Project : USDA ARS

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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

2020 Annual Report

Objectives
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.

Approach
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
Progress was made on all five objectives and their sub-objectives, with the first four objectives under National Program 215, Component 2, Improve the physiology and genetics of animals and plant materials for enhanced health, vitality and utility of pasture, biomass for feed and fuel, and rangeland, and turf systems, and the fifth objective under NP 215 Component 4, Generate strategies to manage grass, forage, and rangeland agroecosystems that simultaneously contribute to environmental conservation and are beneficial to human and animal use. In support of Sub-objective 1A, ARS scientists at Logan, Utah, made progress in identifying populations of bluebunch wheatgrass with superior seedling development under environmental fluctuations. Two controlled experiments were completed with annual grass and biennial weed species to explore ideal water and nutrient regimes for future weed-resistance experimentation with bluebunch wheatgrass populations. In support of Sub-objective 1B, progress was made in elucidating the genetic basis and extent of genotypic variation for drought and salt tolerance in common pasture, rangeland, and turf grasses. Meadow and tall fescue were established in a deficit irrigation experiment, and forage mass determined. Field evaluations were completed for both Kentucky bluegrass and perennial ryegrass under salt stress, and greenhouse evaluations completed for Kentucky bluegrass under drought stress. Molecular genetic research included generating DNA sequences from disomic wheat addition and/or translocation lines containing alien wheatgrass and/or wheat-grass translocation chromosomes. DNA markers of diploid bluebunch wheatgrass were mapped on seven homologous groups of chromosomes and compared with those of bread wheat and barley and reported in GENOME. In support of Sub-objective 1C, to develop pasture and rangeland grass and legume cultivars and germplasm with improved cold, salt, and drought tolerance, field evaluations of orchardgrass and timothy populations were completed for winterhardiness, forage mass, and cell wall digestibility and the best genotypes of each species were selected. Forage production, plant phenotype, and survival of alfalfa were also evaluated under saline conditions, and selected plants were provided to a collaborator. A seed increase field (e.g., Foundation seed) was established for a future release of an alfalfa cultivar with improved drought-tolerance and grazing persistence. In support of Sub-objective 2A, ARS scientists at Logan, Utah, made progress in developing weed resistant plant materials with improved seed yield, seedling establishment, and persistence for conservation and restoration of rangelands. Genotyping and one year of measurements were completed for six seed production traits on 1,309 bluebunch wheatgrass mother plants, which comprise the training population for genomic selection of weed resistance. Testing of this training population was initiated by establishing progeny in the field to evaluate seedling establishment and persistence traits. Progress was made toward releases of improved germplasms of basalt milkvetch with greater vigor and seed production, and salina wildrye with greater spike number per plant, less seed-shattering, and greater overall seed yield. In support of Sub-objective 2B, to identify seeding methodology that increases establishment of desirable plants and reduces weed invasion on rangelands, species mixtures and seeding methodologies were identified to increase the success of Conservation Reserve Plantings (CRP) in the United States. Controlled experiments were completed with Thurber’s needlegrass and bluebunch wheatgrass to explore optimal watering regimes by comparing them to slow and fast developing squirreltail and bluegrass varieties to refine growing conditions. In support of Objective 3, ARS scientists at Logan, Utah, continued to develop new plant materials with improved nutritive value and forage productivity. Breeding for the new cultivars, ‘AlkarXL’ tall wheatgrass and ‘Highwest’ meadow bromegrass were completed and release notices submitted. Data were collected at two locations for forage mass and nutritive value in support of a putative tall fescue cultivar release. A QTL population was established, an RNAseq study conducted and sequenced, and an association population was developed in a three-pronged approach to finding genes affecting perennial ryegrass forage quality. Orchardgrass breeding populations were screened for water soluble carbohydrate concentration and forage mass. Genotyping and one year of measurements were completed for eight seed production traits on 2,233 intermediate wheatgrass mother plants, which comprise the training population for genomic selection of improved forage and seed traits. Testing of this training population was initiated by establishing progeny in the field to evaluate forage and seed production traits. In support of Sub-objective 4A, to identify genetic methods that improve the efficiency of developing reduced maintenance turfgrass germplasm, ARS scientists at Logan, Utah, have initiated genome sequencing of Kentucky bluegrass, hard fescue, and annual bluegrass using new PacBio technology and Big Data servers. These sequenced genomes will provide a source for comprehensive detection and sorting of gene families necessary to improve cool-season turfgrasses. In support of Sub-objective 4B, to determine the extent of Genotype x Environment x Management interactions on reduced maintenance turfgrass performance, plants of crested, intermediate, thickspike, and western wheatgrass were selected for improved turf and established in the field to enable them to hybridize. The turf potential of these species was described in peer-reviewed journal article. To extend the utilization of drought-tolerant warm-season turf, multiple warm-season turf grass species were evaluated for cool temperature color retention in the Intermountain climate. In support of Objective 5, to identify efficient pasture and rangeland-based grazing strategies that simultaneously improve economic and environmental sustainability of livestock production, ARS scientists at Logan, Utah, completed forage nutritive analyses from a grass-legume mixture grazing study. Multivariate analysis to determine the forage traits primarily influencing dry matter intake by dairy heifers was initiated.

Accomplishments
1. AlkarXL, a new tall wheatgrass cultivar developed for use on saline semiarid lands. With the urban spread in the western United States, farmers and ranchers rely more and more on marginally productive soils that are frequently high is salinity to produce forage. Tall wheatgrass is one of the most salt tolerant grasses used for fall and winter livestock grazing on dryland saline soils. ARS scientists at Logan, Utah, in collaboration with seed companies developed and released a new tall wheatgrass cultivar ‘AlkarXL’ with better forage quality for use on saline soils. Across multiple locations, years, and harvests, AlkarXL’s produced 6,773 kg/ha of forage mass, which was on average 14% greater than five common tall wheatgrass cultivars, and AlkarXL’s July crude protein (CP) of 6.2% was 11% greater than the check cultivars. AlkarXL also had greater CP in October from regrowth (12.8%) than these cultivars and was well above the 7% CP level needed by grazing ruminant livestock. Seed of AlkarXL is now commercially available, providing an improved forage grass for marginal saline rangelands.

2. Identification of genes instrumental in turfgrass salt tolerance. Cool season turfgrasses are increasingly subjected to salty effluent irrigation or grown in saline soils. However, most current cultivars of Kentucky bluegrass are not adapted to saline conditions, so there is a need to better understand the Kentucky bluegrass response to salt stress and develop more salt tolerant germplasm. ARS researchers at Logan, Utah, have identified salt tolerant Kentucky bluegrass germplasm and the specific genes associated with the salt tolerance. DNA markers are now being developed for these genes, thus providing critical genomic tools for understanding the genetic control of salt tolerance in cool-season grasses and reducing up to 50% of the time (e.g., typically requires approximately 10 years) to develop marketable Kentucky bluegrass varieties with improved salt tolerance.

3. Dramatic shoot/root response differences among grasses provide clues to successful rangeland restoration. Grasses are the most important group of plants used in rangeland seedings where wildfire and invasive species threaten desired intermountain ecosystems. While some grasses establish readily in intermountain environments, many native species struggle to establish. Therefore, ARS researchers in Logan, Utah, sought to uncover the reasons for this by examining the effect of water on root and shoot growth of seven species. Crested wheatgrass, cheatgrass, and western wheatgrass increased both root and shoot biomass in response to water, while four other native grasses also increased shoot growth but curtailed root growth. These dramatic differences may help to explain why crested wheatgrass and cheatgrass readily establish on semiarid rangelands, while many native grasses have limited seedling establishment. This finding will enhance the development of improved seedling establishment in the more recalcitrant native species, thereby improving the success of re-seeding efforts, and ultimately making western rangelands more fire and weed resistant.

4. Mixtures of tall fescue with alfalfa and birdsfoot trefoil improve growth performance and economic return of beef steers. High nitrogen (N) fertilizer costs and increased environmental stewardship have renewed interest in grass–legume pastures. However, it was not clear how grass-legume mixtures would compare to fertilized grass for forage and livestock growth in highly productive, irrigated environments. Therefore, ARS researchers at Logan, Utah, compared herbage mass, nutritive value, steer growth performance and economics of binary mixtures of tall fescue with alfalfa (TF+ALF) and birdsfoot trefoil (TF+BFT) to tall fescue with (TF+N) and without N fertilizer (TF–N). Overall, TF+BFT and TF+ALF pastures had slightly less herbage, but better nutritive value and increased steer growth performance compared to TF+N, without the added cost of fertilizer. Net returns for TF+BFT and TF+ALF were $1197/ha and $846/ha, respectively. These high economic returns for TF+BFT and TF+ALF were 2.4 and 1.7 times greater than TF+N, respectively, and competitive with many other crops grown in the region, demonstrating an alternative to public land grazing when high-quality irrigated pastures are available.

5. Ecological indicators for evaluating resilience of sagebrush ecosystems. Sagebrush habitat for wildlife, including elk, deer, and sage-grouse is currently imperiled due to conifer encroachment, wildfire, and climate change. Millions of dollars are spent annually by land and wildlife management agencies to evaluate and recover these sagebrush habitats. Thus, determining recovery rates of sagebrush is critically needed in order to prioritize conservation efforts. ARS researchers at Logan, Utah, in collaboration with Utah State University and the Nature Conservancy evaluated post-disturbance recovery of sagebrush ecosystems to fire. Monitoring criteria, based on sagebrush age and size, were identified as valuable indicators to compare and prioritize conservation efforts over variable landscapes. Furthermore, results indicated that within 10 years, critical ecosystem components (indicators), such as perennial grass and forb abundance substantially recovered. These results offer an optimistic outlook for future recovery of sagebrush ecosystems, particularly for the suitability of sage-grouse habitat. This information provides land and wildlife management agencies a cost-saving tool for documenting and prioritizing sagebrush recovery after wildfire.

6. Seed mass is an indicator of growth strategy in bluebunch wheatgrass. Bluebunch wheatgrass is the most widely used perennial native grass for restoration seedings in the western Great Basin. Seed mass varies among populations, but most widely used sources feature relatively low seed mass. ARS researchers at Logan, Utah, examined the relationship between seed mass and subsequent seedling growth among bluebunch wheatgrass populations. They discovered that populations with higher seed mass produced seedlings with greater shoot and root biomass, whereas, those with less seed mass produced seedlings with greater surface area of leaves and roots. Thus, high seed mass favors short-term growth, while greater surface area of leaves and roots is more conducive to long-term growth. This growth strategy concept may be useful for matching bluebunch wheatgrass populations to specific site conditions, thereby increasing the success of rangeland re-seedings and making them more weed resistant.

7. Two closely-related wheatgrass species display contrasting traits - perhaps explaining why they occupy distinct habitats. Thickspike and Snake River wheatgrass are two closely related native grasses used for rangeland restoration, but they differ in their choice of habitat. ARS researchers at Logan, Utah, found that, in contrast to Snake River wheatgrass, thickspike wheatgrass displayed traits associated with a low-nutrient growth strategy, including, less leaf surface area (e.g., thick leaves) and greater leaf carbon-to-nitrogen ratio. This finding was consistent with the habitat, infertile sandy soils, that thickspike wheatgrass typically occupies. Surprisingly, populations of thickspike wheatgrass also displayed a high seedling growth rate and established very well relative to other native grasses. This discovery has prompted ARS scientists to seek to develop thickspike wheatgrass germplasm specifically adapted to the infertile, highly disturbed soil conditions that result from repeated wildfires.

8. Pioneering report on the genetic control of compatibility in grass legumes mixtures. High nitrogen (N) fertilizer costs and increased environmental stewardship have renewed interest in grass–legume pastures. It has been hypothesized that the genetic control of forage traits, especially biomass, for grass plants growing in grass-legume mixtures is different than when in a grass monoculture, however, this is largely unvalidated, especially at the DNA level. ARS researchers at Logan, Utah, used an experimental intermediate wheatgrass population to examine the effect of three competition environments (widely spaced-plants, grass-legume mixture sward, and grass monoculture sward) on classical and molecular genetic measures associated with biomass, plant morphology, and forage nutritive value. The study verified that the genetic control of grass biomass in a monoculture versus a grass-legume mixture is only partially the same, with additional genes expressed in monoculture, and that biomass in widely spaced-plants versus swards is predominantly under different genetic control. These results indicate that selection for improved grass biomass will be most successful when conducted within the targeted monoculture or grass-legume mixture sward environment per se. This pioneering report on the genetic control of mixture compatibility at the DNA level is especially important as scientists work to develop grasses and legumes specifically adapted for mixtures. These novel mixtures, comprised of compatible grass and legume varieties, are projected to increase forage and livestock productivity of pasture and rangelands while decreasing dependence on petroleum-based commercial fertilizer.

U.S. DEPARTMENT OF AGRICULTURE

Forage and Range Research: Logan, UT