Location: Plant Physiology and Genetics Research2011 Annual Report
1a. Objectives (from AD-416)
Objective 1: Develop enhanced germplasm and cultivars for low input, high yielding, cost-competitive oilseed, latex, and biomass crops as bio-fuels and bio-based products. Objective 2: Determine the physiological, biochemical, and molecular factors limiting the growth and yield of oilseed, latex, and biomass crops that could be targeted for improvement in a conventiional and/or molecular breeding program. Objective 3: Develop economical production systems for new/alternative industrial crops.
1b. Approach (from AD-416)
Germplasm that has been previously collected as well as new germplasm collections will be evaluated for important characteristics to meet the objectives. Evaluation data and seed will be sent to the appropriate curators for entry into the National Plant Germplasm System. Standard and molecular breeding procedures will be used in selecting and improving germplasm to develop enhanced germplasm with increased levels of desired traits such as oil content, specific fatty acid profiles, latex and resin contents, yield, resistance to biotic and abiotic stresses, and biomass. Production systems will be developed and evaluated to provide farmers with profitable and sustainable management practices. New and improved analytical procedures will be developed as needed to evaluate germplasm for desired traits and potential co-producers. Formerly 5347-21410-004-00D (5/08).
3. Progress Report
Lesquerella: Research on lesquerella breeding and production was limited to increasing seed of a new germplasm line being proposed for release and completion of manuscripts by the Research Geneticist who transferred to the National Center for Genetic Resources Preservation (NCGRP). Interspecific hybrids have been identified with hydroxyl fatty acids (HFA) close to 70%. Efforts to develop stable transformation methods for Lesquerella to further improve oil and agronomic traits are ongoing. Significant progress was made in manipulating biosynthetic pathways to improve yield traits of Lesquerella. Lesquerella was transformed with genes from either castor bean or jojoba to potentially increase the total amount of hydroxyl fatty acid in seed oil, or produce novel types of liquid waxes that contained hydroxyl fatty acids. First generation transgenic plants carrying the novel genes have been identified, and recovery of seed is underway to determine the extent of oil modification. Guayule: Regrowth from genetically modified germplasm lines was evaluated for morphological traits and rubber and resin contents. Preliminary analyses of the results do not indicate any significant increases in rubber, resin or biomass yield compared to the non-transformed control plants. A greenhouse study was completed to evaluate ploidy levels in guayule germplasm obtained from the USDA-ARS collection at Parlier, CA. Additional germplasm screenings were conducted of field grown plants for a genetically modified population, a traditional breeding population, and open pollinated germplasm obtained from the USDA-ARS collection at Parlier, CA. Additional diploid plants needed for developing new germplasm have been identified in the traditional breeding population and a range of ploidy levels identified in the traditional breeding population and the germplasm collection. Other oilseeds: Selection nurseries were conducted for camelina and improved germplasm was identified for further evaluation. Rubisco activation was measured both in vivo and by assaying Rubisco activase activity. Photosynthetic performance and yield in camelina are acutely sensitive to inhibition by moderate heat stress. A chimeric Rubisco activase has been constructed to improve thermotolerance of the enzyme. Recombinant proteins have been purified for testing of thermotolerance and the ability to activate camelina Rubisco.
1. Rapid method for determining guayule ploidy levels developed. Genetic improvement through modern plant breeding is needed to increase guayule yield potential and suitability for commercialization. Determining the ploidy level of publicly available guayule accessions would help to accelerate the development of stable, high yielding cultivars. ARS scientists at Maricopa, Arizona in cooperation with a scientist at Kansas State University adapted flow cytometry to examine the ploidy of guayule accessions available from the National Plant Germplasm System, a transgenic breeding population, and a traditional breeding population. The data revealed a natural polyploid series, ranging from diploid (2n=2x=36) to pentaploid (2n=5x=90), with tetratploid (4x) being the predominant ploidy in the traditional breeding population and the guayule accessions in the national Plant Germplasm System. Notably, the integration of ploidy and pedigree data uncovered complex ploidy variation in guayule breeding programs. The frequency and range of ploidy variation observed in this germplasm will help to direct future breeding efforts as well as linkage analysis and genome-wide association studies benefiting the guayule breeders, geneticists, curators, and other guayule researchers as well as the guayule industry.
2. Reproductive and vegetative characteristics of Lesquerella. Lesquerella is a new oilseed crop being developed for production in the Southwestern USA. For maximum yields growers need to know optimum planting and harvest dates for the crop. Utilizing three planting dates (fall, winter, and spring) the effects of planting date on the reproductive and vegetative growth of lesquerella were characterized by ARS scientists at Maricopa, Arizona, showing that fall planting dates were optimum for maximum yields. These results will be useful to growers and the lesquerella industry in planning production systems and planting and harvesting dates.
3. Disruption of gene in plants results in increased in oil content. All plants produce small amounts of oil in their leaves, but the mechanisms involved in regulating this process are not understood. As part of a collaborative effort with scientists at the University of Guelph, University of North Texas, and University of Texas Southwestern Medical Center at Dallas, scientists at the ARS lab in Maricopa have identified an alpha-beta hydrolase-type gene in Arabidopsis that, when mutated, results in a 10-fold increase in the amount of oil present in plant leaves, with no changes in amount of oil present in the seeds. This work, supported by a grant from the Department of Energy, opens new avenues of research for producing high amounts of energy-dense oils in crop plants. Since the biomass of leaves and stems of plants is significantly greater than that of seeds (the traditional source of plant oils), producing even modest amounts of oils in leaves and stems of biomass crops could significantly increase the amount of oil recovered from a given area of land. Results will be useful to researchers increasing the oil content of plants for use in bio-fuels.
4. Sink strength limits rubber production in guayule. Guayule stems and roots contain a significant amount of natural rubber that accumulates in the winter when plants are dormant. To determine how rubber synthesis can be increased in guayule, carbon assimilation and partitioning were measured in plants grown under summer- and winter-like conditions and under winter-like conditions with CO2 enrichment. Results show that plants maintain a high rate of photosynthesis and accumulate non-structural carbohydrates and rubber in the vegetatively dormant state. Enrichment with CO2 in the vegetatively dormant state increased carbohydrate content but not rubber content. This indicates that efforts to increase rubber synthesis in guayule should focus on increasing sink strength or developing alternative sinks for rubber storage. Results will be useful to researchers trying to increase rubber content in guayule.
5. New method developed for measuring Rubisco activase activity. Rubisco activase is an important enzyme in determining heat tolerance of photosynthesis and yield in plants. Using a new method evaluating leaf extracts to determine the activity of rubisco activase in plants, it was found that even moderate heat stress in camelina reduced seed weight, seed number, photosynthetic performance and yield. Increased heat tolerance will increase yields of important crop plants. Results will be useful to researchers studying heat stress in plants and those researchers trying to increase heat tolerance through molecular methods.
6. Optimum harvest height determined for guayule. The commercialization of guayule for hypoallergenic latex has renewed interest in production factors such as harvesting height and frequency. A study was conducted by an ARS researcher at Maricopa, Arizona, in cooperation with a researcher at the University of Arizona on five guayule lines with variable plant height to determine the effects of harvesting at 50% of plant height compared to the recommended 100% at 2, 3, and 4 years of growth. Harvesting at 100% of plant height gave higher yields than harvesting at 50% of plant height at all harvest dates. Harvesting at 100% after three and four years of growth gave the highest yields. Optimum harvesting schemes at 100% of plant height need to be developed for each line and environment. These results will benefit guayule growers, processors, and researchers by reducing harvest costs and maximizing yields.
7. Remote sensing system developed for optimizing agronomic practices in Lesquerella. Lesquerella is a new oilseed crop being developed for production in the Southwestern USA. Determining optimum fertilization application times and optimum harvest times for this crop is difficult with current technology. Utilizing a multi-spectral camera, ARS scientists at Maricopa, Arizona, developed an image system for monitoring flowering in lesquerella that could be used for determining optimum times for fertilizer applications and optimum harvest dates. The results from this study will be useful to growers in optimizing fertilizer application times and harvest dates for Lesquerella, and reducing our dependence upon imported castor oil.
8. Guayule and cotton processing byproducts hold great promise as fiber fillers in thermoplastic composites. The use of relatively inexpensive and alternative sources of fiber filler is important for the long-term sustainability of the natural fiber reinforced thermoplastic composite industry. Currently wood fiber is used, but prices are increasing due to competition for the fiber for other uses. Three ARS scientists (two at Maricopa, Arizona and one at Lubbock, Texas) cooperated with scientists from the University of Arkansas and industry to evaluate cotton gin wastes and guayule bagasse left after rubber extraction as possible sources of fiber to replace wood fibers. Results show that these fiber sources alone or better in combination could be used as fiber fillers in thermoplastic composites. Use of these waste products in a recyclable product such as thermoplastic composites would reduce the amount of wastes going to landfills and enhance the value of these crops. These results will benefit the Cotton and Guayule Industries and growers.
9. Titan peanut cultivar released. From 1995 to 2002, the U. S. federal support price for peanuts decreased 47% forcing farmers to grow other crops and reducing peanut acreage in Virginia from more than 100,000 ha in 1995 to 12,000 ha in 2010. One way farmers maintain profitability is to grow Virginia-type peanuts which receive a premium for super-extra-large kernels, extra-large kernels, and jumbo pods. Scientists at Virginia tech University, N.C. State University, and USDA-ARS, Maricopa Arizona developed and released a new peanut cultivar, Titan with an exceptionally high content of jumbo pods, super extra large kernels, and extra large kernels. The release of Titan will help meet the demand for larger peanuts needed by the gourmet, in-shell, and green-boiling industries, thus providing growers and the industry with more profit.
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