Evidence for natural resistance towards trifloxystrobin in <Emphasis Type="Italic">Fusarium graminearum</Emphasis>

A collection of 55 Fusarium graminearum (Gibberella zeae) strains isolated between 1969 and 2009 in Belgium, Canada, Germany, Italy, Luxembourg, or the USA belonging to the three known chemotypes (3-acetylated deoxynivalenol, 15-acetylated deoxynivalenol and nivalenol) were screened for their sensitivity towards the fungicide trifloxystrobin using a liquid culture assay. None of the isolates was completely inhibited by trifloxystrobin concentrations up to 3 mM. For comparison, prothioconazole completely inhibited fungal growth of a standard isolate at concentrations as low as 0.007 mM. The maximum level of inhibition, which could be obtained by trifloxystrobin, ranged from 14 to 65% among the strains tested and was not significantly affected by the country of origin or by the chemotype. The absence of significant differences in resistance levels between the countries of origin and chemotypes as well as the fact that strains isolated before the market introduction of strobilurins in 1996 also showed a high level of resistance is evidence that this is largely a case of natural resistance and not primarily related to strobilurin use in agriculture.     

Mechanisms of resistance to organophosphorus insecticides in populations of the obliquebanded leafroller Choristoneura rosaceana (Harris) (Lepidoptera: Tortricidae) from southern Ontario

Populations of Choristoneura rosaceana (Harris) from orchards in Ontario were shown to be resistant to azinphos-methyl and to other types of organophosphorus insecticides. Resistance extended to methyl carbamates and to methomyl. The laboratory population used for these assays and selected with azinphosmethyl was also resistant to the pyrethroid, cypermethrin. Resistance was associated with increased esterase activity and was reduced by the addition of the synergist DEF. IEF studies of esterases also indicated increased activity in resistant populations, but did not identify any unique esterases associated with the resistance. Resistance was highly correlated (r = 0.78) with elevated esterases but not with increased glutathione-S transferase activity (r = 0.13). Other mechanisms did not appear to be related.     

Fractal dimension and shape parameters of asexual Fusarium spores from selected species: Which species can be distinguished?

Journal of Plant Diseases and Protection - Fungi of the genus Fusarium are prominent plant pathogens producing various toxic secondary metabolites. Digital microscopic images were taken from the...