Method validation and dissipation kinetics of the novel HPPD-inhibiting herbicide cypyrafluone in winter wheat using QuEChERS method coupled with UPLC-MS/MS.

Cypyrafluone, a novel hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicide, can successfully control a wide species of grass and broadleaf weed in wheat fields. However, the dissipation behaviors and terminal residues of cypyrafluone in wheat fields remain unclear. Here, a simple, accurate, and dependable approach for the analysis of cypyrafluone in soil, wheat plant, and grain was constructed utilizing an adapted QuEChERS extraction combined with UPLC-MS/MS. For accurate quantification, matrix-matched calibrations with high linearity (R2 >0.99) were employed to eliminate matrix interference. The method possessed high accuracy with recoveries in the range of 85.5%- 100.6% and precision with relative standard deviations < 14.3%, as well as high sensitivity with limits of quantifications of 0.001 mg kg-1 in the three matrixes. The dissipation kinetics and terminal residues of cypyrafluone were determined at two separate locations with different climates, soil types and cropping systems in 2018. The half-lives of cypyrafluone in soil and wheat plant were 1.47-1.55 d and 1.00-1.03 d, respectively. At harvest, the terminal residue values of cypyrafluone detected in wheat plants were 0-0.0025 mg kg-1 and 0.0044-0.0057 mg kg-1 at the recommended dose and 1.5 times of the recommended dose, respectively, and 0.0049 mg kg-1 of this herbicide was detected in grain at 1.5 times of the recommended dose, which was below the maximum residue limit (MRL). Finally, the risk quotient for cypyrafluone ranged from 0.33% to 0.81% (<1) for different age groups in China, indicating that the impact of residues from the cypyrafluone application on wheat was acceptable. These findings above will offer scientific guidelines for cypyrafluone application in the wheat field ecosystem.

Cypyrafluone, a 4-Hydroxyphenylpyruvate Dioxygenase Inhibitor to Control Weed in Wheat Fields.

As a bleaching herbicide, cypyrafluone was applied postemergence in wheat fields for annual weed control; especially, this herbicide possesses high efficacy against cool-season grass weed species such as Alopecurus aequalis and Alopecurus japonicus. In this study, the target of action of cypyrafluone on 4-hydroxyphenylpyruvate dioxygenase (HPPD) inhibition was confirmed. This herbicide caused severe foliar whitening symptoms at 5-7 days after treatment (DAT) and death of the whole plant within 10 DAT. Significant increases in phytoene content and significant decreases in kinds of carotenoid and chlorophyll pigments were observed. The content of chlorophyll pigments in cypyrafluone-treated Spirodela polyrhiza decreased upon the addition of homogentisic acid (HGA), which indicated that cypyrafluone prevents the HGA production, possibly by inhibiting the catalytic activity of 4-HPPD. Indeed, cypyrafluone strongly inhibited the catalytic activity of Arabidopsis thaliana HPPD produced by Escherichia coli, which was approximately 2 times less effective than mesotrione. In addition, overexpression of Oryza sativa HPPD in rice and A. thaliana both conferred a high tolerance level to cypyrafluone on them. Molecular docking found that cypyrafluone bonded well to the active site of the HPPD and formed a bidentate coordination interaction with the Fe2+ atom, with distances of 2.6 and 2.7 Å between oxygen atoms and the Fe2+ atom and a binding energy of -8.0 kcal mol-1.

Fitness costs associated with acetyl-coenzyme A carboxylase mutations endowing herbicide resistance in American sloughgrass (Beckmannia syzigachne Steud.).

Weed resistance to herbicide can be conferred by gene mutations, and some mutations can cause pleiotropic effects in some cases. We investigated the pleiotropic effects associated with five specific ACCase mutations (Ile1781Leu, Trp2027Cys, Ile2041Asn, Asp2078Gly, and Gly2096Ala) on the plant growth, seed production, and resource competitiveness in American sloughgrass.Resistant plants (M/M) homozygous for specific ACCase mutation and susceptible wild-type plants (W/W) were derived from single heterozygous mother plant (M/W) by genotyping. Plant growth assay and neighborhood experiments were performed to quantify variation between M/M plants and W/W plants.The Ile1781Leu mutation resulted in slight increases in plant growth in pure stands and improved resource competitiveness under low-competition conditions in pot experiments, but no clear variation was observed under high competitive pressure or field conditions. During competition with wheat plants under field conditions, American sloughgrass plants containing Ile2041Asn ACCase exhibited a significantly lower (12.5%) aboveground biomass but no distinct differences in seed production or resource competitiveness. No significant detrimental pleiotropic effects associated with Gly2096Ala were detected in American sloughgrass.The Trp2027Cys mutation distinctly reduced seed production, especially under high competitive pressure, but did not significantly alter plant growth. The Asp2078Gly mutation consistently reduced not only plant growth and seed production but also resource competitiveness. Synthesis. The Trp2027Cys and Asp2078Gly mutations led to significant fitness costs, which may reduce the frequency of resistance alleles and reduce the propagation speed of resistant weeds in the absence of ACCase inhibitor herbicides. The Ile1781Leu, Ile2041Asn, and Gly2096Ala mutations displayed no obvious fitness costs or displayed very small fitness penalties, which would likely have no effect on the establishment of resistant weeds in the field.

Synthesis and Herbicidal Activity of α-(Substituted Phenoxybutyryloxy or Valeryloxy)alkylphosphonates and 2-(Substituted Phenoxybutyryloxy)alkyl-5,5-dimethyl-1,3,2-dioxaphosphinan-2-one.

On the basis of our work on the modification of alkylphosphonates 1, a series of α-(substituted phenoxybutyryloxy or valeryloxy)alkylphosphonates (4-5) and 2-(substituted phenoxybutyryloxy)alkyl-5,5-dimethyl-1,3,2-dioxaphosphinan-2-one (6) were designed and synthesized. The bioassay results indicated that 14 of title compounds 4 exhibited significant postemergence herbicidal activity against velvetleaf, common amaranth, and false daisy at 150 g ai/ha. Compounds 5 were inactive against all tested weeds. Compounds 6 exhibited moderate to good inhibitory effect against the tested dicotyledonous weeds. Structure-activity relationship (SAR) analyses showed that the length of the carbon chain as linking bridge had a great effect on the herbicidal activity. Broad-spectrum tests of compounds 4-1, 4-2, 4-9, 4-30, and 4-36 were carried out at 75 g ai/ha. Especially, 4-1 exhibited 100% inhibition activity against the tested dicotyledonous weeds, which was higher than that of glyphosate.