title: A psbA mutation in Kochia scoparia (L) Schrad from railroad rights-of-way with resistance to diuron, tebuthiuron and metribuzin.
abstract: Kochia [Kochia scoparia (L) Schrad] has become resistant to many herbicides used in cropland and railroad rights-of-way in North Dakota and Minnesota. Kochia scoparia plants that had survived annual treatments with diuron and tebuthiuron were sampled along railroad rights-of-way in North Dakota and Minnesota. The samples were screened in the greenhouse for resistance to diuron, tebuthiuron, metribuzin and bromoxynil from 0.5x to 32x the recommended use rates. A resistant K scoparia accession (MN-3R) was confirmed with resistance up to 16-fold higher than recommended use rates for tebuthiuron and diuron and up to 4-fold higher for metribuzin. However, the resistant K scoparia accession was susceptible to bromoxynil even at 50% of the recommended use rate. The herbicide binding region of the psbA gene fragment of eight resistant (R) and seven susceptible (S) K scoparia accessions was PCR-amplified and sequenced for detection of mutations. The psbA gene of four R K scoparia accessions was mutated at residue 219 with substitution of isoleucine for valine (GenBank accession number AY251265). The seven S K scoparia accession sequences were wild-type at this residue (GenBank accession number AY251266). The other four R accessions sequences showed a previously known triazine R mutation with substitution of glycine for serine at residue 264. All 15 K scoparia accessions were wild-type at all other psbA residues within the region analyzed. Resistance to diuron, tebuthiuron and metribuzin among the railroad rights-of-way K scoparia is probably due to the mutation at residue 219 of the psbA gene in some plants, but due to the previously reported Ser(264)Gly substitution in other plants. Target-site resistance associated with a change of valine to isoleucine at residue 219 of the psbA target-site in weeds has previously been reported for Poa annua L selected in diuron-treated grass seed fields, and for Amaranthus powelli S Wats selected in linuron-treated carrot fields. This is the first report of the mutation in herbicide-resistant K scoparia.
authors.affiliation: Department of Plant Sciences, North Dakota State University, Fargo, 58105, USA. mengistu.workineh@ndsu.edu
authors.forename: Lemma W
authors.initials: LW
authors.lastname: Mengistu
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Christoffers
authors.forename: Rodney G
authors.initials: RG
authors.lastname: Lym
mesh_terms: D000818:Animals; D027467:Bassia scoparia / Q000187:drug effects* / Q000235:genetics*; D004237:Diuron / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004351:Drug Resistance / Q000235:genetics; D005798:Genes, Bacterial / Q000235:genetics; D006540:Herbicides / Q000494:pharmacology; D008782:Methylurea Compounds / Q000494:pharmacology*; D008910:Minnesota; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009658:North Dakota; D045332:Photosystem II Protein Complex / Q000235:genetics*; D011890:Railroads; D014227:Triazines / Q000494:pharmacology*
chemical_list: D006540:Herbicides; D008782:Methylurea Compounds; D045332:Photosystem II Protein Complex; D014227:Triazines; D004237:Diuron; C010346:tebuthiuron; C009235:metribuzin