Monitoring for resistance in Botrytis cinerea from strawberry to seven chemical classes of fungicides in the eastern United States
D. FERNANDEZ-ORTUNO (1), P. K. Bryson (1), A. Grabke (1), G. Schnabel (1). (1) Clemson University, Clemson, SC, U.S.A.
Chemical control of gray mold of strawberry caused by <i>Botrytis cinerea</i> Pers. is essential to prevent pre- and postharvest fruit decay; however, resistance to multiple chemical classes of fungicides including anilinopyrimidines (APs), dicarboxamides (DCs), hydroxyanilides (HAs), methyl benzimidazole carbamates (MBCs), phenylpyrroles (PPs), quinone outside inhibitors (QoIs), or succinate dehydrogenase inhibitors (SDHIs) was found recently in <i>B. cinerea</i> from strawberry fields in the Carolinas. Resistance to DCs, HAs, MBCs, QoIs, and SDHIs, was caused by point mutations in the corresponding target genes (<i>Daf1</i>, <i>Erg27</i>, <i>b-tubulin, Cytb</i>, and <i>SdhB</i>); however, resistance mechanisms for APs and PPs are still unknown. A resistance-monitoring program was implemented to help growers determine location-specific resistance profiles. The analysis of samples from Arkansas, Florida, Georgia, Kansas, Maryland, North Carolina, South Carolina, and Virginia strawberry fields revealed <i>B. cinerea</i> isolates resistant to multiple chemical classes, including the PP fungicide fludioxonil, and to several SDHI fungicides not yet available for gray mold control. Our results indicate that resistance to some chemical classes including APs, HAs, MBCs, QoIs, and SDHIs is widespread and resistance DCs and PPs is emerging.
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