Legume plants form intimate symbiotic relationships with soil bacteria called rhizobia. Rhizobia are essential for plants because they convert nitrogen into a form that legumes can use for growth and reproduction. The legume I will use this summer, Medicago lupulina, form associations with several known species of rhizobia in Southern Ontario, but there is tremendous genetic diversity of rhizobia strains in soils even within a species. It is also known that plant growth varies depending on the type of strain its roots are infected with- some bacteria strains are better nutrient providers then others. At present, we know little about how rhizobia strain diversity affects other aspects of plant ecology. I am studying whether the type of rhizobia strain affects a plants ability to defend against its natural enemies, such as insects and pathogens. Agriculture heavily relies on rhizobia for crop production, but some rhizobia strains inoculations that are currently used may make plants more susceptible to plant damage, which leads to increased pesticide application.
Anna Simonsen, Ecology and Evolutionary Biology, University of Toronto