Location: Forage-animal Production Research2011 Annual Report
1a. Objectives (from AD-416)
The long-term goal of this project is to improve competitiveness and sustainability of forage-based enterprises in the transition zone of the Eastern half of the United States of America. Over the next five years we will focus on the following objectives as determined by stakeholder input and ARS National Program 215 (Rangeland, Pastures and Forages) approval. Objective 1. Improve persistence, productivity, and quality of forage grasses and legumes for use in the transition zone of the Eastern and Midwestern U.S. Subobjective 1.A. Determine relative interactions between tall fescue (TF) and endophytes involved in regulating plant growth, forage quality, and persistence under a variety of environmental conditions. Subobjective 1.B. Identify, characterize, and manipulate useful traits (chemical, physical, genetic) to develop forages that are: biologically diverse, tolerant of biotic and abiotic stresses, competitive, high quality for animal production, persistent, and easy to establish and maintain. Objective 2. Improve animal and forage productivity on forage-based systems through optimal combinations of forages, supplementation and grazing systems tailored to animal needs and environmental conditions. Subobjective 2.A. Evaluate forage production characteristics relevant to plant and animal performance on pastures containing new novel endophyte-infected (EI) TFs. Subobjective 2.B. Develop a forage system for the upper transition zone that utilizes warm season perennial grasses to improve animal performance and profitability. Subobjective 2.C. Identify the abiotic/biotic components and mechanisms of the plant-animal-environment interface impacting pasture production and environmental quality factors.
1b. Approach (from AD-416)
Forage systems provide low-cost feed, conserve soil and water resources, and mitigate man’s impact on the environment. Limited basic biological information exists on how plant and/or fungal metabolites affect forage plant quality, persistence, and production. Even less information exists on the cross-talk mechanism between tall fescue (the predominant forage of the transition zone) and its endophyte. Furthermore, little is known about the impact that forage and/or fungal metabolites have on their pasture ecosystems. Gaps in our current knowledge are hindering researchers’ abilities to predict and select best combinations of forages and management systems for use by various forage-animal production enterprises. Aiding researchers to develop new forage varieties, forage systems, and management recommendations will require an improved understanding of both metabolite (plant and fungal) profiles and their biological functions at the molecular and organismal levels. Such understanding of metabolites, molecular mechanisms, and whole-organism responses, and of their impact on plant quality, persistence, and production, is necessary for improving sustainability of forage-based enterprises. This Project Plan, through the development and utilization of cutting-edge technologies and real-world testing, proposes to decipher the complex interactions within the animal-plant-environment interface. In order to accomplish this task and improve sustainability of forage-based enterprises, the following two objectives are proposed: 1) Improve persistence, productivity, and quality of forage grasses and legumes for use in the transition zone of the Eastern and Midwestern United States; and 2) Improve animal and forage productivity on forage-based systems through optimal combinations of forages, supplementation, and grazing systems tailored to animal needs and environmental conditions. These objectives are focused on the predominant forage of the transition zone, tall fescue, as well as on its alternatives and companion species. Accomplishing these objectives will improve sustainability of forage-based enterprises through improved forages, forage management and systems, and basic understanding of the plant/fungal metabolite effects on forage plant persistence and production, as well as consequent effects on the structure and function of pasture ecosystems.
3. Progress Report
Forages provide low-cost animal feed and feedstock for bioenergy, conserve soil and water resources, and help mitigate man’s impact on the environment. Increasing the utilization of forages through understanding of the animal-plant-environment interface leads to more informed decisions regarding management protocol development for capitalizing on forage’s beneficial effects: production of a safe and nutritious food supply, sustainability of rural communities and the environment. ARS plant scientists are developing alternatives to and researching the biology of toxic endophyte (fungus)-infected tall fescue for reducing toxicity in grazing animals. Fescue toxicosis associated with this forage is estimated to cost U.S. producers nearly one billion dollars annually. Understanding the crosstalk mechanisms between the endophyte and its host, tall fescue, would be a major step toward developing control methods for toxicant production, and continue to capture of environmental stress tolerance. To understand these mechanisms, ARS plant scientists at the Lexington, KY, location analyzed the genes being expressed in an additional 2 tall fescue clone pairs. Clone pairs have identical plant genetics, with one of the pair having the endophyte. The data is currently being examined to determine what is differentially expressed as a result of the endophyte’s presence. This is a necessary step in developing the clones as research models for study of crosstalk mechanisms during environmental stress (e.g., drought). Further, initial experiments have been conducted toward transforming the genetics of the tall fescue plant by over-expressing or knocking down expression of certain traits via gene manipulation. These types of studies aid in understanding the endophyte/tall fescue relationship and may offer potential control measures for the toxicity as well as improved stress tolerance in the plant. Additional progress for this project is provided in the report documenting the unit’s collaborative research conducted under a Specific Cooperative Agreement entitled “Improving Sustainability of Forage-Based Production” between ARS and the University of Kentucky (UK).
1. Fungal endophyte effects on plant species diversity, plant production, and trace gas fluxes. The common toxic fungal endophyte known to be in symbiosis with tall fescue across the United States has been shown to reduce surrounding plant diversity and enhance soil carbon storage; however, it is not known whether emerging novel endophytes will similarly affect these ecological parameters. University of Kentucky researchers working under a Specific Cooperative Agreement with the Lexington, KY, location and in collaboration with ARS scientists determined whether 2 novel endophytes currently on the market (AR-542 and AR-584) have similar effects to the common toxic strain on plant diversity when in symbiosis with tall fescue. In addition, an evaluation of whether soil trace gas fluxes are affected by endophyte presence and genotype was completed. These researchers showed that the effects of these novel endophytes on plant diversity and production are less than those of the common toxic strain, but are still different from endophyte-free tall fescue alone. They also showed that these novel endophyte associations promote trace gas loss to the atmosphere at certain times of the year. These results suggest that replacement of tall fescue infected with the common toxic strain of fungal endophyte with the more animal 'friendly' novel endophytes will have ecological consequences.
2. Soil enzyme activity in endophyte-infected and -free fescue. Endophyte-infected fescue may adversely affect soil function in terms of metabolic activity. University of Kentucky researchers working under a Specific Cooperative Agreement with the ARS scientists at Lexington, KY, measured enzyme activity in forage transition systems to see this effect. Over a two-year period we sampled soil enzyme activity at two depths and 16 locations in a sinkhole for 4 forage treatments. Enzyme activity was highly stratified by depth, being 5-10 times higher at 0-10 cm depth than 10-20 cm depth. Activity was somewhat stratified by location, being higher in the center of sinkholes than on the slopes. Activity was significantly reduced by processes to kill existing grasses and replace with fescue varieties. Level of endophyte infection was not a consistently significant effect. It is the process of replacing existing forage rather than replacement by endophyte-free species that dominates the soil enzyme activity. The data indicate that stand replacement will impair soil nutrient cycling for at least one year. Thus, it may be necessary to apply higher fertilizer rates in order to promote good stands in the affected fields for future use (e.g., grazing, environmental buffer zones).
3. Nutrient transport in response to forage transition. Establishing new forages in sinkholes could lead to adverse soil water quality. University of Kentucky researchers working under a Specific Cooperative Agreement with the ARS scientists at Lexington, KY, installed resin lysimeters at a sinkhole pasture site and measured nutrient leaching at 50 cm depth over a one-year period. Nutrient loss was dramatic in the period following the transition from old to new pasture variety. Potassium in particular was a major cation loss. In spring, after nitrogen (N) fertilization, there was a significant increase in N loss, but there was very little impact of fescue type on that loss. The most significant effect on nutrient leaching was position in the sinkhole itself, being greatest in slope positions with the shallowest soils. Nutrient loss resulting from transition to endophyte-free fescue is unlikely to be as important in sinkhole pasture environments as the actual effect of removing the existing vegetation and having diminished root intensity during the initial transition period. Thus, nutrient applications during the transition should be applied in a planned and careful approach.
4. Baculovirus infection of the armyworm feeding on spiny- or smooth-edged leaf blades. Standard tall fescue cultivars have abundant edge spines along the leaf margins, but grass breeders have developed new cultivars with smooth leaf margins for increased palatability to livestock. Since physical leaf structures such as spines may be important in facilitating infection of armyworms with an important baculovirus that controls pest outbreaks, it was possible that armyworm outbreaks might be more severe when caterpillars fed on smooth-edged grasses. University of Kentucky researchers working under a Specific Cooperative Agreement with ARS scientists at Lexington, KY, showed that a baculovirus is not less infective when caterpillars feed on smooth-edged grass blades. Smooth textured grasses may be planted for improved livestock performance without increased risk of damage from armyworm outbreaks.Bacetty, A.A., Snook, M.E., Glenn, A.E., Noe, J.P., Nagabhyru, P., Bacon, C.W. 2009. Chemotais disruption in protylenchus scribneri by tall fescue root extracts and alkaloids. Journal of Chemical Ecology. 35:844-850.