Research Accomplishment Reports 2011

Influence of Tall Fescue Cultivar and Endophyte Genotype Combinations on Root System Architecture, Exudate Composition and Soil Biogeochemical Processes

D.H. McNear
Department of Plant and Soil Sciences

 

Non-Technical Summary

Tall fescue (Tf) covers greater than 15 million hectares within the United States and is considered one of the most desirable forage species for grazing livestock. Tall fescue has garnered a lot of attention because the shoot-specific fungal endophyte it harbors produces toxic alkaloids resulting in animal sickness and loss of productivity. As a result novel endophyte infected varieties have been produced that maintain the positive attributes of the resident fungus, but eliminates the alkaloids toxic to grazing animals.

While much of the attention has been directed toward resolving the toxicity issues associated with the above ground portions of the plant, only anecdotal evidence exists on how altering this shoot-specific fungus-plant relationship alters rhizosphere processes. There is evidence from pastures dominated by common toxic endophyte infected Tf that there is a slower turnover of C and other nutrients which has been indirectly attributed to (among other things) alterations in microbial community composition (a topic we are addressing in a concurrent proposal). It has also been postulated that the fungus-plant relationship can change root system architecture and root exudate chemistry which in turn influences the mechanism these plants use to access nutrients from the soil.

The research proposed herein will provide important and novel data on how fungal-endophyte genotype and Tf-cultivar combinations alter root system architecture and root exudate chemistry and what influence this has on nutrient acquisition and cycling in the rhizosphere. The proposed study will be unique from other studies on this topic in that it will integrate plant physiological analysis with advanced analytical techniques and classical soil chemical methods to identify changes in root system architecture and root exudate chemistry specific to fungal and Tf genotypic combinations to elucidate their effects on nutrient acquisition and cycling in the rhizosphere.

These goals will be accomplished by coupling a novel high throughput root system architecture screening method with methodical analytical mass spectrometric and chromatographic analyses of root exudate chemistry from novel and common toxic endophyte infected and endophyte free tall fescue varieties to assess their influence on nutrient acquisition using conventional soil chemical techniques.

Results from this research will generate basic knowledge on how an agriculturally-important, widely occurring plant-fungal symbiosis impacts plant physiology, soil chemical properties, nutrient use and cycling. Understanding how plant endophytes alter plant physiology and soil chemical processes can be applied to improving food and energy crop productivity and provide insights into the structure and function of natural ecosystems.