Search Results (19)

This study aims to characterize for the first time the insect assemblage associated with sown, introduced guayule (Parthenium argentatum A. Gray, Asteraceae) in Castilla-La Mancha, Spain, and identify potential relationships with the crop. Insect sampling was conducted using nets and pan traps during spring and early summer, coinciding with the flowering period of the plant. A total of 352 insect species/morphospecies across 12 orders were identified. Diptera, Coleoptera, Hemiptera, and Hymenoptera were the most species-rich and abundant orders. Within these orders, Muscidae, Syrphidae, Tenebrionidae, Dermestidae, Miridae, Halictidae, and Apidae were the most numerous families. Guayule flowering intensity increased gradually until mid-June, aligning with the peak activity of pollinating Diptera. The majority of the identified insects (74.4%) were potential pollinators, while nearly 50% were detritivores and approximately 30% were herbivorous. The similarity in insect families and functional roles observed in this study to previous studies in the USA and Mexico suggest that guayule may serve as a similar trophic resource for insects in Spain, despite being a non-native species. Full article

Guayule (Parthenium argentatum A. Gray) is a valuable domestic source for rubber and resin. At its center of origin in the Northern Mexico and Southern Texas deserts, guayule, a perennial shrub, is hybridized with its relative species mariola (Parthenium incanum Kunth). As rubber and resin are the main products derived from guayule, there is interest in using guayule bagasse as a bioenergy feedstock to meet the growing bioenergy and biofuel demands. This study aimed to explore and characterize phenotypic diversity in cell wall constituents (lignin, cellulose, and hemicellulose) and their yields among 51 guayule and mariola genotypes under two irrigation regimes (well-watered and water-stressed). Significant genotypic and environmental effects were observed for lignin, cellulose and hemicellulose concentrations, and yields, indicating the wide genetic variability of the collection for bioenergy-related traits. Moderate to high entry-mean heritability values for lignin, cellulose, and hemicellulose suggest that selection is feasible to enhance genetic gain. Significant positive correlations were found among cellulose and hemicellulose concentrations and yields, indicating the possibility to select multiple traits together during breeding cycles. High positive correlations between rubber and resin and lignin, cellulose, and hemicellulose yields highlight the opportunity to develop guayule germplasm with enhanced multi-use traits for industrial applications. Wide variations in drought stress indices (stress tolerance index, yield index, and yield stability index) underscore the environmental impact on the lignocellulosic traits. Several genotypes were identified with high stress index scores and could be parental candidates for improving guayule for arid and semi-arid sustainable agricultural systems. The current study is the first to characterize the phenotypic diversities in guayule and mariola for lignocellulosic components and yield, providing the foundation for future breeding efforts aimed at enhancing guayule’s value for diverse production goals and environmental conditions. Full article

Guayule (Parthenium argentatum A. Gray) has the potential to be an alternative source of rubber if its co-products can be exploited on an industrial scale. Among the co-products that have garnered interest are the essential oils (EOs), which can reach relatively high yields. In the present study, the production and profile of EOs from two guayule accessions, AZ-3 and AZ-5, across different flowering stages (5 months) were analyzed under two irrigation regimes (100% and 50% of crop water evapotranspiration) and compared with control plants that received no additional water, (considered as a water-stress condition). The results showed that the extracted EO yield was consistently higher in the AZ-3 accession than in the AZ-5, especially under water-stress conditions, and that the flowering stage significantly affected the yield irrespective of the accession. Furthermore, differences in EO composition were observed between accessions, with AZ-3 containing more monoterpenes and AZ-5 containing more sesquiterpenes. The yields obtained underline the economic potential of guayule EO production, especially under water-stress and flowering conditions, and position it favorably against other aromatic plants. These results provide valuable insights for optimizing guayule cultivation to increase EO yields, with both economic and environmental benefits. Full article

Rubber (cis-1,4-polyisoprene) is produced in cytosolic unilamellar vesicles called rubber particles (RPs), and the protein complex responsible for this synthesis, the rubber transferase (RTase), is embedded in, or tethered to, the membranes of these RPs. Solubilized enzyme activity is very difficult to achieve because the polymerization of highly hydrophilic substrates into hydrophobic polymers requires a polar/non-polar interface and a hydrophobic compartment. Using guayule (Parthenium argentatum) as a model rubber-producing species, we optimized methods to isolate RP unilamellear membranes and then a subset of membrane microdomains (detergent-resistant membranes) likely to contain protein complexes such as RTase. The phospholipid and sterol composition of these membranes and microdomains were analyzed using thin-layer chromatography (TLC) and liquid chromatography tandem mass spectroscopy (LC-MS/MS). Our data indicate that RP membranes consist predominantly of phosphatidic acid-containing membrane microdomains (DRMs or “lipid rafts”). Proteomic analyses of guayule RP membranes and membrane microdomains identified 80 putative membrane proteins covering 30 functional categories. From this population, we have tentatively identified several proteins in multiple functional domains associated with membrane microdomains which may be critical to RTase function. Definition of the mechanisms underlying rubber synthesis will provide targets for both metabolic engineering and breeding strategies designed to increase natural rubber production in latex-producing species. Full article

Rubber and resin are potentially important products of guayule (Parthenium argentatum A. Gray) that can assure the profitability of this crop as an agricultural alternative for the semi-arid areas of central and eastern Spain. This study analyzes, for the first time, the changes in rubber and resin production across 27 guayule accessions (traditional and modern) and along three cycles under the agroclimatic conditions of Castilla-La Mancha, simulating industrial management with a biannual harvest. The rubber content (% of dry mass) increased from 4.2% in one-year-old plants to 6.6% in two-year-old plants, but decreased after harvesting. Contrastingly, the rubber yield doubled in contiguous sampling, reaching a mean of 303.6 kg ha⁻¹, with a maximum yield of 341.2 kg ha⁻¹ after the first harvest. Three patterns of rubber production were established based on the production periods. A similar analysis was performed for resin production, which was heterogeneous across accessions belonging to the same rubber groups. In this case, three independent groups were established to classify the resin accumulation profiles following the same criteria of production periods. Here, we demonstrate that biannual harvesting has the potential to enhance rubber accumulation in summer, although more research is needed for its adaption to current harvesting techniques in this area. Full article

Water and soil salinity continuously rises due to climate change and irrigation with reused waters. Guayule (Parthenium argentatum A. Gray) is a desert perennial shrub native to northern Mexico and the southwestern United States; it is known worldwide for rubber production and is suitable for cultivation in arid and semiarid regions, such as the Mediterranean. In the present study, we investigated the effects of high and increasing concentrations of sodium chloride (NaCl) on the growth and the morphophysiological and biochemical characteristics of guayule to evaluate its tolerance to salt stress and suitability in phytomanagement and, eventually, the phytodesalinisation of salt-affected areas. Guayule originates from desert areas, but has not been found in salt-affected soils; thus, here, we tested the potential tolerance to salinity of this species, identifying the toxicity threshold and its possible sodium (Na) accumulation capacity. In a hydroponic floating root system, guayule seedlings were subjected to salinity-tolerance tests using increasing NaCl concentrations (from 2.5 to 40 g L⁻¹ and from 43 to 684 mM). The first impairments in leaf morphophysiological traits appeared after adding 15 g L⁻¹ (257 mM) NaCl, but the plants survived up to the hypersaline conditions of 35–40 g L⁻¹ NaCl (about 600 mM). The distribution of major cell cations modulated the high Na content in the leaves, stems and roots; Na bioconcentration and translocation factors were close to one and greater than one, respectively. This is the first study on the morphophysiological and (bio)chemical response of guayule to different high and increasing levels of NaCl, showing the parameters and indices useful for identifying its salt tolerance threshold, adaptative mechanisms and reclamation potential in high-saline environments. Full article

Natural rubber (cis-1,4-polyisoprene, NR) is an important raw material utilized widely in the manufacturing of medical, agricultural, and industrial products. Rubber tree (Hevea brasiliensis) and several alternative rubber-producing plants (Taraxacum kok-saghyz, Lactuca sativa, and Parthenium argentatum) have the capability to produce high-quality NR. With the progress of genome sequencing, similar rubber biosynthesis pathways have been discovered among different rubber-producing plant species. NR is synthesized and stored in rubber particles, which are specialized organelles comprising a hydrophobic NR core surrounded by a lipid monolayer and membrane-bound proteins. The rubber transferase complex is considered to be the pivotal enzyme involved in catalyzing NR biosynthesis. However, the exact compositions of the RT complex in rubber-producing plants remain elusive and poorly understood. Here, we review the progress of genome sequencing, natural rubber biosynthesis, and the components of the RT complex in rubber-producing plants. We emphasize that identifying the detailed components of the RT complex holds great significance for exploring the mechanism of NR biosynthesis and accelerating molecular breeding in rubber-producing plants. Full article

Guayule (Parthenium argentatum, A. Gray) is a perennial desert shrub with ratoon-cropping potential for multiple harvests of its natural rubber, resin, and bagasse byproducts. However, yield expectations, water use requirements, and irrigation scheduling information for ratooned guayule are extremely limited. The objectives of this study were to evaluate dry biomass (DB), contents of rubber (R) and resin (Re) and yields of rubber (RY) and resin (ReY) responses to irrigation treatments, and develop irrigation management criteria for ratooned guayule. The water productivity (WP) of the yield components were also evaluated. Guayule plants that were direct-seeded in April 2018 were ratooned and regrown starting in April 2020, after an initial 2-year harvest at two locations in Arizona: Maricopa and Eloy on sandy loam and clay soils, respectively. Plots were irrigated with subsurface drip irrigation (SDI) at 50, 75, and 100% replacement of crop evapotranspiration (ET_c), respectively, and furrow irrigation at 100% ET_c replacement, as determined by soil water balance measurements. The Eloy location did not include the 100% irrigation treatment under SDI due to unsuccessful regrowth for this specific treatment. The irrigation treatments at the locations were replicated three times in a randomized complete block design. After 21–22 months of regrowth, the guayule plants were harvested in plots. The results showed that DB increased with the amount of total water applied (TWA, irrigation plus precipitation), while R and Re were reduced at the highest TWA received at both locations. Ultimately, the SDI treatments with 75% ET_c replacement resulted in the best irrigation management in terms of maximizing RY and ReY, and WP for both locations and soil types. Compared to the initial 2-year direct-seeded guayule crop, ratooned guayule required less TWA and attained higher DB, RY, and ReY, as well as higher WP, with average increases of 25% in dry biomass, 33% in rubber yield, and 32% in resin yield. A grower’s costs for planting the initial direct-seeded guayule crop would be offset by the additional yield revenue of the ratooned crop, which would have comparatively small startup costs. Full article

Approximately one-third of the waste biomass from the cultivation of guayule (Parthenium argentatum A. Gray) for natural rubber production is leaf tissue; however, whether it can be valorized is not known. Guayulins and argentatins are potential high-value products that can be recovered from guayule resin during rubber/latex processing. Argentatins are highly abundant in guayule stem resin; however, unlike the guayulins, their occurrence in leaves has not been investigated. The present study determined the content of argentatins and isoargentatins A and B in the leaves of a pure guayule accession (R1040) and two hybrids (CAL-1 and AZ-2) under conditions of irrigation and non-irrigation. The resin content in leaves was ~10%, which provides a suitable starting point for economic exploitation. The highest production of argentatins occurred in plants under irrigation, with yields of 4.2 and 3.6 kg ha⁻¹ for R1040 and AZ-2, respectively. The R1040 accession had the highest percentage of resin and the greatest total argentatin content (24.5 g kg⁻¹ dried leaf), principally due to the abundance of argentatin A. Contrastingly, CAL-1 consistently showed the lowest argentatin content based on dried leaf weight and production (0.6 kg ha⁻¹). The substantial abundance of argentatins in guayule leaves suggests the potential for future exploitation. Full article

Guayule (Parthenium argentatum Gray) is a perennial desert shrub currently under investigation as a viable commercial alternative to the Pará rubber tree (Hevea brasiliensis), the traditional source of natural rubber. Previous studies on guayule have shown a close association between morphological traits or biomass and rubber content. We collected multispectral and RGB-derived Structure-from-motion (SfM) data using an unmanned aircraft system (UAS; drone) to determine if incorporating both high-resolution normalized difference vegetation index (NDVI; an indicator of plant health) and canopy height (CH) information could support model predictions of crop productivity. Ground-truth resource allocation in guayule was measured at four elevations (i.e., tiers) along the crop’s vertical profile using both traditional biomass measurement techniques and a novel volumetric measurement technique. Multiple linear regression models estimating fresh weight (FW), dry weight (DW), fresh volume (FV), fresh-weight-density (FWD), and dry-weight-density (DWD) were developed and their performance compared. Of the crop productivity measures considered, a model predicting FWD (i.e., the fresh weight of plant material adjusted by its freshly harvested volume) and incorporating NDVI, CH, NDVI:CH interaction, and tier parameters reported the lowest mean absolute percentage error (MAPE) between field measurements and predictions, ranging from 9 to 13%. A reduced FWD model incorporating only NDVI and tier parameters was developed to explore the scalability of model predictions to medium spatial resolutions with Sentinel-2 satellite data. Across all UAS surveys and corresponding satellite imagery compared, MAPE between FWD model predictions for UAS and satellite data were below 3% irrespective of soil pixel influence. Full article

The extensive use of synthetic pesticides has created considerable concern for both human health and the environment, which has prompted the search for safer alternatives, such as the resin of guayule (Parthenium argentatum). Thus, in the present study, we aimed to test the biopesticide activity of crude guayule resin and three derived fractions and compare them to reference products that act against four of the most economically significant plant pests: Tetranychus urticae, Bemisia tabaci, Myzus persicae and Frankliniella occidentalis. None of the guayule products caused plant damage. The crude guayule resin and the hexane and ethyl acetate fractions displayed moderate to high contact mortality against T. urticae and B. tabaci, as well as moderate to high antifeedant activity against T. urticae, B. tabaci and M. persicae. No significant activity was observed against F. occidentalis. A correlation analysis of the activity and fraction composition revealed that guayulins C and D, isoargentatins A and B, argentatins A, B and D and an unknown compound C6 were likely responsible for the contact mortality. By contrast, the antifeedant activity appeared to be caused by guayulins A and B against T. urticae and B. tabaci and by guayulins C and D and argentatin B against M. persicae. The feeding reduction in F. occidentalis was associated with an unknown compound C2 and argentatin C. Therefore, guayule appears to be a promising novel biopesticide. Full article

The guayulins are a family of sesquiterpene compounds that consist of an isoprenoid nucleus substituted either by trans-cinnamic or p-anisic acid, and are present only in the resinous fraction of the rubber plant guayule (Parthenium argentatum, Gray). While the natural role of the guayulins remains enigmatic, they may serve as a defense function against other plants or herbivores by virtue of the accumulation of cinnamic acid. Prior research has suggested seasonal variation in guayulin content, which has been shown to decrease as winter arrives in two different varieties. In the present study, the effect of guayulins has been evaluated in 13 different accessions cultivated under the same conditions during autumn. A general reduction in guayulin content was found in the stems from all varieties between the September and November harvest, which was accompanied by an increase in the resin content. With respect to individual guayulins, while guayulin A was the most prominent member during most of the year, guayulin C had more prominence when temperature started to decrease. In this seasonal period, the production of each member of the guayulin family in the leaves was very balanced. Full article

Natural rubber is an essential material, especially for plane and truck tyres but also for medical gloves. Asia ranks first in the production of natural rubber, of which the Hevea tree is currently the sole source. However, it is anticipated that this source alone will not be able to fulfill the growing demand. Guayule, a shrub native to northern Mexico and southern United States, may also contribute. This plant not only contains polyisoprene, but also resin, a mixture of lipids and terpenoids. This review summarizes various aspects of this plant, from the usage history, botanical description, geographical distribution and cultivation practices, down to polyisoprene and resin biosynthesis including their distribution within the plant and molecular composition. Finally, the main processes yielding dry rubber or latex are depicted, as well as the properties of the various extracts along with economic considerations. The aim is to provide a wide picture of current knowledge available about this promising crop, a good feedstock candidate for a multiple-product biorefinery. Full article

Guayule (Parthenium argentatum Gray) is a promising alternative source to Hevea brasiliensis for the production of natural rubber, which can reach levels of 8–9% under industrialized farming conditions. The most common method for determining rubber concentration is by accelerated solvent extraction (ASE), a technique developed by the Dionex Corporation and almost exclusively performed with the Dionex ASE-200 or 350 systems. Herein, it is sought to apply and adapt the most common methods used in the literature for the Dionex system to another extraction platform, the BÜCHI Speed Extractor E-914. Results showed that using a sand sandwich method to confine the sample in the center and exploiting a larger cell volume (80 mL) for extraction prevents the occurrence of overpressure and problems with clogging. Under optimized conditions, the coefficient of variation was <15% for both resin quantification for samples containing 5.0–15.8% of resin and for rubber quantification for samples with 1.7–10.3% rubber content. The extraction time for resin (2 cycles of 5 min each) was smaller than for rubber (2 cycles of 20 min each). It would be interesting to carry out interlaboratory comparisons to standardize the method at an international level. Full article

The perennial shrub guayule (Parthenium argentatum A. Gray) has gained interest as a potential source of natural and hypoallergenic rubber in Southern Europe. Although, native to northern Mexico, it is suited to semi-arid and Mediterranean environments. A research study was conducted in Sardinia (Italy) to evaluate adaptation and biometric traits of introduced guayule lines and to determine the contents and yields of rubber and resin obtainable from its aboveground biomass. Seedlings of the accessions AZ-1, AZ-2, P803, and 11591 were field transplanted in 2015 at two locations of southern, and northern Sardinia, respectively, differing for annual precipitation. Plant survival rate, height and width, trunk diameter, leaf chlorophyll concentration and photosystem photochemical efficiency were monitored. Shoots were harvested at 30 months after transplanting and were partitioned into twigs and remaining stems and its rubber and resin contents were determined. Location markedly affected plant survival rates and biometric traits. Dry matter yield of aboveground components as well as contents of rubber and resin and plant rubber and resin yields differed significantly among accessions under comparison. We found that AZ1 and 11591 were the most successful accessions at southern Sardinia site, whereas 11591 was the only accession exhibiting a satisfactory plant survival rate in the northern location. Full article