Characterization of Monilinia fructicola Strains Resistant to Both Propiconazole and Boscalid

• DOI: 10.1094/pdis-10-12-0924-re
• Publication Date: 2012-12-20T21:52:08Z
• Authors: F. Chen; X. Liu; S. Chen; E. Schnabel; G. Schnabel
• Keywords: Propiconazole; EC50; Monilinia fructicola

In 2011 and 2012, significant brown rot disease caused by Monilinia fructicola was observed in a peach orchard Spartanburg County, SC, despite preharvest fungicide applications of demethylation inhibitor (DMI), quinone outside (QoI), succinate dehydrogenase (SDHI) fungicides. All 22 isolates obtained from this were sensitive to the QoI fungicide, azoxystrobin, methyl benzimidazole carbamate (MBC) thiophanate-methyl. Five resistant DMI propiconazole, selected, together with five propiconazole-sensitive isolates, for further investigations. One 10 propiconazole but SDHI boscalid (EC50 = 0.42 μg/ml), 3 intermediate sensitivity 0.72 2.1 μg/ml); 2 boscalid; ≥ 1 (isolate MD22) both boscalid. Disease incidence on detached fruit treated formulated or significantly higher MD22 compared control isolate. Continued monitoring resistance same 2012 revealed an increase 22.7% 34.7%, 4.5% 18.4%. Propiconazole always associated presence 'Mona' mobile element located upstream sterol 14α-demethylase (MfCYP51) gene. To investigate whether mutations subunits enzyme involved resistance, portions M. SdhA, SdhB, SdhC, SdhD genes cloned analyzed sensitive, boscalid-resistant, 6 dual-resistant isolates. Although sequence variation found among no single change correlated resistance. Interestingly, analysis collected orchards 2001 2002, prior registration boscalid, range sensitivities 0.03 3.46 μg/ml) including boscalid-resistant The baseline population unexpected requires investigation.