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Barnyardgrass (Echinochloa crus-galli (L.) P. Beauv.), one of the worst weeds in paddy fields in China, has been frequently reported evolving resistance to acetyl-CoA carboxylase (ACCase) inhibiting herbicides. However, in the previous research, more attention was paid to target-site resistance (TSR) mechanisms, the non-target-site resistance (NTSR) mechanisms have not been well-established. In this study, the potential mechanism of resistance in a metamifop-resistant E. crus-galli collected from Kunshan city, Jiangsu Province, China was investigated. Dose-response assays showed that the phenotypic resistant population (JS-R) has evolved 4.3-fold resistance to metamifop compared with the phenotypic susceptible population (YN-S). The ACCase CT gene sequencing and relative ACCase gene expression levels studies showed that no mutations were detected in the ACCase CT gene in both YN-S and JS-R, and there was no significant difference in the relative ACCase gene expression between YN-S and JS-R. After the pre-processing of glutathione-S-transferase (GSTs) inhibitor NBD-Cl, the resistance level of JS-R to metamifop was reversed 18.73%. Furthermore, the GSTs activity of JS-R plants was significantly enhanced compared to that of YN-S plants. UPLC-MS/MS revealed that JS-R plants had faster metabolic rates to metamifop than YN-S plants. Meanwhile, the JS-R popultion exhibited resistant to cyhalofop-butyl and penoxsulam. In summary, this study presented a novel discovery regarding the global emergence of metabolic resistance to metamifop in E. crus-galli. The low-level resistance observed in the JS-R population was not found to be related to TSR but rather appeared to be primarily associated with the overexpression of genes in the GSTs metabolic enzyme superfamily. [Display omitted] • Echinochloa crus-galli evolved resisitant to metamifop in China. • The resistance of Echinochloa crus-galli to metamifop was not related to target-site resistance. • We provide evidence of the metabolic resistance to metamifop mediated by GSTs in Echinochloa crus-galli in China. • Echinochloa crus-galli metamifop-resistant population also evolved resisitant to cyhalofop-butyl and penoxsulam. [ABSTRACT FROM AUTHOR]

Flixweed (Descurainia sophia L.) is widely distributed in winter wheat (Triticum aestivum L.) fields in the North China Plain and has evolved resistance to herbicides, including the acetolactate synthase (ALS) inhibitor florasulam. However, the florasulam resistance status of flixweed in the North China Plain is poorly understood, which hinders the integrated management of this weed in winter wheat production systems. Thus, 45 flixweed populations were collected in wheat fields in these areas, and their sensitivity to florasulam and ALS-inhibitor-resistant mutation diversity were assessed. Meanwhile, alternative herbicides/herbicide mixtures for the control of florasulam-resistant flixweed were screened and evaluated under greenhouse and field conditions. Of the populations, 30 showed florasulam resistance (RRR and RR), 9 had a high risk of evolving florasulam resistance (R?) and 6 were susceptible. These populations had 5.3 to 345.1-fold resistance to florasulam, and 4 ALS resistance mutations (P197H, P197S, P197T and W574L) were observed. The subsequent herbicide sensitivity assay showed that the SD-06 population (with ALS1 P197T and ALS2 W574L mutations) exhibited cross-resistance to all ALS inhibitors tested, but was sensitive to MCPA-Na, fluroxypyr, carfentrazone-ethyl and bipyrazone. Meanwhile, the other HN-07 population with non-target-site resistance (NTSR) also showed resistance to all tested ALS inhibitors, and it was "R?" to MCPA-Na while sensitive to fluroxypyr, carfentrazone-ethyl and bipyrazone. The field experiments were conducted at the research farm where the SD-06 population was collected, and the results suggested that florasulam at 3.75–4.5 g ai ha−1 had little efficacy (0.6–12.1%), whereas MCPA-Na + carfentrazone-ethyl (87.1–91.2%) and bipyrazone+fluroxypyr (90.1–97.8%) controlled the resistant flixweed. Unlabelled Image • Florasulam resistance in flixweed is prevalent in wheat in the North China Plain. • An available weed map was established for scientific management of flixweed. • Both TSR and NTSR were existed in florasulam-resistant flixweed populations. • Alternative herbicides were screened for control of florasulam-resistant flixweed. [ABSTRACT FROM AUTHOR]

A rapid and simple method based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) of sample preparation using QuEChERS was developed for detecting residues of QYR301, a new HPPD-inhibiting herbicide, in rice plant (straw), water, soil, rice hull and brown rice (BR). To eliminate matrix interference, matrix-matched calibrations with satisfactory linearity (R2 > 0.99) were used for accurate quantification. The method showed recoveries of 90.3–108.1% and relative standard deviations (RSDs) < 11%. The limits of quantification (LOQ) for QYR301 were 0.005 mg kg−1 in all five matrixes. Furthermore, the dissipation kinetics and terminal residues of QYR301 were determined at two sites in 2018. The days for 50% dissipation (DT 50) of QYR301 in rice plants, water and soil were 3.6–4.4, 0.7–3.0 and 4.3–8.0 d, respectively, which indicated that QYR301 is a short-persistence herbicide. Moreover, no QYR301 residues were detected in BR, rice hull and straw collected at harvest following its application at 1.0 or 1.5 × of the recommended high rate. These results will help organizations and governments establish related principles/laws regarding the use of QYR301 in terms of environmental protection, food safety and other potential aspects. Image 1 • QYR301 is a new HPPD-inhibiting herbicide applied post emergence in paddy fields. • Liquid chromatography tandem mass spectrometry with modified QuEChERS was developed. • Evaluated degradation dynamics of QYR301 in the open field. • QYR 301 was not detected in all samples collected at harvest time. [ABSTRACT FROM AUTHOR]