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Controlling Sclerotinia sclerotiorum in Glycine max by targeting oxalic acid production using host-induced gene silencing

Megan Mccaghey: University of Wisconsin-Madison

<div><em>Sclerotinia sclerotiorum</em>, the causal agent of Sclerotinia stem rot (SSR), is a yield-limiting, fungal pathogen of <em>Glycine max</em>. The pathogenic success of <em>S. sclerotiorum</em> requires the secretion of oxalic acid (OA), a key virulence factor for this pathogen. Virus-induced gene silencing (VIGS) using <em>Bean pod mottle virus</em> (BPMV) was used to target OA biogenesis in <em>S. sclerotiorum</em>. A sequence of 366 bp, corresponding to the fungal oxaloacetate acetylhydrolase (<em>Ssoah1</em>), was cloned into a BPMV vector in an antisense orientation. BPMV constructs were introduced into <em>G. max</em> using particle bombardment, and viral symptoms paired with RT-PCR were used to confirm viral replication prior to inoculation. Disease progress and target mRNA levels were monitored over a five-day period. Remarkably, plants containing BPMV vectors targeting Ss<em>oah</em>1 showed enhanced resistance to <em>S. sclerotiorum</em> compared to empty-vector control plants, in three replicated experiments. These results provide evidence supporting host-induced gene silencing targeting virulence factors as a viable strategy to control SSR. Our study also evaluated exogenous applications of dsRNA and sRNA to limit fungal growth and OA production <em>in vitro</em> and <em>in planta</em>. Genetic resistance to SSR is inadequate in commercial soybean varieties, while fungicidal control can be inconsistent and expensive. Herein, we propose that RNAi strategies will provide new tools for resistance to <em>S. sclerotiorum</em> in <em>G. max</em>.</div>