Guayule and Russian dandelion as alternative sources of natural rubber

Natural rubber, obtained almost exclusively from the Para rubber tree (Hevea brasiliensis), is a unique biopolymer of strategic importance that, in many of its most significant applications, cannot be replaced by synthetic rubber alternatives. Several pressing motives lead to the search for alternative sources of natural rubber. These include increased evidence of allergenic reactions to Hevea rubber, the danger that the fungal pathogen Microcyclus ulei, causative agent of South American Leaf Blight (SALB), might spread to Southeast Asia, which would severely disrupt rubber production, potential shortages of supply due to increasing demand and changes in land use, and a general trend towards the replacement of petroleum-derived chemicals with renewables. Two plant species have received considerable attention as potential alternative sources of natural rubber: the Mexican shrub Guayule (Parthenium argentatum Gray) and the Russian dandelion (Taraxacum koksaghyz). This review will summarize the current production methods and applications of natural rubber (dry rubber and latex), the threats to the production of natural rubber from the rubber tree, and describe the current knowledge of the production of natural rubber from guayule and Russian dandelion.     

First report of Bipolaris bicolor causing a leaf spot disease on rubber tree

The rubber tree (Hevea brasiliensis) is the only resource for commercial natural rubber production and thus has economic importance in Southeast Asia. A spot disease on the leaves of a rubber tree was first discovered in 2017 in Hainan, China. In this study, the fungal isolate MA1 from the infected tissues was determined to be a pathogen of the spot disease by satisfying Koch's postulates. The isolate MA1 was identified as Bipolaris bicolor based on the morphological characteristics and multigene phylogenetic analysis. Among fungicides, prochloraz, iprodione and pyraclostrobin significantly inhibited hyphal growth of B. bicolor under in vitro conditions. This study constitutes the first report on the association of B. bicolor with leaf spot disease of rubber trees worldwide.     

气候变化背景下橡胶树物候研究进展

橡胶树(Heveabrasiliensis)是广布于热带地区的经济林木，是战略物资天然橡胶的主要来源，其物候学的研究对胶园生产管理和评估热带地区植被对全球气候变化的响应方面具有重要意义。早期的物候研究主要服务于苗木繁育、割胶规划和抗逆栽培等生产应用；利用遥感监测植被物候日趋成熟，已广泛应用于橡胶树并成为主流的物候监测方法；橡胶树物候具有明显的时空异质性，对气候变化的响应较为复杂，其中温度和降水是关键影响因子，同时内因(品系、基因和树龄等)和外因(种植密度、地理位置和农业措施等)也共同影响了其物候。为更好服务天然橡胶产业的可持续发展和热区气候变化科学研究，未来的橡胶树物候研究应重点关注多源遥感数据的协同重建、物候指标提取算法的普适化和遥感预测模型的精准化。该文系统梳理了橡胶树物候的监测方法、服务价值、时空格局，提出了存在问题及未来研究方向。     

The rubber tree (Hevea brasiliensis Muell. Arg.) homologue of the LEAFY/FLORICAULA gene is preferentially expressed in both male and female floral meristems

The rubber tree (Hevea brasiliensis Muell. Arg.) is an important source of natural rubber in tropical regions and, as with many woody species, shows a long juvenile phase. To understand the genetic and molecular mechanisms underlying the reproductive process in rubber trees, H. brasiliensis RRIM600 flower and inflorescence development have been characterized, the rubber tree FLORICAULA/LEAFY (FLO/LFY) orthologue, HbLFY, cloned, and its expression patterns were analysed during vegetative and reproductive development. The rubber tree, similar to other Euphorbiaceae species, produces lateral inflorescences containing male, female, and bisexual flowers. HbLFY is expressed in lateral meristems that give rise to inflorescences and in all flower meristems, consistent with a role in reproductive development. Complementation studies using Arabidopsis lfy mutants indicated that the biological function of LFY might be conserved among Brassicaceae and Euphorbiaceae species.     

Establishment of new crops for the production of natural rubber

Natural rubber is a unique biopolymer of strategic importance that, in many of its most significant applications, cannot be replaced by synthetic alternatives. The rubber tree Hevea brasiliensis is the almost exclusive commercial source of natural rubber currently and alternative crops should be developed for several reasons, including: a disease risk to the rubber tree that could potentially decimate current production, a predicted shortage of natural rubber supply, increasing allergic reactions to rubber obtained from the Brazilian rubber tree and a general shift towards renewables. This review summarizes our knowledge of plants that can serve as alternative sources of natural rubber, of rubber biosynthesis and the scientific gaps that must be filled to bring the alternative crops into production.     

Guayule and Russian Dandelion as Alternative Sources of Natural Rubber

ABSTRACT

Natural rubber, obtained almost exclusively from the Para rubber tree (Hevea brasiliensis), is a unique biopolymer of strategic importance that, in many of its most significant applications, cannot be replaced by synthetic rubber alternatives. Several pressing motives lead to the search for alternative sources of natural rubber. These include increased evidence of allergenic reactions to Hevea rubber, the danger that the fungal pathogen Microcyclus ulei, causative agent of South American Leaf Blight (SALB), might spread to Southeast Asia, which would severely disrupt rubber production, potential shortages of supply due to increasing demand and changes in land use, and a general trend towards the replacement of petroleum-derived chemicals with renewables. Two plant species have received considerable attention as potential alternative sources of natural rubber: the Mexican shrub Guayule (Parthenium argentatum Gray) and the Russian dandelion (Taraxacum koksaghyz). This review will summarize the current production methods and applications of natural rubber (dry rubber and latex), the threats to the production of natural rubber from the rubber tree, and describe the current knowledge of the production of natural rubber from guayule and Russian dandelion.     

Natural rubber,Hevea brasiliensis (Willd. ex A. Juss.) Müll. Arg, germplasm collection in the Amazon Basin, Brazil: A retrospective

Hevea brasiliensis (Willd. ex A. Juss.) Müll. Arg., whose center of diversity is the Amazon basin, is the major source of commercial rubber in the world. In the 1970s, the need for new Hevea germplasm arose from the realization that there was a gradual erosion of the genetic variability of the rubber clones in many natural rubber plantations. This erosion occurred because most of the clones in cultivation were derived from the few surviving seeds collected in 1876 by Henry Wickham. Therefore, to broaden the genetic base of the major producers of natural rubber, it became necessary to undertake an expedition to the Amazon basin to obtain materials for the ‘gene pool’ in these populations. This expedition, called “Germplasm 81,” was organized in four stages. Initially, there was a 1976 seminar organized by the International Rubber Research and Development Board (IRRDB); then, in 1977, a Hevea workshop took place, also organized by the IRRDB. A preliminary mission by IRRDB officials to several countries in South America and the Caribbean followed in 1978. Finally, the Germplasm exercise by scientists from IRRDB countries (Cote d’lvoire, Indonesia, Malaysia, Nigeria, and Thailand), China, and Brazil took place from January to April of 1981. A ‘dummy run’ to test the viability of seeds from Manaus, Brazil, was undertaken in 1979. The Germplasm collection covered three Brazilian states: Acre, Mato Grosso, and Rondônia. Collection teams traveled into the remotest parts of the Amazon rain forests looking for high-yielding and disease-resistant trees from which to collect seeds, budwood, and seedlings growing around the trees. Three teams collected a total of 64,256 seeds, 1413 meters of budwood, and 1160 seedlings. Following agreements with the Brazilian government, collected seeds were divided on a 50-50 basis between IRRDB and Brazil Materials for Brazil were retained in Manaus, while those for the IRRDB were initially sent to Britain for phytosanitary treatment and then to Guadeloupe for further quarantine in 1982, before being sent to Asian and African reception centers. Scientists who participated in the exercise had to undergo quarantine in a temperate country for at least one week before returning to their research institutions. This quarantine was an attempt to avoid the spread of the deadly South American leaf blight (SALB) disease. This disease has prevented Brazil from becoming a major world producer of natural rubber, despite attempts made by Goodyear and Firestone Rubber Companies, as well as Henry Ford in the early 1900s     

The powdery mildew disease of rubber (Oidium heveae) is jointly controlled by the winter temperature and host phenology

International Journal of Biometeorology - Rubber powdery mildew disease (Oidium heveae) is a serious threat to natural rubber production (Hevea brasiliensis) in some rubber developing regions of...     

橡胶草90年来主要研究成果及最新研究进展

天然橡胶是重要的国防战略物质,巴西橡胶树（Hevea brasiliensis（Willd.ex A.Juss.） Muell.Arg）是天然橡胶的唯一来源,天然橡胶商业化形式极为单一,潜在的供给不足问题亟待解决。因此,寻找可替代巴西橡胶树的产胶植物一直受到全世界高度重视。蒲公英属橡胶草（Taraxacum kok-saghyz Rodin）根部含有与橡胶树橡胶类似的天然橡胶分子,该植物主要分布在温带和寒带地区,具有易于机械化收获、生长周期短、遗传转化相对容易等特点,是最具开发潜力的产胶植物。本文对橡胶草90年（1931-2018）来的研究历史和主要成果进行了概括,对近10年取得的最新成果进行了深度分析,并预测橡胶草在未来天然橡胶产业中的作用,期望为开展橡胶草商业化生产和橡胶生物合成相关基础研究提供一定的参考。     

South American palaeobotany and the origins of neotropical rainforests

Extant neotropical rainforest biomes are characterized by a high diversity and abundance of angiosperm trees and vines, high proportions of entire-margined leaves, high proportions of large leaves (larger than 4500 mm2), high abundance of drip tips and a suite of characteristic dominant families: Sapotaceae, Lauraceae, Leguminosae (Fabaceae), Melastomataceae and Palmae (Arecaceae). Our aim is to define parameters of extant rainforests that will allow their recognition in the fossil record of South America and to evaluate all known South American plant fossil assemblages for first evidence and continued presence of those parameters. We ask when did these critical rainforest characters arise? When did vegetative parameters reach the level of abundance that we see in neotropical forests? Also, when do specific lineages become common in neotropical forests? Our review indicates that evidence of neotropical rainforest is exceedingly rare and equivocal before the Palaeocene. Even in the Palaeocene, the only evidence for tropical rainforest in South America is the appearance of moderately high pollen diversity. By contrast, North American sites provide evidence that rainforest leaf physiognomy was established early in the Palaeocene. By the Eocene in South America, several lines of evidence suggest that neotropical rainforests were diverse, physiognomically recognizable as rainforest and taxonomically allied to modern neotropical rainforests. A mismatch of evidence regarding the age of origin between sites of palaeobotanical high diversity and sites of predicted tropical climates should be reconciled with intensified collecting efforts in South America. We identify several lines of promising research that will help to coalesce previously disparate approaches to the origin, longevity and maintenance of high diversity floras of South America.     

A novel cDNA from Parthenium argentatum Gray enhances the rubber biosynthetic activity in vitro

Natural rubber (cis-1,4-polyisoprene) is an isoprenoid compound produced exclusively in plants by the action of rubber transferase. Despite a keen interest in revealing the mechanisms of rubber chain elongation and chain length determination, the molecular nature of rubber transferase has not yet been identified. A recent report has revealed that a 24 kDa protein tightly associated with the small rubber particles of Hevea brasiliensis, therefore designated small rubber particle protein (SRPP), plays a positive role in rubber biosynthesis. Since guayule (Parthenium argentatum Gray) produces natural rubber similar in size to H. brasiliensis, it is of critical interest to investigate whether guayule contains a similar protein to the SRPP. A cDNA clone has been isolated in guayule that shares a sequence homology with the SRPP, thus designated guayule homologue of SRPP (GHS), and the catalytic function of the protein was characterized. Sequence analysis revealed that the GHS is highly homologous in several conserved regions to the SRPP (50% identity). In vitro functional analysis of the recombinant protein overexpressed in E. coli revealed that the GHS plays a positive role in isopentenyl diphosphate incorporation into high molecular weight rubbers as SRPP does. These results indicate that guayule and Hevea rubber trees contain a protein that is similar in its amino acid sequence and plays a role in isopentenyl diphosphate incorporation in vitro, implying that it contributes to the enhancement of rubber biosynthetic activity in rubber trees.     

Synchronous flowering of the rubber tree (Hevea brasiliensis) induced by high solar radiation intensity

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.     

橡胶草90年来主要研究成果及最新研究进展

天然橡胶是重要的国防战略物质,巴西橡胶树( Hevea brasiliensis (Willd. ex A. Juss.) Muell. Arg)是天然橡胶的唯一来源,天然橡胶商业化形式极为单一,潜在的供给不足问题亟待解决。因此,寻找可替代巴西橡胶树的产胶植物一直受到全世界高度重视。蒲公英属橡胶草( Taraxacum kok-saghyz Rodin)根部含有与橡胶树橡胶类似的天然橡胶分子,该植物主要分布在温带和寒带地区,具有易于机械化收获、生长周期短、遗传转化相对容易等特点,是最具开发潜力的产胶植物。本文对橡胶草90年(1931 - 2018)来的研究历史和主要成果进行了概括,对近10年取得的最新成果进行了深度分析,并预测橡胶草在未来天然橡胶产业中的作用,期望为开展橡胶草商业化生产和橡胶生物合成相关基础研究提供一定的参考。     

西双版纳地区热带季节雨林与橡胶林林冠水文效应比较研究

季节雨林和橡胶林是西双版纳热带森林系统中可以代表原始林和大面积种植的人工林两种林型,采用水量平衡法,利用对以上两种林分林冠水文各分量1996～2001年的观测结果,初步分析其林冠水文效应,结果表明：一年内,季节雨林林冠截留量660．6mm,树干径流量80．7mm,穿透降雨量,853．2mm,分别占同期降雨总量的41．43％、5．24％、53．74％;橡胶林林冠截留量393．5mm,树干径流量104．1mm,穿透降雨量1096．8mm,分别占同期降雨总量的24．68％、6．68％、67．85％;两种林分森林水文各分量干、雨季差异显著,在研究中还发现,季节雨林中树干径流量随径级的增大而减小,干季出现密林(季节雨林)的穿透降雨量大于疏林(橡胶林)的反常现象;与我国其他地区相比,季节雨林和橡胶林有较大的林冠截留率及干流率。     

Studies on the Eeo-Physiological Indices of Rubber Trees at Chilling Temperature

Rubber trees (Hevea brasilieasis Muell-Arg.) like other tropical trees, are very sensitive to chilling temperature. It may cause metabolic disturb ances and make severe injuries to the tree. The ecophysiological indices introduced in this paper are transpiration rate, osmotic pressure, pretoplasmic viscosity, protoplasmic permeability and water content. These indices can be used to estimate relative cold resistance of different clones or individual rubber seedlings. The results our measurements are summarized in the following table.     

Laticiferous plants of economic importance

Gutta-gums figure prominently in international trade. For more than 100 years the United States has been, and continues to be, the principal cousumer of these raw materials. Trade reports issued by the U. S. Department of Commerce indicate that during 1960 approximately 11,717,000 pounds of these forest products, with an aggregate value of $6,536,792, were imported, mostly from Malaysia, Central America, and northern South America. These commodities are still furnished mainly by “wild” trees. Plantation development has been limited to small-scale propagation of guttapercha (Palaquium gutta Burck) in Indonesia and Malaya and recently of chilte (Cnidoscolus spp.) in western Mexico. In comparison with Hevea brasiliensis (Willd. ex Adr. Juss.) Muell. Arg., Castilla elastica Cerv., and other species of rubber, relatively little has been published on the sources of gutta-gums.     

Monoterpene emissions from rubber trees (Hevea brasiliensis) in a changing landscape and climate: chemical speciation and environmental control

Emissions of biogenic volatile organic compounds (VOCs) have important roles in ecophysiology and atmospheric chemistry at a wide range of spatial and temporal scales. Tropical regions are a major global source of VOC emissions and magnitude and chemical speciation of VOC emissions are highly plant-species specific. Therefore it is important to study emissions from dominant species in tropical regions undergoing large-scale land-use change, for example, rubber plantations in South East Asia. Rubber trees ( Hevea brasiliensis ) are strong emitters of light-dependent monoterpenes. Measurements of emissions from leaves were made in the dry season in February 2003 and at the beginning of the wet season in May 2005. Major emitted compounds were sabinene, α -pinene and β -pinene, but β -ocimene and linalool also contributed significantly at low temperature and light. Cis -ocimene was emitted with a circadian course independent of photosynthetic active radiation (PAR) and temperature changes with a maximum in the middle of the day. Total isoprenoid VOC emission potential at the beginning of the wet season (94 μg gdw⁻¹ h⁻¹) was almost two orders of magnitude higher than measured in the dry season (2 μg g dw⁻¹ h⁻¹). Composition of total emissions changed with increasing temperature or PAR ramps imposed throughout a day. As well as light and temperature, there was evidence that assimilation rate was also a factor contributing to seasonal regulating emission potential of monoterpenes from rubber trees. Results presented here contribute to a better understanding of an important source of biogenic VOC associated with land-use change in tropical South East Asia.     

Phytoseiidae mites associated with Hevea spp. from the Amazon region: a hidden diversity under the canopy of native trees

Despite the Amazon Forest being the largest tropical forest in the world, and cradle of rubber trees (Hevea brasiliensis), no studies have aimed to report the occurrence of mites associated with native trees from this ecosystem. Our survey investigates the phytoseiid mites associated with five species of native rubber trees from nine sites of the Amazon Forest, and also presents a major review of phytoseiid species from natural vegetation in Brazil. We found a total of 1305 mites, belonging to 30 species, of which seven were new to science, Amblydromalus akiri sp. nov., Amblyseius chicomendesi sp. nov., Amblyseius duckei sp. nov., Amblyseius manauara sp. nov., Iphiseiodes katukina sp. nov., Iphiseiodes raucuara sp. nov. and Typhlodromips igapo sp. nov.; beyond two new records for Brazil, Iphiseiodes kamahorae and Amblyseius martus. Our results emphasize the importance of Amazon native trees as an unexplored source of predator mites, which in turn may be further studied as biological control agents of pest mites on rubber trees. The impressive diversity, endemism and rate of new species found highlight the importance of studies on arthropod communities associated with the Amazon vegetation.     

巴西橡胶树(Hevea brasiliensis)微管相关蛋白全长cDNA克隆及表达分析

从巴西橡胶树Hevea brasiliensis差减cDNA文库中分离到微管相关蛋白（Microtubule-associated protein,MAPs）基因片段,根据该基因片段序列信息,设计特异引物,采用cDNA末端快速扩增技术RACE（Rapid Amplification ofcDNA Ends）进行差异片段的5＇和3＇端的扩增,获得了长度为788bp的全长cDNA,该基因在GenBank中的登录号为AY461412.序列分析表明该基因包含完整的开放阅读框,编码144个氨基酸,与微管相关蛋白基因家族具有很高的同源性,推测该基因是微管相关蛋白基因.半定量RT-PCR检测证实它在胶乳中的表达强于叶中,胁迫处理（伤害及乙烯处理）使其表达上调.