Endophyte Effects on Nutrient Pools & Microbial Communities in Tall Fescue Pastures of the Southeastern US

Photo by Tim Phillips

At a site in Watkinsville, GA, highly endophyte infected tall fescue stands has been shown to support  greater soil C and N pools and altered microbial activity (Franzluebbers et al. 1999, 2005). Endophyte-produced alkaloids, by both increasing plant production and persistence during drought and reducing levels of above- and belowground herbivory and litter decomposition rates, are thought to be the primary mechanism through which soil nutrient pools are enhanced. My first graduate student, Jacob Siegrist, performed a litter decomposition experiment with alkaloid-laden, endophyte-infected (E+) and alkaloid-free, endophyte-free (E-) tall fescue material. He found that similar to other studies E+ material degraded more slowly than E- material; however, given the large differences in alkaloid quantity between the two litter types, it was surprising this statistical difference in decomposition rates wasn't larger (Siegrist et al. 2009). Jacob and postdoc, Javed Iqbal, also tested the generality of the Georgia soil nutrient pool results across a broad geographic range in the upper southeastern transition zone of the U.S. They found enhanced soil organic carbon, total nitrogen, recalcitrant particulate organic matter pools, and altered microbial biomass and communities in E+ vs. E- tall fescue stands throughout this geographic zone, suggesting that this aboveground fungal endophyte symbiosis has widespread effects on soil biology and biochemistry, and that high prevalence of the aboveground endophyte increases C sequestration capacity of tall fescue stands throughout the southeastern USA (Iqbal et al. 2012).
Postdoc, Javed Iqbal, also evaluated whether fungal endophyte presence and genotype (wild-type common toxic endophyte; AR-584, AR-542 - two novel endophytes, each producing a reduced and unique suite of alkaloids) within a single variety of tall fescue alters soil-to-atmosphere gas exchange, soil nutrient pools, soil microbial community composition, plant production and species composition, and litter decomposition.

This fungal genotype project is located in Lexington, KY, and is the North American experiment participating in the EndoGas international project.

Associated Manuscripts:
Kalosa-Kenyon, E., L.C. Slaughter, J.A. Rudgers, and R.L. McCulley. 2018. Asexual Epichloë endophytes do not consistently alter arbuscular mycorrhizal fungi colonization in three grasses. American Midland Naturalist 179:157-165.
Slaughter, L.C. and R.L. McCulley. 2016. Aboveground Epichloë coenophiala – grass associations do not affect belowground fungal symbionts or associated plant, soil parameters. Microbial Ecology 72: 682-691.
Saikkonen, K., T.D. Phillips, S.H. Faeth, R.L. McCulley, I. Saloniemi, and M. Helander. 2016. Performance of endophyte infected tall fescue in Europe and North America. PLOS ONE 11(6):e0157382. doi: 10.1371/journal.pone.0157382.
Guo, J., R.L. McCulley, T.D. Phillips, and D.H. McNear, Jr. 2016. Fungal endophyte and tall fescue cultivar interact to differentially effect bulk and rhizosphere soil processes governing C and N cycling. Soil Biology & Biochemistry 101:165-174.
Rojas, X., J. Guo, J.W. Leff, D.H. McNear Jr., N. Fierer, and R.L. McCulley. 2016. Infection with a shoot-specific fungal endophyte (Epichloe) alters tall fescue soil microbial communities. Microbial Ecology. doi: 10.1007/s00248-016-0750-8.
Helander, M., T. Phillips, S.H. Faeth, L.P. Bush, R. McCulley, I. Saloniemi, and K. Saikkonen. 2016. Alkaloid quantities in endophyte-infected tall fescue are affected by the plant-fungus combination and environment. Journal of Chemical Ecology. doi: 10.1007/s10886-016-0667-1.
Jokela, K.J., D.M. Debinski, and R.L. McCulley. 2015. Effects of non-native grass species and endophyte infection on the development and survival of Tawny-edged skippers (Lepidoptera: Hesperiidae). Environmental Entomology. doi: 10.1093/ee/nvv151.
Slaughter, L.C., A.E. Carlisle, J.A. Nelson, and R.L. McCulley. 2015. Fungal endophyte symbiosis alters nitrogen source of tall fescue host, but not nitrogen fixation in co-occurring red clover. Plant & Soil. doi: 10.1007/s11104-015-2510-9.
Guo, J., R.L. McCulley, and D.H. McNear, Jr. 2015. Tall fescue cultivar and fungal endophyte combinations influence plant growth and root exudate composition. Frontiers in Plant Science 6: article 183. doi: 10.3389/fpls.2015.00183.
Iqbal, J., J.A. Nelson, and R.L. McCulley. 2013. Fungal endophyte presence and genotype affect plant diversity and soil-to-atmosphere trace gas fluxes. Plant and Soil 364:15-27.
Iqbal, J., J.A. Siegrist, J.A. Nelson, and R.L. McCulley. 2012.  Fungal endophyte infection increases carbon sequestration potential of southeastern U.S.A. tall fescue stands. Soil Biology & Biochemistry 44:81-92.
Siegrist, J.A., R.L. McCulley, L.P. Bush, and T.D. Phillips. 2010. Alkaloids may not be responsible for endophyte-associated reductions in tall fescue decomposition rates.  Functional Ecology 24: 460-468.
Please contact Rebecca for copies.
Javed Iqbal measuring trace gas in Lexington, KY tall fescue plots. 

Javed Iqbal measuring trace gas in Lexington, KY tall fescue plots.