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SPECIAL SESSION: Impacts of agricultural fungicides on clinical anti-fungal resistance - Panel Discussion

Azole fungicides in agricultural systems: cereal disease control and resistance development in Aspergillus fumigatus
Bart Fraaije - Rothamsted Research.

Azole drugs and fungicides, inhibitors of sterol 14?-demethylase, an enzyme essential for ergosterol biosynthesis, are used in medicine (e.g. itraconazole and voriconazole), veterinary applications (e.g. itraconazole and imazalil), cosmetics (e.g. ketoconazole and clotrimazole), material preservation (e.g. propiconazole and azaconazole) and agriculture (e.g. myclobutanil and prothioconazole). They have been used since the mid-1970s for control of foliar and seed borne diseases in cereals in the UK. Due to differences in chemical properties and disease spectrum, different molecules have been introduced and withdrawn from the market over time but, due to their efficacy and slow resistance development, azoles have maintained their position as the most widely used fungicide group. The status of azole resistance in soil populations of Aspergillus fumigatus from commercial cereal fields and the Broadbalk long-term winter wheat experiment with and without fungicide applications was determined. Only low numbers of highly resistant strains, CYP51A TR34/L98H or TR46/Y121F/T289A, were detected. Strains carrying CYP51A F46Y/M172V/E427K were found more frequently but showed only low levels of azole insensitivity. Few highly resistant strains were also found in air populations, including novel CYP51A variants, but higher frequencies were found in some plant produce and environments. Based on these results, we conclude that broad-acre cereal production is not a ‘hot spot’ for resistance development.