Location: Wheat, Sorghum and Forage Research2014 Annual Report
The overall objectives of this continuing long-term project are to develop improved perennial grasses, management practices, and technologies for use in grazing lands and biomass energy production systems in the central USA. Over the next five years, the following specific objectives will be addressed. (1) Develop best management practices for Midwest and central Great Plains perennial grass, mixed grass, and grass-legume pastures to increase livestock production, provide biomass feedstocks for bioenergy production, and maintain ecosystem services; (2) Develop new cool- and warm-season grass cultivars and native legume germplasm for Midwest and Great Plains growing conditions; and (3) Identify biomass characteristics that impact conversion efficiency to liquid fuels. Utilize this information to develop improved breeding criteria and improved management practices.
Improved perennial grasses and legumes and associated management practices will be developed for use in the Central Great Plains and Midwest for bioenergy production and grazing when grown on land that is unsuitable or marginal for grain crop production. Perennial plant breeding technologies will be used to develop the improved cultivars. Improved management methods will be developed to fully utilize the genetic potential of the new cultivars by enhancing establishment, yields, and utilization by livestock, and all aspects of biomass energy crop production. Basic molecular biology and biochemistry/physiology information will be developed that will improve the breeding and management products. The project is a continuation of a long-term perennial grass project that has plant materials, management, and basic science studies in various stages of development and completion. Research will be conducted on both C3 (cool-season) and C4 (warm-season) grasses because both are needed in the region to maximize the length of the grazing season. Switchgrass, big bluestem, and indiangrass will be the primary C4 species and will be developed for use in both bioenergy and livestock production systems. Smooth and meadow bromegrass and intermediate, tall, and western wheatgrass will be bred for use in cool-season pastures. Native legumes will be enhanced for use with C4 grasses in biomass production systems. Grass technologies from this research when utilized on 6 million hectares in the Midwest could produce biofuels for 15 million cars. Beef production per hectare from pastures with new cultivars and improved management could be improved by 10 to over 25%.
Objective 1: Studies are in progress to identify molecular triggers that can predict dormancy in switchgrass seeds. Switchgrass seed lots were assayed for germination and response to applied chemicals that might stimulate germination. One seed lot with a strong response to hydrogen peroxide was used to obtain transcriptome data (expressed genes) using next-generation sequencing technologies. A 3-year bromegrass grazing trial was completed and livestock performance and nutritive value results were summarized. A new smooth bromegrass cultivar is in the release process based on the results of this grazing trial. The third year of a warm-season grass grazing trial was initiated and has produced excellent beef cattle gains in both pure stands and mixtures. Year 17 of the long-term switchgrass and no-till corn bioenergy study was initiated and the plots of Liberty switchgrass inserted into the study 2-years ago were established. Analysis of nutrient removal is progressing. Multi-location field trials of switchgrass, big bluestem, and perennial grass mixtures in NE, IA, IL, IN, MN, and WI are fully established and biomass and quality analysis is expanding our understanding of how perennial grasses will perform in different environments and has resulted in numerous technology transfer opportunities. Objective 2: Polycross nurseries of crosses of advanced experimental strains of six switchgrass, two sand bluestem, and four bromegrass populations established in FY13 were managed, harvested for biomass, and samples processed for quality evaluation. Four big bluestem populations were advanced to the next generation of selection. Biomass and seed harvests of smooth bromegrass, intermediate wheatgrass and tall wheatgrass breeding nurseries from previous evaluation years were completed as scheduled. Some advanced generations of perennial grasses experienced significant winterkill in FY14. The winter survival of high-yielding lowland switchgrass plants moved north of their adaptation region is often related to the hardiness of the below-ground tissues. Understanding the molecular and biochemical mechanisms that underlie dormancy and winter-survival is essential. During FY14, both next-generation sequencing and metabolite analyses were completed on switchgrass crown and rhizome tissues obtained from a number of populations with varying levels of winter hardiness. Analysis of these large datasets is generating large amounts of sequence data to be deposited in publically available databases. Native legume evaluations were maintained and seed production completed as scheduled. Objective 3: Plants were significantly damaged by early winter weather. Plants will be collected during FY14 and it is likely that all subsequent Milestones can be met.
1. Understanding gene expression profiles of mineral transporters and mineral content in switchgrass tissues can lead to improved biomass quality and production practices. Mineral nutrition is an important aspect of plant growth, and plant mineral composition can affect ethanol conversion efficiencies. Using a combination of biochemical and bioinformatics tools, ARS scientists in Lincoln, NE in collaboration with University of Nebraska scientists, discovered the expression patterns and profiles of a large array of mineral transporters in different switchgrass tissues. Mineral analysis suggested that some minerals were more likely to be transported from the shoots to the rhizomes at the end of the growing season. This research will be used to develop breeding strategies to improve switchgrass and other warm-season grasses for use in the bioenergy sector.
2. Winter-hardiness can be a limiting factor in the production of high-yielding switchgrass germplasm across the Central Great Plains. ARS scientists in Lincoln, NE and colleagues from the University of San Diego integrated new and published data to develop models that might explain the cellular and molecular events impacting winter-hardiness in switchgrass populations. These models can be used to test the roles of key genes, and potentially provide genetic markers that can be exploited to improve winter-hardiness in elite, high-yielding switchgrass germplasm. The results will have application to the improvement of winter-hardiness in other warm-season perennial grasses.
3. Switchgrass stands managed for bioenergy are invaded by other grasses. Switchgrass is considered the model perennial grass for bioenergy and has been planted for forage and conservation purposes for more than 75 years. However, there is a concern that switchgrass grown as a biofuel crop could, in turn, invade other plant communities. ARS scientists in Lincoln, NE demonstrated for the first time that switchgrass managed as a biofuel crop is not invasive, but is invaded by other grass species. Following 10 years of different management practices, soil fertility and harvest management appear to dictate which grasses will invade switchgrass. Applying no N fertilizer caused switchgrass to decline and other warm-season and cool-season grasses to increase. Applying at least 60 kg N ha-1 was adequate N to meet switchgrass growth demands, limit stand invasion by other grasses, and maintain quality switchgrass stands. Harvesting switchgrass once each year in August with no N fertilization caused switchgrass stands to be replaced by cool-season grasses. Harvesting switchgrass after fall dormancy resulted in fewer invasions by other regionally-aggressive grasses. These results demonstrate that switchgrass is more prone to being invaded by other grasses than becoming invasive itself.
Koch, K.G., Fithian, R., Heng-Moss, T.M., Bradshaw, J.D., Sarath, G. 2014. Evaluation of tetraploid switchgrass populations (Panicum virgatum L.) for host suitability and differential resistance to four cereal aphids. Journal of Economic Entomology. 107:424-431.
Sarath, G., Baird, L., Mitchell, R. 2014. Senescence, dormancy and tillering in perennial C4 grasses. Plant Science. 217-218C (2014):140-151.
Koch, K.G., Heng-Moss, T.M., Bradshaw, J.D., Sarath, G. 2014. Categories of resistance to greenbug and yellow sugarcane aphid (homoptera: aphididae) in three tetraploid switchgrass populations. BioEnergy Research. 7: 909-918. DOI 10.1007/s12155-014-9420-1
Asmaradasa, B.S., Donze-Reiner, T., Heng-Moss, T., Sarath, G., Amundsen, K. 2014. Characterizing differential gene expression in polyploid grasses lacking a reference transcriptome. OA Biotechnology. 3:1.
Palmer, N.A., Saathoff, A., Donze-Reiner, T., Waters, B., Heng-Moss, T., Twigg, P., Tobias, C.M., Sarath, G. 2014. Global changes in mineral transporters in tetraploid switchgrasses (Panicum virgatum L.). Frontiers in Plant Science. 4:1-12.
Schmer, M.R., Vogel, K.P., Varvel, G.E., Follett, R.F., Mitchell, R.B., Jin, V.L. 2014. Energy potential and greenhouse gas emissions from bioenergy cropping systems on marginally productive cropland. PLoS One. 9:e89501. DOI:10.1371/JOURNAL.PONE.0089501 2014.
Vogel, K.P., Mitchell, R., Sarath, G., Casler, M.D. 2014. Registration of 'liberty' switchgrass. Journal of Plant Registrations. 8:242-247. DOI:10.3198/jpr2013.12.0076crc.