PARENT SESSION
Poster Session 24: Agro-Ecology
Wednesday, August 10, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
Is there a role for mycorrhizal fungi in genetically-modified, herbicide-tolerant cropping systems?
Powell, Jeff*,1, Kuczynski, Eva1, Klironomos, John1, 1 University of Guelph, Guelph, ON, Canada
ABSTRACT- Genetically-modified, herbicide-tolerant (GMHT) cropping systems have been adopted extensively by growers in North America. In GMHT systems, herbicides are often applied later in the season, allowing weed biomass to accumulate and, potentially, promoting populations of pathogenic fungi that have the capacity for saprotrophic growth. In addition, recent research suggests that these pathogenic fungi may be stimulated by glyphosate (Roundup), a broad-spectrum, systemic herbicide frequently used in GMHT systems. However, many weedy plants in agricultural systems are also hosts of arbuscular mycorrhizal (AM) fungi, which may protect crop plants from pathogenic fungi. AM fungi may benefit further in GMHT cropping systems due to reduced tillage intensity. The goal of our research is to evaluate the effects of glyphosate-tolerant cropping systems on the structure and functioning of AM and pathogenic fungal communities, and the results of early investigations are presented here. In 2004, field plots containing conventional or glyphosate-tolerant soybean varieties were sampled in order to characterize the fungal communities associated with weed plants, treated either with glyphosate or conventional herbicides. In addition, we conducted greenhouse experiments with glyphosate-tolerant soybean in order to evaluate the interactive effects of glyphosate use and the presence of AM fungi on population dynamics of two soybean pathogens, Fusarium solani and Pythium ultimum. Results suggest that complex interactions among AM fungi, pathogenic fungi, and weedy plants may arise in GMHT cropping systems, with consequences for disease dynamics and crop yields.
Key words: arbuscular mycorrhizal fungi, crop diseases, genetically modified crops, pathogenic fungi