In recent years, Fusarium head blight (FHB) is the most
aggressive fungal disease and growing threat to the economic sustainability of
cereal crop production in Manitoba due to yield loss and downgrade grain quality as
several mycotoxins contamination occurred in FHB infected grains. In our
lab, Fusarium poae (Fp) and F. graminearum (Fg) were frequently isolated from FHB infected grains of
barley and oats. Four fungicides, namely, caramba (metconazole), prosaro
(prothioconazole+tebuconazole), proline (prothioconazole), folicur
(tebuconazole) were tested against representative isolates of Fp (n=13) and Fg (n=13). These 26 isolates were
selected from nearly 300 Fp and Fg strains isolated from commercial
barley and oat fields of Manitoba, based on chemotypes diversity, virulence
factors, mycelial growth performances and genotyping by sequencing (GBS).
Fungicide sensitivity was quantified by measuring the radial growth of the
cultures on PDA (potato dextrose agar) media amended at two concentrations of
fungicides (active ingredient: 0.01 and 0.10 mg/L). Two-way analyses of
variance (ANOVA) revealed on average, Fp isolates
were statistically less sensitive to all four fungicides, compared to Fg regardless of doses. Specifically,
the redial growth of the Fp-MRC585
strain can not be restricted (24%, 5%, 2%, 3% inhibition) by the higher
concentration of caramba, prosaro, proline and folicur amended plates,
respectively. Similarly, the Fg-MRC572
strain also can not be restricted (< 10% inhibition) to folicur, not the
other three fungicides. This study confirmed the Caramba was consistent in
controlling both Fp and Fg isolates tested. This in-vitro assay suggests that the
selective pressure exerted by these commonly used fungicides may impact the
population dynamics of FHB species, most likely the increasing insensitivity
towards newly evolving/shifting F. poae communities in the
regions due to different intrinsic characteristics and tolerance ability of these
field isolates. The current results would assist Manitoba small grain producers
to select effective fungicides in the integrated FHB management strategies.