A University of Michigan researcher is using the common milkweed plant to study the connections between root systems and plant defenses and how humans may one day control those links.

The research is being conducted by Mark D. Hunter, a professor at the University of Michigan who has dual appointments with the School of Natural Resources and Environment and the Department of Ecology and Evolutionary Biology within the College of Literature, Science, and the Arts. The National Science Foundation is funding the work through a four-year, $650,000 grant.

The research data will contribute to the understanding of how diverse plant species, from agricultural crops through forest trees, use root fungi in their defense strategies, Hunter said. Using the data, researchers may be able propose how to manipulate root fungi to protect plants important to humans or render defenseless those considered to be invasive pests.

The work builds on a common understanding of plant biology. All plants worldwide must defend themselves from being damaged by their enemies, including insects, deer and pathogens. These defenses range from the physical, such as thorns, spines and tough leaves, to chemical, such as cyanide and steroids. As plants try to defend themselves, most make use of nutrients provided to them by fungi (called mycorrhizae) that live in their roots.

In what is basically a barter system, plants provide the fungi with sugar while the fungi provide plants with minerals such as phosphorus and nitrogen.

The strength of plant defenses may vary with the amount of fungus in their roots and the identity of their fungal partners, but this has never been studied in detail, Hunter said. Using the common milkweed as a study plant, his research will explore how the strength of plant defense varies with the fungal colonization of roots. It also will examine how variation in plant and fungal identity contributes to the defense, and how natural variation in soil nutrients influences the barter system. His experiments also will explore the effects of root fungi on insect herbivores.

Understanding the role of mycorrhizal fungi in plant defense is of value to insect pest managers and those wishing to control invasive plant species, Hunter said. The work is potentially transformative because it challenges the accepted notion that mycorrhizae play no significant role in the expression of plant defense, he said.í‚   The project represents the initial steps in a long-term effort to understand the relative contributions of plant genotype and arbuscular mycorrhizal (AM) fungal genotype to the defensive phenotype of plants.

The association between mycorrhizal fungi and their host plants provides an excellent system in which to study mutualism-induced changes in phenotype, he added.

Field sampling at the University of Michigan Biological Station (UMBS) and subsequent genetic analyses will establish relationships among AM fungal colonization, plant-defensive phenotype and herbivore densities under field conditions.

Hunter said the research is important for another reason: It provides a forum through which to train future biologists in universities and local area schools. In particular, the project supports the doctoral research Rachel Vannette in the College of Literature, Science, and the Arts.

Moreover, the project will be linked to the education and research mission of the U-M Frontiers Master's Program, which Hunter directs. Each summer, the program hosts groups at the UMBS that are underrepresented in the ecological sciences. The Frontiers program is housed within the Department of Ecology and Evolutionary Biology.

The research project will also contribute to other UMBS programs including Research Experiences for Undergraduates, Integrative Graduate Education and Research Traineeship, and public outreach initiatives.

Hunter joined SNRE in 2006, where he primarily teaches master's-level courses and students. But he also teaches an introductory biology course for U-M undergraduates. His appointment is split between SNRE and the Department of Ecology and Evolutionary Biology within the College of Literature, Science, & the Arts.

He divides his current research among several related interests: the role of plant chemistry in the population dynamics of herbivores; the links between the population dynamics of herbivores and ecosystem processes in the habitats in which they live; and the application of ecological theory to environmental issues.

About the School of Natural Resources and Environment
The School of Natural Resources and Environment's overarching objective is to contribute to the protection of the Earth's resources and the achievement of a sustainable society. Through research, teaching, and outreach, faculty, staff, and students are devoted to generating knowledge and developing policies, techniques and skills to help practitioners manage and conserve natural and environmental resources to meet the full range of human needs on a sustainable basis.
http://www.snre.umich.edu/

About the Frontier Master's Program
The Frontiers Master's Program in Ecology and Evolutionary Biology at the University of Michigan has three primary goals: to bring students to the study of ecology and evolution who might not otherwise have considered it; to give students opportunities to learn about the full range of subjects in ecology and evolution; and to prepare students to succeed in top-rated Ph.D. programs in ecology and evolution. http://www.eeb.lsa.umich.edu/eeb/graduates/frontiers.html