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Identification of the G143A mutation associated with QoI resistance in Cercospora beticola field isolates from Michigan, United States
Author(s) -
Bolton Melvin D,
Rivera Viviana,
Secor Gary
Publication year - 2013
Publication title -
pest management science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.296
H-Index - 125
eISSN - 1526-4998
pISSN - 1526-498X
DOI - 10.1002/ps.3358
Subject(s) - cercospora , fungicide , biology , sugar beet , leaf spot , pathosystem , genotype , mutation , veterinary medicine , horticulture , genetics , inoculation , gene , medicine
BACKGROUND: Cercospora leaf spot (CLS), caused by the fungus Cercospora beticola , is the most serious foliar disease of sugar beet ( Beta vulgaris L.) worldwide. Disease control is mainly achieved by timely fungicide applications. In 2011, CLS control failures were reported in spite of application of quinone outside inhibitor (QoI) fungicide in several counties in Michigan, United States. The purpose of this study was to confirm the resistant phenotype and identify the molecular basis for QoI resistance of Michigan C. beticola isolates. RESULTS: Isolates collected in Michigan in 1998 and 1999 that had no previous exposure to the QoI fungicides trifloxystrobin or pyraclostrobin exhibited QoI EC 50 values of ⩽0.006 µg mL −1 . In contrast, all isolates obtained in 2011 exhibited EC 50 values of > 0.92 µg mL −1 to both fungicides and harbored a mutation in cytochrome b ( cytb ) that led to an amino acid exchange from glycine to alanine at position 143 (G143A) compared with baseline QoI‐sensitive isolates. Microsatellite analysis of the isolates suggested that QoI resistance emerged independently in multiple genotypic backgrounds at multiple locations. A real‐time PCR assay utilizing dual‐labeled fluorogenic probes was developed to detect and differentiate QoI‐resistant isolates harboring the G143A mutation from sensitive isolates. CONCLUSION: The G143A mutation in cytb is associated with QoI resistance in C. beticola . Accurate monitoring of this mutation will be essential for fungicide resistance management in this pathosystem. Copyright © 2012 Society of Chemical Industry