iTRAQ-based quantitative proteomic analysis reveals proteomic changes in three fenoxaprop- P -ethyl-resistant Beckmannia syzigachne biotypes with differing ACCase mutations

Fenoxaprop-P-ethyl, mesosulfuron-ethyl, and isoproturon resistance status in Beckmannia syzigachne from wheat fields across Anhui Province, China

Severe infestations of American sloughgrass (Beckmannia syzigachne (Steud.) Fernald) in wheat fields throughout Anhui Province, China, pose a significant threat to local agricultural production. This study aims to evaluate the susceptibility of 37 B. syzigachne populations collected from diverse wheat fields in Anhui Province to three commonly used herbicides: fenoxaprop-P-ethyl, mesosulfuron-ethyl, and isoproturon. Single-dose testing revealed that out of the 37 populations, 31, 26, and 11 populations had either evolved or were evolving resistance to fenoxaprop-P-ethyl, mesosulfuron-ethyl, and isoproturon, respectively. Among them, 25 populations displayed concurrent resistance to both fenoxaprop-P-ethyl and mesosulfuron-ethyl, while eight exhibited resistance to all three tested herbicides. Whole-plant bioassays confirmed that approximately 84% of the fenoxaprop-P-ethyl-resistant populations manifested high-level resistance (resistance index (RI) ≥10); 62% of the mesosulfuron-ethyl-resistant populations and 82% of the isoproturon-resistant populations exhibited low- to moderate-level resistance (2 ≤ RI <10). Three distinct target-site mutations were identified in 27% of fenoxaprop-P-ethyl-resistant populations, with no known resistance mutations detected in the remaining herbicide-resistant populations. The inhibition of cytochrome P450s (P450s) and/or glutathione S-transferases (GSTs) substantially increased susceptibility in the majority of resistant populations lacking mutations at the herbicide target site. In conclusion, resistance to fenoxaprop-P-ethyl and mesosulfuron-ethyl was widespread in B. syzigachne within Anhui Province's wheat fields, while resistance to isoproturon was rapidly evolving due to its escalating usage. Target-site mutations were present in approximately one-third of fenoxaprop-P-ethyl-resistant populations, and alternative mechanisms involving P450s and/or GSTs could explain the resistance observed in most of the remaining populations.

Molecular basis for the resistance of American sloughgrass to aryloxyphenoxypropionic acid pesticides and its environmental relevance: A combined experimental and computational study

Organic pesticides are one of the main environmental pollutants, and how to reduce their environmental risks is an important issue. In this contribution, we disclose the molecular basis for the resistance of American sloughgrass to aryloxyphenoxypropionic acid pesticides using site-directed mutagenesis and molecular modeling and then construct an effective screening model. The results indicated that the target-site mutation (Trp-1999-Leu) in acetyl-coenzyme A carboxylase (ACCase) can affect the effectiveness of the pesticides (clodinafop, fenoxaprop, cyhalofop, and metamifop), and the plant resistance to fenoxaprop, clodinafop, cyhalofop, and metamifop was found to be 564, 19.5, 10, and 0.19 times, respectively. The established computational models (i.e. wild-type/mutant ACCase models) could be used for rational screening and evaluation of the resistance to pesticides. The resistance induced by target gene mutation can markedly reduce the bioreactivity of the ACCase-clodinafop/fenoxaprop adducts, and the magnitudes are 10 and 102, respectively. Such event will seriously aggravate environmental pollution. However, the biological issue has no distinct effect on cyhalofop (RI＝10), and meanwhile it may markedly increase the bioefficacy of metamifop (RI＝0.19). We could selectively adopt the two chemicals so as to decrease the residual pesticides in the environment. Significantly, research findings from the computational screening models were found to be negatively correlated with the resistance level derived from the bioassay testing, suggesting that the screening models can be used to guide the usage of pesticides. Obviously, this story may shed novel insight on the reduction of environmental risks of pesticides and other organic pollutants.