Tuesday, November 14, 2006 - 1:15 PM

Mycorrhizal and Soil-borne Pathogen Colonization of Four Soybean Varieties in Iowa.

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

Vesicular-arbuscular mycorrhizae (VAM) colonize soybean roots and establish a symbiotic association with the plant. There are numerous reports of the benefit of VAM colonization for plants that include an improved water status, and acquisition of macronutrients and micronutrients through fungal hyphae. It has been suggested that VAM also protect plant against soil-borne pathogens, although the major benefit associated to VAM is an increased phosphorus uptake due to an increased surface area for absorption provided by the fungal mycelium. Previous research has suggested the long term soybean-corn rotation may have selected for VAM species that have a detrimental effect in root health. Previous research that has used soil fumigation as a tool to answer this question has yielded variable results. The objective of this study was to compare VAM colonization and incidence of the soil-borne pathogens Pythium, Rhizoctonia, and Phytophthora early in the season using four soybean varieties under a fumigated and a non-fumigated system. The experiment was a randomized complete block design in a split plot arrangement with four replications with fumigation as the whole plot and variety as the subplot. The experiment was conducted from 2004-2005 at three locations in Iowa. At each location, two hectares of land were fumigated with Telone-35 (Dow Agroscience). Four soybean varieties were used (SOI2642, NKS32G5, PB291N, and S25J5).Vesicular-arbuscular mycorrhizae colonization was determined by the intercept method and pathogens were identified with ELISA.  The results of two years of experiments are presented and discussed.