AbstractAnthracnose, caused by Colletotrichum gloeosporioides, is one of the most important diseases in grape‐growing regions worldwide. In Jiangsu Province of China, quinone‐outside inhibitor fungicides (QoIs) have been extensively sprayed as disease control for more than 10 years. A spore germination assay of 64 isolates obtained from 32 commercial vineyards was used to assess isolate sensitivity to azoxystrobin and 62 were found to be resistant to azoxystrobin. The biological fitness of QoI‐resistant (QoIR) isolates was significantly lower than the sensitive isolates (QoIS) in terms of mycelial growth and conidiation. Nucleotide sequence alignment of CgCytb genes from the QoIR and QoIS isolates revealed that two point mutations (F129L and G143A) are involved in the QoI resistance. Isolates with the G143A mutation expressed high resistance to azoxystrobin, whereas isolates carrying the F129L mutation exhibited moderate resistance. Positive cross‐resistance was observed between azoxystrobin and kersoxim‐methyl, pyraclostrobin, or benzothiostrobin, but not with fluazinam. This study provides important information for management of QoIR populations of C. gloeosporioides in the field.
