Location: Forage-animal Production Research2013 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:
This final report documents progress made in meeting objectives of the 2007-2012 Project Plan. Over 75,000 tall fescue sequences were obtained from sequencing reverse transcribed ribonucleic acid (RNA) from various tissues and different conditions. These sequences can be used to monitor expression under differing environmental conditions to improve tall fescue persistence and forage quality. A number of red clover genes were identified as being similar to soybean flowering genes and will ultimately be used to determine genetic control of flowering in perennial species. An in silico approach was used to map over 1,000 red clover genes with known genetic locations to the Medicago truncatula genome. Broad regions of similarity and identification of numerous chromosomal rearrangements between the two genomes will be valuable in studying genetic expression in forage legumes. A simple analytical method with high performance liquid chromatography was developed to extract and quantify water-soluble carbohydrates. A procedure was developed to increase the large scale extraction efficiency and partial purification of the ergot alkaloids in infected fescue seed to improve our ability to control amounts of ergot alkaloids exposed to digestion and absorption. RNA profiling of clone pairs of endophyte-infected and -free tall fescue was performed to evaluate the effects of the endophyte on host plant gene expression under unstressed and water deficit conditions. A determination was made of tiller recovery and accumulations of metabolites between three clone pairs of endophyte-infected and -free tall fescue plants under water deficit stress. A late maturing tall fescue genotype infected with the AR584 non-toxic endophyte was found to alleviate fescue toxicosis in steers and generate higher animal carrying capacities than Jesup MaxQ, the standard non-toxic endophyte infected tall fescue, in the early summer. It was determined that chemical seed head suppression in late vegetative growth of toxic endophyte fescue can reduce fescue plant losses while maximizing suppression of seed heads. A technique using near infrared reflectance spectroscopy was developed to determine grass species composition in manure from horses, which will serve as a tool in studying relationships between species composition in the diet and pasture species composition. Differences in chemical, physical, and biological characteristics were found between soils from adjacent stands of endophyte-infected and -free fescue located at 13 sites across southeastern USA. Carbon sequestration by endophyte-infected fescue stands was greater than for stands of endophyte-free fescue. It was determined that endophytes do not affect nutrient leaching, and that earthworm distribution depended more on forb content and monoculture than on endophyte status. Scientists determined that populations of herbivorous and predatory arthropods differed little among pasture grasses containing toxic and non-toxic endophytes. Armyworms grew equally well on fescue differing in leaf blade texture, and their susceptibility to virus infection did not differ between armyworm feeding on smooth and spiny grass blades.
1. Alignment of Medicago (M.) Truncatula and red clover chromosomes: A comparative genomics tool to advance genetic improvement of red clover. The genetic improvement of red clover is hampered by a lack of genetic tools namely due to its cross-pollination nature. However, red clover is closely related to the model legume M. Truncatula, where the genome has been sequenced, providing an opportunity to use genomic information available from M. Truncatula for genetic improvement of red clover. Publically available mapping data in red clover were superimposed onto the chromosomal locations of M. Truncatula, thereby generating a putative chromosomal map of red clover. Broad regions of similarity between the two species were identified, as well as locations where chromosomal rearrangements have occurred. This work provides a step towards utilizing a molecular approach for red clover improvement.
2. Flowering in forage legumes. Flowering is a complex trait, regulated by large number of genes from several genetic pathways interacting with the environmental conditions. In addition, the factors that regulate flowering in legumes had not yet been elucidated. Using the available genomic resources in the model legume soybean (Glycine max) as it became available, putative genes were isolated and were verified to function similarly to regulate flowering as shown for the model species. Ribose nucleic acid was isolated from the forage legume. A number of genes, similar to the soybean flowering genes, have been found from the sequencing project and isolated. The genetic overlap between red clover and soybeans will be used to determine how these genes affect flowering in a perennial species.
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