Sethoxydim herbicide at sublethal dose synergizes biocontrol of green foxtail by Pyricularia setariae via triggering ABA-activated pathways and bZIP60
Gary Peng: Agric & Agri-Food Canada
<div>Applying sethoxydim at 0.1× label rate (sublethal) dramatically enhances the biocontrol of herbicide-sensitive (HS) <em>Setaria viridis</em> [green foxtail (GFT)] by the mycoherbicide fungus <em>Pyricularia setariae</em>. In this study, GFT transcriptomes were analyzed to elucidate the mechanism for the herbicide effect. Reference transcriptomes of HS and herbicide-resistant (HR) GFT were constructed via <em>de novo</em> assembly of RNA-seq data using a mixture of samples from several growth stages of HS and HR GFT biotypes, separately. Analysis of differentially regulated biological processes showed that the sethoxydim treatment suppressed photosynthesis in HS plants, especially the C4-specific phosphoenolpyruvate carboxylase kinase. It also induced ABA-activated signaling pathways as well as a bZIP transcriptional factor 60 (bZIP60), coinciding with the enhanced biocontrol of GFT-HS by <em>P. setariae</em>. On HR plants, the herbicide treatment failed to induce the ABA pathway or bZIP60, and did not improve the biocontrol. An exogenous application of ABA to HS plants produced effects similar to that by sethoxydim; it enhanced the expression of bZIP60 and synergized the biocontrol by <em>P. </em>setariae. This is the first use of RNA-seq to decipher the mechanism of a sublethal rate of herbicide to synergize weed biocontrol. This method provides a better understanding of the modes of action in the synergized GFT biocontrol, and a new approach to improve the efficacy and practicality of weed biocontrol.</div>
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