title: Identification of a new PSII target site psbA mutation leading to D1 amino acid Leu218 Val exchange in the Chenopodium album D1 protein and comparison to cross-resistance profiles of known modifications at positions 251 and 264.
abstract: BACKGROUND
  Resistance of Chenopodium album to triazinones and triazines can be caused by two amino acid exchanges, serine-264-glycine (Ser(264) Gly) and alanine-251-valine (Ala(251) Val), in the chloroplast D1 protein. This paper describes the identification of a biotype with a leucine-218-valine (Leu(218) Val) switch found in German sugar beet fields with unsatisfactory weed control. A greenhouse experiment has been performed to compare the resistance profile of the newly identified biotype with biotypes that carry the Ser(264) Gly and Ala(251) Val mutations.
  
  
  RESULTS
  Application rate-response curves obtained from the greenhouse experiment showed that the Leu(218) Val exchange induced significant resistance against the triazinones but not against terbuthylazine. The level of resistance against the triazinones was higher in the Ser(264) Gly and Ala(251) Val biotypes compared with the Leu(218) Val biotype. All biotypes tested were more resistant to metribuzin than to metamitron. Following terbuthylazine treatment, Ser264 Gly displayed a high level of resistance, Ala(251) Val showed moderate resistance. A PCR-RFLP assay for Ser(264) Gly has been extended to include detection of Ala251 Val and Leu(218) Val mutations.
  
  
  CONCLUSIONS
  The D1 Leu(218) Val substitution in C. album confers significant resistance to triazinones. This suggests that Leu(218) Val is involved in the binding of triazinones. First establishment of the resistance profiles of the three psbA mutations suggests that these mutations have been independently selected.
authors.affiliation: Institute of Sugar Beet Research, Department of Phytopathology, Holtenser Landstrasse 77, D-37079, Göttingen, Germany.
authors.forename: Heike
authors.initials: H
authors.lastname: Thiel
authors.forename: Mark
authors.initials: M
authors.lastname: Varrelmann
mesh_terms: D019943:Amino Acid Substitution; D001665:Binding Sites; D027463:Chenopodium album / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics*; D004780:Environment, Controlled; D004791:Enzyme Inhibitors / Q000378:metabolism / Q000633:toxicity; D053209:Herbicide Resistance / Q000235:genetics*; D006540:Herbicides / Q000378:metabolism / Q000633:toxicity; D009154:Mutation; D045332:Photosystem II Protein Complex / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics*; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D015183:Restriction Mapping
chemical_list: D004791:Enzyme Inhibitors; D006540:Herbicides; D045332:Photosystem II Protein Complex
keywords: Chenopodium album; PCR-RFLP; cross-resistance; photosystem II inhibitor; psbA gene