Does endophyte status of tall fescue impact mycorrhizal colonization of native species commonly planted in grassland restorations?

Background/Question/Methods

Grassland restorations in the eastern U.S. frequently involve eradication of tall fescue (Schedonorus phoenix), which often harbors a fungal endophyte (Neotyphodium coenophialum), followed by planting seed of native species. Limited evidence suggests endophyte-infected tall fescue suppresses mycorrhizal abundance and colonization of other plant species. Using a greenhouse experiment, we tested whether mycorrhizal colonization of four native plant species (Chamaecrista fasciculata, Echinacea purpurea, Panicum virgatum, and Schizachyrium scoparium) differed when grown in soil originating from endophyte-infected (EI) tall fescue, endophyte-free (EF) tall fescue, and “fescue-naïve” or forested stands (FO). Soils from four replicates of each type of stand were collected from three sites. Half of each soil sample was steam-sterilized, and five replicate plants for each of the four species were planted (1440 plants total). We grew plants for two months, and then measured oven-dry above- and belowground biomass. Root subsamples were dyed with trypan blue, and ten 1-cm sections were used to make a single microscope slide for each plant. Slides were scored for mycorrhizal colonization using the magnified intersections method with 30 discrete views. Statistical analyses tested for effects of stand type, steam sterilization, and stand*steam sterilization on biomass and mycorrhizal colonization within each plant species.

Results/Conclusions

Plant biomass was significantly affected by steam sterilization for all four species. In three species (Echinacea, Panicum, and Schizachyrium), plants from sterilized soil had higher biomass than those from non-sterilized soil, but for the N-fixer, Chamaecrista, biomass was higher in non-sterilized soil, presumably due to benefits of rhizobium (nodules were observed on roots from non-sterilized soil but were largely absent from sterilized soil, and those from sterilized soil appeared chlorotic). Stand type significantly affected biomass for two of the species; however, differences were between tall fescue and forested soils and varied by species. There were no differences in plant biomass between EI and EF tall fescue soils for any species. Mycorrhizal colonization of Echinacea roots from one site was significantly higher in plants grown in non-sterilized soil and was significantly lower for the plants from the forest compared to either tall fescue soils. These preliminary results suggest no significant decrease in mycorrhizal colonization in EI soil compared to EF. If these results hold true for the other species and sites, land managers might expect the same potential mycorrhizal colonization for the four species we studied, whether planting into areas previously occupied by EI or EF tall fescue.