Predominance of Banana Epiphytic Fungal Isolates with Resistance to Azoxystrobin, a Quinone Outside Inhibitor (QOI) Fungicide

The emergence of fungicide-resistance in epiphytic fungi poses a significant challenge in crop disease management and in the microbial ecology of the crop phyllosphere. This study thus investigated the sensitivity of twenty-five epiphytic fungal isolates from sigatoka-infected banana leaves to a commercial formulation (suspension concentrate) of azoxystrobin, using a fungicide-ammended plate assay. Out of the twenty-five isolates, only one was sensitive (E*C_{50} = 0.6mu*g / m * l) to azoxystrobin, while the rest were resistant with E*C_{50} ranging from 1.02 mu*g / m * l to 8, 902.15mu*g / m * l . The observed resistance suggests that resistance to azoxystrobin may have persisted in the field, given the information that the majority of the source farms claim no fungicide use. This also raises concern of the effects of Qol fungicide on the epiphytic mycobiome of the crop. Overall, the study emphasizes the need for continuous monitoring of Qol resistance and the effects of fungicide use on the diverse epiphytic fungal community.