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Control of cereal pathogens in the light of resistance development in Europe

Gerd Stammler: BASF SE

<div>Fungal pathogens in cereals have a significant impact on yield and quality. In wheat, <em>Zymoseptoria tritici, Blumeria graminis</em> f.sp. <em>tritici, Puccinia triticina, </em>and <em>Fusarium</em> spp. are important European pathogens, while in barley <em>Pyrenophora teres, Ramularia collo-cygni and Rhynchosporium commune </em>play a key role. Fungicides for disease control include QoIs, SBIs and SDHIs. In countries with intensive QoI use, QoI resistance conferred by the G143A exchange in the <em>cyt</em> <em>b</em> has now developed in most important cereal pathogens, except for rusts, <em>R. commune</em> and <em>P. teres</em>. SBIs have been used for more than 30 years to control cereal diseases. Mutations in the <em>cyp51</em> gene are responsible for sensitivity changes with the most advanced evolution of <em>cyp51</em> taking place in <em>Z. tritici,</em> with many different haplotypes. Additionally, <em>cyp51</em> overexpression and enhanced efflux have also been detected as resistance mechanisms. An analysis of several hundred <em>Z. tritici</em> isolates from across Europe show a different distribution of <em>cyp51</em> haplotypes and <em>cyp51</em> overexpression over Europe. Despite this, SBIs are still very important tools in cereal disease control, as well as for resistance management in partnership with the highly effective SDHIs. SDHI resistance has been detected for <em>P. teres </em>and <em>R. collo-cygni</em>. Several mutations in the <em>sdh</em> genes cause resistance and form a complex situation in these two pathogens. <em>sdh</em> mutations have also been found in field isolates of <em>Z. tritici</em>, but the mutation pattern and dynamic is highly different to the barley pathogens. Knowledge on fitness costs by (multiple) resistance and the effects of management strategies might help in the development of sustainable disease control strategies including also non-chemical approaches.</div>