Overexpression of the sterol 14alpha-demethylase gene (MgCYP51) in Mycosphaerella graminicola isolates confers a novel azole fungicide sensitivity phenotype

A - Papers appearing in refereed journals

Cools, H. J., Bayon, C., Atkins, S., Lucas, J. A. and Fraaije, B. A. 2012. Overexpression of the sterol 14alpha-demethylase gene (MgCYP51) in Mycosphaerella graminicola isolates confers a novel azole fungicide sensitivity phenotype. Pest Management Science. 68 (7), pp. 1034-1040.

AuthorsCools, H. J., Bayon, C., Atkins, S., Lucas, J. A. and Fraaije, B. A.
Abstract

BACKGROUND: The recent evolution towards resistance to azole fungicides in European populations of the wheat pathogen Mycosphaerella graminicola has been caused by the progressive accumulation of mutations in MgCYP51 gene, encoding the azole target sterol 14a-demethylase. Particular combinations of mutations have been shown specifically to affect the interaction of the MgCYP51 protein with different members of the azole class. Although additional mechanisms, including increased MgCYP51 expression and enhanced active efflux, have been proposed, the genetic changes underlying these mechanisms are unknown. RESULTS: Analysis of the azole sensitivities of recent M. graminicola isolates identified a novel phenotype, seemingly independent of changes in MgCYP51 coding sequence. Characterised by a 7-16-fold reduction in in vitro sensitivity to all azoles tested and by growth on seedlings at higher doses of azoles in glasshouse tests compared with isolates carrying the same MgCYP51 variant (L50S, S188N, I381V, ?Y459/G460, N513K), isolates with this phenotype constitutively overexpress MgCYP51 by between 10- and 40-fold compared with the wild type. Analysis of sequences upstream of the predicted MgCYP51 translation start codon identified a novel 120 bp indel, considered to be an insertion, in isolates overexpressing MgCYP51. CONCLUSIONS: The identification of an insertion in the predicted MgCYP51 promoter in azole-resistant isolates overexpressing MgCYP51 is the first report of a genetic mechanism, other than changes in target-site coding sequence, affecting sensitivity to multiple azoles in field isolates of M. graminicola. The identification of recent isolates overexpressing MgCYP51 confirms the ongoing evolution and diversification of resistance mechanisms in European populations of M. graminicola. Copyright (c) 2012 Society of Chemical Industry

KeywordsAgronomy; Entomology
Year of Publication2012
JournalPest Management Science
Journal citation68 (7), pp. 1034-1040
Digital Object Identifier (DOI)doi:10.1002/ps.3263
PubMed ID22411894
Open accessPublished as non-open access
Funder project or codePDM
FunderHGCA - Home Grown Cereals Authority
BASF
Bayer
DuPont
Syngenta
Velcourt
SAC
ADAS
Biotechnology and Biological Sciences Research Council
DEFRA - Department for Environment, Food and Rural Affairs UK
PublisherWiley
Grant IDBBE02257X1
BBE0218321
LK09133
ISSN1526-498X

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