Location: Plant Physiology and Genetics Research2013 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.
3. Progress Report:
This is the final report for project 5347-21410-005-00D, which was terminated in June, 2013 and replaced with project 5347-21410-006-00D, "Genetic Improvement and Phenotyping of Cotton, Bioenergy and Other Industrial Crops". See the FY2013 Annual Report of the new project for additional information. Progress was made on all 3 objectives and their sub-objectives, all of which are under the ARS Plant Genetic Resources, Genomics and Genetic Improvement NP 301 Action Plan. Most of this research project focused on lesquerella, which is an emerging oilseed crop that produces an industrially important fatty acid (lesquerolic acid) in its seed oil, and guayule, which is a desert shrub being developed as an alternative source of natural rubber. Our first Objective focused on development of enhanced germplasm and cultivars for low input, high yielding, cost-competitive oilseed, latex, and biomass crops. Using conventional breeding methods, several varieties of lesquerella were developed with lesquerolic acid content above 65%, oil content above 35%, adapted for spring planting, or showed improved branching and shatter resistance. For guayule, methods of ploidy analysis were developed, and germplasm was evaluated for future use in breeding programs. Direct manipulation of rubber production pathways for enhanced rubber synthesis was explored using transgenic approaches that involved a collaboration between ARS scientists, Yulex Corporation, which is a local company focused on extraction and distribution of guayule rubber, and Mendel Biotechnology, which provided transgenes for the study. In other research on non-food crops, a day-neutral variety of Vernonia galamensis, which produces an industrially important epoxy fatty acid in the seed oil, was developed and released. For Objective 2, research focused on determining the physiological, biochemical and molecular factors that limit the growth and yield of oilseed, latex, and biomass crops. For guayule, CO2 enrichment studies demonstrated that “sink strength”, and not carbon availability, was limiting for rubber production. A comprehensive analysis of gene expression in guayule bark tissues was also conducted to determine which genes might be involved in production of rubber, but surprisingly, expression of genes generally thought to correlate with rubber synthesis did not change. In Objective 3, efforts focused on improving the economics of new/alternative industrial crop production systems. For lesquerella, remote sensing methods were developed and utilized for optimizing fertilizer applications and harvesting dates. For guayule, methods were developed for rapid extraction and analysis of rubber, alternative uses of guayule waste were explored (including particle boards and thermoplastics), conditions of post-harvest plant storage were optimized, and many agronomic factors such as plant harvest height, herbicide application, irrigation, and nitrogen application were optimized for maximizing rubber yields. Many of these results directly benefit end-users such as Yulex Corporation and Bridgestone, who are interested in developing tires made from renewable, sustainable sources of natural rubber.
1. Identification of enzymes important for production of high value waxes in plant seeds. The desert shrub, jojoba, produces a liquid wax in its seeds that can be extracted and used in formulations of skin creams and cosmetics. If produced on a larger scale, liquid wax from jojoba could be used as an environmentally friendly replacement for hydraulic fluids, motor oil, or transmission fluids. One approach for producing higher amounts of jojoba-type liquid waxes is to use transgenic techniques to produce the wax in higher yielding platform crops such as oilseed rape or camelina. To do so requires knowledge of the genes involved in both the synthesis of the liquid wax in seeds, as well as the enzymes required for breakdown of the oil to support post-germinative growth. Scientists from the UK, Canada, and the ARS lab in Maricopa, Arizona, have identified and functionally characterized two of the key enzymes in jojoba that are involved in breaking down the waxes to support post-germinative growth. The genes encoding these enzymes will be very useful in designing crop plants that are engineered to produce high amounts of liquid waxes in developing seeds, and will have greatest immediate impact on scientists and research programs that are focused on production of value added, renewable chemicals in the seeds of plants.
Rajangam, A.S., Gidda, S.K., Craddock, C., Mullen, R.T., Dyer, J.M., Eastmond, P.J. 2012. Molecular characterization of the fatty alcohol oxidation pathway for wax-ester mobilization in germinated jojoba seeds. Plant Physiology. 161:72-80.