Tracking the fates of exotic and local VA mycorrhizal fungi: methods and patterns

Abstract

Vesicular-arbuscular (VA) mycorrhizal fungi are an abundant component of the soil biota in most terrestrial ecosystems, and represent a distinct trophic group (biotrophic) from most of the rest of the soil microbial biomass (saprotrophic). Vesicular-arbuscular mycorrhizal fungi are comprised of a wide diversity of species and are often transplanted between habitats to increase plant growth. We tested the use of polyclonal antibodies on field and pot samples that might allow us both to differentiate VA mycorrhizal fungi from soil saprophytic fungi, and between introduced and native VA mycorrhizal fungi. The immunofluorescent antibody technique is advantageous in that it is easy and relatively inexpensive. In addition, fluorescent antibodies allowed for rapid differentiation of our introduced VA mycorrhizal fungus from indigenous saprophytic extramatrical hyphae. However, the specificity is not high against other VA mycorrhizal hyphae of similar taxonomic status, but is applicable clearly when the exotic VA mycorrhizal fungus is a different genus from the local fungi. This ability to differentiate an introduced fungus by its positively fluorescing external hyphae allows the researcher to undertake survival and developmental studies that are not limited by the constraints of infrequent or patchy sporulation. Using this technique, we determined that exotic VA mycorrhizal fungi can survive for up to 2 years even with competition from the local endophytes, and that the vertical placement of the inoculum can affect the survival of the exotic fungi at our sagebrush steppe research site in south-western Wyoming.