Sensitivity of and of Peach in China to Multiple Classes of Fungicides and Characterization of Pyraclostrobin-Resistant Isolates.

Anthracnose, mainly caused by species complex including and , is a devastating disease of peach. Chemical control has been widely used for years, but management failures have increased with the commonly used fungicides. Therefore, screening of sensitivity of spp. to fungicides with different modes of action is needed to make proper management strategies for peach anthracnose. In this study, the sensitivity of 80 isolates of . and . was screened for pyraclostrobin, procymidone, prochloraz, and fludioxonil based on mycelial growth inhibition at discriminatory doses. Results showed that . and . isolates were highly resistant to procymidone and fludioxonil with 100% resistance frequencies to both fungicides, but sensitive to prochloraz, i.e., no resistant isolates were found. For pyraclostrobin, 74% of . isolates showed high resistance, 26% showed low resistance, and all of the . isolates showed low resistance. No positive cross-resistance was observed between pyraclostrobin and azoxystrobin even when they are members of the same quinone outside inhibitor (QoI) fungicide group or between pyraclostrobin and non-QoIs. Resistant isolates to QoI fungicides were evaluated for the fitness penalty. Results showed that no significant differences except for the mycelial growth rates that were detected between high- and low-resistance isolates of . . Molecular characterization of the gene revealed that the G143A point mutation was the determinant of the high resistance in . . This study demonstrated the resistance status of . and . to different fungicides and briefly discussed implications of that resistance. Demethylation inhibitor fungicides were found to be the best option among the different chemicals studied here, to control peach anthracnose in China.