Soilborne Rhizoctonia, Microdochium, and Fusarium species are major causal agents of seedling and stem-base diseases of wheat. Currently, seed treatments are considered the most effective solution for their control. Rhizoctonia solani anastomosis groups (AGs) 2-1 and 5, R. cerealis, Microdochium, and Fusarium spp., were used in series of field experiments to determine their capability to cause soilborne and stem-base disease and to quantify their comparative losses in the establishment and yield of wheat. The effectiveness and response to seed treatment formulated with 10 g sedaxane and 5 g fludioxonil 100 kg^-1 against these soilborne pathogens were also determined. Our results showed that damping-off caused by soilborne R. cerealis was associated with significant reductions in the emergence and establishment, resulting in stunted growth and low plant numbers. The pathogen also caused sharp eyespot associated with reductions in the ear partitioning index. R. solani AG 2-1 and AG 5 were weakly pathogenic and failed to cause significant damping-off, root rot, and stem-base disease in wheat. Fusarium graminearum and F. culmorum applied as soilborne inoculum failed to cause severe disease. Microdochium spp. caused brown foot rot disease and soilborne M. nivale reduced wheat emergence. Applications of sedaxane and fludioxonil increased plant emergence and reduced damping-off, early stem-base disease, and brown foot rot, thus providing protection against multiple soilborne pathogens. R. cerealis reduced the thousand grain weight by 3.6%, whereas seed treatment including fludioxonil and sedaxane against soilborne R. cerealis or M. nivale resulted in a 4% yield increase.

Annabel Hunt

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