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Poster Session: Biology and Disease Management - Mycology

31-P

Interactions between Fusarium virguliforme and other common fungal pathogens in soybean root rot complexes.
C. M. Floyd (1), D. M. MALVICK (2)
(1) University of Minnesota, St Paul, MN, U.S.A.; (2) University of Minnesota, St. Paul, MN, U.S.A.

Many species of Fusarium and other root-rotting fungi commonly infect soybean roots with and without visible symptoms of infection. This includes F. virguliforme (FV), the cause of sudden death syndrome (SDS). Roots of soybean plants with SDS symptoms in MN typically also contain other fungal pathogens. Little is known about interactions between fungal species in soybean roots. The objective of this study was to determine how soybean growth and SDS symptoms are affected by co-inoculations with FV and F. oxysporum (FO), F. solani (FS), and Clonostachys rosea (CR). Greenhouse trials were conducted with soybean cvs. susceptible and partially resistant to SDS. FV and one of the other fungi were mixed at equal ratios into potting soil and seeds were planted. Foliar SDS severity, root rot, and biomass were assessed ~30 days after planting. Across two trials of co-inoculations with FV and FO or FS, root rot and foliar symptoms were significantly (α=0.05) reduced and biomass significantly increased for one or more of the pairings, compared to FV alone (varieties pooled). In one of two FV+CR trials, root rot was significantly (α=0.05) lower with both pathogens compared to FV alone (varieties pooled). In other FV co-inoculation studies with Fusarium or Clonostachys, no significant treatment differences were detected. These studies suggest that significant interactions can occur between root-infecting fungi and they indicate challenges of working with interactions.