SYSTEMATIC BIOLOGY OF INVASIVE AND EMERGING PLANT PATHOGENIC FUNGI
Title: A mutualistic interaction between a fungivorous nematode and a fungus within the endophytic community of Bromus tectorum
Submitted to: Fungal Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 21, 2012
Publication Date: May 15, 2012
Citation: Baynes, M.A., Russell, D.M., Newcombe, G., Carta, L.K., Rossman, A.Y., Ismaiel, A.A. 2012. A mutualistic interaction between a fungivorous nematode and a fungus within the endophytic community of Bromus tectorum. Fungal Ecology. 5:610-623.
Interpretive Summary: Cheatgrass is an invasive weed that covers over 60 million acres in western North America outcompeting native grasses and serving as a fire hazard. Fungi and nematodes that live inside cheatgrass without causing harm contribute to the ability of this weed to live successfully in new habitats. In this study the interaction between two endophytic organisms was characterized. A fungus-eating nematode was found living inside cheatgrass along with a specific fungus. In the laboratory it was demonstrated that the nematode prefers this fungus to others in the cheatgrass. It is unclear if the fungus and nematode were already present when the cheatgrass arrived in North America or if the organisms started living with the cheatgrass after it invaded. This research will be used to understand why cheatgrass is such a successful noxious weed and may provide ideas to weed scientists on how cheatgrass can be controlled.
In its invaded range in western North America, Bromus tectorum can host more than 100 sequence-based phylotypes of endophytic fungi of which an individual cheatgrass plant hosts a subset. In general, research suggests that recruitment of a particular subset of endophytes by an individual plant will be determined by plant genotype, the environment, and dispersal of locally available endophytes. Discovery of a strong association between a fungivorous nematode, Paraphelenchus acontioides, and an endophytic fungus, Fusarium cf. torulosum, in B. tectorum led to an investigation of the role of the nematode in structuring endophyte communities in British Columbia and Colorado. In greenhouse and laboratory experiments, we determined that P. acontioides preferred F. cf. torulosum to other endophytic fungi from the Colorado site, and that it increased the relative abundance of F. cf. torulosum within the endophyte community. The ‘cultivation hypothesis’ was thus supported, i.e., that the fungivorous nematode was using living cheatgrass plants to ‘cultivate’ its preferred fungus. Host plant growth was unaffected by this cultivation of F. cf. torulosum by P. acontioides within the tissues of the plant host.