Location: Plant Physiology and Genetics Research2009 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 breding 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 devised and evaluated utilizing traditional plus new/alternative crops to develop systems that provide farmers 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: The third year of field studies to determine heat units needed for optimum growth and development with relationship to seed yield and oil quality of lesquerella was completed. Homozygous populations with 0% linoleic, 0% linolenic, 0% lesquerolic + 85% oleic acids were developed. A population with seed oil contents over 35% was evaluated in the field. Methods were developed for stable genetic transformation of Lesquerella fendleri and Lesquerella pallida. Plants were transformed with a castor bean hydroxylase gene to establish proof of principle and also test whether expression of additional hydroxylase activity in seeds can raise the level of hydroxyl fatty acid in seed oil, similar to the high amounts of hydroxyl fatty acids observed in castor oil. First generation transgenic plants have been obtained, and studies are continuing to test for stability of the newly introduced trait in subsequent plant generations. Guayule: Transgenic guayule lines with Mendel Technology were evaluated in the field for morphological traits and in the laboratory for 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-transgenetic parent. Samples from herbicide tests completed in 2008 are being evaluated for rubber and resin contents to determine if herbicides used in plant establishment affected rubber and resin yields. A three year field study was completed at Halfway, Texas to screen for cold tolerance in guayule germplasm. Samples were taken for biomass yield and rubber and resin concentration determination. A new test was established based on preliminary analyses of these results which showed there are differences in the germplasm for cold tolerance in guayule germplasm at this location. The first year of a study to determine the effects of month of harvest on guayule rubber, resin, and biomass yields and the subsequent regrowth of plants following harvest was conducted. A study was initiated to determine if a ploidy analyzer could be used to accurately reflect ploidy levels in guayule germplasm. Methods were developed for accelerated solvent extraction of resin and rubber from guayule tissue. These methods, coupled with the development of more rapid and accurate procedures for measuring resin and rubber, increased the speed of germplasm evaluation in field and growth chamber studies of guayule. Other oilseeds: Selection nurseries were established for camelina and vernonia and improved germplasm identified for further evaluation and crossing.
1. Planting date and temperature impact on lesquerella growth and development -- Optimum planting dates and growing temperatures for lesquerella need to be defined in order to maximize yields. Fall and spring plantings were established over three years and compared for the number of buds, flowers, and siliques (seed) as well as total plant biomass and seed yield produced weekly corresponding to the available heat units. ARS scientists in Maricopa, AZ, found that spring planting had a shorter growing season and lower yield than fall planting in Arizona. The optimum temperature for seed development was between 70 and 85 degrees Fahrenheit. The results indicated that reduced yields from spring plantings may still be a viable option for growers due to fewer inputs and lower production costs.
2. Enzymes involved in fat production are located in specific regions of plant cells. Fats are essential components of all plant cells and make up the bulk of the “oil” that is stored in developing seeds. Many enzymes are involved in the production of fats, but little is known about how these enzymes are organized in plant cells to carry out their various functions. In collaboration with scientists at the University of Guelph, Ontario, Canada, ARS scientists at Maricopa, AZ have demonstrated that a certain class of enzymes called GPATs (glycerol-3-phosphate acyltransferases) are located in distinct areas of the cell. The GPAT enzymes perform the first step in formation of certain types of fat, and knowledge of their cellular properties helps to unravel the details about how fats are produced in plants. This information will be of immediate benefit to other scientists interested in fat production, and will be useful in longer term efforts to produce plants with altered or higher amounts of vegetable oils.
3. Development of methods for rapid extraction and analysis of rubber and resin from guayule. The commercially-valuable products of the alternative crop, guayule, are resin and rubber. These products are difficult to extract and analyze. New methods were developed for automated extraction of the plant tissue and for improved speed and accuracy of rubber and resin analysis. ARS scientists in Maricopa, AZ, discovered that by increasing the rate of sample through-put, the new methods allow germplasm to be evaluated more rapidly to select superior varieties of guayule for commercialization in arid agriculture systems.
4. Commercialization of guayule as a source of latex for the manufacture of medical products is becoming a reality. Four potential problems have been identified with the liquid waste stream from latex extraction – 1) an unpleasant odor, 2) negative effects on soil properties, 3) loss of latex in the waste liquid, and 4) treatment and disposal costs. Results of research conducted by ARS scientists in Maricopa, AZ, showed that the unpleasant odor of the waste streams can be corrected, negative effects on soil properties can be overcome by recycling two of the waste streams and minimal treatment of the third waste stream, and lost latex can be recovered by recycling two of the waste streams. The results from this initial study indicate that the potential problems associated with the waste streams generated during guayule latex production can be overcome relatively easy and result in potential beneficial use of the waste streams, resulting in reduced treatment and disposal costs.
5. Effects of plant population and planting date effects on guayule latex, rubber, and resin yields. Guayule is being commercialized in the southwestern USA utilizing new germplasm lines that have not been fully evaluated for the effects of various agronomic practices on their biomass, latex, rubber, and resin yields. ARS scientists in Maricopa, AZ, evaluated three of the lines being used in commercialization for biomass, latex, rubber, and resin concentrations and yields at two plant populations (recommended and 2X recommended), two transplant dates (fall and spring), and six harvest dates (1 year old – 3.5 years old). Results showed little effect of transplanting date or plant population, but that spring harvests were better than fall harvests and the lines AZ-1 and AZ-3 had greater biomass, while AZ-5 had a higher content of latex, rubber, and resin . These results will be of benefit to the new guayule industry to determine optimum transplanting and harvesting dates, plant populations, and lines to use in guayule production.
6. Post-harvest storage effects on guayule latex, rubber, and resin contents and yields. Guayule is a new crop being commercialized for hypoallergenic latex production. Since natural processes that occur in the plant following harvest result in loss of latex almost immediately and immediate processing of shrub for latex on a commercial scale is not feasible, a storage system that maintains latex concentration and yield is needed. ARS scientists in Maricopa, AZ, compared nine different storage systems to fresh harvested shrub. Results showed that keeping harvested shrub moist prior to latex extraction maintained latex yields and concentration compared to dry storage, increasing extractable latex yields by as much as 100%. The recommendations developed from this research on postharvest storage of guayule will allow growers and processors more flexibility in their harvesting and processing schedules.O'Quin, J.B., Mullen, R.T., Dyer, J.M. 2009. Addition of an N-terminal epitope tag significantly increases the activity of plant fatty acid desaturases expressed in yeast cells. Applied Microbiology and Biotechnology. 83:117-125.