2026 Volume 51 Issue 4 Pages 224-233
Rice blast caused by Pyricularia oryzae (syn. Magnaporthe oryzae) is a major fungal disease of rice, and QoI fungicides are widely used for its control. Here, we established a conidium-based assay for evaluating mycovirus-associated fungicide responses using Magnaporthe oryzae chrysovirus 1-A (MoCV1-A)-infected and virus-free isogenic isolates. The conidial development of the two isolates was compared in the presence of azoxystrobin (AZ). MoCV1-A infection significantly reduced sensitivity to AZ at the conidial stage, although infected isolates remained susceptible at higher AZ concentrations. Quantitative RT-PCR showed that transcript levels of genes associated with mitochondrial respiration, cAMP–PKA signaling, and melanin biosynthesis were maintained in MoCV1-A-infected conidia following AZ treatment. The ATP levels of MoCV1-A-infected conidia also were consistently higher than those of virus-free conidia before and after AZ treatment. These results suggest that MoCV1-A infection reduces QoI sensitivity by maintaining cellular energy homeostasis under fungicide stress through a mechanism distinct from target-site mutations.
