%A Yanniccari,Marcos %A Gigón,Ramón %A Larsen,Adelina %D 2020 %J Frontiers in Plant Science %C %F %G English %K Ryegrass,Marker-trait associations,Multiple-resistance,Non-target site resistance (NTSR),Target-site resistance (TSR) %Q %R 10.3389/fpls.2020.600301 %W %L %M %P %7 %8 2020-November-16 %9 Original Research %# %! Cross-resistance in Lolium spp. %* %< %T Cytochrome P450 Herbicide Metabolism as the Main Mechanism of Cross-Resistance to ACCase- and ALS-Inhibitors in Lolium spp. Populations From Argentina: A Molecular Approach in Characterization and Detection %U https://www.frontiersin.org/articles/10.3389/fpls.2020.600301 %V 11 %0 JOURNAL ARTICLE %@ 1664-462X %X Knowledge about the mechanisms of herbicide resistance provide valuable insights into evolving weed populations in response to selection pressure and should be used as a basis for designing management strategies for herbicide-resistant weeds. The selection pressure associated with reactive management against glyphosate-resistant Lolium spp. populations would have favored the herbicide resistance to ACCase- and ALS-inhibitors. This work was aimed to determine the sensitivity of 80 Argentinean Lolium spp. populations to ALS- and ACCase-inhibitor herbicides for use in wheat or barley and to study the mechanisms of resistance involved. Sensitivity to pinoxaden and iodosulfuron-mesosulfuron were positively correlated (r = 0.84), even though both affect different target sites. Inhibitors of cytochrome P450 monooxygenases (P450s) increased the sensitivity to pinoxaden and iodosulfuron-mesosulfuron in 94% of herbicide-resistant populations and target-site ACCase resistance mutations were detected only in two cases. Polymorphic variants were obtained with a pair primer designed on P450 sequences, cluster analysis discriminated around 80% of susceptible and P450-metabolic resistant plants sampled from a single population or different populations. Five markers corresponding to herbicide sensitivity were identified to be significantly associated with phenotypic variance in plants. Resistance to ALS- and ACCase-inhibitor herbicides were closely related, challenging the rotation of herbicides of both sites of action as a practice against resistance. In that sense, the use of pinoxaden and iodosulfuron-mesosulfuron would have provoked a selection on P450 genes that conduced a convergence of P450-metabolism based resistant Lolium spp. populations, which was detected by markers in a contribution to elucidate the molecular basis of this type of resistance.