Frequency of mutations associated with fungicide resistance and population structure of Mycosphaerella graminicola in Tunisia
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The occurrence of fungicide resistance in Mycosphaerella graminicola populations from Tunisia was investigated by examining mutations known to be associated with strobilurin and azole resistance. Few mutations associated with fungicide resistance were detected. No evidence for strobilurin resistance was found among 357 Tunisian isolates and only two among 80 sequenced isolates carried mutations associated with azole resistance. A network analysis suggested that these mutations emerged independently from mutations found in previously described European populations. The population genetic structure of M. graminicola in Tunisia was analyzed using variation at 11 microsatellite loci. Populations in Tunisia were characterized by high gene and genotype diversity. All populations were in gametic equilibrium and mating type proportions did not deviate from the 1:1 ratio expected under random mating, consistent with regular cycles of sexual reproduction. In combination with a high degree of gene flow among sampling sites, M. graminicola must be considered a pathogens with high evolutionary potential. Thus, control strategies against Septoria blotch in Tunisia should be optimized to reduce the emergence and spread of resistant isolates.
KeywordsDMI fungicides Gene flow QoI fungicides Parallel evolution Septoria tritici
We thank Marcello Zala, Stefano Torriani, Megan McDonald and Joanna Bernardes de Assis for technical support and helpful discussions. The Genetic Diversity Center of ETH Zurich provided facilities for collecting molecular data. This project was supported by the Swiss government through the Federal Commission for Scholarships for Foreign Students (FCS; RefNr: 20080384) who sponsored SB.
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