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The current method used in latex industries to determine the volatile fatty acids contents of Hevea brasiliensis latex is steam distillation. However, the accuracy of the method has been debated for some time. We assessed the accuracy of the method and developed a new, more reliable high-performance liquid chromatographic method of determining acids in latex. The volatile fatty acids (formic, acetic, propionic, butyric, and valeric acids) and nonvolatile organic acids (oxalic, malic, lactic, citric, and succinic acids) in latex are directly determined simultaneously for the first time with high sensitivity and without losses during sample preparation. To avoid errors from derivatization, an acid-resistant Prevail HPLC column and a gradient mobile phase of 25 mM potassium dihydrogen phosphate (pH 2.5) and acetonitrile were employed. Under optimum conditions, the calibrations of both types of acids demonstrated satisfactory correlation coefficients of ≥0.990, with limits of detection ranging from 0.02 to 395 mM. The developed method demonstrated the profiles of acids in field and concentrated latex of the same batch. Moreover, the evolution of the profiles of all studied acids in both types of latex during a 3-month period was also revealed.

Recent and rapid expansion of rubber [Hevea brasiliensis (Willd. ex A. Juss.) Müll. Arg.] plantations requires understanding their effects on soil physicochemical properties and soil quality. An ideal testbed for analyzing such land-use change and its impacts is Hainan Island, the largest tropical island in China, which in recent decades has seen a dramatic expansion in the rubber industry. Based on 14 soil physicochemical properties at two soil depths (0-20 and 20-40 cm), a comprehensive assessment index was established using principal component analysis to assess soil qualities under rubber plantations (RPs; monoculture and intercropping) and five additional land-use types (areca palm [Areca L.], eucalyptus [Eucalyptus loxophleba Benth.] and banana [Musa L.] plantations, secondary forest, and tropical rainforest [TR]). The following results were obtained: (a) total porosity, ammoniacal N, total P, available P, and soil organic matter were vital soil physicochemical properties contributing to the comprehensive assessment index; (b) the comprehensive assessment indices of RPs were significantly lower than those of TR and areca palm plantation; (c) intercropping improves most soil physicochemical properties in RPs comparing monoculture and intercropped RPs; and (d) redundancy analysis demonstrated that land-use type interacted with climatic, geographical, and edaphic factors and collectively explained about half of the variation in the soil physicochemical properties across the study area. Deteriorating soil quality by converting TR to RPs and other land-use types provides another reason to protect TRs, especially on area-limited islands like Hainan.

Summary Natural rubber (NR) is a nonfungible and valuable biopolymer, used to manufacture ~50 000 rubber products, including tires and medical gloves. Current production of NR is derived entirely from the para rubber tree (Hevea brasiliensis). The increasing demand for NR, coupled with limitations and vulnerability of H. brasiliensis production systems, has induced increasing interest among scientists and companies in potential alternative NR crops. Genetic/metabolic pathway engineering approaches, to generate NR‐enriched genotypes of alternative NR plants, are of great importance. However, although our knowledge of rubber biochemistry has significantly advanced, our current understanding of NR biosynthesis, the biosynthetic machinery and the molecular mechanisms involved remains incomplete. Two spatially separated metabolic pathways provide precursors for NR biosynthesis in plants and their genes and enzymes/complexes are quite well understood. In contrast, understanding of the proteins and genes involved in the final step(s)—the synthesis of the high molecular weight rubber polymer itself—is only now beginning to emerge. In this review, we provide a critical evaluation of recent research developments in NR biosynthesis, in vitro reconstitution, and the genetic and metabolic pathway engineering advances intended to improve NR content in plants, including H. brasiliensis, two other prospective alternative rubber crops, namely the rubber dandelion and guayule, and model species, such as lettuce. We describe a new model of the rubber transferase complex, which integrates these developments. In addition, we highlight the current challenges in NR biosynthesis research and future perspectives on metabolic pathway engineering of NR to speed alternative rubber crop commercial development.

Hydroxynitrile lyase (HNL)-catalysed stereoselective synthesis of β-nitro alcohols from aldehydes and nitroalkanes is considered an efficient biocatalytic approach. However, only one S-selective HNL-Hevea brasiliensis (HbHNL)-exists that is appropriate for the synthesis of (S)-β-nitro alcohols from the corresponding aldehydes. Further, synthesis catalysed by HbHNL is limited by low specific activity and moderate yields. We have prepared a number of (S)-β-nitro alcohols, by kinetic resolution with the aid of an R-selective HNL from Arabidopsis thaliana (AtHNL). Optimization of the reaction conditions for AtHNL-catalysed stereoselective C-C bond cleavage of racemic 2-nitro-1-phenylethanol (NPE) produced (S)-NPE (together with benzaldehyde and nitromethane, largely from the R enantiomer) in up to 99 % ee and with 47 % conversion. This is the fastest HNL-catalysed route known so far for the synthesis of a series of (S)-β-nitro alcohols. This approach widens the application of AtHNL for the synthesis not only of (R)- but also of (S)-β-nitro alcohols from the appropriate substrates. Without the need for the discovery of a new enzyme, but rather by use of a retro-Henry approach, it was used to generate a number of (S)-β-nitro alcohols by taking advantage of the substrate selectivity of AtHNL.

Monocultural rubber plantations have replaced tropical forest, causing biodiversity loss. While protecting intact or semi‐intact biodiverse forest is paramount, improving biodiversity value within the 11.4 million hectares of existing rubber plantations could offer important conservation benefits, if yields are also maintained. Some farmers practice agroforestry with high‐yielding clonal rubber varieties to increase and diversify incomes. Here, we ask whether such rubber agroforestry improves biodiversity value or affects rubber yields relative to monoculture.\ud \ud We surveyed birds, fruit‐feeding butterflies and reptiles in 25 monocultural and 39 agroforest smallholder rubber plots in Thailand, the world's biggest rubber producer. Management and vegetation structure data were collected from each plot, and landscape composition around plots was quantified. Rubber yield data were collected for a separate set of 34 monocultural and 47 agroforest rubber plots in the same region.\ud \ud Reported rubber yields did not differ between agroforests and monocultures, meaning adoption of agroforestry in this context should not increase land demand for natural rubber. Butterfly richness was greater in agroforests, where richness increased with greater natural forest extent in the landscape. Bird and reptile richness were similar between agroforests and monocultures, but bird richness increased with the height of herbaceous vegetation inside rubber plots.\ud \ud Species composition of butterflies differed between agroforests and monocultures, and in response to natural forest extent, while bird composition was influenced by herbaceous vegetation height within plots, the density of non‐rubber trees within plots (representing agroforestry complexity) and natural forest extent in the landscape. Reptile composition was influenced by canopy cover and open habitat extent in the landscape. Conservation priority and forest‐dependent birds were not supported within rubber.\ud \ud Synthesis and applications. Rubber agroforestry using clonal varieties provides modest biodiversity benefits relative to monocultures, without compromising yields. Agroforests may also generate ecosystem service and livelihood benefits. Management of monocultural rubber production to increase inter‐row vegetation height and complexity may further benefit biodiversity. However, biodiversity losses from encroachment of rubber onto forests will not be offset by rubber agroforestry or rubber plot management. This evidence is important for developing guidelines around biodiversity‐friendly rubber and sustainable supply chains, and for farmers interested in diversifying rubber production.

Background The hornworn Erinnyis ello is the major pest of natural rubber crops in Colombia, mainly controlled using toxic chemical insecticides. The use of E. ello Betabaculovirus is an environmentally sustainable alternative for its control. The aim of the present work was to characterize a prototype biopesticide formulation and evaluate its efficacy under different conditions. Results Quality control evaluations of formulated biopesticide revealed that all the parameters evaluated were under the permissible level. The lethal concentrations LC50 and LC90 of the biopesticide were 4.3 × 103 and 5.5 × 104 occlusion bodies (OBs) mL-1 , respectively. Biopesticide efficacies against second and fourth instar larvae under greenhouse conditions were higher than 80%. Evaluation of two application rates in a clonal garden resulted in 84% and 88% efficacy, comparable to that obtained with the chemical. The biopesticide in a commercial plantation showed efficacies between 74% and 82%. Biopesticide post-application persistence was estimated at least in 1 week under field natural conditions. Results allowed selection of the lowest evaluated dose (1 × 1011 OBs ha-1 ) as the basis for further field evaluations. Conclusion Formulated ErelGV showed high efficacy to control the hornworm in rubber crops and high potential to be included in integrated pest management programs, thus it could be an interesting alternative to replace agrochemicals. © 2018 Society of Chemical Industry.

SWEET proteins play an indispensable role as a sugar efflux transporter in plant development and stress responses. The SWEET genes have previously been characterized in several plants. Here, we present a comprehensive analysis of this gene family in the rubber tree, Hevea brasiliensis. There are 36 members of the SWEET gene family in this species, making it one of the largest families in plant genomes sequenced so far. Structure and phylogeny analyses of these genes in Hevea and in other species demonstrated broad evolutionary conservation. RNA-seq analyses revealed that SWEET2, 16, and 17 might represent the main evolutionary direction of SWEET genes in plants. Our results in Hevea suggested the involvement of HbSWEET1a, 2e, 2f, and 3b in phloem loading, HbSWEET10a and 16b in laticifer sugar transport, and HbSWEET9a in nectary-specific sugar transport. Parallel studies of RNA-seq analyses extended to three other plant species (Manihot esculenta, Populus trichocarpa, and Arabidopsis thaliana) produced findings which implicated MeSWEET10a, 3a, and 15b in M. esculenta storage root development, and the involvement of PtSWEET16b and PtSWEET16d in P. trichocarpa xylem development. RT-qPCR results further revealed that HbSWEET10a, 16b, and 1a play important roles in phloem sugar transport. The results from this study provide a foundation not only for further investigation into the functionality of the SWEET gene family in Hevea, especially in its sugar transport for latex production, but also for related studies of this gene family in the plant kingdom.

HMG-CoA reductase (HMGR) is a key enzyme in the mevalonate pathway for sterols and cytosolic isoprenoid production. Although HMGR kinases from spinach, barley, and cauliflower tissues have been strongly suggested as members of SNF1-related protein kinases 1 (SnRK1), the phosphorylation and inactivation of HMGR by plant SnRK1s has not been demonstrated. In this study, we elucidated that AKIN10, an Arabidopsis SnRK1, acts as an HMGR kinase. The recombinant AKIN10 phosphorylates and inactivates AtHMGR1S using recombinant GRIK1 as the AKIN10 activator. In contrast, AKIN10-GRIK1 fails to inactivate AtHMGR1S-S577A, suggesting that this is achieved through Ser577 phosphorylation. Moreover, phosphorylation is detected not only in AtHMGR1S but also in AtHMGR1S-S577A, suggesting the presence of a novel regulatory mechanism of plant HMGR.

Indonesia lost more tropical forest than all of Brazil in 2012, mainly driven by the rubber, oil palm, and timber industries. Nonetheless, the effects of converting forest to oil palm and rubber plantations on soil organic carbon (SOC) stocks remain unclear. We analyzed SOC losses after lowland rainforest conversion to oil palm, intensive rubber, and extensive rubber plantations in Jambi Province on Sumatra Island. The focus was on two processes: (1) erosion and (2) decomposition of soil organic matter. Carbon contents in the Ah horizon under oil palm and rubber plantations were strongly reduced up to 70% and 62%, respectively. The decrease was lower under extensive rubber plantations (41%). On average, converting forest to plantations led to a loss of 10 Mg C ha(-1) after about 15 years of conversion. The C content in the subsoil was similar under the forest and the plantations. We therefore assumed that a shift to higher δ(13) C values in plantation subsoil corresponds to the losses from the upper soil layer by erosion. Erosion was estimated by comparing the δ(13) C profiles in the soils under forest and under plantations. The estimated erosion was the strongest in oil palm (35 ± 8 cm) and rubber (33 ± 10 cm) plantations. The (13) C enrichment of SOC used as a proxy of its turnover indicates a decrease of SOC decomposition rate in the Ah horizon under oil palm plantations after forest conversion. Nonetheless, based on the lack of C input from litter, we expect further losses of SOC in oil palm plantations, which are a less sustainable land use compared to rubber plantations. We conclude that δ(13) C depth profiles may be a powerful tool to disentangle soil erosion and SOC mineralization after the conversion of natural ecosystems conversion to intensive plantations when soils show gradual increase of δ(13) C values with depth.

Summary � In Hevea brasiliensis, an alkaline/neutral invertase (A/N-Inv) is responsible for sucrose catabolism in latex (essentially the cytoplasm of rubber-producing laticifers, the source of natural rubber) and implicated in rubber yield. However, neither the gene encoding this enzyme nor its molecular and biochemical properties have been well documented. � Three Hevea A/N-Inv genes, namely HbNIN1, 2 and 3, were first cloned and characterized in planta and in Escherichia coli. Cellular localizations of HbNIN2 mRNA and protein were probed. From latex, active A/N-Inv proteins were purified, identified, and explored for enzymatic properties. � HbNIN2 was identified as the major A/N-Inv gene functioning in latex based on its functionality in E. coli, its latex-predominant expression, the conspicuous localization of its mRNA and protein in the laticifers, and its expressional correlation with rubber yield. An active A/NInv protein was partially purified from latex, and determined as HbNIN2. The enhancement of HbNIN2 enzymatic activity by pyridoxal is peculiar to A/N-Invs in other plants. � We conclude that HbNIN2, a cytosolic A/N-Inv, is responsible for sucrose catabolism in rubber laticifers. The results contribute to the studies of sucrose catabolism in plants as a whole and natural rubber synthesis in particular.

Plant Breed.ISI Document Delivery No.: AJ4WPTimes Cited: 0Cited Reference Count: 31Cited References: Argout X, 2008, BMC GENOMICS, V9, DOI 10.1186/1471-2164-9-512 BESSE P, 1994, THEOR APPL GENET, V88, P199, DOI 10.1007/BF00225898 Conesa A, 2005, BIOINFORMATICS, V21, P3674, DOI 10.1093/bioinformatics/bti610 Cubry P, 2013, BMC GENOMICS, V14, DOI 10.1186/1471-2164-14-10 Ellis JR, 2007, HEREDITY, V99, P125, DOI 10.1038/sj.hdy.6801001 Feng SP, 2009, MOL BREEDING, V23, P85, DOI 10.1007/s11032-008-9216-0 Garcia D, 2011, PHYSIOL MOL PLANT P, V76, P126, DOI 10.1016/j.pmpp.2011.07.006 Gupta PK, 2005, PLANT MOL BIOL, V57, P461, DOI 10.1007/s11103-005-0257-z Gupta S, 2013, PLANT BREEDING, V132, P367, DOI 10.1111/pbr.12070 Kumar Yadav H., 2010, TREE GENET GENOMES, V7, P207 Le Guen V., 2008, EXPLORATION DIVERSIT Le Guen V, 2011, PLANT BREEDING, V130, P294, DOI 10.1111/j.1439-0523.2010.01774.x Le Guen V, 2009, TREE GENET GENOMES, V5, P673, DOI 10.1007/s11295-009-0218-9 Lespinasse D, 2000, THEOR APPL GENET, V100, P127, DOI 10.1007/s001220050018 Li DJ, 2012, BMC GENOMICS, V13, DOI 10.1186/1471-2164-13-192 Liu KJ, 2005, BIOINFORMATICS, V21, P2128, DOI 10.1093/bioinformatics/bti282 Ohyama A, 2009, MOL BREEDING, V23, P685, DOI 10.1007/s11032-009-9265-z Perovic D, 2009, MOL BREEDING, V23, P641, DOI 10.1007/s11032-009-9262-2 Perrier Xavier, 2003, P31 Perrier X., 2006, DARWIN SOFTWARE Pootakham W, 2012, PLANT BREEDING, V131, P555, DOI 10.1111/j.1439-0523.2012.01982.x Rafalski JA, 2010, CURR OPIN PLANT BIOL, V13, P174, DOI 10.1016/j.pbi.2009.12.004 Rozen S, 2000, Methods Mol Biol, V132, P365 SAITOU N, 1987, MOL BIOL EVOL, V4, P406 Seguin Marc, 2003, P277 Souza LM, 2009, CONSERV GENET RESOUR, V1, P75, DOI 10.1007/s12686-009-9018-7 Triwitayakorn K, 2011, DNA RES, V18, P471, DOI 10.1093/dnares/dsr034 Tyrka M, 2008, J APPL GENET, V49, P127, DOI 10.1007/BF03195605 Varshney RK, 2005, TRENDS BIOTECHNOL, V23, P48, DOI 10.1016/j.tibtech.2004.11.005 Vigouroux Y, 2005, GENETICS, V169, P1617, DOI 10.1534/genetics.104.032086 Wen Mingfu, 2010, BMC Res Notes, V3, P42, DOI 10.1186/1756-0500-3-42Cubry, Philippe Pujade-Renaud, Valerie Garcia, Dominique Espeout, Sandra Le Guen, Vincent Granet, Francoise Seguin, MarcFrench National Research Agency (Agence Nationale pour la Recherche; contrat ANR/Genoplante) [GPLA07017C]This work was performed as part of the CIRAD - Michelin collaborative project 'Genesalb' supported by a grant from the French National Research Agency (Agence Nationale pour la Recherche; contrat ANR/Genoplante no GPLA07017C). We thank the Montpellier Languedoc-Roussillon Grand plateau technique regional for hosting the SSR genotyping activities. ESTtik database was made available by the SouthGreen bioinformatics platform at http://southgreen.cirad.fr/. We thank Ronan Rivallan for technical help, Xavier Argout for computational procedures and data retrieving, Gerald Oliver for keeping some vegetal material in a greenhouse in Montpellier, Jean-Marc Thevenin and Fabien Doare for providing us with some fresh material from CIRAD's Pointe Combi Centre (French Guyana) collection.Wiley-blackwellHoboken; Despite its economic importance and recent genome release, the need for molecular tools for Hevea brasiliensis is high. In the frame of a disease resistance study, EST sequences were retrieved from public database or generated by sequencing SSH libraries. Sequences were trimmed and microsatellite motifs searched using an ad hoc bioinformatic pipeline, and pairs of primers for the amplification of candidate markers were generated. We found a total of 10499 unigenes from both sources of sequences, and 673 microsatellites motifs were detected using the default parameters of the pipeline. Two hundred sixty-four primer pairs were tested and 226 (85.6%) successfully amplified. Out of the amplified candidate markers, 164 exhibited polymorphism. Relationships based on dendrograms using simple matching index and diversity statistics based on EST-SSRs were compared with Genomic SSRs, showing the potentialities of EST-derived microsatellites for resistance studies but also for population genetics approaches.

OBJECTIVES: Latex from Hevea brasiliensis (natural rubber tree primarily cultivated for its rubber particles) has no known primary metabolic function, although its biological role is as a plant defence system. The present study has evaluated specific anti‐proliferative effects of latex whole C‐serum and its subfractions, on human cancer cell lines. MATERIALS AND METHODS: Cell viability assay using MTT, DNA fragmentation assay and real‐time PCR were used to evaluate the cytotoxic effects of latex whole C‐serum and its subfractions on the cell lines. RESULTS: MTT assay revealed very low LC (50) values, 2.0 and 280 ng/ml, for DCS and DCP treatments, respectively. DCS was proven to be more potent compared to DCP, in conferring specific anti‐proliferative effects on the cancer cell lines. The study also indicated that anti‐proliferative activity of pre‐heated C‐serum fractions diminished significantly. CONCLUSION: Although noteworthy cell death was reported, DNA fragmentation assay and real‐time PCR confirmed that that induced by latex C‐serum subfractions was not promoted via the classical apoptotic signalling pathway.

Hydroxynitrile lyases (HNLs) catalyze the cleavage of cyanohydrins to yield hydrocyanic acid (HCN) and the respective carbonyl compound and are key enzymes in the process of cyanogenesis in plants. In organic syntheses, HNLs are used as biocatalysts for the formation of enantiopure cyanohydrins. We determined the structure of the recently identified, R-selective HNL from Arabidopsis thaliana (AtHNL) at a crystallographic resolution of 2.5 Å. The structure exhibits an α/β-hydrolase fold, very similar to the homologous, but S-selective, HNL from Hevea brasiliensis (HbHNL). The similarities also extend to the active sites of these enzymes, with a Ser-His-Asp catalytic triad present in all three cases. In order to elucidate the mode of substrate binding and to understand the unexpected opposite enantioselectivity of AtHNL, complexes of the enzyme with both (R)- and (S)-mandelonitrile were modeled using molecular docking simulations. Compared to the complex of HbHNL with (S)-mandelonitrile, the calculations produced an approximate mirror image binding mode of the substrate with the phenyl rings located at very similar positions, but with the cyano groups pointing in opposite directions. A catalytic mechanism for AtHNL is proposed, in which His236 from the catalytic triad acts as a general base and the emerging negative charge on the cyano group is stabilized by main-chain amide groups and an α-helix dipole very similar to α/β-hydrolases. This mechanistic proposal is additionally supported by mutagenesis studies.

A natural rubber was identified and characterized for the first time in the latex of the perennial Mediterranean shrub Euphorbia characias. Four different methods, i.e., acetone, acetic acid, trichloroacetic acid, and Triton® X-100, followed by successive treatments with cyclohexane/ethanol, were employed to extract the natural rubber. The rubber content was shown to be 14% (w/v) of the E. characias latex, a low content compared with that of Hevea brasiliensis (30-35%) but a similar content to other rubber producing plants. E. characias rubber showed a molecular weight of 93,000 with a M(w) /M(n) of 2.9. (1) H NMR, (13) C NMR, and FTIR analysis revealed the characteristic of the cis-1,4-polyisoprene typical of natural rubber. These results provided novel insight into latex components and will ultimately benefit the broader understanding of E. characias latex composition.

Background: The aim of this work was to study the new bone tissue formation af- ter bone morphogenetic protein type 2 (rhBMP-2) and P-1 application, using 5 and 10 lg of each, combined to a material carrier, in critical bone defects. Methods: It was used 70 Wistar rats (male, 250 g) that were divided in 10 groups with seven animals on each. Groups are the following: criti- cal bone defect only, pure monoolein gel, 5 lg of pure P-1, 5 lg of pure rhBMP-2, 5 lg of P-1/monoo- lein gel, 5 lg of rhBMP-2/monoolein gel, 10 lg of pure P-1, 10 lg of pure rhBMP-2, 10 lg of P-1/ monoolein gel, 10 lg of rhBMP-2/monoolein gel. Animals were sacrificed after 4 weeks of the surgi- cal procedure and the bone samples were submitted to histological, histomorphometrical, and im- munohistochemical evaluations. Results: Animals treated with pure P-1 protein, in both situations with 5 lg and 10 lg, had no significant difference (P > 0.05) for new bone formation; other groups treated with 10 lg were statistically significant (P < 0.05) among themselves and when compared with groups in which it was inserted the monoolein gel or critical bone defect only (P < 0.05). In the group involving the 10 lg rhBMP-2/monoolein gel association, it was observed an extensive bone formation, even when compared with the same treatment without the gel carrier. Conclusion: Using this experimental animal model, more new bone tissue was found when it was inserted the rhBMP-2, especially when this protein was combined to the vehicle, and this process seems to be dose dependent. Microsc. Res. Tech. 00:000-000, 2011. V C 2011 Wiley-Liss, Inc.

Fertilization is one of the key inputs to ensure healthy growth of rubber trees [Hevea brasiliensis (Willd. ex A. Juss.) Mull. Arg.] and maintain the nutrient balance of a rubber plantation. The main objective of this study was to develop and implement a nutrient balance based model to recommend fertilizer for individual rubber trees. We reviewed the theory of nutrient balance, then developed a model to integrate with geographic information system technology, and subsequently provided a detailed description of aboveground nutrient consumption (used for tree growth and latex production) and soil-supplied nutrient estimation, which was the key step in the model. A case study from a state farm on Hainan Island in China compared the model-derived results with existing recommendations, which were derived from the foliar analysis model with several decades of cultivation experience. Comparative analysis results showed the mean fertilizer rate of urea, single superphosphate, KCI, and total fertilizer rate was consistent with the existing recommendations. The model optimized the fertilizer application because the model included stand age and soil fertility, thus reduced the cost and ensured the rational use of natural resources. Implementation of this model serves as a supplement and complementary method associated with a foliar analysis model. Furthermore, it also can be used directly as a site-specific fertilizer recommendation at Hainan State Farm using soil sampling data when leaf sample data are lacking to implement the foliar analysis model.

Leaf decomposition, an important component of the organic matter dynamics in streams, has been widely examined in temperate regions but much less documented in tropical regions. We report here the first study of leaf decomposition in a Sri Lankan stream. The litterbag technique was used. Coarse (8 mm) and fine (100 µm) litterbags, that included or excluded macroinvertebrates respectively, were used to enclose leaves of three dominant riparian tree species: native Ochlandra stridula (bamboo), and the introduced Alstonia macrophylla and Hevea brasiliensis (rubber). A fourth set of litterbags contained a mixture of these three species. Leaf colonization by macroinvertebrates was highest in the early stages of the decomposition process on Hevea leaves but invertebrate densities declined later. The opposite colonization effect was observed on the native Ochlandra leaves: slow colonization with continuing low densities from the beginning to the end of the process. Decomposition of all three species was significantly faster in the coarse than in the fine mesh bags. Alstonia, which has the softest leaf tissue, was most rapidly decomposed while Ochlandra, with its tough structure, was the slowest. Among the invertebrates, insects were the most important leaf colonizing animals, with Diptera, Coleoptera and Trichoptera the most dominant. The invertebrate variety in the mixed bags was higher than in the single-species leaf bags, where Chironomidae dominated the colonizing assemblages. This study has shown that toughness, indicated by the ‘specific weight of leaf tissue’, and the quality of the leaves was more important in determining breakdown rates than their origin. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Efficient sucrose loading in rubber-producing cells (laticifer cells) is essential for retaining rubber productivity in Hevea brasiliensis, but the molecular mechanisms underlying the regulation of this process remain unknown. Here, we functionally characterized a putative Hevea SUT member, HbSUT3, mainly in samples from regularly exploited trees. When expressed in yeast, HbSUT3 encodes a functional sucrose transporter that exhibits high sucrose affinity with a K(m) value of 1.24 mm at pH 4.0, and possesses features typical of sucrose/H(+) symporters. In planta, when compared to the expression of other Hevea SUT genes, HbSUT3 was found to be the predominant member expressed in the rubber-containing cytoplasm (latex) of laticifers. The comparison of HbSUT3 expression among twelve Hevea tissues demonstrates a relatively tissue-specific pattern, i.e. expression primarily in the latex and in female flowers. HbSUT3 expression is induced by the latex stimulator Ethrel (an ethylene generator), and relates to its yield-stimulating effect. Tapping (the act of rubber harvesting) markedly increased the expression of HbSUT3, whereas wounding alone had little effect. Moreover, the expression of HbSUT3 was found to be positively correlated with latex yield. Taken together, our results provide evidence favouring the involvement of HbSUT3 in sucrose loading into laticifers and in rubber productivity.

As a result of attempts to isolate and identify various groups of organic compounds which occur naturally in Hevea latex, e.g., proteins, lecithins, amino acids, amines and betaines, alkaloids, and fat acids, resin acids, sterols and wax alcohols, the author developed some years ago a general scheme for the systematic analysis of latex. This paper, in completion, contains further details of the first fractions which are obtained on application of the general scheme, and which therefore have been called main fractions. Since it appeared desirable for several reasons to limit the analytical investigations to latex of one definite Hevea clone, the figures given below apply exclusively to fresh unammoniated latex of clone Tjirandji 1 (Tjir 1) tapped in the Tjiomas experimental garden near Buitenzorg. The recorded percentages are averages of figures obtained from several duplicate estimations.

A very simple method is described for isolating the phospholipids occurring in Hevea latex, which have been identified as lecithins. Further, the presence of a glucoside which appears to be loosely attached to the lecithins, has been established in the product originally obtained. Investigation of the composition of the centrifuge sludge from latex is being continued.

For the purpose of determining the weight distribution curve of the rubber particles in Hevea latex according to their diameter, two methods were employed, namely a photomicrographic dispersoid analysis and a sedimentation analysis. In addition to the fact, that the first method is very laborious, its precision doet not prove to be high mainly because a significant percentage of the particles is too small to be determined microscopically in the visible spectrum. Sedimentation analysis with the help of a modified pipette method according to Andreasen was found, however, to be very suitable for the purpose. By an accurate regulation of the viscosity, specific gravity and temperature of the suspension it became possible to determine the weight distribution curve of latex to a diameter of about 0.4 μ within a creaming time of 10 to 14 days, while the total percentage of still smaller particles was also determined at the same time. This method is accurate not too laborious and lends itself very well to series investigations.

This work reports a systematic comparative study of the technological properties of natural lattices and rubbers extracted from Hancornia speciosa Gomes and Hevea brasiliensis [(Willd. ex Adr. de Juss.) Muell.-Arg.] (clone RRIM 600) trees from 11 collections in Brazil throughout 2004. Natural rubber latex particle sizes and distributions were quite similar with an average diameter around 1 μm. Molecular weight, Wallace plasticity, and Mooney viscosity values were approximately the same for both rubbers. Fourier transform infrared spectroscopy peaks characteristic of natural rubber were observed for both Hancornia and Hevea. The measured differences in technological properties included lower values for Hancornia dry rubber content, % ash, % nitrogen, and plasticity retention index but higher value for acetone extract. Interestingly, nitrogen and protein content were much lower in Hancornia, suggesting that it may have important applications in nonallergic rubber uses. This represents the first report of lacticifer-produced low-protein natural rubber. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

The defence responses of calli and seeds of two cultivars (resistant; BPM-24 and susceptible; RRIM600) of the rubber tree, Hevea brasiliensis, against zoospores and elicitin purified from its pathogen, Phytophthora palmivora, were investigated. Both zoospores and elicitin induced the biosynthesis of the phytoalexin, scopoletin (Scp), in Hevea calli ranging from 5 x 10 5 to 4.5 x 10 6 zoospores/ml and 0.5 to 2 μg elicitin/g fresh weight of calli. At the highest concentration of zoospores (4.5 x 10 6 zoospores/ml) or elicitin (2 μg/g fresh weight of calli), the rate of Scp production was fastest but then it rapidly decreased and produced lower peak value than detected at the optimum concentration. The decline of Scp level at the highest zoospore/elicitin concentration was correlated to the amount of cell death measured by Evans Blue method. Peroxidase (POD) activities in Hevea calli were also measured using the optimum level of zoospores or elicitin. Induction of Scp preceded the production of Scp POD and o-dianisidine POD then followed by the guaiacol POD. The Scp and POD accumulations were approximately two to three times higher in the resistance cultivar than those in the susceptible one. As the responses of the calli to elicitin were faster than those to the zoospores, it demonstrates that zoospores require more time to act on the host cells. The pattern of Scp and POD activities monitored in elicitin-treated Hevea seeds was similar to that of Hevea calli after treating with zoospores or elicitin. Therefore, the callus cultures could be used as a tool for studying other defence mechanisms in H. brasiliensis. The achieved knowledge will be applied to enhance resistance and led to the protection of Hevea young seedlings from the pathogen in the plantation.

Even if biocatalysis is finding increasing application, it still has to gain widespread use in synthetic chemistry. Reasons for this are limitations that enzymes have with regard to substrate range, reaction scope, and insufficient selectivity with unnatural compounds. These shortcomings can be challenged by enzyme and/or substrate engineering, which are employed to alter substrate specificity and enhance the enzyme selectivity toward unnatural substrates. Herein, these two approaches are coupled to improve the hydroxynitrile lyase catalyzed synthesis of 2-hydroxy-(4'-oxocyclohexyl)acetonitrile (4). The ketone functionality is masked as an enol ether, and the oxynitrilase of Hevea brasiliensis is engineered towards this masked substrate to give the product with a high optical purity and to drastically lower the amount of enzyme needed.

This study aimed at screen for antimicrobial activity present in the non-rubber constituents of rubber latex of Hevea brasiliensis against various microbial strains. An antimicrobial protein, hevein was extracted from the bottom fraction after centrifugation and purified by acetone fractionation and anion exchange chromatography on a DEAE-Sepharose Fast Flow column. This procedure was more efficient and rapid than the previously described procedures. The antimicrobial activity was investigated and revealed that hevein, a small (4.7 kDa) cysteine-rich protein, had strong antimicrobial activity, especially against Candida spp. including Candida albicans, Candida tropicalis and Candida krusei. The MIC80 value for hevein was as low as 12 microg ml(-1) with C. tropicalis ATCC 750. Higher MIC80 values were obtained for C. albicans ATCC 10231 (95 microg ml(-1)) and C. krusei ATCC 6258 (190 microg ml(-1)). To confirm the antifungal activity, hevein also inhibited the growth of those fungi in a disk diffusion assay and its inhibition was enhanced when a Hevea latex protease inhibitor was also included. Hevein at a concentration of 30 microg ml(-1) also caused a Ca2+-dependent aggregation of C. tropicalis yeast cells. These data indicate that hevein can inhibit the growth of certain potential oral fungal pathogens.

Hevein has been found to be an essential element in coagulation of rubber particles in latex of rubber trees. In a previous study, we cloned a 1,241-bp fragment of a 5' upstream region of the hevein gene by genome walking. This fragment was analyzed by a 5' end nested deletion method in the present study, fused with a uidA (gus) gene to produce a series of tested constructs, which were transferred into C-serum of latex and the Gus activities were detected. Results showed that the fragment from -749 to -292 was sufficient for expression of gus gene in latex, and the fragment from -292 to -168 was crucial in response to abscisic acid inducement. In a transient transgenic test of rubber leaf with particle bombardment, construct Hev749 conferred gus-specific expression in veins, in which the latex tubes mainly distributed. This implies that the fragment from -749 to -292 was laticiferous-specific.

We have demonstrated that multiple crude enzyme lysates containing a hydroxynitrile lyase can be used for the enantioselective synthesis of cyanohydrins from aldehydes in microchannels. Using a microreactor setup, two important parameters were efficiently screened consuming only minute amounts of reagents. More importantly, results from the continuous flow reaction were fully consistent with results obtained from larger batchwise processes in which a stable emulsion was formed.

How tropical trees flower synchronously near the equator in the absence of significant day length variation or other meteorological cues has long been a puzzle. The rubber tree (Hevea brasiliensis) is used as a model to investigate this phenomenon. The annual cycle of solar radiation intensity is shown to correspond closely with the flowering of the rubber tree planted near the equator and in the subtropics. Unlike in temperate regions, where incoming solar radiation (insolation) is dependent on both day length and radiation intensity, insolation at the equator is due entirely to the latter. Insolation at the upper atmosphere peaks twice a year during the spring and autumn equinoxes, but the actual solar radiation that reaches the ground is attenuated to varying extents in different localities. The rubber tree shows one or two flowering seasons a year (with major and minor seasons in the latter) in accordance with the solar radiation intensity received. High solar radiation intensity, and in particular bright sunshine (as distinct from prolonged diffuse radiation), induces synchronous anthesis and blooming in Hevea around the time of the equinoxes. The same mechanism may be operational in other tropical tree species.

3-Tetrahydrothiophenone (4) and 4-phenylthiobutan-2-one (7) were used as masked 2-butanone equivalents to give the corresponding cyanohydrins 5 (79 % yield, 91 % ee) and 8 (95 % yield, 96 % ee) in an enzymatic cyanohydrin reaction applying the hydroxynitrile lyase (HNL) from Hevea brasiliensis. After hydrolysis and desulphurisation the desired intermediate (S)-2-hydroxy-2-methylbutyric acid (10) was obtained with 99 % ee. Interestingly, when applying (R)-selective HNL from Prunus amygdalus again the (S)-cyanohydrin 5 was formed (62 % ee). The absolute configuration of 5 was verified by crystal structure determination of the corresponding hydrolysis derived carboxylate. The fact that both enzymes yield the same enantiomer was analysed and interpreted by molecular modelling calculations.

Guayule (Parthenium argentatum) is under cultivation in the southwestern United States as an alternative source of natural rubber free from proteins that cause Type I latex allergies. However, since guayule lacks the protein-polymer interactions present in Hevea latex, its physical and chemical properties may differ. The solvent-soluble (Sol) and insoluble (Gel) fractions from guayule and Hevea natural rubbers were isolated through a solubilization/centrifugation deproteinization process. Protein could be reduced or removed by centrifugation, or concentrated in the gel fraction for both Hevea and guayule rubber. Separation of the sol fraction of Hevea rubber reduced the overall protein level, in some cases to below detection limits, without impacting rubber thermo-oxidative stability. Notably, no detectable cross reactions took place between guayule protein antibodies and Hevea-based materials, nor vice-versa. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42051.

Summary Background Hevea brasiliensis latex serum is commonly used as the in vivo and in vitro reference antigen for latex allergy diagnosis as it contains the full complement of latex allergens. Objective This study quantifies the concentrations of the significant allergens in latex serum and examines its suitability as an antigen source in latex allergy diagnosis and immunotherapy. Methods The serum phase was extracted from centrifuged latex that was repeatedly freeze-thawed or glycerinated. Quantitation of latex allergens was performed by two-site immunoenzymetric assays. The abundance of RNA transcripts of the latex allergens was estimated from the number of their clones in an Expressed Sequence Tags library. Results The latex allergens, Hev b 1, 2, 3, 4, 5, 6, 7 and 13, were detected in freeze-thawed and glycerinated latex serum at levels ranging from 75 (Hev b 6) to 0.06 nmol/mg total proteins (Hev b 4). Hev b 6 content in the latex was up to a thousand times higher than the other seven latex allergens, depending on source and/or preparation procedure. Allergen concentration was reflected in the abundance of mRNA transcripts. When used as the antigen, latex serum may bias the outcome of latex allergy diagnostic tests towards sensitization to Hev b 6. Tests that make use of latex serum may fail to detect latex-specific IgE reactivity in subjects who are sensitized only to allergens that are present at low concentrations. Conclusion Latex allergy diagnostics and immunotherapy that use whole latex serum as the antigen source may not be optimal because of the marked imbalance of its constituent allergens.

Summary Background Allergy to latex of Hevea brasiliensis is a frequent problem. In spite of the significant progress of research, the identity and cross-reactivity of some latex allergens are unknown. Objective To identify, among the fully characterized latex proteins, those with a higher probability to be allergenic. Methods We used in silico techniques (amino acid sequence comparison and molecular modelling) to identify potential new allergens among the known proteins of H. brasiliensis. Results Cu/Zn superoxide dismutase, heat shock protein and calmodulin of H. brasiliensis show highly significant (E

Summary Background Hev b 4 is an allergenic natural rubber latex (NRL) protein complex that is reactive in skin prick tests and in vitro immunoassays. On SDS-polyacrylamide gel electrophoresis (SDSPAGE), Hev b 4 is discerned predominantly at 53–55 kDa together with a 57 kDa minor component previously identified as a cyanogenic glucosidase. Of the 13 NRL allergens recognized by the International Union of Immunological Societies, the 53–55 kDa Hev b 4 major protein is the only candidate that lacks complete cDNA and protein sequence information. Objective We sought to clone the transcript encoding the Hev b 4 major protein, and characterize the native protein and its recombinant form in relation to IgE binding. Methods The 5 0 /3 0 rapid amplification of cDNA ends method was employed to obtain the complete cDNA of the Hev b 4 major protein. A recombinant form of the protein was over-expressed in Escherichia coli. The native Hev b 4 major protein was deglycosylated by trifluoromethane sulphonic acid. Western immunoblots of the native, deglycosylated and recombinant proteins were performed using both polyclonal antibodies and sera from latex-allergic patients. Results The cDNA encoding the Hev b 4 major protein was cloned. Its open reading frame matched lecithinases in the conserved domain database and contained 10 predicted glycosylation sites. Detection of glycans on the Hev b 4 lecithinase homologue confirmed it to be a glycoprotein. The deglycosylated lecithinase homologue was discerned at 40 kDa on SDS-PAGE, this being comparable to the 38.53 kDa mass predicted by its cDNA. Deglycosylation of the lecithinase homologue resulted in the loss of IgE recognition, although reactivity to polyclonal rabbit anti-Hev b 4 was retained. IgE from latex-allergic patients also failed to recognize the non-glycosylated E. coli recombinant lecithinase homologue. Conclusion The IgE epitopes of the Hev b 4 lecithinase homologue reside mainly in its carbohydrate moiety, which also account for the discrepancy between the observed molecular weight of the protein and the value calculated from its cDNA.

Microsatellite markers were developed and evaluated in Hevea brasiliensis, an important crop species producing natural rubber of commercial utility. Of eight microsatellite markers, four were found to be highly informative, amplifying a total of 19 alleles when evaluated against 27 cultivated Hevea clones/genotypes. Power of discrimination of the microsatellite loci was in the range of 0.62-0.89, with a mean of 0.76 indicating these microsatellites could be valuable genetic markers for diversity characterization. A combination of four microsatellite markers was successfully used to discriminate uniquely all the 27 Hevea clones and some clone-specific allelic profiles were generated. Cross-species amplification of the markers developed in H. brasiliensis had also been demonstrated with two other Hevea species, H. benthamiana and H. spruceana, indicating a high degree of sequence homology at the flanking regions. Sequence analysis of the repeat region at the 3′-UTR of the hydroxymethylglutaryl-coenzyme A reductase gene, containing clusters of AG repeats in 15 clones, revealed the existence of two alleles based on the repeat length polymorphisms. Homozygosity as well as heterozygosity for both the alleles had also been detected among the clones. Frequency of homozygotes for the smaller allele (allele-1) was found to be lower than the larger allele (allele-2) among the primary clones of H. brasiliensis.

The solution-state conformations of N,N',N"-triacetyl chitotriose (1) and other potential chitinase inhibitors 2-4 were studied using a combination of NMR spectroscopy (NOESY) and molecular mechanics calculations. Determination solely of the global energy minimum conformation was found to be insufficient for an agreement with the NMR results. An appropriate consistency between the NMR experimental data and theoretical calculations was only reached by assessing the structures as population-weighted average conformers based on Boltzmann distributions derived from the calculated relative energies. Analogies, but also particular differences, between the synthetic compounds 2-4 and the naturally-occurring N,N',N"-triacetyl chitotriose were found. Furthermore, the conformation of compounds 1 and 2 when bound to hevamine was also studied using transferred NOESY experiments and the binding process was found to impart a level of conformational restriction on the ligands. The preferred conformation as determined for 1 in the bound state to hevamine belonged to one of the conformational families found for the compound when free in solution, although full characterisation of the bound-state conformations was impeded due to severe signal overlap. Saturation transfer difference NMR experiments were also employed to analyse the binding epitopes of the bound compounds. We thus determined that it is mainly the acetyl amido groups of the trisaccharide and the heterocyclic moiety which are in close contact with hevamine.

Foresight is a powerful tool for imagining possible futures, for raising public awareness, for helping decision-making and addressing questions related to the relationship between science and society. In this article we make a critical analysis of two foresight exercises organized by a research institution. A precise description of the exercises conducted on the futures of the cocoa commodity chain and the hevea commodity chain helps to understand the possible processes of a foresight exercise, what foresight can achieve and what kinds of difficulties can occur. From these experiences, proposals are made to facilitate the development of strategic intelligence in a research institution and improve the linkages between foresight, evaluation and programme formulation. The role of foresight in transforming knowledge and in pushing a closed system into a political arena is also shown. (Resume d'auteur)

The effects of the maturation and storage of naturally coagulated latex, generally termed cuplumps, on some bulk rheological properties and on parameters characterizing the macromolecular chain length were investigated for natural rubbers of different clonal typologies. The sensitivity of the clonal material to the degradative effects of cuplump maturation increased with the level of tree energetic metabolism, with the most metabolically active plant materials (e.g., PB 235) being most sensitive, whereas the less active clone PB 217 was less sensitive. A definite relationshipevolves between Hevea tree metabolism and the stability of the structure of the biosynthesized rubber. The results presented here highlight at a macromolecular level the effects of maturation previously demonstrated on bulk processing parameters. © 2002 Wiley Periodicals Inc

The presence of the oxidative reactions of the pentose phosphate pathway in hevea latex and their interaction with the biosynthesis of rubber are demonstrated using radioisotopes. During the second oxidation–reduction reaction of the pentose phosphate pathway the tritium in C3 of glucose-6-phosphate is transported as tritiated nicotinamide adenine dinucleotide phosphate and serves to reduce [3-14C] 3-hydroxy-3-methylglutaryl coenzyme A to mevalonate. Reduced nicotinamide adenine dinucleotide phosphate is the inter-connection between these two metabolic routes present in hevea latex, thus the hydrogens of glucose end up in rubber. © 2000 Society of Chemical Industry

Summary Thirty-six Hevea clones were inoculated with conidia of Microcyclus ulei, the causal agent of South American Leaf Blight in an air-conditioned chamber. Components of disease resistance such as latent period, infectious period, lesion size, percentage of damaged leaf area, number of lesions, spore production and stromatic generation period were studied during a single infection cycle. The clones were easily separated on the basis of these characters that were evaluated under controlled conditions. The main components that were highly correlated were the spore production, lesion size and number of lesions with the percentage of damaged leaf area. Others, such the stromatic generation period, were slightly correlated with all other components; latent period and infectious period was slightly correlated with the lesion size; and lesion size was slightly correlated with lesion density. For screening of varieties, damaged leaf area and spore production were the two components that should be considered the most important. Furthermore, the clones were tested for their capacity to produce scopoletin, a phytoalexin of Hevea, and to produce lignins in their infection sites. A strong correlation was observed between scopoletin accumulation and clone resistance. Moreover, strong lignin accumulation was often associated with a longer stromatic generation period. These two physiological reactions could interfere by limiting fungal development in several clones. However, neither scopoletin nor lignin accumulation could individually explain the behaviour of all clones.

Kinetic evidence is presented for the occurrence in Hevea latex particles of a trace substance that retards the hydrochlorination reaction. No retardation effect is observed with synthetic polyisoprene latex. The chemical nature of the retarder in Hevea latex particles is not known, but it is likely to be a basic substance. Its retardation action reflects its power to deactivate the reactive precursor of the hydrochlorination reaction, which is interpreted as a form of ion pair (H+, Cl−). A constant amount of the precursor is deactivated by the retarder, irrespective of the temperature or the pressure of the hydrochlorination reaction.

The applicability of random amplified polymorphic DNA (RAPD) markers in the cultivated rubber tree, Hevea, was evaluated using 43 decamer oligonucleotide primers in a set of 24 clones selected in different South-East Asian countries. A total of 220 0.35–3.5 kb DNA fragments were amplified, of which 111 were polymorphic. Of these, 80 fragments (RAPD markers) which were repeatable and clearly scorable across all genotypes were used to estimate genetic distances among the clones tested. The estimated genetic distances ranged from 0.05 (RRII 308 and PB 5/51) to 0.75 (RRIC 100 and SCATC 88–13). A mean genetic distance of 0.5 indicates a rather high genetic variability among the tested clones. As expected, because of the breeding history of Hevea, UPGMA cluster analysis and Principal Coordinate Analysis (PCoA) indicated the absence of a distinct geographical grouping. The possible application of RAPD markers for clone identification and also for analysis of genetic relationships among Hevea clones is discussed.

De jeunes feuilles de différents clones d'Hevea sont infectées en conditions contrôlées par Microcyclus ulei. Six heures après l'inoculation, une fluorescence bleue intense sous UV est émise autour du point de pénétration. La rapidité d'apparition de cette fluorescence sur la majorité des points de pénétration est en relation avec le degré de résistance du clone : 12-36 h chez les clones à résistance totale, 36-120 h chez les clones à résistance partielle de bon niveau et 120 h après inoculation chez les clones à résistance partielle faible. La scopolétine est probablement le seul composé responsable de cette fluorescence. Une accumulation importante de cette coumarine, pourrait stopper l'invasion du pathogène au cours des premières phases de son développement. Quatre jours après l'inoculation, une accumulation intense de lignine concernant quelques cellules autour du site de pénétration, est observée chez les clones à résistance totale. Chez certains clones à résistance partielle, leur accumulation intense et étendue à une large zone autour de la lésion pourrait circonscrire le développement du pathogène

The discovery of rubber is undoubtedly one of the greatest Indian contributions to modern civilisation.(1) I have been a rubber tapper; I am a rubber tapper. I live in stagnant, muddy swamps in the loneliness of the forest with my crew of malarial men cutting the bark of trees that have white blood like that of the gods.(2) ONE HUNDRED AND SEVENTEEN YEARS AGO, one of the most significant events in human history took place--the domestication of the rubber tree, Hevea brasiliensis. This achievement has had far-reaching economic, sociological and even humanitarian results. In 1876, the British imported quite legally--contrary to widely disseminated tales--70,000 seeds of this rubber tree collected in the eastern part of the Brazilian Amazonia. They were transported to England and planted in greenhouses of the Royal Botanic Gardens, Kew. Some 2800 seeds germinated, and the eventually surviving young trees were sent to Ceylon and later to Singapore (2, 7, 12, 13, 14). Almost all of the extensive rubber plantations of the former British and Dutch colonies in Ceylon and southeast Asia and smaller plantations in sundry parts of Africa and elsewhere are based on this one species (2, 7, 8, 19). II HEVEA BRASILIENSIS, native to the Amazon region south of the Amazon River, belongs to the Spurge Family; there are nine other species of Hevea. Two other species, Hevea Benthamiana and Hevea guianensis, yield latex that gives a rubber somewhat inferior to that of Hevea brasiliensis (16). The latex of all the other seven species of Hevea are either hard to coagulate or provide a weak rubber of no use. Even some of these inferior latices might, however, one day be of value to the fast developing plastics industry as "fillers"--chemicals that may alter the physical properties of the new elastomers (15). Botanists still are unsure of the function of latex in the life of the rubber trees, but it may serve a number of purposes. Some 37,000 species of plants in numerous families contain latex, a white or yellowish liquid. Only 7000 contain a substance called caoutchouc that will give usable rubber. It is difficult to realise that one species--Hevea brasiliensis--now supplies approximately 98% of the world's natural rubber, mostly from well-run plantations in Asia, Africa and Ceylon (8). The latex of the commercial rubber tree is an emulsion of complex hydrocarbons which are long-chain molecules made up of hydrogen and carbon in units called isoprene. The latex of Hevea brasiliensis contains up to 6000 of these units; it is a polyisoprene (1, 2, 7, 9). Most of the man-made substitutes--the elastomers popularly called synthetic rubber--have molecules with much fewer isoprene units. Some are better than natural rubber for certain purposes: e.g., when there is contact with petroleum products. But they are still inferior for tires which consume about 75% of the world's production of natural rubber (1, 8). III THE EARLY AMAZONIAN INDIANS had apparently very little use for rubber, according to brief reports by missionaries and explorers. In some tribes, apparently, small waterproof bags coated with rubber were made (6). A major interest in the rubber trees of several species was as a source of food. The seeds of Hevea are toxic, containing a cyanide, but when soaked in water and boiled, this poison is leached out, and the seed can be employed as a food (11). Its use as a nutrient was first reported in 1775 by the French botanist Aublet in his book on the plants of French Guiana in which he described the genus and its first species: Hevea guianensis. At about the same period, in 1770, a British chemist discovered that rubber could erase pencil marks--hence the English word "rubber" (2). When the Portuguese settled in the Amazon, they began to fashion a few articles of rubber; and in 1775, King Joseph of Portugal fostered the manufacture of shoes of rubber in Belem, at the mouth of the Amazon River. …

The involvement of microorganisms in the initial stage of maturation of natural rubber coagula was assessed with five latex treatments that varied in the initial quantity of microorganisms; the treatments ranged from latex added with an antimicrobial agent (3.4 × 104 CFU/mL) to strongly inoculated latex (2.4 × 107 CFU/mL). After 0–6 days of maturation, the obtained rubber was characterized with respect to its physical and structural properties. The Wallace plasticity (P0) and plasticity retention index (PRI) remained constant during maturation with the antibiotic-added treatment. PRI decreased with the maturation time, and the rate was proportional to the initial microorganism concentration. P0 of all inoculated rubber increased for the first 2 days of maturation and decreased after 6 days of maturation. With respect to structural parameters, a higher initial microorganism content corresponded to a higher gel content and a lower weight-average molar mass after maturation, drying, and storage. The inoculated rubber showed a stable value for the number-average molar mass (Mn), in contrast to the noninoculated samples, for which an increase in Mn during maturation was observed. The quantity of microorganisms significantly affected the physical properties and structure of the processed dry rubber. The mechanisms occurring during the initial stage of maturation are complex, and microorganisms are involved not only in the increase in sensitivity to thermooxidation but also in the crosslinking phenomenon between isoprene chains. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

3,5-Di-tert-butyl-4-hydroxybenzyl thioglycollate (DBHBT) was bound to the natural rubber (Hevea Brasilenisis) latex using 4,4'-azobiscyanovaleric (AZBN) acid-ferrous sulfate redox system. The degradation of various dilutions of the master batch as cast films under environmental influence has been investigated using spectroscopic method. Latex-bound DBHBT protects natural rubber latex against environmental degradation with an optimum concentration around 50%. The formation of C0 groups by some pathways independent of OH groups and allylic hydrogen atoms has been suggested in the natural weathering of DBHBT-modified and unprocessed natural rubber.

An unreported foot canker of Hevea seedlings has been proved to be caused by the fungus Nattrassia mangiferae. Sun-scorch predisposes the seedlings to infection.

 Premise of the study: We demonstrated the application of high-throughput 454 sequencing technology in the identifi cation of single nucleotide polymorphism (SNP) markers in Hevea brasiliensis .  Methods and Results: A total of 5883 putative SNP positions were discovered in silico, and 10 biallelic SNP markers were validated from 454-derived EST sequences. The polymorphism information content ( PIC ) and the observed heterozygosity ( H o ) ranged from 0.0963 – 0.5135 and 0.1071 – 0.4643, respectively.  Conclusions: These markers can be useful for the construction of genetic maps, the identifi cation of quantitative trait loci linked to commercially desirable traits, and the study of genetic structure in H. brasiliensis .

Introduction Historical Outline Discovery of Rubber and Improvement of Rubber Properties History of Rubber Trees and Rubber Plantations Latex of Hevea brasiliensis Composition of Hevea Latex Non-Rubber Constituents of Hevea Latex Rubber Particles in Hevea Latex Rubber Particle Membrane C Serum of Hevea Latex Lutoids of Hevea Latex Lutoids and Colloidal Stability of Latex Hevea Latex Metabolism Factors Affecting Rubber and Latex Yields Latex of Other Plants Latex of Guayule Possible Role or Functions of the Latex in Plants Latex of Fungi Diseases Related to Natural Rubber Latex (Latex Allergy) Latex Allergy Latex Protein Allergens Proteins and Allergens in Latex Gloves Cross-Reactivity of Allergens Allergens and Antigens of Latex Products Remarks on Hevea Latex Usage and Allergy Latex Protein Allergens from cDNA Clones Outlook and Perspectives Relevant Patents Keywords: Hevea brasiliensis; latex; natural rubber; rubber particles; laticifers; C-serum; B-serum; lutoids; rubber transferase; hevein; rubber elongation factor (REF); quebrachitol; latex allergy; latex allergens; deproteinized rubber; ethylene; latex flow; latex composition; latex vessels plugging; colloidal stability