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Research Project: Improved Plant Genetic Resources and Methodologies for Rangelands, Pastures, and Turf Landscapes in the Semiarid Western U.S.

Location: Forage and Range Research

2019 Annual Report

The semiarid rangelands, irrigated pastures, and turfgrasses of the western U.S. provide a broad array of critical ecosystem services, but invasive weeds, frequent drought, hotter temperatures, wildfires, and other disturbances are increasing the rate of rangeland and pasture degradation and threaten their long-term productivity. Therefore, the long-term objective of the Forage and Range Research Lab (FRR) is to develop resilient, weed resistant, and productive plant materials and methodologies to help prevent and solve these important natural resource issues. Research will be in the areas of (1) Rangeland Conservation and Restoration, and (2) Pasture and Turf Productivity and Sustainability. Specifically, during the next five years we will focus on the following five objectives: Objective 1: Develop new plant materials for pasture, rangeland, and turf systems with increased resilience to harsh and variable environments. Sub-objective 1A: Identify populations of bluebunch wheatgrass wheatgrass [Pseudoroegneria spicata (Pursh) Á. Löve] with superior seedling development under environmental fluctuations. Sub-objective 1B: Elucidate the genetic basis and extent of genotypic variation for drought and salt tolerance in common pasture, rangeland, and turf grasses. Sub-objective 1C: Develop pasture and rangeland grass and legume cultivars and germplasm with improved cold, salt, and drought tolerance. Objective 2: Develop new plant materials and management practices that decrease the impact of invasive species and improve productivity, utility, and restoration of semiarid rangelands. Sub-objective 2A: Develop weed resistant plant materials with improved seed yield, seedling establishment, and persistence for conservation and restoration of rangelands. Sub-objective 2B: Identify seeding methodology that increases establishment of desirable plants and reduces weed invasion on rangelands. Objective 3: Develop new plant materials with improved nutritive value and forage productivity, thereby increasing livestock performance and carrying capacity of pastures and rangelands. Objective 4: Develop new turfgrass plant materials with improved aesthetic value when grown under reduced maintenance conditions. Sub-objective 4A: Identify genetic methods that improve the efficiency of developing reduced-maintenance turfgrass germplasm. Sub-objective 4B: Determine the extent of Genotype x Environment x Management (GxExM) interactions on reduced maintenance turfgrass performance. Objective 5: Identify efficient pasture and rangeland-based grazing strategies that simultaneously improve economic and environmental sustainability of livestock production.

Traditional plant breeding, augmented by genomics and ecology, multi-location field evaluation, greenhouse microcosm experiment, deficit irrigation and physiological, genomic and molecular marker approaches will be used to achieve project objectives. Sub-objective 1A: Seedling mortality is a threat to revegetation success in semiarid ecosystems. Microcosm experiments will determine the variation for seedling response to environmental gradients of temperature, soil moisture, and nutrients. Sub-objective 1B: Deficit irrigation experiment will determine the feasibility of meadow fescue for the western U.S. Physiological and molecular markers will elucidate the response of turf species to drought and salt stresses; identify and characterize the alien Triticeae genes in wheat that confer salt tolerance and stem rust resistance; and create a DNA map of drought genes in bluebunch wheatgrass. Subobjective 1C: Multi-location evaluation will be employed to develop winter-hardy, drought-tolerant, and/or salt-resistant germplasm of orchardgrass, timothy, and alfalfa. Sub-objective 2A: Native grasses and legumes often lack seed production and establishment. Utah sweetvetch, basalt milkvetch, and Salina wildrye germplasms with improved seed production will be developed. The effect of pre-plant seed treatment on establishment of Utah trefoil will be determined. Genomic selection’s (GS) greatest benefit is when phenotypic evaluation is ineffective; therefore, the potential of GS to improve seed production and establishment in rangeland species will be determined using bluebunch wheatgrass as a model. Subobjective 2B: Many Conservation Reserve Program and Bureau of Land Management plantings in the western U.S. are unsuccessful due to poor establishment of native grasses, legumes and forbs. Seed mixtures that increase seedling establishment success in semiarid regions will be identified. Rapid root development, a potential trait enabling perennial grass seedlings to compete with annual grasses, will be quantified. Objective 3: Recurrent and genomic selection and will develop tall fescue, meadow bromegrass, and tall and intermediate wheatgrass germplasms with improved nutritive value throughout the grazing season. Candidate genes for digestibility will be identified in perennial ryegrass using ribonucleic acid sequencing (RNA-seq) and quantitative trait loci (QTL) analyses. Sub-objective 4A: Kentucky bluegrass and hard fescue have complex genomes that slow their genetic improvement. Genomic and molecular marker approaches will characterize and find functional genes for reduced-maintenance traits. Subobjective 4B: Turfgrass irrigation is not environmentally sustainable, therefore, wheatgrass, bermudagrass, and zoysiagrass will be characterized in mixtures and for color retention in cold temperatures. Objective 5: Reduced dry matter intake (DMI) of pasture by grazing cattle is a major factor limiting livestock performance. Grass-legume pastures that require fewer inputs, have high mass and nutritive value, and have high DMI will be identified.

Progress Report
This report documents progress for the new project 2080-21000-018-00D, “Improved Plant Genetic Resources and Methodologies for Rangelands, Pastures, and Turf Landscapes in the Semiarid Western U.S.” which completed National Program (NP) 215 Grass, Forage, and Rangeland Agroecosystems, Office of Scientific Quality Review (OSQR) review and began in February 2019. This project continues research from the bridging project 2080-21000-016-00D and expired project 2080-21000-014-00D, “Develop Improved Plant Genetic Resources to Enhance Pasture and Rangeland Productivity in the Semiarid Regions of the Western U.S.” See the reports for these previous projects for additional information. Progress was made on all five objectives and their subobjectives. Regarding Sub-objective 1A, progress was made in identifying bluebunch wheatgrass with superior seedling establishment by developing a new technique to measure seedling growth under different temperature regimes with a key change of replacing calorimetric measurements with direct gas exchange measurements. Under Sub-objective 1B, progress was also made in identifying the genetic basis of salt- and drought-tolerance in pasture, rangeland, and turf grasses by; a) establishing plots of meadow fescue in a line-source irrigation experiment to investigate the role of endophyte-infection on drought tolerance; and b) collecting deoxyribonucleic acid (DNA) samples from wheat and tall wheatgrass populations containing stem rust Ug99-resistance and salt tolerance genes. Under Sub-objective 1C, progress was made in developing pasture and rangeland plants with improved cold, drought, and salt tolerance, by establishing trials in six locations, in cooperation with the University of Saskatchewan and Agriculture and Agri-Food Canada, to characterize the winter hardiness and summer drought tolerance of orchardgrass and timothy grass. Under Sub-objective 2A, significant progress was made towards developing weed-resistant rangeland plants by; a) harvesting seed from and sequencing DNA from 1,386 bluebunch wheatgrass plants that will be used to develop genetic models and germplasm with improved seed production and seedling establishment; and, b) establishing evaluation nurseries and initiating additional selection for seed production in Basalt milkvetch, Salina wildrye, and Creeping wildrye. Under Sub-objective 2B, progress was made towards identifying seeding methodology that reduces weed invasion on rangelands by; a) discovering that scarification followed by prechilling is required for germination of Utah trefoil seed; b) quantifying differences in rate of seedling root development in bottlebrush squirreltail, Sandberg’s bluegrass, and other grasses under development using a robot-image collection system to acquire daily images of root development; and, c) preparing study sites for later phases of seedling root experimentation. Regarding Objective 3, progress was made in developing new plant materials with improved nutritive value and forage productivity by: a) collecting forage trait data in support of the future release of new tall wheatgrass, meadow bromegrass, and tall fescue cultivars; b) establishing orchardgrass sward plots for data collection on overall agronomic performance, water-soluble carbohydrate concentration, and cell wall digestibility; c) harvesting seed, measuring forage traits, and sequencing DNA from 2,233 intermediate wheatgrass plants that will be used to develop genetic models and improved germplasm for improved forage and grain production traits; and, d) identifying genes and DNA variants associated with forage and seed production traits of intermediate wheatgrass, with ARS scientists in Salina, Kansas. Regarding Sub-objective 4A, significant progress was made towards identifying genetic methods that improve the efficiency of developing low-maintenance turfgrass by identifying and sequencing the genome of a poly-haploid plant of Kentucky bluegrass and using the resulting assembly to differentiate genes related to vernalization. Under Sub-objective 4B, progress was made towards the evaluation of genotype x environment x management interactions in low-maintenance turf by completing turf evaluations of wheatgrass seeded turf plots and selecting lines for further evaluation and development of new cultivars. Regarding Objective 5, significant progress was made in identifying efficient pasture and rangeland grazing strategies by; a) completing research that identified management strategies that lead to successful establishment of legumes into established grass swards; and b) continuing with grazing studies on grass-legume mixtures with data indicating that energy and digestibility were highly associated with dry matter intake.

1. Gene discovery for grain production in a dual-purpose perennial grain and forage crop. Perennial plants enhance ecosystem services by reducing soil erosion and nutrient runoff/leaching and improving wildlife habitat. As such, perenniality would be a valuable option for grain production, but attempts to capture this complex trait from wheat-perennial wheatgrass hybrids has not been commercially successful. In contrast, efforts to breed intermediate wheatgrass (IWG) itself as a dual-purpose forage and grain crop have demonstrated useful progress and commercial applications such as Kernza® grain, but its grain yields are significantly less than wheat. ARS scientists at Logan, Utah, cooperated with researchers from The Land Institute, Kansas State University, University of Minnesota, and the U.S. Department of Energy to identify chromosome regions and candidate genes associated with 17 grain production traits in intermediate wheatgrass, such as seed size, shattering, and threshing. The researchers identified 42 potential domestication genes that could augment the domestication of IWG and other wild relatives of wheat. These findings will enhance the further development of IWG as a perennial grain, thereby, resulting in increased environmental and economic sustainability of grain production on semi-arid and/or erodible croplands.

2. Discovery of choke-resistant germplasm provides hope for orchardgrass seed production. Orchardgrass is one of the top four cool-season forage grasses worldwide, and an important crop in the grass-seed growing regions of the U.S. However, since 1996 orchardgrass seed production has been reduced up to 30 percent by the disease called choke, caused by an inconspicuous systemic fungal endophyte that quickly grows around the developing grass flowers and “chokes” out seed development. This disease is particularly difficult because no fungicides have been effective in reducing the prevalence of choke, and there are no choke resistant cultivars. ARS scientists at Logan, Utah, initiated development of choke-resistant cultivars by evaluating numerous orchardgrass populations for choke prevalence at two Oregon locations where they found significant environmental variation across years and locations. Some plants were found with little or no choke infection, which will be used for development of choke-resistant cultivars. The research resulted in a seminal publication in Plant Disease, and a Cooperative Research and Development Agreement partnership to develop choke-resistant orchardgrass cultivars.

3. Establishment and persistence needed to restore cheatgrass-infested rangelands. In the Great Basin, invasive annual cheatgrass is estimated to have displaced approximately 25 million acres of native perennial vegetation, leading to catastrophic and costly wildfire cycles. As a result, land management agencies spend millions in re-seeding efforts, but restoring western U.S. rangelands dominated by invasive annuals, such as cheatgrass, to a diverse, healthy, perennial plant-dominated ecosystem can be difficult with native grasses, and most studies don’t look at the long-term effect of such re-seeding efforts. ARS scientists at Logan, Utah, studied seedling establishment and plant persistence over five years of native grasses compared with typically used crested and Siberian wheatgrasses at four locations in Idaho, Wyoming, and Utah, ranging in mean annual precipitation from 11 to 16 inches. Across these four sites, native grass seedling establishment of bottlebrush squirreltail, bluebunch, slender, and Snake River wheatgrasses were similar to Siberian wheatgrass; however, by year five, western, Snake River, and thickspike wheatgrasses were the only native grasses to have plant densities similar to Siberian and crested wheatgrasses. This study documented that in these cheatgrass-infested semiarid regions, many native grasses can establish, but in general lack the ability to persist, leading to continued cheatgrass and wildfire. The research provides important information for land managers making decisions concerning what species to plant on rangeland revegetation projects and indicates that seed mixes that include combinations of species that establish quickly, persist, and compete against invasive annual grasses is necessary for rangeland restoration.

4. A shrub management handbook to enhance rangeland ecosystem services. Shrub encroachment on western U.S. rangelands is a primary threat to forage productivity and ecosystem health. Consequently, ranchers and wildlife managers throughout the region must carefully develop land-management plans using state-of-art ecological principles to meet the forage and habitat needs for livestock production wildlife. ARS scientists at Logan, Utah, with partnering state and federal agencies, used comprehensive datasets they developed to assess and synthesize fundamental ecological principles and produce a five-chapter handbook on shrub management. The handbook was developed to provide ranchers and producers a step-by-step guide to understand and apply science-based principles to enhance shrub management outcomes. By using the handbook, producers will gain valuable information about 1) developing a management plan and how to obtain and use publicly available resources to assist with setting management goals, 2) the comprehensive biology of five primary shrub species that pose the largest threat to agricultural productivity in the region, 3) the various technologies to manipulate shrub abundance and to re-seed using desirable plant materials developed by ARS scientists in Logan, Utah, and lastly, 4) how these treatments and seedings improve habitat for critical wildlife species. In addition, this handbook includes an extensive glossary and list of relevant on-line resources to assist producers obtaining soil surveys, monitoring management success, herbicide technology, shrub reduction technology, and seeding/planting guidelines.

Review Publications
Stonecipher, C.A., Thacker, E., Welch, K.D., Ralphs, M.H., Monaco, T.A. 2019. Long-term persistence of cool-season grasses planted to suppress broom snakeweed, downy brome, and weedy forbs. Rangeland Ecology and Management. 72(2):266-274.
Riginos, C., Veblen, K.E., Thacker, E.T., Gunnell, K., Monaco, T.A. 2019. Disturbance type and sagebrush community type affect plat community struction following shrub reduction. Rangeland Ecology and Management. 72(4):619-631.