Source Of Natural Rubber Research Articles

ISOLATION AND ANALYSIS OF NATIVE DNA AND RNA FROM ROOTS OF RUBBER-PRODUCING SPECIES SCORZONERA TAU-SAGHYZ LIPSCH. ET G.G. BOSSE

Scorzonera tau-saghyz Lipsch. et G.G.Bosse, is endemic species, growing in South Kazakhstan and alternative (to Hevea brasilians) source of natural rubber, related to the Asteraceae Family. Natural rubber (NR) is an indispensable raw material for the production of different products for medicine, automotive and aviation industries. The introduction of tau-saghyz into the culture will make it possible to obtain NC not only in Kazakhstan, but also on the territory of the countries of the Northern latitudes. At the growing phases of ontogenesis of tau-saghyz (April-June) latex is actively synthesized in the leaves and transported to the roots. In our experiments it was necessary to conduct molecular genetic studies of the selected forms of tau-saghyz with high rubber concentration. In this regard, it became necessary to isolate and analyze native DNA and RNA from dry roots. Samples with the highest rubber content were used for DNA extraction. The main problem in the isolation of DNA from the dry roots of tau-saghyz is the significant content of natural rubber. In this research the following commercial kits were used: 1) DNeasy Plant Mini Kit (Qiagene); 2) GenElute Plant Genomic DNA Miniprep Kit (Sigma); 3) NucleoSpin® Plant II / Midi / Maxi kit (Macherey-Nagel). Further DNA isolation was carried out in accordance with the kit manufacturer's protocol. Quantitative DNA analysis was performed using both UV spectrophotometry (Nanodrop) and fluorometric analysis (Qubit) method. DNA extracted by the 2 kit (Sigma) was further purified by precipitation with ethanol and demonstrates satisfactory quality. Functional analysis of isolated DNA samples was performed both by restriction analysis and by DNA amplification. It is worth to mention that for reaction primers that are characteristic of gene AACT (ACETOACETYL-COA TRANSFERASE) Cucumis melo were used. This enzyme catalyzes the first reaction of biosynthesis in the mevalonate pathway, which the final product is IDP (isopentenyl diphosphate). The cis-prenyltransferase (CPT) enzyme catalyzes the biosynthesis of rubber by the sequential addition of IDP to the terminal group of the initiating allylic pyrophosphate (APP). As a result of PCR analysis a putative 1200 bp AAST gene for tau-saghyz was identified. In this study two methods of RNA isolation were chosen: 1. A method widely used for plants of the Cucurbitaceae family; 2. A method approved for plants with a high content of polyphenols. The RNA isolation was carried out as described in the relevant protocols with minor modifications (Verwoerd TC, Dekker BMM, Hoekema A (1989) A small-scale procedure for the rapid isolation of plant RNAs. Nucleic Acids Res 17:2362). The final precipitates were dissolved in 50 µl of water pretreated with diethylpyrocarbonate. Quantitative analysis of RNA was carried out using UV spectrophotometry (Nanodrop). Functional analysis of extracted RNA samples was conducted by cDNA synthesis with usage of reverse transcriptase Superscript IV with the following amplification in PCR. In this reaction the primers specific for CPT gene of Taraxacum kok-saghyz were used. The prospective CPT gene was excised from the gel, purified and cloned into the pJET vector. In the further research it is planned to perform its sequencing and comparison with the CPT gene of Taraxacum kok-saghyz and Hevea brasiliensis.

Reviving Natural Rubber Synthesis via Native/Large Nanodiscs.

Natural rubber (NR) is utilized in more than 40,000 products, and the demand for NR is projected to reach $68.5 billion by 2026. The primary commercial source of NR is the latex of Hevea brasiliensis. NR is produced by the sequential cis-condensation of isopentenyl diphosphate (IPP) through a complex known as the rubber transferase (RTase) complex. This complex is associated with rubber particles, specialized organelles for NR synthesis. Despite numerous attempts to isolate, characterize, and study the RTase complex, definitive results have not yet been achieved. This review proposes an innovative approach to overcome this longstanding challenge. The suggested method involves isolating the RTase complex without using detergents, instead utilizing the native membrane lipids, referred to as "natural nanodiscs", and subsequently reconstituting the complex on liposomes. Additionally, we recommend the adaptation of large nanodiscs for the incorporation and reconstitution of the RTase complex, whether it is in vitro transcribed or present within the natural nanodiscs. These techniques show promise as a viable solution to the current obstacles. Based on our experimental experience and insights from published literature, we believe these refined methodologies can significantly enhance our understanding of the RTase complex and its role in in vitro NR synthesis.

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

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

Rubber (Hevea brasiliensis) Seed shell Activated Carbon Preparation, Characterization and Antibacterial Activity Studies

In Thailand, the rubber tree is widely used as a source of natural rubber and their seeds have been found to be rich in oil production. The seed shell is the residue and not edible but abundantly available in the country. Therefore, the objective of this work was to prepare activated carbon (AC) from rubber seed shells. ACs were produced by chemical activation and their characteristics were investigated. The effects of activation temperature and chemical impregnation time in the agent were examined. Proximate analysis was investigated and the results were within the standard of AC. The adsorption capacity was demonstrated with BET, iodine, and methylene blue number. The best produced AC (700 °C of activation temperature and 24 h of impregnation time) provided the highest BET surface area, iodine and methylene blue number were 923 m2/g, 1,234±24 mg/g and 1,204±10 mg/g, respectively. FT-IR spectrum indicates the presence of oxygen and nitrogen containing surface functional groups such as -OH, -CH3, -CH2, C=C, C-O, and N-H groups. The microstructure of the produced ACs was examined by SEM and the results found that they are porosity. The antibacterial effect results were discovered to be also effective against E. coli and S. aureus after 3 h and 24 h of contact times, respectively. In addition, the prepared AC also provided many properties that are better than those obtained by the commercial AC. Finally, it can be concluded that, AC from rubber seed shell can be applied as a low cost and possible alternate adsorbent.

Alkaline pretreatment of Taraxacum kok-saghyz (TK) roots for the extraction of natural rubber (NR)

Natural rubber (NR) is an essential biomaterial the supply of which is insecure. Taraxacum kok-saghyz (TK), a rubber-producing dandelion, is an alternative source of NR that has excellent potential for commercial development. Scalable methods for rubber extraction at high yield, quality and purity are needed to meet this potential. We previously developed an aqueous, enzymatic method for the extraction and purification of NR from TK roots. Alkaline pretreatment significantly improved the yield of TK NR using this method, but its effects on NR yield, purity and quality at a range of base concentrations and temperatures was not tested. In this study, TK roots (after inulin extraction) were pretreated at sodium hydroxide loading rates of 0, 33, 66 and 132 mg NaOH/g and temperatures of 25, 70, 125 and 160 °C. Treatment with pectinase and cellulase enzymes was used to solubilize root structural carbohydrates and liberate NR. Rubber quality and impurities were then characterized. Results showed that increasing NaOH loading rate and temperature significantly improved rubber yield, but reduced rubber molecular weight and rubber gel content. Rubber purity and thermal properties were largely unaffected by pretreatment conditions. FTIR and SEM analysis revealed that alkaline pretreatment primarily altered protein and other secondary components of TK NR.

Nitrous oxide emissions, N uptake, biomass, and rubber yield in N-fertilized, surface-irrigated guayule

Nitrous oxide (N2O) emissions from N fertilizer applied to row crops makes up a large portion of the greenhouse gas loading to the atmosphere. Guayule (Parthenium argentatum A. Gray) is a desert perennial shrub being promoted for Central Arizona farmers as a source of natural rubber and hypoallergenic latex. Emissions of the greenhouse gas N2O and crop N uptake have not been previously quantified in this multi-year cropping system. A 2.5-year study was conducted on transplanted and surface-irrigated guayule on a Casa Grande sandy loam in Maricopa, AZ to assess the agronomic and environmental responses to N fertilizer application rate. Four N fertilizer rates ranging from 0 to 252 kg N ha−1 were applied as ammonium sulfate in three splits. Nitrous oxide emissions were measured with 1-L vented chambers 34 times over 98 weeks from 17 April 2013 to 6 March 2015 with pauses during winter dormant seasons. Nitrogen rate significantly affected N2O emissions, which ranged from 1.2 to 4.5 kg N ha−1 for the 0 and 252 kg N ha−1 fertilizer rates. Emission factors were 1.5, 1.4, and 1.3 % of the added ammonium sulfate-N emitted as N2O for 84, 168, and 250 kg N ha−1, respectively, which are in the range of those for other better-studied crops such as corn (Zea mays L.) and cotton (Gossypium hirsutum L.) Nitrogen uptake by guayule averaged 191 kg N ha−1 for biomass and rubber yields of 19 Mg ha−1 and 1070 kg ha−1, respectively. There was no effect of N rate on N uptake, biomass, or rubber yields because of initial soil profile nitrate (NO3) levels of 85–150 kg NO3-N ha−1. A N balance of inputs (initial soil NO3, N fertilizer, NO3-N added in irrigation) and outputs (N uptake, N2O, and dinitrogen (N2) emissions) was constructed. Unaccounted-for N was apparently lost as NO3 leaching below the root zone. In conclusion, the informative N2O emissions data presented are the first for guayule, and the N uptake levels reported here can be used in updated, improved N fertilizer recommendations for guayule.

TABLE OF CONTENTS AND LOCALIZATION OF RUBBER IN THE ROOTS OF KOK-SAGHYZ (Taraxacum kok-saghyz Rodin)

This article presents biological features, botanical description, and the results of the anatomical and physiological study of the Dandelion kok-saghyz (Taraxacum kok-saghyz Rodin), a valuable resource plant of world significance. Kok-saghyz is used as a technical culture, a source of high-quality rubber. Natural rubber is widely used in the rubber industry for the production of tires for automobiles, aircrafts, bicycles, as well as shoes, medical gloves and other products. The global rubber industry faces the real danger of the destruction of plantations of the main source of natural rubber - the rubber tree of hevea (Hevea brasiliensis), grown in the tropical humid climate of Southeast Asia, due to its diseases. This has happened in South America, which was originally a world center for the production of natural rubber; it has completely lost its position due to epiphytotics. There is currently a phytosanitary quarantine and a person who was accessed to hevea in South America should not visit the countries of Southeast Asia. Thus, there is a need for reserve additional plant species, the sources of natural rubber in the temperate zone, being adverse for acclimatization of hevea. Dandelion kok-saghyz is recognized as such a promising producer of natural rubber. According to data published, rubber of kok-saghyz sits in the latex vessels of the root, and the rubber content (6 to 14%) depends on the number of circles of the latex vessels (3 to 14). The number of circles of the latex vessels and, therefore, the rubber content in the roots depends on genotype, agricultural background and stage of kok-saghyz ontogenesis. The roots of kok-saghyz are known for high variability in the rubber content even in the same natural population of wild kok-saghyz from 0 to 47.87; 35.85 and 23.58% of the air-dry weight is due to several one-year covers in the root. Kok-saghyz is a highly polymorphic species that can be used in breeding programs. Individual selection provides for the high rubber content in the roots of kok-saghyz (10 to 14%). Currently, kok-saghyz is an important rubber plant with the following features: 1) high percentage of rubber; 2) flowering and fruiting in the first year of life; 3) high quality rubber. Kok-saghyz polymorphism provides for the selection of the most rubber-bearing and most precocious forms of this plant.

A high-throughput quantification of resin and rubber contents in Parthenium argentatum using near-infrared (NIR) spectroscopy

BackgroundGuayule (Parthenium argentatum A. Gray), a plant native to semi-arid regions of northern Mexico and southern Texas in the United States, is an alternative source for natural rubber (NR). Rapid screening tools are needed to replace the current labor-intensive and cost-inefficient method for quantifying rubber and resin contents. Near-infrared (NIR) spectroscopy is a promising technique that simplifies and speeds up the quantification procedure without losing precision. In this study, two spectral instruments were used to rapidly quantify resin and rubber contents in 315 ground samples harvested from a guayule germplasm collection grown under different irrigation conditions at Maricopa, AZ. The effects of eight different pretreatment approaches on improving prediction models using partial least squares regression (PLSR) were investigated and compared. Important characteristic wavelengths that contribute to prominent absorbance peaks were identified.ResultsUsing two different NIR devices, ASD FieldSpec®3 performed better than Polychromix Phazir™ in improving R2 and residual predicative deviation (RPD) values of PLSR models. Compared to the models based on full-range spectra (750–2500 nm), using a subset of wavelengths (1100–2400 nm) with high sensitivity to guayule rubber and resin contents could lead to better prediction accuracy. The prediction power of the models for quantifying resin content was better than rubber content.ConclusionsIn summary, the calibrated PLSR models for resin and rubber contents were successfully developed for a diverse guayule germplasm collection and were applied to roughly screen samples in a low-cost and efficient way. This improved efficiency could enable breeders to rapidly screen large guayule populations to identify cultivars that are high in rubber and resin contents.

Transcriptomic and evolutionary analysis of the mechanisms by which P. argentatum, a rubber producing perennial, responds to drought

BackgroundGuayule (Parthenium argentatum Gray) is a drought tolerant, rubber producing perennial shrub native to northern Mexico and the US Southwest. Hevea brasiliensis, currently the world’s only source of natural rubber, is grown as a monoculture, leaving it vulnerable to both biotic and abiotic stressors. Isolation of rubber from guayule occurs by mechanical harvesting of the entire plant. It has been reported that environmental conditions leading up to harvest have a profound impact on rubber yield. The link between rubber biosynthesis and drought, a common environmental condition in guayule’s native habitat, is currently unclear.ResultsWe took a transcriptomic and comparative genomic approach to determine how drought impacts rubber biosynthesis in guayule. We compared transcriptional profiles of stem tissue, the location of guayule rubber biosynthesis, collected from field-grown plants subjected to water-deficit (drought) and well-watered (control) conditions. Plants subjected to the imposed drought conditions displayed an increase in production of transcripts associated with defense responses and water homeostasis, and a decrease in transcripts associated with rubber biosynthesis. An evolutionary and comparative analysis of stress-response transcripts suggests that more anciently duplicated transcripts shared among the Asteraceae, rather than recently derived duplicates, are contributing to the drought response observed in guayule. In addition, we identified several deeply conserved long non-coding RNAs (lncRNAs) containing microRNA binding motifs. One lncRNA in particular, with origins at the base of Asteraceae, may be regulating the vegetative to reproductive transition observed in water-stressed guayule by acting as a miRNA sponge for miR166.ConclusionsThese data represent the first genomic analyses of how guayule responds to drought like conditions in agricultural production settings. We identified an inverse relationship between stress-responsive transcripts and those associated with precursor pathways to rubber biosynthesis suggesting a physiological trade-off between maintaining homeostasis and plant productivity. We also identify a number of regulators of abiotic responses, including transcription factors and lncRNAs, that are strong candidates for future projects aimed at modulating rubber biosynthesis under water-limiting conditions common to guayules’ native production environment.

Possibility of artocarpus heterophyllus latex as an alternative source for natural rubber

Abstract Natural rubber (NR) has much application in rubber product manufacturing industries, which cannot be replaced by synthetic rubber. At present, Hevea rubber tree is the only economical and commercially viable source of NR. Therefore, the objective of the present research was to find alternative source of NR. NR mainly comprise of cis-1,4 polyisoprene. Artocarpus heterophyllus latex (jackfruit latex) was collected and analyzed to investigate if it can be considered as alternative source of NR. It was found from FTIR, 1H NMR and GC-MS study that jackfruit latex contains both cis-1,4 polyisoprene and trans- 1,4 polyisoprene along with few other chemical constituents. However, molecular weight of jackfruit latex is significantly lower than the NR. Because of low molecular weight polymer and presence of several other chemical constituents as impurity, jackfruit latex does not impart significant mechanical properties in vulcanized rubber compound, but it provides additional wet skid resistance (WSR) and aid in better dispersion of carbon black in rubber compound. Therefore, jackfruit latex cannot be used to replace NR, but can be used as low molecular weight natural resin, especially to improve dispersion of carbon black in rubber compound and to enhance WSR for tire.

NATURAL RUBBER BIOSYNTHESIS: STILL A MYSTERY

ABSTRACT Currently, Hevea brasiliensis (the Brazilian rubber tree) is the only commercially available source of natural rubber (NR) for use in many products, which vary from tires to medical products such as adhesive bandages. H. brasiliensis NR is used in these products because after vulcanization, superior properties, which include elasticity, abrasion resistance, and efficient heat dispersion, result. Issues, such as increasing demand and risk of a single source, make a synthetic (manmade) NR an attractive option. However, after years of research efforts, the exact structure of high-molecular-weight NR is still unproven, and a synthetic NR with similar properties to H. brasiliensis NR still has not been developed. To create a replacement synthetic rubber for H. brasiliensis NR, we believe an understanding of NR biosynthesis is necessary. We present a view of NR biosynthesis from a polymer chemistry viewpoint that is based on insight into the mechanism and kinetics of living carbocationic polymerization.

Rapid and complete removal of guayule (Parthenium argentatum) leaves by cryodefoliation, and freeze and thaw induction of rubber particle coagulation

Production of natural rubber (NR), a vital natural resource for modern economies, currently is completely dependent upon tropical cultivation of the Para rubber tree (Hevea brasiliensis, Müll. Arg). One promising source of alternative rubber is guayule (Parthenium argentatum, Gray), which is currently being developed as an alternative source of NR. Guayule rubber accumulates as rubber particles in bark parenchyma and can be extracted in the form of latex by homogenizing the bark and then separating the latex from the non-latex components by centrifugation. Latex separation and purification processes are significantly hindered by fine solids from the co-homogenized leaves. Therefore, complete removal of leaves before homogenization is highly desired. However, guayule leaves do not naturally abscise and chemical defoliants cannot be utilized since these dehydrate the shrub and coagulate the latex, and physical leaf removal processes are tedious or inefficient. We demonstrate that liquid nitrogen can be used to embrittle the leaves without freezing the bark parenchyma, completely removing the leaves with a single physical blow, and then the defoliated branches can be homogenized with no loss of latex-containing bark and no leaf contamination. Under longer freezing times, rubber coagulation occurred in partially frozen tissue and during slow thawing. Furthermore, we demonstrate that the rubber coagulation, which occurs when guayule branches are frozen through and thawed before homogenization, can be avoided by rapid homogenization of the flash frozen branches in ambient temperature aqueous extraction buffer.

Progress in Direct Seeding of an Alternative Natural Rubber Plant, Taraxacum kok-saghyz (L.E. Rodin)

Natural rubber (NR) is currently sourced from a single species Hevea brasiliensis, which is primarily grown in Southeast Asia and Africa. The Taraxacum kok-saghyz (L.E. Rodin) (TK) plant, which grows in temperate climates and has NR in its roots, has been identified as an additional source for NR in the future. A major challenge to TK becoming a crop is direct seeding. This paper presents research on determining strategies for improving establishment of TK through direct seeding. Field trials were conducted in 2014 and 2015 in Ohio on a Wooster silt loam soil (2.4–2.9% OM) using “wild” TK seed. The study evaluated the impacts of different planting dates (April and May), planter types (broadcasting raw seed and drilling pelleted seed), companion crops, and compost mulch strips on plant stands (i.e., visible TK plant/TK seed drop). Results indicated that drilling of pelleted seed to a depth of 0.6 cm into a thin layer (<1.27 cm) of compost mulch after soil temperatures reach 16 °C (mid-May in Northern Ohio) would give the highest stand by the fall harvest season. These studies provide insight into direct seeding of TK and a baseline to use for evaluating future generations of TK.

Крым-сагыз: особенности растения, перспективы возделывания и селекции (обзор)

Taraxacum hybernum Steven, известный также под названием «крым-сагыз», является одним из потенциальных источников натурального каучука, однако он малоизвестен, в отличие от его «родственника» T. kok-saghyz L. E. Rodin. Обзор посвящен анализу советского опыта культивирования T. hybernum Steven в СССР и рассмотрению перспектив внедрения в современное производство этой культуры в России с учетом современных методов агротехники и биотехнологии. Приведено ботаническое описание растения. Оценено содержание и качество каучука T. hybernum Steven. Содержание каучука невысокое, но качество его превосходит даже гевейный каучук. Степень полимерности углеводорода каучука 2000 – 2970 и выше. Урожай сырых корней T. hybernum Steven двулетнего возраста достигает 100 ц/га, семян — 150 кг/га. Всходы T. hybernum Steven появляются через 8 – 15 дней после посева. Для хорошего прорастания семян требуется не только достаточное количество влаги, но и свободный доступ воздуха в почву. Эти условия наилучшим образом сочетаются при раннем посеве и заделке семян на глубину 1,5 – 2 см. На получение всходов от фактически высеянных семян за 14 дней после посева влияет глубина заделки: на 1 см — 63,6 %, на 2 см — 68,3 %, на 3 см — 47,1 %, на 4 см — 4,3 %. Вес 1000 семян примерно 1 г. Опыт выращивания этой культуры даже в небольших объемах важен для обеспечения ресурсной и стратегической безопасности нашей страны в будущем.

Rooting for new sources of natural rubber

Rooting for new sources of natural rubber

De novo Transcriptome Sequencing of MeJA-Induced Taraxacum koksaghyz Rodin to Identify Genes Related to Rubber Formation

Increase in the consumption of natural rubber (NR) has necessitated the identification of alternative sources of NR. The quality of NR produced by Taraxacum koksaghyz Rodin (TKS) is comparable to that from Hevea brasiliensis (H.brasiliensis), and therefore, TKS is being considered as an alternative source of NR. Here, we sequenced the TKS root transcriptome after wild TKS seedlings were treated with methyl jasmonate (MeJA) for 0, 6, and 24 h. The clean reads generated for each experimental line were assembled into 127,833 unigenes. The Kyoto encyclopedia of genes and genomes pathway prediction suggested that methyl jasmonate regulated secondary metabolism in TKS. Differential expression analysis showed that the expression of HMGCR, FPPS, IDI, GGPPS, and REF/SRPP increased with methyl jasmonate treatment. Interestingly, differential expression analysis of the jasmonate (JA)-related transcription factors (TFs), indicated that certain genes encoding these transcription factors (namely, bHLH, MYB, AP2/EREBP, and WRKY) showed the same expression pattern in the lines treated for 6 h and 24 h. Moreover, HMGCR was up-regulated in the transgenic seedlings overexpressing DREB. We predicted that methyl jasmonate regulated secondary metabolism and affected rubber biosynthesis via the interaction of the JA-related TFs with genes associated with rubber biosynthesis in TKS.

Colchicine-induced polyploidy has the potential to improve rubber yield in Taraxacum kok-saghyz

Taraxacum kok-saghyz (TK), also known as rubber dandelion, is under development as a source of natural rubber but has not been fully domesticated. Rubber yield is highly variable and biomass is low compared with most crops. Therefore, it is imperative to apply breeding methods to improve rubber yield and accelerate the domestication process. One strategy to accelerate breeding is polyploid induction, which could improve rubber concentration and plant size. A gradient of colchicine concentrations ranging from 0% to 0.5% was used to treat approximately 5000 seeds for different periods of time (12h to 96h), followed by use of flow cytometry to confirm induced tetraploids. The optimal treatment of 0.1% colchicine for 48h resulted in an induction efficiency of 56.6%. An early-screening strategy successfully identified 2-month old tetraploid seedlings based on atypical leaf morphology. Comparisons of leaf, stomata, root morphological traits as well as biochemical traits including rubber, resin and inulin/sugars concentration were made between tetraploids and diploids. A 47.7% increase in rubber concentration but a decrease in inulin/sugars concentration was observed in tetraploid plants. However, there was no significant difference in the amount of rubber per root system among the greenhouse-grown plants in this research, likely due to root stunting observed in tetraploids and treated diploids. Evaluation of progeny is needed to circumvent the confounding physiological impact of colchicine treatment. However, the increase of rubber concentration observed in tetraploids suggests that polyploid breeding has the potential to improve rubber yield in TK.

Recurrent Selection for Rubber Yield in Russian Dandelion

Russian dandelion [Taraxacum kok-saghyz (TKS)] is a promising alternative to the Para rubber tree (Hevea brasiliensis) as a source of natural rubber; however, rubber yields must be improved for this undomesticated species to become a profitable new crop. Half-sib family recurrent selection was conducted for four cycles to increase rubber yield, estimated as the product of rubber percentage, and root dry weight per plant. Two distinct populations were developed for adaptation to sand and loam soil types. Rubber percentage increased from 4.17% for the cycle 0 (C0) population to 6.40% for the C4-loam population. Rubber yield also increased from 0.15 to 0.22 g/plant after four selection cycles. Although phenotypic variation was observed, selection had no effect on root weight; all populations averaged 3.70 g/plant. Rubber yield and percentage and root dry weight were not increased after four selection cycles on sandy soils, likely because of poor adaptation and high environmental variation. Year and soil type affected rubber yields; however, rubber percentage was more stable than root dry weight. Overall, russian dandelion can be improved for rubber yield, and further studies with increased error control should be considered to enhance root dry weight.

Taraxacum kok-saghyz (TK): compositional analysis of a feedstock for natural rubber and other bioproducts

Abstract Natural rubber (NR) is a critical raw material primarily produced in Asia from a single plant species ( Hevea brasiliensis ). This lack of biologic and geographic diversity, coupled with increasing demand, makes it imperative that alternative sources of NR are developed. Taraxacum kok-saghyz (TK) is a rubber-producing dandelion being developed as an alternative to the traditional source of NR. In order to improve the value of this crop and make it competitive with other sources of NR, germplasm improvement, crop production optimization, efficient extraction and purification methods and the valorization of TK co-products are needed. In this study, a compositional analysis of field-grown TK roots was conducted in which total solids, ash content, protein, crude fat, fatty acids, carbohydrates, lignin, and total water-, acetone-, and hexane-extract (rubber) were quantified and characterized. Mass closure was greater than 95%. The analysis showed that 5.4% (g/g root dw) of the root consisted of rubber and 1.7% was acetone extractable (mainly sterols). Approximately 60% (g/g dw) of the root was hot water extractable. Soluble sugars (32%) and proteins (10%) were the most abundant water soluble fractions. Inulin (18%) and sucrose (10%) were the most abundant sugars. Insoluble components included cellulose 9% (glucan), hemicellulose 7% (xylan, mannan, arabinan, galactan), lignin 5%, protein 5% and pectin 3%. This compositional analysis provides a baseline which can be used to assess compositional changes induced by altering plant genetics, environmental conditions and cultivation practices. Based on these results, pathways for TK processing are proposed, and its potential as a biorefinery feedstock is evaluated. This analysis indicates that TK has potential as a source of not only NR but other products and/or raw materials of importance including inulin and proteins.

Overexpression of a Hevea brasiliensis ErbB-3 Binding protein 1 Gene Increases Drought Tolerance and Organ Size in Arabidopsis.

Rubber trees are economically important tropical tree species and the major source of natural rubber, which is an essential industrial material. This tropical perennial tree is susceptible to cold stress and other abiotic stresses, especially in the marginal northern tropics. Recent years, the genome sequencing and RNA-seq projects produced huge amount of sequence data, which greatly facilitated the functional genomics study. However, the characterization of individual functional gene is in urgent demands, especially for those involved in stress resistance. Here we identified and characterized the rubber tree gene ErbB-3 binding protein 1, which undergoes changes in expression in response to cold, drought stress and ABA treatment. HbEBP1 overexpression (OE) in Arabidopsis increased organ size, facilitated root growth and increased adult leaf number by delaying the vegetative-to-reproductive transition. In addition, HbEBP1 OE enhanced the resistance of the Arabidopsis plants to freezing and drought stress, demonstrating that this gene participates in the regulation of abiotic stress resistance. RD29a, RD22 and CYCD3;1 expression was also greatly enhanced by HbEBP1 OE, which explains its regulatory roles in organ size and stress resistance. The regulation of drought stress resistance is a novel function identified in plant EBP1 genes, which expands our understanding of the roles of EBP1 gene in response to the environment. Our results provide information that may lead to the use of HbEBP1 in genetically engineered crops to increase both biomass and abiotic stress resistance.