Amino acid alterations in CYP51 contribute toward reduced triazole sensitivities in a UK field population of Mycosphaerella graminicola

摘要

Mycosphaerella graminicola is the causal agent of Septoria leaf blotch (SLB), an important foliar disease of wheat in Europe. Due to a lack of durable host resistance, and recent widespread emergence of resistance to strobilurin (Qol) fungicides, SLBcontrol is largely dependent on triazoles; the efficacy of which has declined over the last five years. We measured the EC50 values of isolates sampled from triazole-treated and untreated field plots in 2004 alongside a set of historical isolates. Therewere no significant differences in mean sensitivities of isolates from the 2004 plots; however the majority of isolates showed highly reduced sensitivities compared to the historical isolates. PCR-based assays developed to identify alterations in the target-encoding CYP51 gene associated with reduced triazole sensitivity were used to further characterise the population of M. graminicola isolates. Results demonstrate that alterations commonly occur in combination and are widespread among the 2004 population but not among historical isolates, suggesting they contribute to the reduction in sensitivity.