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Poster: Biology & Disease Mgmt: Biological Control


Reduction of soybean sudden death syndrome (Fusarium virguliforme) by seed treatment with Bradyrhizobium japonicum
T. HUYNH (1), T. Huynh (1), X. Yang (1), S. Navi (1), X. Li (1) (1) Iowa State University, U.S.A.; (2) Iowa State University, U.S.A.

Soybean sudden death syndrome (SDS), caused by Fusarium virguliforme, is a major soil-borne disease in soybean production in America. In North America, epidemics of the disease occurred in years when soybeans were planted early in growing seasons. Previous study by Scherm and Yang (1996) showed that F. virguliforme infected soybean in cool soil temperatures. Because infection of symbiont Bradyrhizobium japonicum requires minimum temperature of 17.50C, higher than the minimum for F. virguliforme infection, we hypothesize that infections of F. virguliforme prior to establishment of B. japonicum in soybean affects SDS occurrence in early planting. From 2013 to 2015, experiments were conducted in a greenhouse and fields to determine the effects of seed treatments with B. japonicum on the occurrence of soybean sudden death syndrome. Results of greenhouse and field studies showed that seed treatments with B. japonicum inoculum reduced SDS foliar symptom expression by 50% and 20% in greenhouse and field, respectively. Increase in soybean nodulation and increase in yield in field experiment were also observed. Our results suggest that seed treatment with B. japonicum can reduce SDS foliar symptoms. The mechanisms of the suppressive effects on F. virguliforme by B. japonicum are under investigation to improve the potential of using this measure for disease control.