EndoGas
Red Fescue Project in Spain
Cool season grasses cover significant acreage in temperate locations, providing forage for pastoral grazing systems and contributing to ecosystem services such as biodiversity and soil carbon sequestration. Many of these grasses are capable of forming symbiotic associations with fungal endophytes that can enhance the environmental stress tolerance of the host plant and confer anti-herbivore and -pathogen activity. Such symbiotic associations have been manipulated in agronomic and turf cool season grasses for ~20 years, by seed industries eager to capitalize on the natural ‘benefits’ of the symbiosis. While effects of these grass-endophyte associations on aboveground parameters (such as animal production, plant production, and plant and insect diversity) have been well-studied, much less work has been done to evaluate whether there are effects on belowground parameters. Recent studies have shown that for at least one grass species, tall fescue, fungal endophyte presence can stimulate soil carbon sequestration, and fungal endophyte strain can alter the flux of two important greenhouse gases, CO2 and N2O, from the soil to the atmosphere. To our knowledge, there has been no equivalent work exploring whether these types of endophyte effects are also observed in other important cool season grass species or in other locations. To fill this knowledge gap, we propose to quantify fungal endophyte symbiotic effects on greenhouse gas (GHG) emissions and soil carbon sequestration for three cool season grasses (meadow fescue, red fescue, and tall fescue) that are common in Europe and the United States. We will utilize existing projects located primarily in Finland, Spain, and the United States to achieve this objective. By exploring whether plant-microbe symbiotic interactions can promote environmental benefits, by lowering GHG emissions and increasing soil carbon sequestration, while simultaneously continuing to support agricultural production, our research may directly improve agricultural sustainability of temperate grasslands worldwide and help mitigate future additional changes to atmospheric GHG concentrations.
Collaborators: Kari Saikkonen (MTT-Finland), Marjo Helander (Turku-Finland), and Iñigo Zabalgogeazcoa (CSIC – Spain), Beatriz Rodríguez Vázquez de Aldana (IRNASA, CSIC- Spain)
Funding Source: FACCE-JPI
Activities to Date
Endophyte Effects on Nutrient Pools & Microbial Communities in Tall Fescue Pastures of the Southeastern US
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:
Please contact Rebecca for copies.
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.
Can manipulation of fungal endophyte diversity positively influence tall fescue pasture sustainability and ecosystem functioning?
Biodiversity is an ecological characteristic that supports ecosystem services in both managed and non-managed systems. Humans can purposefully enhance or reduce biodiversity at many levels within agricultural landscapes. While studies have evaluated the roles of plant and insect biodiversity on ecological processes, such as production and pollination, little research to date has explored effects of plant-microbe symbiotic diversity on agroecosystem functionality, in part because it is difficult, if not impossible, to experimentally control plant-microbe interactions in the field. Utilizing the well-characterized grass – vertically transmitted fungal endophyte system, we will explore whether community-level symbiotic diversity influences managed cool-season pasture ecosystem services, including yield, forage quality, plant and insect diversity, soil-to-atmosphere greenhouse gas emissions, and soil carbon sequestration. Tall fescue (Schedonorus arundinaceus) is a dominant forage grass of the eastern half of the U.S., covers significant acreage, and often hosts the fungal endophyte, Epichloë coenophiala. Presence and genetic strain of the endophyte can be manipulated, and several fescue cultivars containing different strains of E. coenophiala or entirely endophyte-free are available to producers today. Seed lots consist of a population of fescue, but when endophyte-infected, typically only one strain of endophyte is present within a labeled cultivar. Therefore, planted fescue pastures tend to have low endophyte symbiotic diversity. We hypothesize that increasing endophyte symbiotic diversity within the tall fescue community will enhance pasture provisioning, regulating, and supporting ecosystem services.
In Fall 2016, we planted 80 5m x 5m plots into the following symbiotic diversity treatments...
Endophyte status and strains have been confirmed, and former graduate student, Mahtaab Bagherzadeh, collected insect diversity, trace gas fluxes, and other soil data since.
Collaborators: Jen White and Carolyn Young
SymDiv was featured in the Alliance for Grassland Renewal newsletter. Read here