Pathogenicity of Fusarium Species on Different Plant Parts of Spring Wheat Under Controlled Conditions

Most of the Fusarium species responsible for Fusarium head blight of wheat in Saskatchewan, Canada, have also been isolated from discolored subcrown internodes/crowns of wheat. It was therefore of interest to compare the susceptibility of heads and ground/underground tissue of wheat to isolates of Fusarium species from different sources. Controlled-environment pathogenicity tests were conducted on heads, seeds, and seedlings of spring wheat. Overall, F. culmorum and F. graminearum were the most pathogenic species, although the former was more pathogenic than the latter. F. equiseti and F. poae were the least pathogenic species, whereas F. avenaceum had intermediate pathogenicity in the head and seed tests, but low pathogenicity in the seedling test. There was a similar pathogenicity among isolates of each Fusarium species from different sources to heads and ground/underground plant parts, indicating a lack of adaptation of these isolates. Our observations suggest that Fusarium inoculum on or in infected seed or plant debris might infect plants at or below soil level, which could then become a source of inoculum for infection of heads in the following season(s). Survival of fungal inoculum in underground plant parts might be important during dry conditions.