Identifying molecular components of reduced demethylation inhibitor (DMI) fungicide sensitivity in Blumeria graminis f.sp. tritici
Emily Meyers: Department of Entomology and Plant Pathology, North Carolina State University
<div><em>Blumeria graminis</em> f.sp. <em>tritici </em>(Bgt), the causal agent of wheat powdery mildew, occurs annually in states along the eastern seaboard of the United States (US) and infects wheat worldwide. Reduced sensitivity to DMI fungicides has been observed in both European and Australian Bgt populations. The first evaluation of DMI sensitivity in US Bgt populations was conducted with isolates collected from 15 US states. Sensitivity to two DMIs (tebuconazole and prothioconazole) was measured for 380 isolates, with a third DMI (metconazole) measured for 100 isolates. A large range in DMI sensitivity was observed, with a significantly larger reduction in sensitivity observed in eastern US states compared to central Great Plains states. Discovering the molecular drivers of DMI sensitivity in US Bgt populations will assist in addressing fungicide resistance in US wheat production and add to understanding how fungicides influence the global Bgt population. Targeted partial genome sequencing of phenotyped isolates identified genetic components related to the observed differences in DMI sensitivity. Sequencing of the DMI-targeted CYP51 gene revealed a Y136F mutation that significantly correlates with reduced sensitivity to tebuconazole (P<0.001, R<sup>2 </sup>=0.11); however, 17 tebuconazole-insensitive isolates lack the mutation and 67 sensitive isolates have Y136F. Future analyses will evaluate more SNPs for DMI sensitivity association and qPCR analysis of CYP51 for expression and copy number.</div>
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