber and rubber-based agroforestry systems. Particularly in mature systems, NO3− and available P levels were close to zero below 30 cm soil depth. Introducing Flemingia macrophylla into young rubber plantations increased soil NH4+ and NO3− in the 0–90 cm soil layer and available P in the 0–10 cm soil layer. Over the long term, cultivation of rubber plantations increased the depletion of total P in the 0–50 cm soil layer, available iron (Fe) and manganese (Mn) in the 30–90 cm soil layer, available copper (Cu) and zinc (Zn) in the 0–90 cm soil layer, accompanied by a decrease in soil pH and increase in exchangeable aluminum (Al) in the 0–90 cm soil layer. Notably, soil exchangeable Al levels exceeding 2.0 cmol kg−1 appeared to induce aluminum toxicity. Furthermore, soil pH below 5.2 triggered a sharp release of exchangeable Al within the 0–90 cm soil layer of rubber plantations, with soil available P nearing zero when exchangeable Al levels assed 7.3 cmol kg−1. Our findings underscore the profound impact of long-term rubber plantation cultivation on surface and deep soil properties. Addressing soil degradation in these deep soil layers poses significant challenges for future soil restoration efforts.

Genetic diversity analysis and core germplasm bank construction in cold resistant germplasm of rubber trees (Hevea brasiliensis)

The rubber tree, Hevea brasiliensis (Willd. ex Adr. de Juss.) Muell. Arg., is the sole plant worldwide utilized for the commercial production of natural rubber. Following years of breeding, there exists a wide array of germplasm differentiation in rubber trees. The exploration of diversity and population structure within rubber tree germplasm resources, alongside the establishment of core germplasm resources, is instrumental in elucidating the genetic background and facilitating the effective utilization and management of these resources. By employing SNP molecular marker technology, 195 rubber tree resources were amplified, their genetic diversity analyzed, and a fingerprint map was subsequently constructed. Through this process, the cold-resistant core germplasm of rubber trees was identified. The results revealed that the PIC, He, and pi values ranged from 0.0905 to 0.3750, 0.095 to 0.5000, and 0.0953 to 0.5013, respectively. Both group structure analysis and cluster analysis delineated the accessions into two groups, signifying a simple group structure. A core germplasm bank was established with a sampling ratio of 10%, comprising 21 accessions divided into two populations. Population G1 consists of 20 accessions, while population G2 comprises 1 accession. The research findings have led to the creation of a molecular database that is anticipated to contribute to the management and subsequent breeding applications of rubber tree accessions.

Genome-Wide Analysis of the SRPP/REF Gene Family in Taraxacum kok-saghyz Provides Insights into Its Expression Patterns in Response to Ethylene and Methyl Jasmonate Treatments.

Taraxacum kok-saghyz (TKS) is a model plant and a potential rubber-producing crop for the study of natural rubber (NR) biosynthesis. The precise analysis of the NR biosynthesis mechanism is an important theoretical basis for improving rubber yield. The small rubber particle protein (SRPP) and rubber elongation factor (REF) are located in the membrane of rubber particles and play crucial roles in rubber biosynthesis. However, the specific functions of the SRPP/REF gene family in the rubber biosynthesis mechanism have not been fully resolved. In this study, we performed a genome-wide identification of the 10 TkSRPP and 2 TkREF genes' family members of Russian dandelion and a comprehensive investigation on the evolution of the ethylene/methyl jasmonate-induced expression of the SRPP/REF gene family in TKS. Based on phylogenetic analysis, 12 TkSRPP/REFs proteins were divided into five subclades. Our study revealed one functional domain and 10 motifs in these proteins. The SRPP/REF protein sequences all contain typical REF structural domains and belong to the same superfamily. Members of this family are most closely related to the orthologous species T. mongolicum and share the same distribution pattern of SRPP/REF genes in T. mongolicum and L. sativa, both of which belong to the family Asteraceae. Collinearity analysis showed that segmental duplication events played a key role in the expansion of the TkSRPP/REFs gene family. The expression levels of most TkSRPP/REF members were significantly increased in different tissues of T. kok-saghyz after induction with ethylene and methyl jasmonate. These results will provide a theoretical basis for the selection of candidate genes for the molecular breeding of T. kok-saghyz and the precise resolution of the mechanism of natural rubber production.

Support medium development for 3D printing natural rubber latex via direct ink writing in the support bath technique

The direct manufacturing of rubber products from natural rubber latex through 3D printing, particularly extrusion in air, faces challenges in creating intricate shapes. Research suggests that utilizing 3D printing with extrusion in a support medium, known as direct ink writing (DIW), is effective for crafting complex-shaped rubber products. However, few studies have explored 3D printing natural rubber as a support medium. This study focuses on formulating a support medium for the DIW printing of natural rubber by incorporating triethanolamine (TEA) and alcohol in varying proportions. Key characteristics, such as viscosity, were assessed for each formulation, along with essential printing parameters, such as speed and flow rate. A suitable support liquid consisting of TEA (2.5 g), alcohol (160 g), Carbopol (1.5 g), and water (200 g) was determined for DIW printing natural rubber. The optimal settings were determined to be a nozzle size of 0.85 mm, a speed of 30 mm/s, and a flow rate of 30 mm3/s. Comparative results from the forming process indicate that 3D-printed rubber specimens exhibit poorer mechanical properties than traditionally molded specimens, owing to material uniformity. The vulcanized rubber system with the EV pattern exhibited superior mechanical characteristics. The developed support medium for DIW printing shows potential for use in intricate natural rubber products; however, further exploration of additional parameters is crucial for advancing complex-shaped natural rubber manufacturing using 3D printers.

Hydro Priming Efficacy on Rubber Plant Seeds (Hevea brasiliensis) Growth

Among the plantation products, rubber is critical to economic activity within Indonesia. Rubber is also identified as one of Indonesia's export products, which is significant as an export revenue source apart from the oil and gas sector. Malaysia is the world's second-largest rubber producer and exporter of natural rubber after Indonesia. Besides having more open export opportunities and stimuli, the domestic rubber market is still large. Therefore, this study aims to ascertain the efficiency of hydro priming of rubber seeds on germination time and power as well as sprout height. The research was conducted in the greenhouse at the experimental garden in the Faculty of Agriculture KU IMS in Kuantan Singingi, which are given at geographical coordinates 00 00-10 00 LS 1010 02 – 1010 55 BT. The research was conducted in November-December 2023. The questionnaire survey was conducted in November and December of 2023. The average air temperature of the research location for November and December 2023 was 28. ranges from 8 0C to 32 0C with relative humidity of about 81%. The research approach was conducted in a qualitative manner utilizing mathematical techniques. Data is generally put in a tabular form and analyzed. Various treatment levels were under Control, 12h, 24h, 36h and 48h of hydro priming. In this research, the parameters recorded include time taken for germination, germination strength and sprout height. According to the outcomes of the assessments made in this study, the hydro priming treatment conducted on the rubber plant seeds showed the fastest germination time characteristics in the 48-hour treatment, which is 3. 4 days. The maximum germination capacity was observed in the hydro-priming treatment of 36 hours, which was 90. 0%. On the other hand, the tallest observation parameter of the height of the sprouts was in 48 hrs of Hydro Priming, with a height of 26. 3 cm

Exhaustive identification and characterization of Colletotrichum siamense and Colletotrichum fructicola as causative agents of circular leaf spot disease of rubber tree (Hevea brasiliensis) in India

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.

Utilization of waste high calcium oxide fly ash as hybrid activator for vulcanization of natural rubber/carbon black composites: Reducing zinc oxide requirement

A high calcium oxide fly ash (FA), a by-product waste of electric power generation has been used as hybrid activator in natural rubber (NR) composites filled with carbon black (CB). The aim of using FA is to reduce the environmental contamination by zinc oxide (ZnO) needed as activator for sulfur-vulcanization/crosslinking in final NR products. The FA was varied by adding in the composites with and without ZnO, and it was observed that chemical crosslinking could be generated although no ZnO was used anymore. The synergistic FA/ZnO-blend with FA 9 phr and ZnO 3 phr presented the best fit for the NR/CB composites, where it showed a proper crosslink density, reinforcement efficiency, cure characteristics, and mechanical properties in terms of modulus, tensile strength, elongation at break and tear resistance. This relates to the inorganic composition of the FA, in particular calcium oxide (CaO), which induces the thermal conductivity throughout the NR matrix and activates crosslinking between the NR molecules. The results showed effective use of FA in the composites, which can be applied to the CB-based formulations used in commercial NR applications like tires, barriers, and elastic stopper.

Interclonal variability in sensitivity to wind breakage: Comparative analysis of the mechanical behaviour of stems of two Hevea clones

The rubber tree (Hevea brasiliensis) is the main source of natural rubber production, with more than 14 million tonnes produced each year. Unfortunately, throughout their economic lifespan on the plantation (between 35 and 40 years), heveas trees are sensitive to wind damage, especially trunk breakage. Over a 30-year period, it is estimated that losses due to the wind breakage of tree stems reach nearly 40%. Industrial hevea plantations are organized in monoclonal plots. Clones are selected based on their productivity, disease resistance, etc., but not for their mechanical behaviour or sensitivity to wind-induced breakage, as breeders lack the appropriate tools to assess these criteria. Field observations highlight variations among clones in their susceptibility to wind breakage, underscoring the increased importance of evaluating mechanical criteria. Among the known causes of these differences in Hevea trees are competition between latex production and growth, crown shape and the presence of tension wood. In this article, we investigated the mechanical behaviour of the stems of two Hevea clones. One, IRCA825, is recognized as very sensitive, while the other, IRCA41, is known for its resistance to wind breakage. We measured biomechanical parameters such as trunk bending stiffness (EI), green wood stiffness (E) and modulus of rupture (MOR). To assess these parameters, we performed bending tests until breakage on standing trees of clonal fields in Ivory Coast, followed by wood characterisation tests in laboratory. A comparative analysis of the bending tests revealed that clones IRC825 and IRCA41 exhibit equivalent trunk bending stiffness. Nevertheless, IRCA41 differs from IRCA825 by having higher green wood stiffness and breaking strength, attributes that mainly explains its higher wind resistance. Comparative analysis of the wood structure indicated that the differences in wood stiffness and breaking strength are mainly attributed to the higher wood density in IRCA41 compared to IRCA825, with no discernible differences in microfibril angle and specific modulus.