Identification of a new PSII target site psbA mutation leading to D1 amino acid Leu218Val exchange in the Chenopodium album D1 protein and comparison to cross-resistance profiles of known modifications at positions 251 and 264
Resistance of Chenopodium album to triazinones and triazines can be caused by two amino acid exchanges, serine-264-glycine (Ser264Gly) and alanine-251-valine (Ala251Val), in the chloroplast D1 protein. This paper describes the identification of a biotype with a leucine-218-valine (Leu218Val) 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 Ser264Gly and Ala251Val mutations.
Application rate–response curves obtained from the greenhouse experiment showed that the Leu218Val exchange induced significant resistance against the triazinones but not against terbuthylazine. The level of resistance against the triazinones was higher in the Ser264Gly and Ala251Val biotypes compared with the Leu218Val biotype. All biotypes tested were more resistant to metribuzin than to metamitron. Following terbuthylazine treatment, Ser264Gly displayed a high level of resistance, Ala251Val showed moderate resistance. A PCR-RFLP assay for Ser264Gly has been extended to include detection of Ala251Val and Leu218Val mutations.
The D1 Leu218Val substitution in C. album confers significant resistance to triazinones. This suggests that Leu218Val 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. © 2013 Society of Chemical Industry