title: Cross-resistance profile of mesosulfuron-methyl-resistant Italian ryegrass in the southern United States.
abstract: Diclofop-resistant Lolium species (ryegrass) is a major weed problem in wheat production worldwide. This study was conducted to determine the resistance pattern of diclofop-resistant ryegrass accessions from the southern United States to mesosulfuron-methyl, a recently commercialized herbicide for ryegrass control in wheat; to determine the cross-resistance pattern of a Lolium multiflorum Lam. (Italian ryegrass) accession, 03-1, to acetolactate synthase (ALS) and acetyl-CoA carboxylase (ACCase) inhibitors; and to determine the resistance mechanism of Italian ryegrass to mesosulfuron-methyl. Seventeen ryegrass accessions from Arkansas and Louisiana, including standard resistant and susceptible accessions, were used in this experiment. Fourteen of the 17 accessions were more resistant (four- to > 308-fold) to diclofop than the standard susceptible biotype. One accession, 03-1, was resistant to mesosulfuron-methyl as well as to other ALS inhibitor herbicides such as chlorsulfuron, imazamox and sulfometuron. Accession 03-1, however, did not show multiple resistance to the ACCase inhibitor herbicides diclofop, fluazifop, clethodim, sethoxydim and pinoxaden, nor to glyphosate. The in vivo ALS activity of the 03-1 biotype was less affected by mesosulfuron-methyl than the susceptible biotype. This indicates that the resistance mechanism of Italian ryegrass to mesosulfuron-methyl is partly due to an alteration in the target enzyme, ALS. It is concluded that diclofop-resistant ryegrass in the southern United States can be generally controlled by mesosulfuron-methyl. However, mesosulfuron-methyl must be used with caution because not all ryegrass populations are susceptible to it. There is a need for more thorough profiling of ryegrass resistance to herbicides.
authors.affiliation: Department of Crop, Soil and Environmental Sciences, University of Arkansas, Fayetteville, AR 72704, USA.
authors.forename: Yong In
authors.initials: YI
authors.lastname: Kuk
authors.forename: Nilda R
authors.initials: NR
authors.lastname: Bugos
mesh_terms: D000095:Acetolactate Synthase / Q000037:antagonists & inhibitors; D000103:Acetyl-CoA Carboxylase / Q000037:antagonists & inhibitors; D001131:Arkansas; D018432:Drug Resistance, Multiple; D055768:Halogenated Diphenyl Ethers; D053209:Herbicide Resistance; D006540:Herbicides / Q000494:pharmacology*; D008129:Lolium / Q000187:drug effects*; D008145:Louisiana; D010647:Phenyl Ethers / Q000494:pharmacology; D013453:Sulfonylurea Compounds / Q000494:pharmacology*
chemical_list: D055768:Halogenated Diphenyl Ethers; D006540:Herbicides; D010647:Phenyl Ethers; D013453:Sulfonylurea Compounds; C521745:mesosulfuron-methyl; C012891:dichlorfop-methyl; D000095:Acetolactate Synthase; D000103:Acetyl-CoA Carboxylase