Location: Forage-animal Production Research2008 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
Research conducted under this project improves forage management and ecosystem stability through enhanced understanding of plant-endophyte associations, impacts of endophytes on pasture ecology, secondary/fungal metabolite functions within forages, and the utilization of alternative forages and forage systems and addresses National Program (NP) 215, Rangeland, Pastures and Forages, Action Plan Component 2, “Pasture Management Systems to Improve Economic Viability and Enhance the Environment”. Specifically, this research addresses Problem Statements D (Need for appropriate plant materials to improve the economic viability and enhance the environment in pasture-based livestock systems), and E (Need for economically viable pasture-livestock systems for the Mid-South that enhance the environment). Further, a high level of cooperation is required between this NP 215 project and the companion NP 101 project (6440-32360-001-00D) at the Forage-Animal Production Research Unit. Specific progress made this cycle (new since February 2008) includes: development of two rice protein isoaspartyl methyltransferase (PIMT) genes have been isolated; analysis of expression of the rice PIMT genes in rice plants have been initiated; one partial PIMT gene (similar to the rice PIMT2 gene) has been isolated; an ecdysone inducible promoter has been expressed in rice plants as a model system for monocots and analysis of the gene expression for the reference gene, GUS, is currently underway; data collection for the first year of a forage variety evaluation trial comparing animal and pasture performance of wild type endophyte-infected tall fescue and two novel endophyte-infected tall fescues (1 newly developed) has been completed. The bridging project (6440-21310-002-00D) contains additional progress report information relevant to this project. Further information is available in the Annual Report for the Congressionally mandated Specific Cooperative Agreement (6440-21310-002-05S, Continuation of Improved Forage Livestock Production Systems) that is partially funded by this project. Likewise, relevant information is available in the sister project (6440-32630-001-00D, Optimizing the Biology of the Animal-Plant Interface for Improved Sustainability of Forage-based Animal Enterprises) to this project. NP 215, Component: 2, Problem Statement: D and E.
1. Understanding Tall Fescue/Fungal Endophyte Effects on Nutrient Cycling in Southeastern U.S. Pastures. Localized research from Georgia found that endophyte-infected tall fescue pastures supported larger soil nutrient pools, suggesting that this important agricultural plant-fungal endophyte symbiosis plays a role in carbon sequestration and promoting soil fertility. We investigated whether this finding was geographically robust (i.e., found at multiple sites). We identified and sampled >13 tall fescue pastures, with paired, adjacent endophyte-infected and endophyte-free plots, located throughout the southeastern United States. Surface soils were analyzed for organic carbon and total nitrogen and microbial community composition and biomass. Showed that the Georgia findings are robust in that endophyte-infection appears to enhance the ability of tall fescue pastures to store carbon and enhance soil fertility across the southeastern U.S., although effects on the microbial communities are less pronounced. These results highlight that the tall fescue–endophyte symbiosis can have significant environmental impacts in addition to well known animal health issues, and suggest that more research is needed to understand the mechanisms producing these results. NP 215, Component 2, Problem Statement E.
2. Evaluating horse pastures in Central Kentucky. Research regarding microscopic analysis of horse manure to determine diet composition was initiated because pregnant mares grazing pastures containing tall fescue are vulnerable to tall fescue toxicity and a validated method of readily assessing tall fescue consumption in production mares was not available. This research showed that microscopic analysis (i.e., microhistological analysis) of grass fragments from horse manure can be used to determine the percentage of individual cool season grasses that horses are consuming on pasture. This finding may prove to be a useful diagnostic tool to predict the potential for fescue toxicity or diagnose extent of exposure in horses grazing fescue pastures in the central and eastern U.S. NP 215, Component 2, Problem Statement E.
3. Spatial Variability of Soil and Chemical Properties in an Endophyte-Free Fescue Pasture Compared to an Orchard Grass/Perennial Ryegrass Pasture. Forage transition is expected to influence soil physical and chemical properties in the short and long term. However, direct comparisons of how forages effect soil properties are limited. Therefore, this research examined chemical and physical properties in two uniformly flat pastures seeded with endophyte-infected and endophyte-free forage varieties. We determined that spatial distribution of nutrients by depth and distance were not similar. Whereas, in an endophyte-infected fescue pasture all nutrients, with the exception of pH and K, had considerable spatial variability, an orchard grass pasture exhibited spatial variability by depth, but had far less variability by distance. Forage choice has consequences on soil properties that will impact management decisions. NP 215, Component 2, Problem Statement E.
4. Plant age/clipping effect on alkaloid accumulation. Endophyte-infected (E+) tall fescue (TF) accumulates peramine, ergot, and loline alkaloids (LA) with the LA’s present in much greater amounts than the other alkaloids. The predominant LA’s present are N-formyl and N-acetyl loline. Accumulation of LA’s is a significant determinant for ecological fitness. Distribution of LA’s and relationship to endophyte distribution have not been fully determined. Research was conducted to determine endophyte distribution in TF and accumulation of LA’s in different plant tissues. Demonstrated in flowering plants: greatest LA abundance is in the spikelet with much lesser amounts in descending order in the rachis, stem, leaf sheath and leaf blade; endophyte was highest in the rachis with leaf blades containing the least; positive linear correlation existed between endophyte amount and LA’s in the stem, rachis, and leaf blade; small amounts of LA’s were present in roots from plants grown in soil or sand culture but not roots grown in solution culture. Demonstrated in vegetative plants: LA’s are highest in the pseudostem with lesser amounts in the leaf blade; pseudostem contained >/= 2X more endophyte than the blade; no significant correlation between endophyte and LA concentration exists; LA concentrations were similar in initial harvest from 3 to 13 weeks after seeding followed by increasing alkaloid contents. Results indicate that the LA’s are translocated within the plant such that analysis of endophyte content is not sufficient to determine location of the LA’s within plants when interpreting herbivore (esp. insect) feeding studies. NP 215, Component 2, Problem Statement D.
5. Significant Activities that Support Special Target Populations
University of Kentucky Spindletop Research Farm Field Day June 12, 2008 in Lexington, KY. Research results were presented to cattle and horse producers (many small operations). University of Kentucky Pasture Management Update February 28, 2008 in Lexington, KY. Research results were presented to horse producers (many small operations).
Tavva, V.S., Palli, S.R., Dinkins, R.D., Collins, G.B. 2008. Improvement of a Monopartite Ecdysone Receptor Gene Switch and Demonstration of its Utility in Regulation of Transgene Expression in Plants. FEBS Journal. 275:2161-2176. doi:10.1111/j.1742-4658.2008.06370.x