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Fungicide sensitivity study of European Zymoseptoria tritici populations using large scale phenotyping and targets-based amplicon sequencing.

Stefano Torriani: Syngenta Crop Protection

<div><em>Zymoseptoria tritici</em>, the causal agent of Septoria tritici blotch is the most severe pathogen of wheat worldwide. Sustainable management of <em>Z. tritici</em> and other wheat diseases is mainly relying on correct fungicide spray programs. Monitor evolution and variation in fungicide sensitivity of pathogen populations is essential to provide accurate recommendation and it is considered by Food and Agriculture Organization of the United Nations (FAO) an integral part of the integrated pest management strategy. <em>Z. tritici</em> evolved target site resistance mechanisms to the major fungicide classes currently available (QoIs, DMIs and SDHIs). Resistance alleles to QoI, DMI and SDHI have been described in target genes <em>cytb</em>, <em>cyp51</em> and <em>sdhB/C/D</em>, respectively. Some <em>Z. tritici</em> isolates might also express weak multidrug adaptation mainly associated to overexpression of the major facilitator gene <em>mfs1</em>. In this study we describe the results from the correlation between a high throughput genotype approach based on an Illumina amplicon sequencing and the fungicide sensitivity phenotype of 384 single spore field isolates collected from 11 European countries in 2016 toward two SDHIs, seven DMIs and one multisites. A deep understanding of geographic distribution and fungicide cross resistance profile of the most relevant resistant genotypes as well as the distribution of multiple resistances is essential to frame the impact to disease control and to propose sound new anti-resistance strategies.</div>

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