Source: UNIVERSITY OF NEVADA submitted to
RABBIT BRUSH: A NEW HIGH VALUE RUBBER CROP FOR NEVADA
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
TERMINATED
Funding Source
HATCH
Reporting Frequency
Annual
Accession No.
0204073
Grant No.
(N/A)
Project No.
NEV00336
Proposal No.
(N/A)
Multistate No.
(N/A)
Program Code
(N/A)
Project Start Date
Jul 1, 2005
Project End Date
Jun 30, 2008
Grant Year
(N/A)
Project Director
Shintani, D.
Recipient Organization
UNIVERSITY OF NEVADA
(N/A)
RENO,NV 89557
Performing Department
BIOCHEMISTRY
Non Technical Summary
Natural rubber is an irreplaceable material required for the manufacture of aircraft and automobile tires, medical devices and engineering materials and is considered an important strategic commodity in a manner similar to crude oil. Currently Hevea brasiliensis (Brazilian Rubber Tree) is the sole source of commercial natural rubber in the world. Because 90% of the rubber tree crop is grown in Southeast Asia, global exports of this important product can be threatened not only by disease and climate related crop failures, but also by political and economic factors. For these reasons, domestic sources of natural rubber have been sought for several decades. One alternative to the Brazilian Rubber Tree is the Nevada native plant Chrysothamus nauseosus (Rabbit Brush). Rabbit Brush has been reported to produce high quality rubber with yields ranging from 1.5 % to 6.5% of shoot dry weight. Because Rabbit brush thrives in marginal soil with very low water requirements, it could be developed into an ideal crop for Nevada's unique environment. Dry land farming of Rabbit Brush for rubber production could provide Nevada Farmers with a high value crop which can be grown in previously uncultivated areas of Nevada.
Animal Health Component
(N/A)
Research Effort Categories
Basic
100%
Applied
(N/A)
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
20122491000100%
Knowledge Area
201 - Plant Genome, Genetics, and Genetic Mechanisms;

Subject Of Investigation
2249 - Rubber, gum, and resin plants, general/other;

Field Of Science
1000 - Biochemistry and biophysics;
Goals / Objectives
The focus of this research proposal is to understand rubber biosynthesis in the native Nevadan plant species Chrysothamus nauseosus (Rabbit Brush). Since Rabbit Brush is a wild specie, initial studies will be performed to determine the variation in rubber production present among wild stands grown in various location within the Nevada Great Basin Region. Seed collected from high rubber yielding lines will then be collected and propagated for use in further studies. Because Rabbit Brush is known to accumulate rubber when subjected to heat and drought stress, we will use these lines to investigate the effect of various environmental factors on rubber production in Rabbit Brush. Specific Objectives 1)Collect tissue and seed material from wild stands of Rabbit Brush to identify hyper rubber-producing lines. 2)Analyze individual samples for total rubber content and rubber quality. 3)Determine the developmental pattern of rubber accumulation in Rabbit Brush grown under controlled conditions. 4)Study the effect of drought, heat and salt stress on rubber production in Rabbit Brush.
Project Methods
I. Collection of wild Rabbit Brush Our selection of collection sites will be based on information from previous surveys and will focus on Northern Nevada and Eastern California. Based on previous work (Hegerhorst et al., 1988), areas of particular interest will include Gerlach, NV; Golconda, NV, Honey Lake, CA; Benton, CA; Walker River Area, NV; Carson Valley, NV; Quinn River Area, NV. To ensure that we will be able to return for subsequent sampling of the same site, we will record the exact position of the site using Global Positioning Satellite readings and digital photographic records. II. Rubber extraction Plant material will be lyophilized until dry, 1 to 3 days. The Rabbit Brush will then be coarsely ground in Waring blender for 1 minute, placed in liquid nitrogen and finely ground using Wiley mill with a 2-4 mm screen. The ground material will then be extracted using our newly purchased Dionex Accelerated Solvent Extraction (ASE) system. The method has been worked out for both woody and herbaceous plant tissue The extracted rubber is then dried under nitrogen gas, weighed and saved further analyses. This method allows for the consistent extraction of >95% of the rubber present in the plant material. III. Rubber Analyses The molecular weight of natural rubber varies significantly between and within plant species. As such all samples will be subjected to gel permeation chromatography (GPC) to determine the variation in rubber molecular weight among Rabbit Brush grown in different environments. Rubber samples will be fractionated using two Polymer Labs Gel 10 micron mixed-B exclusion columns connected in series and a tetrahyrofuran mobile phase and the molecular weight will be determined using polymer standard of known molecular weight. IV. Developmental Analyses of rubber deposition in Rabbit Brush Seeds from high rubber producing Rabbit Brush individuals will be germinated in the greenhouse. After 12 months of growth, rubber will be extracted and analyses as described above. Individual plants yielding high rubber levels will be asexually propagated in vitro using established micropropagation techniques developed specifically for Rabbit Brush (Upadhyaya et al., 1985). The clonally propagated material will then be used to determine the developmental timing of rubber deposition in Rabbit Brush. Plants will be established in the early spring and tissue will be harvested from plants every two weeks until flowering in the fall. V. Effect of abiotic stress on rubber production in rabbit brush Once the developmental profile of rubber deposition has been determined, the effect of various abiotic stresses; including drought stress, salt stress, and heat stress; on rubber production will be studied. Just prior to the developmental stage where rubber deposition begins, clonal material will be subjected to salt, heat and drought stresses. These studies will be performed in collaboration with Grant Cramer in the Department of Biochemistry who is currently performing similar studies on wine grapes.

Progress 07/01/05 to 06/30/08

Outputs
OUTPUTS: The focus of this research proposal is to understand rubber biosynthesis in the native Nevadan plant species Chrysothamus nauseosus (Rabbit Brush). Since Rabbit Brush is a wild species, initial studies will be performed to determine the variation in rubber production present among wild stands grown in various location within Nevada's Great Basin Region. Seed collected from high rubber yielding lines will then be collected and propagated for use in further studies. Findings: Major Findings; 1)Rubber quantity and quality was affected by environmental conditions and specific habitat. 2)In young stems, rubber content increased as summer temperatures increased. Conversely, as temperature decreased in the fall, rubber content also decreased. 3)Rubber accumulated to higher levels in older tissues than in young tissues. 4)Rabbit brush produced low molecular weight rubber (~30,000 daltons) relative to that analyzed from the Brazilian rubber tree or Guayule (1,000,000 daltons). 5)Rabbit brush rubber particles lack some of them major rubber particle proteins observed in Guayule and the Brazilian rubber tree. This difference may help explain the difference in molecular weight observed in these rubber producing species. PARTICIPANTS: Graduate Student Upul hathwaik TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
Natural rubber is an irreplaceable material required for the manufacture of aircraft and automobile tires, medical devices and engineering materials and is considered an important strategic commodity in a manner similar to crude oil. Currently Hevea brasiliensis (Brazilian Rubber Tree) is the sole source of commercial natural rubber in the world. Because 90% of the rubber tree crop is grown in Southeast Asia, global exports of this important product can be threatened not only by disease and climate related crop failures, but also by political and economic factors. For these reasons, domestic sources of natural rubber have been sought for several decades. One alternative to the Brazilian Rubber Tree is the Nevada native plant Chrysothamus nauseosus (Rabbit Brush). Rabbit Brush has been reported to produce high quality rubber with yields ranging from 1.5 % to 6.5% of shoot dry weight. Because Rabbit brush thrives in marginal soil with very low water requirements, it could be developed into an ideal crop for Nevada's unique environment. Dry land farming of Rabbit Brush for rubber production could provide Nevada Farmers with a high value crop which can be grown in previously uncultivated areas of Nevada.

Publications

  • No publications reported this period


Progress 01/01/07 to 12/31/07

Outputs
We have identified high rubber producing rabbit brush lines from wild accessions. Seeds from these plants have been planted in our green houses and we will examine these progeny for rubber content as they mature. In addition, we have done more detailed work to look at changes in rubber content in the different plant tissues over the spring and summer. From these results we have observed differences between different tissues in regards to the molecular weight of the rubber and the amount of rubber produced. Preliminary results showed that the low molecular weight rubber was produced in the new growth tissue while higher mnolecular weight rubber was produced in the older woody tissue and within the roots. In terms of rubber yields, the older woody tissue and the roots contained significantly more rubber than the new growth tissue.

Impacts
The wild accessions collect through these studies will provide the initial germplasm required for the selection of high yielding rubber lines. These lines will prove essential for the development of elite rabbit brush lines for possible commercial consideration. The development of rabbit brush into a commercial rubber crop would provide Nevada agriculture with a high value crop that would require low agronomic inputs (i.e. irrigation water and fertilizer). Furthermore since rabbit brush thrives on marginal soils, rabbit brush will not compete for land resources with current crop species and would increase farm acreage to land previously thought to be unsuitable to agriculture.

Publications

  • Hathwaik, U., Shintani, D. (2007) Screening wild Chysothamus nauseosus (rabbitbrush)populations for variation in rubber content and quality. Phytochemical Society of North America Annual Meeting, St. Louis, MO July 21 - 24.
  • Hathwaik, U., Durant, K., Villaluz, J.E., Harmon, D., Young, J.A., Shintani, D.K. (2006) Screening wild rabbitbrush (Chysothamus nauseosus) populations for variation in rubber content and quality. Association for Advancement of Industrial Crops Annual Meeting, San Diego, CA,October 12-14.
  • Hathwaik, U., Durant, K., Harmon, D., Young, J.A. Shintani, D.K. (2006) Screening wild Rabbit Brush (Chrysothamus nauseous) populations for variation in rubber content and quality. Annual Meeting of the American Society of Plant Biologist, Boston, MA, August 5-9.


Progress 01/01/06 to 12/31/06

Outputs
Over the past two years we screened wild stands of Chrysothamus nauseosus (rubber rabbit brush) from various sites in the Nevada Great Basin Region for differences in rubber content. With the help of Dr. James Young at USDA-ARS, we collected Rabbit Brush samples from following areas. Ione CA, Steam Boat creek at Main station UNR farm, Eagle Valley Sand Dunes, Ione Davils Garden Modoc County CA, Robbins Roost Smoke Creek NV, Noble-Chna, Verdi Low Sagebrush, Dog Valley Summit, Southeast Reno, Sand Mountain, Kossok Mountain, Slat Mountain Summit Mineral County and Fallon south pasture. Initial analyses revealed that rabbit brush collected from the Eagle Valley Sand Dunes and Sand Mountain had the highest amount of rubber with yields ranging from 10 to 14 mg rubber per gram dry weight. Plants collected from the other areas contain only small amounts of rubber ranging from a low of >1 mg/ gm dry weight to a high of 5 mg/ gm dry weight. Since this initial collection we have expanded our collections to three new sites that were previously described in the literature to possess high rubber yielding rabbit brush plants. These sites included the Black Rock Desert playa outside Gerlach, the hills bordering the playa just off of Soldier's Meadow Road, and the southeastern foothills of the Selenite Mountain Range. The rubber content of these plants proved to be comparable to plants collect from the Eagle Valley and Sand Mountain sand dunes. We have expanded our study to look at seasonal changes in rabbit brush rubber content. Previous studies report that rabbit brush accumulates rubber in response to high temperature and low soil moisture content. Therefore, we repeatedly sampled individual plants from the Eagle Valley, Black Rock playa, Soldier's Meadow Road and Selenite Range sites for seasonal changes in rubber content. For consistency, the new growth portions of the plants were sampled. This typically included 6 to 12 inches of the green portions of the shoot ends. From this study we observed two patterns of seasonal rubber accumulation. Plants from the Eagle Valley and Black Rock sites accumulated rubber throughout the summer until mid September when rubber content as a function of dry weight began to drop. It is likely that this drop is associated with an increase in biomass resulting from a late season growth spurt in plants from these two sites. On the other hand, plants sampled from the Soldier's Meadow Road and Selenite Range did not show the decreases in rubber content, but instead continued to accumulate rubber throughout the sampling which ran through late September. At the end of the season, we collected seeds from each of the sampled plants. We intend to plant several individual from each line in a common garden to determine if the variation we observed in rubber content was due to geographic and environmental factors or due to genetic variation. These studies are currently under way.

Impacts
The wild accessions collect through these studies will provide the initial germplasm required for the selection of high yielding rubber lines. These lines will prove essential for the development of elite rabbit brush lines for possible commercial consideration. The development of rabbit brush into a commercial rubber crop would provide Nevada agriculture with a high value crop that would require low agronomic inputs (i.e. irrigation water and fertilizer). Furthermore since rabbit brush thrives on marginal soils, rabbit brush will not compete for land resources with current crop species and would increase farm acreage to land previously thought to be unsuitable to agriculture.

Publications

  • Hathwaik, U., Durant, K., Villaluz, J.E., Harmon, D., Young, J.A., Shintani, D.K. (2006) Screening wild rabbitbrush (Chysothamus nauseosus) populations for variation in rubber content and quality. Association for Advancement of Industrial Crops Annual Meeting, San Diego, CA, 10/14/2006.
  • Hathwaik, U., Durant, K., Harmon, D., Young, J.A. Shintani, D.K. (2006) Screening wild Rabbit Brush (Chrysothamus nauseous) populations for variation in rubber content and quality. Annual Meeting of the American Society of Plant Biologist, Boston, MA, 8/5/2006.


Progress 01/01/05 to 12/31/05

Outputs
During the late fall and early winter of 2005, with the help of Jim Young (USDA ARS)we have collected seed and bark tissues several wide accessions of Chrysothamus nauseosus (Rabbit Brush)from several regions of Northwestern Nevada. We are in the process of adapting rubber extraction and analyses methods developed for Guayule to Rabbit Brush. We are also germinating seed from these accession in the greenhouse.

Impacts
The goal of this project is to screen wild accession of Rabbit Brush for superior rubber production. Once such lines have been identified, breeding schemes will be developed to help with the genetic improvement of this rubber producing plant species. The development of hyper rubber producing Rabbit Brush could significantly impact of agriculture in the Great Basin Region by allowing for the introduction of a new high value crop to the region.

Publications

  • No publications reported this period