Sensitivity of Botrytis cinerea From Nectarine/Cherry in China to Six Fungicides and Characterization of Resistant Isolates.

Botrytis cinerea, the causal agent of gray mold, can result in considerable preharvest and postharvest losses in many economically valuable plant species. Fungicides were widely used to minimize such losses, but fungicide resistances were detected frequently. In the present study, we collected 164 isolates from nectarine and cherry in China and tested the sensitivity to six fungicides. Among the tested isolates, 71 (43.3%) were resistant to azoxystrobin, 14 (8.5%) to cyprodinil, 7 (4.3%) to boscalid, 4 (2.4%) to carbendazim, 1 (0.6%) to iprodione, and no isolates were found to be resistant to fludioxonil. The EC50 value and resistance factor (RF) of resistant isolates were determined. Fitness analysis showed that there were no significant differences between sensitive and resistant isolates for osmotic stress and pathogenicity, while more conidia production was observed for some resistant isolates. Control efficacy of fungicides showed that the resistant isolates could not be controlled efficiently by using corresponding fungicides. The point mutation G143A was detected in the Cyt b gene of the isolates resistant to azoxystrobin, while the point mutation H272R of SdhB gene was confirmed in boscalid-resistant isolates, and mutations E198V/A of TUB2 gene and mutation I365S of BcOs1 occurred in carbendazim-resistant and iprodione-resistant isolates, respectively. These results indicate that the occurrence of fungicide resistance greatly threatens the management of gray mold on stone fruits nectarine and cherry.