Methods for detecting QoI resistance in Pyricularia oryzae using fungal suspension drop assay

Abstract

We developed a simple method to test the quinone outside inhibitor (QoI) resistance of Pyricularia oryzae, which causes rice blast on Oryza sativa. After single spore isolation and incubation on potato dextrose agar (PDA) medium, 4-mm squares of fungal mycelia were picked and ground with 100 μl sterilized water. This suspension containing fungal mycelia (10 μl) was dropped on PDA medium containing 1, 10, or 100 ppm azoxystrobin. After 3–4 days incubation, sensitivity or resistance was determined by the presence or absence of mycelial growth. This method was easier and showed an accuracy similar to that of DNA analysis. We concluded that this method is useful for QoI sensitivity tests of rice blast fungus.