2022 Volume 2022 Issue 73 Pages 81-84
In Hokkaido, QoI fungicides have been used for controlling apple diseases. The high-risk of resistant strains of Venturia inaequalis, which cause apple scab, is also well known. We investigated the sensitivity of isolates of V. inaequalis in Hokkaido to QoI fungicides. We conducted polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP)-based analysis (Fontaine et al., 2009) to detect the G143A mutation of mitochondrial cytochrome b in V. inaequalis. The PCR-RFLP results showed that approximately 85% of all samples contained this mutation. We also observed that isolates with this mutation grew on a medium that had been treated with a QoI fungicide. Thus, a high proportion of V. inaequalis strains present in Hokkaido were resistant to QoI fungicides. When the resistant isolates were inoculated and sprayed with a QoI fungicide, the fungicide did not have the desired control effect.
