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。     

橡胶草的研究进展

天然橡胶是一种不可替代的重要战略工业原料, 用途广泛。巴西橡胶树作为天然橡胶的主要来源, 受种植面积限制, 难以满足全球日益增长的对天然橡胶的需求。而南美叶疫病也是巴西橡胶树(Hevea brasiliensis)安全的潜在威胁。蒲公英属产胶植物(橡胶草)最早发现于20世纪30年代, 可产生高质量的天然橡胶, 具有生长周期短、地理适应范围广、适合机械化生产等特点, 被认为是一种理想的产胶备选作物。该文从橡胶草种质资源、遗传改良、栽培技术及产胶生物学机制等方面综述了国内外橡胶草的研究进展和存在的问题, 并为我国开展橡胶草相关研究提出建议。     

天然橡胶溯源

植物界约有900个属,大约1．2万种植物含有乳液,其中在76个科的约2000种植物中含有橡胶,重要的产胶植物除了大激科的巴西橡胶树外,还有菊科的橡胶草和银胶菊、杜仲科的杜仲、桑科的印度榕、大前科的木薯橡胶等,由于巴西橡胶树具有胶乳产量高、橡胶品质好、经济寿命长的特点,加上栽培容易,采割方便,生产成本低的优点,而成为人＿工栽培最重要的橡胶植物。自巴西橡胶树在东南亚引种成功后,其产甲已占世界天然橡胶总产量的99％以＿t,;B前世界上有41个种植巴西橡胶树的国家．种植面积约为1000万公顷,年产干胶50O多万吨。巴西橡胶树…     

产胶植物橡胶转移酶的研究进展

天然橡胶合成中,橡胶转移酶催化异戊二烯焦磷酸的多聚化过程,这一过程对天然橡胶的品质及产量至关重要。橡胶转移酶及其性质、橡胶生物合成分子机理及橡胶的分子量大小决定机制是亟待解决的重要科学问题。本文介绍了以巴西橡胶树为主的产胶植物橡胶转移酶的性质和生物学功能,对橡胶转移酶的分离与鉴定及其活性调节等研究进展进行了综述。     

橡胶树“死皮”及其防控策略探讨

天然橡胶是一种重要的工业原料,在2 000多种产胶植物中,巴西橡胶树(Hevea brasiliensisMuell.Arg.)以橡胶含量高、质量好、经济寿命长、易采收等独特优点成为天然橡胶的主要来源。作为典型的热带雨林乔木,全球适合橡胶树种植的土地资源极其有限,因而增加橡胶树的单位面积产量一直都是橡胶生产的核心任务。随着高产无性系的大力推广和乙烯利刺激割胶制度的广泛应用,橡胶单产目前已达到了前所未有的高度。然而,由于种种原因,橡胶树产排胶过程中会出现割线局部或全部不排胶的现象,即所谓的"死皮"。"死皮"给橡胶生产带来了巨大的损失(每年造成的干胶损失已超过15%),目前已成为制约橡胶树单产提高的主要因素。由于"死皮"成因的复杂性,至今对"死皮"的发生发展规律知之甚少。结合生产实践,讨论了不同"死皮"类型的主要特征和发生规律,并针对不同"死皮"类型、严重程度提出了一些切实可行的防控策略。     

天然橡胶生产的高产高效措施

世界上人工栽培的橡胶树原产于巴西亚马逊河流域,故称为巴西橡胶树。我国云南于1904年开始引种巴西橡胶树,1906年引入海南岛。新中国成立后,我国天然橡胶有了长足的发展,从1950年200吨,至1994年37万吨,增加1850倍！主产区海南省,产胶量占全国的60％以上,累计提供国产天然胶200多万吨。目前我国天然橡胶年产量居世界第四位,植胶面积居第五位。事实推翻了国外关于北纬15度以北不能种橡胶树的传统论断,我同天然橡胶业正成功地在北纬18－24度之间得到不断发展。然而,我国华南常受风、寒、旱等不良因素危害,橡胶破位面积产链和劳动生…     

植物体中橡胶的合成

橡胶是最重要的天然产物之一。它含于很多植物的乳液中,可是只有其中某些如巴西橡胶树(Hevea brasiliensis),山橡胶草(Scorzonera lausa ghyz),银色橡胶菊(Parthenium argentatum)等植物才有工业上的意义。根据橡胶本身的化学性质,它是由很多异戊二烯单位用1,4位联结而构成的碳氢化合物(顺式):     

巴西橡胶树的分子生物学研究进展

巴西橡胶树是一种重要的热带经济作物,由于橡胶树体内橡胶含量多,且容易采收,所以橡胶树一直是天然橡胶的商业来源。相比于模式植物和粮食等经济作物来说,分子生物学研究显滞后。,而且橡胶树是多年生乔木,经济性状多集中于胶乳,因此研究难度大,研究也不多,本就巴西橡胶的分子生物学方面的研究进行综述。     

橡胶树HbCBF1蛋白的原核表达及其CRT结合活性分析(简报)

巴西橡胶树（Hevea brasiliensis）,是大戟科橡胶树属植物．原产于巴西亚马逊河流域,是典型的热带高大乔木．所生产的橡胶是天然橡胶的重要来源。在我国．橡胶树栽培区主要分布在北纬18°到24°．冬季常常遭到寒潮和冷空气的侵袭。30多年来的植胶历史证明．寒害是我国植胶区较为严重的自然灾害．是影响我国橡胶栽培的主要自然灾害之一。对橡胶树进行低温、抗寒生理研究,明确橡胶树的低温反应和抗寒机制．在理论和实践上都有重要意义。     

橡胶树产胶量影响因素

橡胶树(Hevea brasiliensis)的乳状汁液是天然橡胶的最主要来源,其产胶量受很多因素的制约。本文从气象因子、土壤营养成分、常见病虫害、割胶制度和技术、品种和胶园管理等方面综合分析了影响橡胶树产胶量的因素及相关机理。温度、降雨和太阳辐射是影响产胶量的主要气象因子,它们相互影响并以累加效应作用于橡胶产胶;主要土壤营养元素氮、钾、磷和镁通过影响光合作用等影响胶乳合成,并因影响胶乳的稳定性而影响排胶;此外,病虫害、割胶制度和技术、橡胶树品种、树龄及胶园管理措施等都会对产胶量产生相应的影响。综合对以上影响因素及机理的分析,本文旨在为橡胶树产胶的科学研究和生产实践提供理论参考。     

Genetic diversity and evolutionary patterns of Taraxacum kok‐saghyz Rodin

Taraxacum kok‐saghyz Rodin (TKS) is an important potential alternative source of natural inulin and rubber production, which has great significance for the production of industrial products. In this study, we sequenced 58 wild TKS individuals collected from four different geography regions worldwide to elucidate the population structure, genetic diversity, and the patterns of evolution. Also, the first flowering time, crown diameter, morphological characteristics of leaf, and scape of all TKS individuals were measured and evaluated statistically. Phylogenetic analysis based on SNPs and cluster analysis based on agronomic traits showed that all 58 TKS individuals could be roughly divided into three distinct groups: (a) Zhaosu County in Xinjiang (population AB, including a few individuals from population C and D); (b) Tekes County in Xinjiang (population C); and (c) Tuzkol lake in Kazakhstan (population D). Population D exhibited a closer genetic relationship with population C compared with population AB. Genetic diversity analysis further revealed that population expansion from C and D to AB occurred, as well as gene flow between them. Additionally, some natural selection regions were identified in AB population. Function annotation of candidate genes identified in these regions revealed that they mainly participated in biological regulation processes, such as transporter activity, structural molecule activity, and molecular function regulator. We speculated that the genes identified in selective sweep regions may contribute to TKS adaptation to the Yili River Valley of Xinjiang. In general, this study provides new insights in clarifying population structure and genetic diversity analysis of TKS using SNP molecular markers and agronomic traits.     

Wild trees in the Amazon basin harbor a great diversity of beneficial endosymbiotic fungi: is this evidence of protective mutualism?

It has been shown that the disappearance of, or drastic changes in, ancestral and indigenous (or native) endosymbiotic microbiota can lead to many adverse health consequences. However, the effects of changes in beneficial endosymbionts in plants are poorly known (except for mycorrhizal and rhizobial associations). We sampled and compared endophytes from hundreds of trees belonging to the economically important genus Hevea, the source of natural rubber, in their native range in the Amazon basin and in plantations. We also conducted antagonism tests to determine the potential effects that some of these endophytes may have on selected plant pathogenic fungi. The natural and indigenous endosymbiotic mycota of the rubber tree (Hevea) contains a high diversity of beneficial fungi that may protect against pathogens (protective mutualism). In contrast, plantation trees have a reduced and different diversity of these beneficial fungi. We propose that abundance, and not just presence, of competitive fungal strains and species (i.e., Trichoderma and Tolypocladium) create a protective effect against pathogens in wild trees. This study provides support for the importance of mutualistic endosymbionts in plant health and ecosystem resilience, and calls for awareness of their potential loss by human-related activities.     

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.     

Antioxidant Sources from Leaves of Russian Dandelion

Taraxacum kok‐saghyz (TKS) is a dandelion species native to Kazakhstan, Uzbekistan and north‐west China, considered as a promising alternative source of natural rubber from its roots. The aim of this study was to investigate the possible exploitation of TKS leaves, a rubber byproduct, as a source of phenolic compounds with antioxidant properties for potential applications in forage, nutraceutical and pharmacological fields. Two accessions (TKS016, TKS018) grown under Mediterranean conditions of Sardinia were evaluated at vegetative and flowering stages. The leaves of TKS018 had the highest antioxidant capacity (19.6 mmol trolox equivalent antioxidant capacity 100 g^?1), total phenolic (106.4 g gallic acid equivalent kg^?1), tannic phenolics (58.5 g gallic acid equivalent kg^?1) and total flavonoid contents (22.9 g catechin equivalent kg^?1). At both phenological stages, TKS016 showed significantly lower values than TKS018 in 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH), total phenolic and tannic phenolics. Six individual molecules were identified, namely chlorogenic, cryptochlorogenic, caffeic, sinapic, chicoric and 3,4‐dimethoxycinnamic acids. Chicoric (8.53–10.68 g kg^?1 DW) and chlorogenic acids (4.18–7.04 g kg^?1 DW) were the most abundant. TKS leaves represent a valuable source of chicoric acid with potential application as antioxidant to be used as herbal medicine and nutrition for production of healthy food/feed.     

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.     

Historical and recent achievements in the field of microbial degradation of natural and synthetic rubber

This review intends to provide an overview of historical and recent achievements in studies of microbial degradation of natural and synthetic rubber. The main scientific focus is on the key enzymes latex-clearing protein (Lcp) from the Gram-positive Streptomyces sp. strain K30 and rubber oxygenase A (RoxA) from the Gram-negative Xanthomonas sp. strain 35Y, which has been hitherto the only known rubber-degrading bacterium that does not belong to the actinomycetes. We also emphasize the importance of knowledge of biodegradation in industrial and environmental biotechnology for waste natural rubber disposal.     

Micro‐organisms in latex and natural rubber coagula of Hevea brasiliensis and their impact on rubber composition,structure and properties

Natural rubber, produced by coagulation of the latex from the tree Hevea brasiliensis, is an important biopolymer used in many applications for its outstanding properties. Besides polyisoprene, latex is rich in many nonisoprene components such as carbohydrates, proteins and lipids and thereby constitutes a favourable medium for the development of micro‐organisms. The fresh rubber coagula obtained by latex coagulation are not immediately processed, allowing the development of various microbial communities. The time period between tree tapping and coagula processing is called maturation, during which an evolution of the properties of the corresponding dry natural rubber occurs. This evolution is partly related to the activity of micro‐organisms and to the modification of the biochemical composition. This review synthesizes the current knowledge on microbial populations in latex and natural rubber coagula of H. brasiliensis and the changes they induce on the biochemistry and technical properties of natural rubber during maturation.     

Population Genetics of the Rubber-Producing Russian Dandelion (Taraxacum kok-saghyz)

The Russian dandelion, Taraxacum kok-saghyz (TKS), is a perennial species native to Central Asia that produces high quality, natural rubber. Despite its potential to help maintain a stable worldwide rubber supply, little is known about genetic variation in this species. To facilitate future germplasm improvement efforts, we developed simple-sequence repeat (SSR) markers from available expressed-sequence tag (EST) data and used them to investigate patterns of population genetic diversity in this nascent crop species. We identified numerous SSRs (1,510 total) in 1,248 unigenes from a larger set of 6,960 unigenes (derived from 16,441 ESTs) and designed PCR primers targeting 767 of these loci. Screening of a subset of 192 of these primer pairs resulted in the identification of 48 pairs that appeared to produce single-locus polymorphisms. We then used the most reliable 17 of these primer pairs to genotype 176 individuals from 17 natural TKS populations. We observed an average of 4.8 alleles per locus with population-level expected heterozygosities ranging from 0.28 to 0.50. An average pairwise F_ST of 0.11 indicated moderate but statistically significant levels of genetic differentiation, though there was no clear geographic patterning to this differentiation. We also tested these 17 primer pairs in the widespread common dandelion, T. officinale, and a majority successfully produced apparently single-locus amplicons. This result demonstrates the potential utility of these markers for genetic analyses in other species in the genus.