TY - JOUR T1 - Pyroxasulfone resistance in <em>Lolium rigidum</em> conferred by enhanced metabolic capacity JF - bioRxiv DO - 10.1101/116269 SP - 116269 AU - R Busi AU - A Porri AU - TA Gaines AU - SB Powles Y1 - 2017/01/01 UR - http://biorxiv.org/content/early/2017/03/13/116269.abstract N2 - Author Contributions RB and AP designed and performed the experiments. RB, AP, TG, SP wrote the manuscript.One sentence summary This study provides novel insight into herbicide resistance conferred by GST-based detoxification to allow proactive intervention to minimize weed resistance evolution.Abstract The evolution of herbicide-resistant weed populations in response to synthetic herbicide selective pressure is threatening safe weed control practices achieved by these molecules. In Australia multiple-resistant populations of annual ryegrass (Lolium rigidum) are effectively controlled by soil-applied herbicides which provide adequate weed control.In this study we define the mechanistic basis of the experimentally-evolved resistance to the soil-applied herbicide pyroxasulfone in a L. rigidum population. TLC and HPLC-MS provide biochemical confirmation that pyroxasulfone resistance is metabolism-based with identification and quantification of pyroxasulfone metabolites formed via a glutathione conjugation pathway in pyroxasulfone-resistant L. rigidum plants. The observed over-expression of two putative resistance-endowing GST genes is consistent with pyroxasulfone-resistance in parental plants (P6) and positively correlated to pyroxasulfone resistance in F1 pair-cross progenies. Thus, a major detoxification mechanism involves glutathione conjugation to pyroxasulfone and GST over-expression in pyroxasulfone-resistant L. rigidum plants. The definition of the genetic basis of metabolic resistance in weeds can be a first crucial step towards chemical means to reverse resistance and improve long-term weed resistance management. ER -