Correlation of the F129L mutation in Pyrenophora teres, the pathogen of net blotch of barley, with the efficacy of QoI fungicides

Abstract

The cytochrome b F129L mutation has been detected in several plant pathogens including Pyrenophora teres, the causal agent of net blotch of barley. Isolates of this pathogen were obtained from different parts of the UK and from other European countries for determination of the presence of F129L mutation and its effect on the performance of several QoI fungicides. Results from in vitro assays of fungicides tested showed that the pathogen was inhibited on QoI amended agar medium but the mutations compromised fungal inhibition: isolates with F129L mutation had greater EC50 values than wild type isolates for all QoI fungicides tested. Experiments carried out in planta using barley seedlings also showed variation between the level of disease control provided by different QoI fungicides ; for example picoxystrobin showed greater efficacy than azoxystrobin. It is concluded that determination of the effects of fungicide resistance mutations should be based on genotyping, combined with both in vitro and in planta evaluations of activity.