Impact of changes in the target P450 CYP51 enzyme associated with altered triazole-sensitivity in fungal pathogens of cereal crops.

Control of diseases caused by fungi in both medicine and agriculture is heavily dependent on the use of triazoles. As a consequence, resistance to triazoles is a threat to both human health and the sustainability of agricultural production systems. In human pathogens, particularly Candida albicans, mutations encoding alterations in the target cytochrome P450 sterol 14alpha-demethylase (CYP51; where CYP is cytochrome P450) enzyme are the primary determinants of triazole resistance. In fungal pathogens of cereals, CYP51A1 modifications, some at positions known to contribute to a resistant phenotype in human pathogens, have also been identified in isolates with altered triazole-sensitivity. However, unlike medicine where resistance to triazoles is a major clinical problem, failures of triazoles to control crop diseases in the field are rare with mean population sensitivities generally remaining low, perhaps due to differences in the selection pressures imposed on human and cereal pathogen populations. Nonetheless, the biological potential for resistance exists, and the question remains as to whether widespread triazole resistance can develop in an important cereal pathogen.