SOIL ORGANIC MATTER AND NUTRIENT CYCLING TO SUSTAIN AGRICULTURE IN THE SOUTHEASTERN USA
Location: Athens, Georgia
Title: Soil microbial community function, structure, and glomalin in response to tall fescue endophyte infection
Submitted to: Plant and Soil
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 24, 2010
Publication Date: October 16, 2010
Citation: Buyer, J.S., Zuberer, D.A., Nichols, K.A., Franzluebbers, A.J. 2010. Soil microbial community function, structure, and glomalin in response to tall fescue endophyte infection. Plant and Soil Journal. DOI: 10.1007/S11104-010-059Z-Y. 339:410-412. 2011.
Interpretive Summary: Tall fescue plants are naturally infected with a fungus that offers host-plant resistance to environmental and biological stresses, but through its production of toxic chemical compounds causes a variety of health disorders in grazing animals. One of the beneficial ecological consequences of fungus infection is the accumulation of soil organic matter, either through enhanced plant production and/or through reduced soil microbial activity. Scientists at the USDA-Agricultural Research Service in Beltsville MD, Mandan ND, and Watkinsville GA, along with a scientist from Texas A&M University, quantified the changes in soil microbial community structure and function throughout a year of tall fescue growth. Some microbial functions were inhibited by endophyte infection of tall fescue, but effects were subtle. A soil with low microbial biomass was more negatively affected by endophyte infection of tall fescue than a soil with higher microbial biomass, suggesting that a threshold level of challenge may have occurred. The subtle, short-term changes in soil microbial community structure and function in response to endophyte infection support previous observations of long-term changes in soil organic carbon and nitrogen storage in field studies. These results will have implications for producers managing soil quality on the 14 Mha of tall fescue in the eastern USA, for scientists in understanding the mechanisms of plant-soil-microbial interactions, and for policy makers in promoting conservation practices for sequestering soil organic carbon.
Tall fescue [Lolium arundinaceum (Schreb.) S.J. Darbyshire] is naturally infected with a fungal endophyte, Neotyphodium coenophialum, which produces toxic ergot alkaloids that negatively affect herbivores and may alter soil microbial communities. A 60-week mesocosm study with a factorial arrangement of soil type (clay loam and loamy sand) and endophyte infection (with and without) was conducted to determine changes in soil microbial community function (substrate utilization using Biolog), structure (phospholipid fatty acid profile), and glomalin concentration. Microbial utilization of carbohydrate, carboxylic acid, and miscellaneous substrate groups was lower in soil planted to endophyte-infected tall fescue than in soil planted to endophyte-free tall fescue. Gram-positive bacteria, arbuscular mycorrhizae, and glomalin in small (0.25-1.0 mm) and large (>1 mm) water-stable macro-aggregates were also negatively affected by endophyte infection. Although microbial changes due to endophyte infection were not ubiquitous and overwhelming, they were consistent with previous observations for reduced decomposition of tall fescue plant litter infected with wild endophyte, which led to greater soil C sequestration.