Resistance mechanism to acetyl coenzyme A carboxylase inhibiting herbicides in Phalaris paradoxa collected in Mexican wheat fields

Abstract

In this study, we describe the molecular, physiological and agronomic aspects involved in the resistance to acetyl coenzyme A carboxylase inhibiting herbicides (ACCase) observed in one biotype of Phalaris paradoxa from Mexico. Dose–response Assays: The herbicide rate inhibiting plant growth of each biotype by 50% with respect to the untreated control, ED50. Enzyme purification and ACCase assays to determine herbicide rate inhibiting the enzyme of each biotype by 50% with respect to the untreated control, I50. Absorption and Translocation Assays with [14C]diclofop-methyl. Metabolism of diclofop-methyl and its metabolites were identified by thin-layer chromatography. Study of target site resistance mechanism at enzyme and molecular levels. In this work, it has been studied the whole-plant response of Phalaris paradoxa biotypes from Mexico resistant (R) and susceptible (S) to ACCase-inhibiting herbicides: aryloxyphenoxypropionate (APP), cyclohexanedione (CHD) and phenylpyrazoline (PPZ), and the mechanism behind their resistance were studied. To analyse the resistance mechanism, the enzyme ACCase activity was investigated. Results from biochemical assays indicated a target-site resistance as the cause of reduced susceptibility to ACCase inhibitors. The absorption, translocation and metabolism were similar between R and S biotypes. A point mutation never described before was detected within the triplet of glycine at the amino acid position 2096 (referring to EMBL accession no. AJ310767) and resulted in the triplet of serine. This new mutation could explain the loss of affinity for the ACCase-inhibiting herbicides. We found a new mutation, which had never been described before. This mutation was detected within the triplet of glycine at the amino acid position 2096. This new mutation confers cross-resistance to three different chemical groups of ACCase-inhibiting herbicides.