Location: Wheat, Sorghum and Forage Research
2022 Annual Report
Objectives
1. Develop best management practices for annual and perennial grasses to increase livestock production, provide biomass feedstocks for bioenergy, and preserve and maintain the nation’s natural resources. (NP215 1A, 2C, 4B, 4C)
2. Develop new forage and biomass germplasm and cultivars for central U.S. growing conditions. (NP215 1A, 2C)
3. Identify molecular, biochemical and plant characteristics that impact livestock and bioenergy production to develop improved breeding criteria and improved management practices. (NP215 1A, 2C)
Approach
Project objectives are to develop best management practices for annual and perennial grasses for livestock production, provide feedstocks for bioenergy, develop new forage and biomass cultivars for the central U.S., and identify molecular, biochemical, and plant characteristics that impact livestock and bioenergy production and complement breeding and management research. Perennial grass breeding techniques will be refined to design improved cultivars. Improved management methods will be developed to fully utilize the genetic potential of new cultivars by enhancing establishment, yield, and utilization by livestock and by the bioenergy industry. Molecular biology and biochemistry/physiology information will be utilized to improve breeding and management products. The project is a continuation of a long-term perennial grass research program with plant materials, management, and related studies in various stages of development and completion. Research will be conducted on C3 (cool-season) and C4 (warm-season) perennial grasses, and C3 annual grasses. All are needed to maximize the length of the growing season and more fully utilize available land. Switchgrass, big bluestem, and indiangrass are the primary C4 species being evaluated for use in livestock and/or bioenergy production systems. Triticale, a winter annual, will be developed for forage/cover crop use as a double-crop option with early spring grazing and improved soil conservation. New technologies from this research, when utilized on 6 million hectares in the Midwest, could produce biofuels for 15 million cars, increase beef production per hectare by 10%, and increase early spring forage production by 6 million animal unit months.
Applying N fertilizer in the planting year for perennial grasses like switchgrass, big bluestem, and Indiangrass is not well studied and is poorly understood. We will evaluate the interaction of seeding rate, N rate, and N formulation on switchgrass establishment and planting year yield. Although N fertilization on established switchgrass has been studied broadly, little research has been conducted to determine the role of N formulation and application timing. For studies on established stands, we will evaluate the effects of N rate and N formulation (granular vs. foliar-applied) applied at three different growth stages on subsequent switchgrass yield and composition. These studies will serve as baselines and will be expanded to different species and cultivars.
Progress Report
The project has three main components, management, breeding, and molecular biology/biochemistry. This project leads the development of switchgrass into a biomass energy crop and has numerous collaborations. This project has developed most of the grasses and associated management information used for grassland reseeding in the central United States, and much of the management information for switchgrass grown as a biomass energy crop. Fundamental science has been developed on cell wall properties and their genetic control, and information and data are being used extensively in switchgrass genomics. 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 United States.
Objective 1 research continued on developing best management practices for annual and perennial grasses to increase livestock production, provide biomass feedstocks for bioenergy, and preserve and maintain the nation’s natural resources. Precipitation was a limiting factor in 2021, with carryover into 2022. Although annual precipitation in 2021 was only about 4 inches below the long-term mean, precipitation was highly variable and plant growth was severely limited. In 2021, the site received no measurable precipitation in February, March, November, and December and only 0.27 in of precipitation in April. Additionally, the site received 8.11 inches of precipitation in August 2021, more than two times the long-term average. The dry conditions in 2021 carried over to limiting yield in 2022. In Sub-objective 1A, integrated crop-livestock systems for the Great Plains that include smooth bromegrass, switchgrass, triticale, wheat, rye, corn, and soybeans are being evaluated. This project is in a scheduled transition to convert the Shawnee switchgrass pasture to a warm-season grass mixture pasture (seeded in spring 2021) to provide future increased animal performance. The Liberty switchgrass pasture was sprayed with glyphosate in early spring 2021 to reduce cool-season grass invasion then interseeded with Liberty to improve stand density. Due to dry growing conditions in 2021 and early 2022 the pastures were not grazed in 2022 and will be harvested for hay. The dryland corn will be managed as planned. Grazing wheat, rye, and triticale in the spring before planting soybeans produced an average daily gain (ADG) of 2.9 to 3.1 lbs./head/day in 18 grazing days, with total grazing days limited by the dry conditions. In Subobjective 1B, field practices continued and 2022 represents the 25th year of growing switchgrass and no-till corn on marginally productive cropland. This long-term field study is the first to demonstrate that continuous corn and perennial grass systems maintain or mitigate atmospheric GHGs during the agronomic phase of bioenergy production and that soil organic carbon continues to increase on marginally productive croplands. In Subobjective 1C, the field-scale production of Liberty switchgrass, big bluestem, a low-diversity warm-season grass mixture, and Independence switchgrass continued. Dry growing conditions in late 2021 and early 2022 have limited growth in these fields. Post-frost harvests in November 2021 demonstrate the dry growing conditions with dry matter yields ranging from 3.2 tons/acre for the low diversity mixture to 5.4 tons/acre for Independence switchgrass, a reduction of 35-40% from previous years.
Objective 2 research continued to develop new forage and biomass germplasm and cultivars for the central U.S. In Subobjective 2A, five perennial grass species are being bred for both livestock and bioenergy production systems. Breeding values of both parents and progeny are being updated in multi-generational analyses. A genomic selection framework using quantitative trait locus mapping, classical genetics, physiology, transcriptomics, and virology is being evaluated to maximize the genetic potential of switchgrass for biomass yield, quality, and disease (rust and mosaic) resistance. The switchgrass progeny tests were phenotyped for biomass, photosynthesis potential, and diseases. Seeds were collected on the bromegrass and Indiangrass crossing block nurseries. Biomass and quality data were collected on the regional trials. A second generation of three propagation nurseries were planted for potential release of switchgrass cultivars and will need to be repeated. In Subobjective 2B, the crosses have been expanded with several populations of switchgrass. Crosses were made within and across populations as biparental and polycrosses. Seeds were germinated in the greenhouse and seedlings recently transplanted into the field. In Subobjective 2C, as a first in switchgrass, crosses were made between tetraploid and octoploid switchgrass using a 4x-derived octoploid germplasm as a bridge to transfer genes for adaptation and for increasing yield and genetic diversity. Seeds were obtained, germinated, and seedlings recently transplanted into the field. In Subobjective 2D, the phenotypic and genomics data were collected and are being processed to evaluate the potential of integrating genomic selection into breeding switchgrass for forage and bioenergy. The mapping population was phenotyped for biomass, quality, and rust disease. The genotyping of the mapping population was completed and is being merged with the phenotypic data for quantitative trait locus (QTL) mapping and for genomic selection/prediction. In Subobjective 2E, an additional year of biomass yield was collected for select populations. Material is being evaluated for greenhouse crosses.
Objective 3 research continued on Subobjective 3A, switchgrass plants with contrasting responses to rust were grown in a greenhouse and inoculated with rust. Data of responses to rust were recorded and plant tissues collected at regular intervals from infected and non-infected plants. Several biochemical analyses have been completed. For Subobjective 3B, parent plants selected from a field nursery in consultation with a geneticist were transplanted into a new field nursery in fiscal year 2022. Originally, ramets from these parent plants were to be moved to a greenhouse for crossing. Due to the delay imposed by the pandemic, crossing in the greenhouse is projected for fiscal year 2023. Under Subobjective 3C, new genomic data available via Department of Energy, Joint Genomes Institute will be mined for genes unique to different accessions of switchgrass based on research needs.
Accomplishments
1. Handheld near-infrared spectroscopy (NIRS) units provide rapid testing for nitrogen content in warm-season grasses. ARS scientists from Lincoln, Nebraska, and colleagues developed a process to transfer NIRS calibrations from a benchtop to two handheld spectrophotometers to predict N content of switchgrass, big bluestem, and Indiangrass. The handheld units varied by cost and scanning characteristics. The most expensive handheld unit with the greatest spectral capacity produced similar results to the benchtop unit. The less expensive handheld unit with limited spectral capacity was not as accurate and precise as the more expensive handheld unit, but it was still useful for ranking and screening samples. The approaches developed provide a framework to use existing benchtop calibration models in handheld units, allowing scientists and practitioners to rapidly and accurately deploy handheld NIR instruments in the field, reducing the time and expense required to predict plant composition.
2. Proteomic analyses provide gene targets that could improve rust resistance in switchgrass. ARS researchers at Lincoln, Nebraska, in collaboration with scientists at the University of Nebraska completed a proteomic analysis of switchgrass responses to rust infection. Rust infection can lower biomass yields and compromise plant quality. Global analyses of proteins can inform about cellular responses to rust infection and potentially pinpoint genetic traits that differentiate plant resistance mechanisms. Two switchgrass cultivars, Summer which is highly susceptible to rust and Kanlow which is moderately resistant to rust were infected with switchgrass rust under controlled conditions in a greenhouse. Leaves were harvested at routine intervals and extracted proteins quantified by proteomic analyses. We documented proteins that were commonly and uniquely different during the progression of rust infection in the moderately resistant cultivar Kanlow as compared to the rust-susceptible cultivar Summer. Kanlow plants had limited changes to their proteomes and early defense responses were dampened with time, whereas the proteomes of Summer plants had increasing numbers of proteins associated with severe stress. Genes encoding these differentially accumulated proteins will be assessed for contribution to rust resistance/susceptibility in genotyped breeding nurseries.
3. Genetics determines variable climate sensitivity in switchgrass. Polyploidy provides a means by which plants can adapt to new environments, but little is known about how polyploid forms arise and how they may have adaptive advantage. Through a combination of approaches, ARS researchers in Lincoln, Nebraska, in collaboration with numerous colleagues uncovered evidence for the genetic origins, niche differentiation, and differential environmental sensitivity of two polyploid forms (4X, 8X) of switchgrass. These findings suggest that polyploid switchgrasses exist across broad portions of the geographic range of switchgrass because they represent both generalist (8X) and specialist (4X) adaptive strategies. This unique combination of strategies in a single species has allowed switchgrass expansion and will give plant breeders additional resources to increase switchgrass yield and winter survival for bioenergy and other uses.
Review Publications
Edme, S.J., Mitchell, R. 2021. Genetic analysis of yield and quality traits in switchgrass based on population crosses. Agronomy. 11(11):2220. https://doi.org/10.3390/agronomy11112220.
Zhang, L., MacQueen, A., Weng, X., Behrman, K.D., Bonnette, J., Reilley, J.L., Rouguette, F.M., Fay, P.A., Wu, Y., Fritsci, F.B., Mitchell, R., Lowry, D.B., Boe, A.R., Juenger, T.E. 2022. The genetic basis for panicle trait variation in switchgrass (Panicum virgatum). Theoretical and Applied Genetics. 135:2577-2592. https://doi.org/10.1007/s00122-022-04096-x.
Christenson, E., Jin, V.L., Schmer, M.R., Mitchell, R., Redfearn, D.D. 2021. Soil greenhouse gas responses to biomass removal in the annual and perennial cropping phases of an integrated crop livestock system. Agronomy. 11(7). Article 1416. https://doi.org/10.3390/agronomy11071416.
Napier, J.D., Grabowski, P., Lovell, J.T., Bonnette, J., Mamidi, S., Gomez-Hughes, M.J., VanWallendael, A., Weng, X., Handley, L.H., Kim, M.K., Boe, A.R., Fay, P.A., Fritschi, F.B., Jastrow, J.D., Lloyd-Reilley, J., Lowrey, D.B., Matamala, R., Mitchell, R., Rouquette, F.M., Wu, Y., Webber, J., Jones, T., Barry, K., Grimwood, J., Schmutz, J., Juenger, T.E. 2022. A generalist-specialist trade-off between switchgrass cytotypes impacts climate adaptation and geographic range. Proceedings of the National Academy of Sciences(PNAS). 119(15). Article e2118879119. https://doi.org/10.1073/pnas.2118879119.
Hamada, Y., Zumpf, C., Cacho, J., Lee, D., Lin, C., Heaton, E., Boe, A., Boersma, N., Mitchell, R., Negri, C. 2021. Remote sensing-based estimation of advanced perennial grass biomass yields for bioenergy. Land. https://doi.org/10.3390/land10111221.
Rukundo, I., Danao, M., Mitchell, R., Weller, C. 2022. Transfer of a calibration model from a benchtop to a handheld NIR spectrometer to predict nitrogen content of warm-season forage. Biosystems Engineering. https://doi.org/10.1016/j.biosystemseng.2022.04.014.
Muhle, A.A., Palmer, N.A., Edme, S.J., Sarath, G., Yuen, G., Mitchell, R., Tatineni, S. 2022. Effect of cultivars and temperature on synergistic interaction between panicum mosaic virus and satellite panicum mosaic virus in switchgrass. Phytopathology. https://doi.org/10.1007/s00705-022-05412-y.
