Bacterial and fungal microorganisms live in all plant tissues studied to date (Rodriguez 2008). Many of these "endophytes" colonize plants without causing disease or other symptoms, and researchers suspect that they provide benefits to their hosts. Fungal endophytes enhance plant resistance to herbivory (Cheplick 1988) and pathogens (Arnold 2003), increase plant growth and drought resistance, or lay dormant until plant tissues die so they can consume the dead tissue (Rodriguez 2008). Bacterial endophytes provide host plants with nitrogen-rich compounds and enhance the invasibility of exotic weedy species (Rout 2008).
Many endophyte species can live together in the same host. At MPG, we are interested in learning about how these endophytic communities form and what effect they have on plants. Will some endophytes prevent others from colonizing in order to better preserve the resources of their host plant? If so, what implications can this have on the host plant’s lifecycle?
Fungal pathogens can limit the spread of their host plant, but some endophytes prevent these fungal infections. This inhibition of a plant’s natural pathogens may allow it to thrive in areas where it otherwise would not. Weedy species like cheatgrass (Bromus tectorum) have natural fungal pathogens that thrive in almost every population, but these pathogens fail as bio-control agents due to irregular landscape-scale colonization patterns. Could endophyte communities already present in some plants prevent colonization by this pathogen? Research within cheatgrass populations will help us explain the irregular infection rates that we observe at MPG Ranch.
A) Microscopic spores of an endophyte in western white pines. (B) White pine endophyte growing in culture. (C) Collection of endophytes at MPG