Hevea Research Articles

Endophytic Trichoderma species from rubber trees native to the Brazilian Amazon, including four new species.

Fungi belonging to the genus Trichoderma have been widely recognized as efficient controllers of plant diseases. Although the majority of isolates currently deployed, thus far, have been isolated from soil, endophytic Trichoderma spp. is considered to be a promising option for application in biocontrol. In this study, 30 endophytic Trichoderma isolates-obtained from the leaves, stems, and roots of wild Hevea spp. in the Brazilian Amazon-were analyzed using specific DNA barcodes: sequences of internal transcribed spacers 1 and 2 of rDNA (ITS region), genes encoding translation elongation factor 1-α (TEF1-α), and the second largest subunit of RNA polymerase II (RPB2). The genealogical concordance phylogenetic species recognition (GCPSR) concept was used for species delimitation. A phylogenetic analysis showed the occurrence of Trichoderma species, such as T. erinaceum, T. ovalisporum, T. koningiopsis, T. sparsum, T. lentiforme, T. virens, and T. spirale. Molecular and morphological features resulted in the discovery of four new species, such as T. acreanum sp. nov., T. ararianum sp. nov., T. heveae sp. nov., and T. brasiliensis sp. nov. The BI and ML analyses shared a similar topology, providing high support to the final trees. The phylograms show three distinct subclades, namely, T. acreanum and T. ararianum being paraphyletic with T. koningiopsis; T. heveae with T. subviride; and T. brasiliensis with T. brevicompactum. This study adds to our knowledge of the diversity of endophytic Trichoderma species in Neotropical forests and reveals new potential biocontrol agents for the management of plant diseases.

Comparative Assessment of Tree Carbon Sequestration Potential and Soil Carbon Dynamics of Major Plantation Crops and Homestead Agroforestry of Kerala, India

Designing sustainable food and agricultural systems is a pressing need at a time when we already are at the low end of achieving SDG 13 (Climate Action) of reducing carbon emissions. In such a scenario, this study has the potential to provide an insightful framework for policymakers. The major objective of this study is to estimate the carbon sequestration of tree crops, and soil analysis in homestead agroforestry systems (AFS), monocropped rubber plantations, and monocropped coconut plantations in the Alappuzha and Kollam districts of Kerala. The soil carbon parameters analyzed were soil organic carbon (SOC) and labile carbon. Other parameters, such as pH and electrical conductivity of soil, were also measured. The soil of rubber plantations had the least pH (4.8) and EC (79 µS/cm). We found the tree carbon sequestration of rubber trees in the plantations to be the highest (13.8 t C ha−1 year −1) followed by homestead AFS (2.68 t C ha−1 yr−1) and coconut tree plantation (2.08 ± 0.53 t C ha−1 year−1). The tree carbon sequestration potential was significantly (p = 0.003) influenced by the treatments. In soil, the SOC content was highest in the homestead AFS (2.48%). The labile carbon was also found to be higher in the homestead AFS (0.06%) but was least in rubber plantation (0.04%). These results indicate that even though the tree carbon sequestration of homestead AFS is lesser compared to that of large tree plantations such as rubber. The soil carbon pools and other physical and chemical properties of soil promote the valuable contribution that homestead can play in the sustainability of the environment and ensuring food security.

Potential of agroforestry orchards as a conservation set-aside initiative in industrial rubber tree and oil palm plantations for avian biodiversity

Potential of agroforestry orchards as a conservation set-aside initiative in industrial rubber tree and oil palm plantations for avian biodiversity

Molecular Genetic Research and Genetic Engineering of Taraxacum kok-saghyz L.E. Rodin.

Natural rubber (NR) remains an indispensable raw material with unique properties that is used in the manufacture of a large number of products and the global demand for it is growing every year. The only industrially important source of NR is the tropical tree Hevea brasiliensis (Willd. ex A.Juss.) Müll.Arg., thus alternative sources of rubber are required. For the temperate zone, the most suitable source of high quality rubber is the Russian (Kazakh) dandelion Taraxacum kok-saghyz L.E. Rodin (TKS). An obstacle to the widespread industrial cultivation of TKS is its high heterozygosity, poor growth energy, and low competitiveness in the field, as well as inbreeding depression. Rapid cultivation of TKS requires the use of modern technologies of marker-assisted and genomic selection, as well as approaches of genetic engineering and genome editing. This review is devoted to describing the progress in the field of molecular genetics, genomics, and genetic engineering of TKS. Sequencing and annotation of the entire TKS genome made it possible to identify a large number of SNPs, which were subsequently used in genotyping. To date, a total of 90 functional genes have been identified that control the rubber synthesis pathway in TKS. The most important of these proteins are part of the rubber transferase complex and are encoded by eight genes for cis-prenyltransferases (TkCPT), two genes for cis-prenyltransferase-like proteins (TkCPTL), one gene for rubber elongation factor (TkREF), and nine genes for small rubber particle proteins (TkSRPP). In TKS, genes for enzymes of inulin metabolism have also been identified and genome-wide studies of other gene families are also underway. Comparative transcriptomic and proteomic studies of TKS lines with different accumulations of NR are also being carried out, which help to identify genes and proteins involved in the synthesis, regulation, and accumulation of this natural polymer. A number of authors already use the knowledge gained in the genetic engineering of TKS and the main goal of these works is the rapid transformation of the TKS into an economically viable rubber crop. There are no great successes in this area so far, therefore work on genetic transformation and genome editing of TKS should be continued, considering the recent results of genome-wide studies.

Expressional correlation of latex-regeneration genes with latex physiological parameters varies with population type and growth stage in Hevea tree

Expressional correlation of latex-regeneration genes with latex physiological parameters varies with population type and growth stage in Hevea tree

Cover legumes promote the growth of young rubber trees by increasing organic carbon and organic nitrogen content in the soil

Cover crops are often intercropped in rubber plantations to improve utilization of understory space; however, how cover crops promote the growth rate (GR) of young rubber trees remains unclear, as these are largely dependent on the growth time and varieties of cover crops. We conducted a five-year experiment with five cover crop treatments of no cover crop (CK) and cover with four varieties of perennial leguminous crops, namely, Stylosanthes guianensis Reyan No. 2 (RY2), Reyan No. 5 (RY5), Reyan No. 7 (RY7), and Reyan No.10 (RY10). We analyzed changes in total organic carbon (TOC), total nitrogen (TN), and the fractions of labile organic carbon (LOC), mineral nitrogen (MN), and organic nitrogen (ON) in understory soil of young rubber plants (Hevea Brisiliensis cv. Reyan 7–33–97) in tropical China and their effects on the GR. The results showed that cover year and cover crop varieties significantly affected soil TOC, LOC fractions, TN, MN, and ON fractions, as well as GR. Compared to CK, the five-year average GRs of rubber trees covering the RY2, RY5, RY7, and RY10 increased by 12.8%, 41.5% 30.0%, and 43.1%, respectively. Compared with CK, the five-year average nutrients of RY5 and RY10 all increased after covering, whereas the soil NH4+-N of RY2 decreased by 0.3%. Meanwhile, the soil TOC, TN, acid-hydrolyzable ammonium nitrogen (AN), and amino acid nitrogen of RY7 decreased by 10.1%, 13.4%, 6.7%, and 21.3%, respectively. The soil nutrients all show a good linear relationship with GR. We identified TN and MN as the main nutrients for the growth of young rubber plants through linear regression and stepwise regression. In addition, structural equation modeling indicated that TOC was the carrier of nitrogen transformation and utilization in soil. The total effects of TOC, AN, and NH4+-N on GR of rubber trees were 0.55, 0.52, and 0.31, respectively. The results demonstrated that RY5 and RY10 are suitable for young rubber plantation in tropical China as these effectively improved soil nitrogen supply potential, improved soil fertility, and promoted the GR of young rubber trees.

Peptidomic Analysis and Antimicrobial Activity of Serum Peptide from Hevea brasiliensis Clone BPM24.

Hevea brasiliensis is severely affected by the fungal disease caused by Phytophthora spp. Significant loss of rubber yield is widespread and extensive use of chemical fungicides has resulted in health and environmental problems. This work aims to extract and identify the latex serum peptides from a disease tolerant clone of H. brasiliensis, and study the inhibitory efficacy against pathogenic bacteria and fungi. Serum peptides were extracted from H. brasiliensis BPM24 using mixed lysis solution. Low molecular weight peptides were screened and fractionated by solid-phase extraction and then identified by tandem mass spectrometry. Total and fractionated serum peptides were assayed for bacterial and fungal inhibition using broth microdilution and poisoned food methods. An inhibitory control study in the greenhouse was also performed using susceptible clones for pre and postinfection with Phytophthora spp. Forty-three serum peptide sequences were successfully identified. Thirty-four peptides matched with the proteins associated with plant defense response signaling, host resistance, and adverse environmental factors. The inhibitory study of total serum peptides demonstrated antibacterial and anti-fungal properties. The greenhouse study exhibited disease inhibitory efficacy of 60% for the treatment of Phytophthora spp. in post-infected plants and 80% for pre-treated samples. Latex serum peptides from disease tolerant H. brasiliensis revealed several proteins and peptides associated with plant defense and disease resistance. The peptides play a vital role for defense against bacteria and fungi pathogens, including Phytophthora spp. Enhanced disease protection can be obtained when the extracted peptides were applied to the susceptible plants before exposure to the fungi. These findings provided an insight and may pave the way for the development of biocontrol peptides from natural resources.

POLA PENGOMBINASIAN TANAMAN DI KELOMPOK TANI HUTAN SEJAHTERA 4 DESA PESAWARAN TAMAN HUTAN RAYA WAN ABDUL RACHMAN

The pattern of plant combinations is the arrangement of the species of plants that are cultivated in a field. This research aims to analyze the pattern of plant combinations in the arable land of KTH Sejahtera 4 Tahura Wan Abdul Rachman. The research method used is the multiple plot method, direct observation, and interviews. Plots are arranged systematically on the farmers' arable areas. The total area cultivated by KTH Sejahtera 4 Tahura Wan Abdul Rahcman farmers is 36.05 ha. The area of the sample plots made is 1,442 ha with a sampling intensity (IS) of 4%, therefore the number of plots made is 36 plots. The results showed that all farmers applied agroforestry techniques with mixed crop combinations at random. The combination combines MPTS plants, both from the forestry plant group and the agricultural plant group. From the results of the vegetation analysis, it is known that in KTH Sejahtera's arable land 4 plants that have a high level of dominance are cloves (Eugenia aromaticum L.) and nutmeg (Myristica fragrans). According to farmers' opinion, there are three types of plants that are superior, namely cocoa (Theobroma cacao), rubber (Hevea brasiliensis), and coffee (Coffea robusta L.). The plants favored by the farmers are the mainstay of their income.

Ecophysiological responses of Cupuassu tree ecotypes (Theobroma grandiflorum) in an agroforestry system designed with rubber trees in Colombian Amazon

Ecophysiological responses of Cupuassu tree ecotypes (<i>Theobroma grandiflorum</i>) in an agroforestry system designed with rubber trees in Colombian Amazon

The effect of callus induction media for somatic embryo formation in Hevea brasiliensis Muell. Arg

The method for micro-propagation of rubber (Hevea brasiliensis Muell. Arg) by somatic embryo has been conducted. The aim of the research will describe the effect of media used for callus induction on the somatic embryo formation of rubber plants. Embryonic callus had been induction in 3 media, i.e.; MH1, MH2, and MH3. After callus induction, all callus were induced in media for embryo somatic expression. Maturation of cotyledons was performed using liquid media with filter paper as a bridge to absorb the media. The results showed that the percentage of callus was induced differently for each media. MH3 media was the best media for callus induction with 62.5% of callus forms, but for embryonic callus, MH1 was the best media. Not all of the calluses could be expressed to become somatic embryos. Most calluses derived from MH1 media were the best callus for somatic embryos formed.

Wood quality of ten clonal progenies of rubber tree as raw material for bioenergy

Wood quality of ten clonal progenies of rubber tree as raw material for bioenergy

GEOSPATIAL DISTRIBUTION OF FOREST SPECIES IN THE BOTANICAL GARDEN OF RECIFE, PERNAMBUCO, BRAZIL

The adoption of appropriate strategies for the conservation and management of forest ecosystems associated with the Atlantic Forest depends on understanding the pattern of spatial distribution of forest species, mainly in protected areas. Thus, this study aimed to evaluate the geospatial distribution of forest species in a fragment of Atlantic Forest (Lowland Dense Ombrophilous Forest) in the Botanical Garden of Recife, Pernambuco, Brazil. The phytosociological study was carried out by the plot method, with 40 plots of 10 m x 25 m, systematically distributed, where all living individuals that showed circumference at 1.3 m above the ground ≥ 15 cm were identified and georeferenced. To identify the existence of floristic similarity between the plots, the obtained data were subjected to hierarchical cluster analysis. The spatial variability of forest species was characterized using geostatistical analysis. The data were interpolated by kriging, followed by the construction of thematic maps of spatial distribution. Hierarchical cluster analysis revealed the formation of two groups of plots. The forest species Artocarpus heterophyllus, Dialium guianense, Helicostylis tomentosa, Hevea brasiliensis, Pouteria durlandii and Thyrsordium spruceanum showed spatial dependence. The use of geostatistics allowed visualizing the spatial distribution arrangements and identifying the concentration sites of these species. Information on the geospatial distribution of forest species can be used for the preservation, conservation and management of forest remnants.

Genome-Wide Identification of β-1,3-Glucanase Genes in Hevea brasiliensis

β-1,3-glucanase is one of the pathogenesis-related proteins well-known for their antifungal properties which can be abundantly found in Hevea brasiliensis. Utilization of β-1,3-glucanase in the genetic improvement of H. brasiliensis is very important as the high susceptibility to various fungal infections has challenged the current natural rubber industry. A few nucleotide sequences for β-1,3-glucanase have been reported and their role in biotic stress management has been demonstrated. Being a multigene family, it is necessary to identify and characterize more isoforms of β-1,3-glucanase to select the most suitable isoform to be utilized in genetic improvement. In the current study, we conducted a genome-wide identification of β-1,3-glucanases in H. brasiliensis, their classification based on the functional domains and phylogenetic analysis, using different bioinformatics tools. All publicly available nucleotide sequences were collected and curated by eliminating sequences that lack glycoside hydrolase family 17 (GH 17) domain as well as the partial and closely identical sequences and obtained 14 full-length sequences. The sequences were categorized into 4 distinct classes (I-IV) based on their functional domains and C-terminal extension. Class III and IV which lack the carbohydrate-binding C-terminal X8 domain are the largest classes identified with 5 β-1,3-glucanase each while 4 β-1,3-glucanase contain a variable C-terminal X8 domain. Phylogenetic analysis showed the clustering of β-1,3-glucanases into six major clades (I-VI) based on the domains. Clades I and II were identified as the largest clades with 4 β-1,3-glucanase in each. Several paralogous clusters have been observed for H. brasiliensis indicating the gene family expansion within the species or in the immediate ancestors with possible species-specific function. Further functional characterization is necessary to select the suitable gene to be utilized in genetic improvement and the present study provides a platform for it.

Conversion of Rubber Land Into Palm Oil and Its Effect on Production in North Sumatra

This study aims to analyze the conversion of rubber land to oil palm and its effect on production in North Sumatra. Today many rubber farmers are turning their land into oil palm plantations. So that the famous commodity from North Sumatra, namely, palm oil, is no longer rubber. Whereas previously the rubber plant (Hevea brasiliensis) as a plantation plant that was integrated with the culture of the people of North Sumatra Province had environmentally friendly properties. This study uses descriptive qualitative research methods. Data were collected by observation, interviews, literature study, and document analysis. The results show that smallholder rubber plantations have been the mainstay of the economy of North Sumatra Province since a century ago. Although there has been a change from Rubber Land to Palm Oil Land, currently North Sumatra accounts for 33% of the total national natural rubber production. North Sumatra is the second largest natural rubber producer after South Sumatra.

Monitoring the Severity of Rubber Tree Infected with Powdery Mildew Based on UAV Multispectral Remote Sensing

Rubber tree powdery mildew (PM) is one of the most devastating leaf diseases in rubber forest plantations. To prevent and control PM, timely and accurate detection is essential. In recent years, unmanned Aerial Vehicle (UAV) remote sensing technology has been widely used in the field of agriculture and forestry, but it has not been widely used to detect forest diseases. In this study, we propose a method to detect the severity of PM based on UAV low-altitude remote sensing and multispectral imaging technology. The method uses UAVs to collect multispectral images of rubber forest canopies that are naturally infected, and then extracts 19 spectral features (five spectral bands + 14 vegetation indices), eight texture features, and 10 color features. Meanwhile, Pearson correlation analysis and sequential backward selection (SBS) algorithm were used to eliminate redundant features and discover sensitive feature combinations. The feature combinations include spectral, texture, and color features and their combinations. The combinations of these features were used as inputs to the RF, BPNN, and SVM algorithms to construct PM severity models and identify different PM stages (Asymptomatic, Healthy, Early, Middle and Serious). The results showed that the SVM model with fused spectral, texture, and color features had the best performance (OA = 95.88%, Kappa = 0.94), as well as the highest recognition rate of 93.2% for PM in early stages.

Diversity and assembly of root-associated microbiomes of rubber trees.

Understanding the diversity and assembly of the microbiomes of plant roots is crucial to manipulate them for sustainable ecosystem functioning. However, there are few reports about microbial communities at a continuous fine-scale of roots for rubber trees. We investigate the structure, diversity, and assembly of bacterial and fungal communities for the soil (non-rhizosphere), rhizosphere, and rhizoplane as well as root endosphere of rubber trees using the amplicon sequencing of 16S ribosomal ribonucleic acid (rRNA) and Internally Transcribed Spacer (ITS) genes. We show that 18.69% of bacterial and 20.20% of fungal operational taxonomic units (OTUs) in the rhizoplane derived from the endosphere and 20.64% of bacterial and 20.60% of fungal OTUs from the soil. This suggests that the rhizoplane microbial community was a mixed community of soil and endosphere microbial communities and that microorganisms can disperse bidirectionally across different compartments of the plant root. On the other hand, in the absence of an enrichment or depletion of core bacterial and fungal OTUs in the rhizosphere, little differences in microbial composition as well as a more shared microbial network structure between the soil and the rhizosphere support the theory that the rhizosphere microbial community is a subset of the soil community. A large number of functional genes (such as nitrogen fixation and nitrite reduction) and more enriched core OTUs as well as a less stable but more complex network structure were observed in the rhizoplane of rubber tree roots. This demonstrated that the rhizoplane is the most active root compartment and a hotspot for plant-soil-environment interactions. In addition, bacterial and fungal communities in the rhizoplane were more stochastic compared to the rhizosphere and soil. Our study expands our understanding of root-associated microbial community structure and function, which may provide the scientific basis for sustainable agriculture through biological process management.

Genome-Wide Identification and Expression Analysis of the R2R3-MYB Gene Family in Rubber Trees

The plant MYB transcription factor family featured as highly conserved DNA-binding domains consisting of 1 to 4 imperfect repeats (R). Increasing evidence indicates that MYB genes participates in growth, differentiation, metabolism, and biotic and abiotic stress responses. However, the functions of MYB genes in the rubber tree remain to be deeply elucidated, especially R2R3-MYB gene family. In this study, molecular biology, bioinformatics, and qRT-PCR were used to identify and analyze HbR2R3-MYB gene family members in the rubber tree. A total of 132 members of the R2R3-MYB gene family were identified in the rubber tree based on genome-wide level. Most of the HbR2R3-MYBs were mapped to 17 rubber tree chromosomes except four genes. A phylogenetic analysis divided all the HbR2R3-MYBs into 20 subgroups with Arabidopsis thaliana. MEME analysis showed that the protein of HbR2R3-MYBs was characterized by 9 conserved motifs. Twenty-six representative R2R3 HbMYBs from different subgroups were selected for expression profiles analysis and the results revealed that the HbR2R3-MYBs members showed various expression patterns in different tissues, powdery mildew-infected and ethylene treatment, implying the diversity of their functions in rubber trees. These results provide fundamental knowledge for further studying the response of the HbR2R3-MYB family to stress and regulation latex flow in rubber tree.

Short-Term Evapotranspiration Forecasting of Rubber (Hevea brasiliensis) Plantations in Xishuangbanna, Southwest China

Rubber (Hevea brasiliensis) plantations have high water consumption through evapotranspiration, which can contribute to water scarcity. In addition, there is a lack of spatial observation data and estimation methods for evapotranspiration (ET) for rubber plantations. To alleviate the water stress of expanding rubber plantations caused by seasonal drought in Xishuangbanna, Southwest China, an up to 7 days crop evapotranspiration (ETc) forecast method, “Kc-ET0” for rubber plantations with limited meteorological data, was proposed by using rubber crop coefficient Kc and public weather forecasts. The results showed that the average absolute error (MAE) of forecasted ETc was 0.68 mm d−1, the root mean square error (RMSE) was 0.85 mm d−1, and the average correlation coefficient (R) was 0.69 during the rainy season, while during the dry season these metrics were 0.52 mm d−1, 0.68 mm d−1, and 0.85, respectively. The accuracy of ETc forecast in the dry season was higher. Additionally, Kc was the main factor influencing the accuracy of rubber plantations ETc forecast, while the accuracy of the temperature forecast and the chosen Hargreaves-Samani (HS) model were also considerable. Our results suggested that the “Kc-ET0” short-term rubber plantation ETc forecasting method shows good performance and acceptable accuracy, especially in the dry season. The study provides an important basis for creating ET-based irrigation scheduling for improving regional-scale water management in high water consumption rubber plantations.

Recent Progress on Natural Rubber-Based Materials Containing Metallic and Metal Oxide Nanoparticles: State of the Art and Biomedical Applications

Diseases caused by infections are becoming harder to treat as the antibiotics used become less effective. A combination of strategies to develop active biomaterials that enhance antibacterial effects are desirable, especially ones that cause fewer side effects and promote healing properties. The combination of nanotechnology with substances that have intrinsic antibacterial activity can result in the advance of innovative biomedical materials. In this sense, the goal of this work is to provide a summary of natural rubber latex materials obtained from the Hevea brasiliensis tree loaded with metallic and metal oxide nanoparticles. These nanoparticles have unique size-dependent chemical and physical characteristic that make them appropriate for use in pharmaceutical and medical devices, while natural rubber latex is a natural and biocompatible polymer with an intrinsic antibacterial effect. Moreover, we outline here the origin, extraction methods, and composition of natural rubber latex and different techniques for the synthesis of nanoparticles, including physical, chemical, and biological approaches. Finally, we summarize, for the first time, the state of the art in obtaining natural rubber-based materials with metallic and metallic oxide nanoparticles for biomedical applications.

Do Locals’ Perception of Bushfire Impact on Rubber Trees Match or Mismatch with Empirical Data? Evidence from Edo State, Nigeria

Aim of study: This study determined whether locals’ perception of bushfire impact on rubber trees matched or mismatched with empirical data. Area of study: This investigation was conducted in Rubber Research Institute of Nigeria (RRIN) and six neighboring communities (Uhie, Iyanomo, Obaretin, Obayantor I, Ogbekpen and Obagie) in Edo State, Nigeria. Material and methods: Quantitative data on tree height, canopy, diameter at breast height (DBH) and bark were obtained by direct measurements and field observation in burnt and unburnt rubber plantations. Locals’ perceptive data were obtained through the administration of questionnaire. Descriptive statistics were used to examine data on perception of locals’ while Student-t test was adopted to determine significant differences of tree parameters in burnt and unburnt rubber plantations. Main results: There were significant differences in height, canopy and DBH of rubber trees. Besides incidences of fissured tree bark; reduction in height, canopy and DBH of trees were detected in burnt rubber plantation. Majority of the local’s agreed that bushfire negatively impacted rubber tree parameters and natives’ perception aligned with the experiential results. Highlights: Locals’ perception of bushfire effect on rubber trees accessed through the Likert-type format of questionnaire matched with empirical data.