Monday, November 13, 2006

Effect of Fungicide Seed Treatment on Mycorrhizae Colonization of Soybean (Glycine max [L.] Merr.).

Adriana Murillo-Williams and Palle Pedersen. Iowa State University, 1017 6th Street, Ames, IA 50010

Fungicide seed treatments are commonly used in areas with a known history of seedling diseases to protect the stand when soil moisture is excessive. Seed-applied fungicides protect seedlings from pathogens like Pythium spp., Phytophthora spp., Fusarium spp., and Rhizoctonia spp. Different environmental conditions favor different pathogens. These organisms are ubiquitous in the soil, so infection will occur when conditions are favorable. Beside host resistance the best tool farmers have to protect seeds and minimize the risk of a low stand is to use a seed applied fungicides. These will be effective against a wide range of organisms that may also include non-target fungi like mycorrhizae. Little information exists on the effect of seed-applied fungicides on colonization of vesicular-arbuscular mycorrhiza (VAM), a fungal symbiont that provides the plant with essential nutrients and micronutrients. A two year experiment was conducted at three locations on Iowa to determine the effects of seed treatments on mycorrhizal colonization. Seeds of the soybean variety SOI2642 were treated with different fungicides: Apron (mefenoxam), Maxim XL (fludioxonil), and Apron Maxx (mefenoxam + fludioxonil). The experimental design was a randomized complete block design with four replications. Mycorrhiza colonization was quantified and compared among treatments. Results are presented.