Battle in the dark - Interactions of the fungal pathogen Fusarium culmorum with beneficial microorganisms at the soil-root interface of wheat

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This ongoing study conducted at the Department of Plant Pathology, University of Minnesota, St. Paul, USA, investigates the role of the mycotoxin deoxynivalenol (DON) during root infections of wheat by the fungal pathogen Fusarium culmorum. The main focus is on the interaction between F. culmorum, DON and beneficial rhizobacteria, i.e. Streptomyces spp.. Further, the suppressive effect of DON and F. culmorum, respectively, to Streptomyces spp. is analysed in vitro and in planta. The first phase of this research suggested that besides Streptomyces spp. fluorescent Pseudomonas species are strong inhibitors of soilborne Fusarium species at wheat roots and that F. graminearum besides F. culmorum is a main contributor to Fusarium Foot and Root Rot of wheat and barley in the Upper Great Plains, USA. Therefore, fluorescent Pseudomonas and F. graminearum isolates will be included into the prolonged research stay. The carbon use of the obtained beneficial rhizobacteria (Streptomyces spp. and fluorescent Pseudomonas spp.) from wheat fields of the Upper Great Plains, USA as well as the different Fusarium species and chemotypes being used in this study, will be analysed in a microtiter assay using different carbon sources and concentrations as substrate. This will serve to explain varying antagonistic interactions between suppressive rhizobacteria and soilborne pathogens in cereals. Additionally, it is planned to study the impact of DON for successful wheat root and stem base infections by F. culmorum under field conditions. Experiments on DON as virulence factor for root infection by Fusarium species will be also conducted with barley. In experiments under controlled conditions it is planned to analyze whether the mycotoxin DON is translocated from the stem basis into barley kernels following stem base infections with toxigenic Fusarium species, which might be an additionally source of mycotoxin contamination of mature barley kernels.