title: Lolium rigidum, a pool of resistance mechanisms to ACCase inhibitor herbicides.
abstract: Three diclofop-methyl (DM) resistant biotypes of Lolium rigidum (R1, R2, and R3) were found in different winter wheat fields in Spain, continuously treated with DM, DM + chlortoluron, or DM + isoproturon. Herbicide rates that inhibited shoot growth by 50% (ED50) were determined for DM. There were found that the different biotypes exhibited different ranges of resistance to this herbicide; the resistant factors were 7.2, 13, and 36.6, respectively. DM absorption, metabolism, and effects on ACCase isoforms were examined in these biotypes of L. rigidum. The most highly resistant, biotype R3, contained an altered isoform of ACCase. In biotype R2, which exhibited a medium level of resistance, there was an increased rate of oxidation of the aryl ring of diclofop, a reaction most likely catalyzed by a cytochrome P450 enzyme. In the other biotype, R1, DM penetration was significantly less than that observed in the resistant (R2 and R3) and susceptible (S) biotypes. Analysis of the leaf cuticle surface by scanning electron microscopy showed a greater epicuticular wax density in the leaf cuticles of biotype R1 than in the other biotypes.
authors.affiliation: Departamento de Química Agrícola y Edafología, Universidad de Córdoba, Campus de Rabanales, Edif, Marie Curie, N IV. Km 396, 14071 Córdoba, Spain.
authors.forename: Jose L
authors.initials: JL
authors.lastname: De Prado
authors.forename: Maria D
authors.initials: MD
authors.lastname: Osuna
authors.forename: Antonio
authors.initials: A
authors.lastname: Heredia
authors.forename: Rafael
authors.initials: R
authors.lastname: De Prado
mesh_terms: D000103:Acetyl-CoA Carboxylase / Q000037:antagonists & inhibitors*; D004351:Drug Resistance; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D055768:Halogenated Diphenyl Ethers; D006540:Herbicides / Q000494:pharmacology*; D008129:Lolium / Q000187:drug effects* / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning; D010647:Phenyl Ethers / Q000494:pharmacology; D013030:Spain
chemical_list: D004791:Enzyme Inhibitors; D055768:Halogenated Diphenyl Ethers; D006540:Herbicides; D010647:Phenyl Ethers; C012891:dichlorfop-methyl; D000103:Acetyl-CoA Carboxylase