Fe3+-cysteine enhanced persulfate fenton-like process for quinclorac degradation: A wide pH tolerance and reaction mechanism.

A green, high-efficiency, and wide pH tolerance water remediation process has been urgently acquired for the increasingly exacerbating contaminated water. In this study, a Fe3+/persulfate (Fe3+/PS) system was employed and enhanced with a green natural ligand cysteine (Cys) for the degradation of quinclorac (QNC). The introduction of Cys into the Fe3+/PS system widened the effective pH range to 9 with a superior removal rate for QNC. The mechanism revealed that the Fe3+/Cys/PS system can enhance the ability of degrading QNC by accelerating the Fe3+/Fe2+ redox cycle, maintaining Fe2+ concentration and thereby generating more HO• and SO4•-. The impact factors (i.e., pH, concentrations of PS, Fe3+ and Cys) were optimized as well. This work provides a promising strategy with high catalytic activity and wide pH tolerance for organic contaminated water remediation.

Multiple resistance of Echinochloa phyllopogon to synthetic auxin, ALS-, and ACCase-inhibiting herbicides in Northeast China.

Echinochloa phyllopogon is a self-pollinating allotetraploid weed and a serious threat to global rice production. One sensitive and three multiple-resistant populations collected from two provinces of Northeast China were used to analyze the mechanism of multiple resistance of E. phyllopogon to penoxsulam, metamifop, and quinclorac. Compared with the sensitive population LN12, LN1 showed higher resistance to these three herbicides; LN24 showed medium resistance to penoxsulam and metamifop and higher resistance to quinclorac (274-fold); HLJ4 showed low resistance to penoxsulam and high resistance to metamifop and quinclorac. Target sequence analysis showed no mutations in acetolactate synthase or acetyl-CoA carboxylase genes. In-vitro enzyme activity analysis showed that the activity of the target enzyme of multiple herbicide-resistant populations was similar to that of the sensitive population. The P450 inhibitor, malathion, noticeably increased the sensitivity of LN1, LN24, and HLJ4 to penoxsulam, LN1 to metamifop, and HLJ4 to quinclorac. Under all four treatments, the GSTs activities of resistant and sensitive populations showed an increasing trend from day 1 to day 5, but the sensitivity and activity of GSTs were higher in the multiple-resistant population than that in the sensitive population LN12. This study identified the development of multiple-resistant E. phyllopogon populations that pose a serious threat to rice production in rice fields in Northeast China, preliminarily confirming that multiple-resistance was likely due to non-target-site resistance mechanisms. These populations of E. phyllopogon are likely to be more difficult to control.

Comparison of quintrione and quinclorac on mechanism of action.

Quintrione is a new post-emergence herbicide developed for use in rice; however, the mechanism of action remains unclear. We determined the phytotoxicity of quintrione, and the contributions of hormone levels and lipid peroxidation to phytotoxicity, by comparing them to those induced by quinclorac. We also investigated 4-hydroxyphenylpyruvate dioxygenase (HPPD) activity and carotenoid content following treatment with quintrione by comparing them to those induced by quinclorac and mesotrione. We found that quintrione and quinclorac both inhibited the growth of Echinochloa crusgalli var. zelayensis, but that quinclorac was a little more effective. At 24 h, quintrione and quinclorac significantly increased ethylene production and the contents of abscisic acid (ABA) and indole acetic acid (IAA) compared with the control. No significant differences were observed between quintrione and quinclorac on the three plant hormones. Quintrione and quinclorac also induced the formation of malondialdehyde (MDA), which is associated with lipid peroxidation, with no significant difference between them. Carotenoid content was reduced in E. crusgalli var. zelayensis following treatments with quintrione, quinclorac, and mesotrione. At 120 h, carotenoid contents were significantly higher following the quintrione and quinclorac treatments, in comparison with mesotrione treatment. There were no significant differences between quintrione and quinclorac in the inhibition of HPPD activity, and the effects of both were significantly less than the effect of mesotrione. In summary, E. crusgalli var. zelayensis was susceptible to both quintrione and quinclorac. The mechanism of action of quintrione, like that of quinclorac, was related to levels of plant hormones and lipid peroxidation; however, quintrione was a poor inhibitor of HPPD activity compared to mesotrione.

Multi-walled Carbon Nanotubes Remediate the Phytotoxicity of Quinclorac to Tomato.

In order to remediate the phytotoxicity of quinclorac to tomato by multi-walled carbon nanotubes (MWCNTs), the adsorption of quinclorac to MWCNTs was monitored and the effect of MWCNTs on the phytotoxicity of quinclorac to tomato in soil were studied. The results showed that the Linear equation and Freundlich equation can well fit the adsorption isotherm of quinclorac in the soil containing MWCNTs. The adsorption of quinclorac in soil was significantly enhanced by the addition of MWCNTs; the Kd of soil (1% MWCNTs) was 28.7 times of pure soil. The quinclorac had an obvious inhibitory effect on the growth of tomatoes; serious phytotoxicity was also induced even at the lowest concentration of 0.025 mg/kg. With the MWCNTs content in soil increased to 0.5% and 1%, the phytotoxicity of quinclorac to tomatoes decreased significantly, and the height and fresh weight of tomatoes were even higher than those of the control group, indicating that MWCNTs can promote the growth of tomato. These results provide a reference for resolving the problem of phytotoxicity induced by residual herbicides in farmland.

[Determination of Quinclorac in Livestock Products by LC-MS/MS].

A liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based method was developed for determining quinclorac in livestock products. Quinclorac was extracted from the samples using a solution of acetone and hydrochloric acid mixed in a 99 : 1 ratio. The crude extract was purified with ethyl acetate under basic conditions, followed by quinclorac extraction with ethyl acetate under acidic conditions and analysis using LC-MS/MS. The average recoveries of quinclorac from five livestock products (n=5) fortified at the maximum residue limits or 0.01 mg/kg ranged from 85.6 to 93.5%, with the precision of repeatability ranging from 1.7 to 6.8%. The quantification limit in this analytical method was 0.01 mg/kg. These results suggest that the developed method is useful for analyzing quinclorac in livestock products.

Determination of quinclorac by adsorptive stripping voltammetry in rice samples without sample pretreatment.

A novel voltammetric method with practically no sample pretreatment was developed for determination of Quinclorac (QNC) in rice samples by using a working Carbon Paste Electrode (CPE) modified with ionic liquid, with deposition potential (ED) of -1.43 V for 30 s in NaOH 0.01 mol L-1. The systematic influence of cations and anions of imidazole ionic liquids on the composition of CPE has evaluated. The best electrode composition was 65% (w/w) of graphite powder, 30% (w/w) of mineral oil and 5.0% (w/w) of C4min+BF4- ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate). The matrices analyzed were deionized water and extracts of upland rice: white, brown, peel and seed. The limits of quantification ranged between 0.954 mg kg-1 and 3.61 mg kg-1. The recovery percentages of QNC in rice samples ranged between 90% and 121%. The simplicity and good analytical frequency enable the proposed method to be used to obtain preliminary information on the presence of QNC, prior to the implementation of more detailed, costly and elaborate quantitative analyses. The technique can be applied in the study and evaluation of sorption mechanisms, metabolization of the herbicide in plants and its persistence and degradation in the environment.

Synergistic effect of Pseudomonas putida II-2 and Achromobacter sp. QC36 for the effective biodegradation of the herbicide quinclorac.

Quinclorac (QNC) is an effective but environmentally persistent herbicide commonly used in rice production. However, few studies have investigated its environmental behavior and degradation. In the present study, we carried out microbial cultures in the presence of QNC to observe changes in soil microbiota and to identify species capable of QNC degradation by using high-throughput sequencing of the 16S rRNA. Pseudomonas was the dominant genus, and Pseudomonas putida II-2 and other species were found to be capable of mineralizing QNC as a source of carbon and energy. However, this degradation rate was slow, only reaching 51.5 ± 1.6% for 7 days at 30 °C on QNC + minimal salt medium. Achromobacter sp. QC36 co-metabolized QNC when rice straw was added into the mineral salt medium containing QNC, and a mixed culture of both strains could mineralize approximately 92% of the 50 mg/L QNC after 5 days of cultivation in the presence of rice straw, at 25-35 °C and pH 6.0-8.0. Non-phytotoxicity of tobacco after degradation of QNC by mixed strains was evidenced in a pot experiment. These results suggest that this mixed culture may be useful in QNC bioremediation and can be used as a bio-formulation for agro-economical and industrial application.

Ethylene Biosynthesis Inhibition Combined with Cyanide Degradation Confer Resistance to Quinclorac in Echinochloa crus-galli var. mitis.

Echinochloa crus-galli var. mitis has rarely been reported for herbicide resistance, and no case of quinclorac resistance has been reported so far. Synthetic auxin-type herbicide quinclorac is used extensively to control rice weeds worldwide. A long history of using quinclorac in Chinese rice fields escalated the resistance in E. crus-galli var. mitis against this herbicide. Bioassays in Petri plates and pots exhibited four biotypes that evolved into resistance to quinclorac ranking as JS01-R > AH01-R > JS02-R > JX01-R from three provinces of China. Ethylene production in these biotypes was negatively correlated with resistance level and positively correlated with growth inhibition. Determination of the related ethylene response pathway exhibited resistance in biotypes that recorded a decline in 1-aminocyclopropane-1-carboxylic acid (ACC) content, ACC synthase oxidase activities, and less inducible ACS and ACO genes expressions than the susceptible biotype, suggesting that there was a positive correlation between quinclorac resistance and ethylene biosynthesis inhibition. Cyanides produced during the ethylene biosynthesis pathway mainly degraded by the activity of ß-cyanoalanine synthase (ß-CAS). Resistant biotypes exhibited higher ß-CAS activity than the susceptible ones. Nucleotide changes were found in the EcCAS gene of resistant biotypes as compared to sensitive ones that caused three amino acid substitutions (Asn-105-Lys, Gln-195-Glu, and Gly-298-Val), resulting in alteration of enzyme structure, increased binding residues in the active site with its cofactor, and decreased binding free energy; hence, its activity was higher in resistant biotypes. Moreover, these mutations increased the structural stability of the enzyme. In view of the positive correlation between ethylene biosynthesis inhibition and cyanide degradation with resistance level, it is concluded that the alteration in ethylene response pathway or at least variation in ACC synthase and ACC oxidase enzyme activities-due to less relative expression of ACS and ACO genes and enhanced ß-CAS activity, as well as mutation and increased relative expression of EcCAS gene-can be considered as a probable mechanism of quinclorac resistance in E. crus-galli var. mitis.

Quinclorac resistance induced by the suppression of the expression of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase and ACC oxidase genes in Echinochloa crus-galli var. zelayensis.

We previously reported that the mechanism of quinclorac resistance in Echinochloa crus-galli var. zelayensis may be closely related to ethylene biosynthesis and the detoxification of cyanide. Differences in EcCAS gene sequences and expression levels may result in higher capacity to detoxify cyanide in resistant biotypes, which may avoid cyanide accumulation and avoid more ethylene and cyanide production and then avoid damage. In the present study, we focused on the mechanism of resistance related to ethylene biosynthesis in E. crus-galli var. zelayensis. The fresh weight of susceptible and moderately resistant biotypes were significantly reduced after treatment with quinclorac. However, AOA, an ethylene biosynthesis inhibitor, reduced the impact of quinclorac. On pretreatment with AOA, ethylene production was significantly reduced in the three biotypes. The highly resistant biotype produced less ethylene compared to the other two biotypes. Three ACS and seven ACO genes, which are the key genes in ethylene biosynthesis, were obtained. The expression levels of EcACS-like, EcACS7, and EcACO1 varied in the three biotypes upon treatment with quinclorac, which could be manipulated by AOA. In summary, it is inferred that the expression of EcACS-like, EcACS7, and EcACO1 can be stimulated to varying extent after quinclorac treatment in three E. crus-galli var. zelayensis biotypes, which consequently results in varying levels of ethylene production. Lower expression of these three genes results in more resistance to quinclorac, which may also be related to quinclorac resistance in E. crus-galli var. zelayensis.

Decay of Quinclorac in Acidic Paddy Soil and Risk Evaluation to the Subsequent Crop, Tobacco (Nicotiana tabacum L.).

Quinclorac is a selective herbicide commonly used in China to control monocotyledonous weeds in paddy fields. A field experiment was conducted to quantify the environmental behavior of quinclorac in acidic paddy soil under rice (Oryza sativa L.) field conditions, and to evaluate the risk of its residues to the subsequent crop of tobacco (Nicotiana tabacum L.). Rice was sprayed once with quinclorac 50% WP at 562.5, 375.0, or 187.5 g a.i. ha-1 at 7 days after transplanting the seedlings. Decay of quinclorac in paddy field soil followed first-order kinetics, with a half-life of 28.29-30.27 days. At harvest time, 0.090, 0.074 and 0.034 mg kg-1 of quinclorac were found in soils following the above-described treatments, respectively. Leaves of the subsequent crop, tobacco, sown the year after the quinclorac treatments, exhibited different dose-dependent degrees of visible phytotoxicity symptoms.

Resistance to quinclorac caused by the enhanced ability to detoxify cyanide and its molecular mechanism in Echinochloa crus-galli var. zelayensis.

Quinclorac, an auxin-type herbicide, is widely used to control barnyardgrass and some dicotyledon weeds. Echinochloa crus-galli var. zelayensis, a variety of E. crus-galli (L.) Beauv., is widespread in China and some populations have resistance to quinclorac. E. crus-galli var. zelayensis seeds with varying sensitivity to quinclorac were used in the present study. The expression of the ADP/ATP carrier protein (ANT) gene, which plays an important role in the maintenance of cellular energy balance, dramatically rose in the S biotype after exposure to quinclorac, while no change was found in two R biotypes. The activity of ß-cyanoalanine synthase (ß-CAS), which is the key enzyme for cyanide degradation, was higher in two R biotypes than in the S biotype before and after treatment with quinclorac. One single-nucleotide difference was detected in the EcCAS gene of two R biotypes compared with the S biotype. The nucleotide change, which caused one amino acid substitution, replacing Methionine (Met)-295 with Lysine (Lys)-295 in the two R biotypes, which are same as the rice ß-CAS gene at this position. In addition, EcCAS gene expression was higher in the two R biotypes than in the S biotype. In conclusion, ß-CAS may play a crucial role in the resistance of E. crus-galli var. zelayensis to quinclorac. EcCAS gene mutation and higher gene expression may enhance the activity of ß-CAS to avoid the accumulation of toxic cyanide in resistant populations, thus contributing to the resistance mechanism of E. crus-galli var. zelayensis. to quinclorac.

Complementary RNA-Sequencing Based Transcriptomics and iTRAQ Proteomics Reveal the Mechanism of the Alleviation of Quinclorac Stress by Salicylic Acid in Oryza sativa ssp. japonica.

To uncover the alleviation mechanism of quinclorac stress by salicylic acid (SA), leaf samples of Oryza sativa ssp. Japonica under quinclorac stress with and without SA pre-treatment were analyzed for transcriptional and proteomic profiling to determine the differentially expressed genes (DEGs) and proteins (DEPs), respectively. Results showed that quinclorac stress altered the expression of 2207 DEGs (1427 up-regulated, 780 down-regulated) and 147 DEPs (98 down-regulated, 49 up-regulated). These genes and proteins were enriched in glutathione (GSH) metabolism, porphyrin and chlorophyll metabolism, the biosynthesis of secondary metabolites, glyoxylate and dicarboxylate metabolism, and so on. It also influenced apetala2- ethylene-responsive element binding protein (AP2-EREBP) family, myeloblastosis (MYB) family and WRKY family transcription factors. After SA pre-treatment, 697 genes and 124 proteins were differentially expressed. Pathway analysis showed similar enrichments in GSH, glyoxylate and dicarboxylate metabolism. Transcription factors were distributed in basic helix-loop-helix (bHLH), MYB, Tify and WRKY families. Quantitative real-time PCR results revealed that quinclorac stress induced the expression of glutathion reductase (GR) genes (OsGR2, OsGR3), which was further pronounced by SA pre-treatment. Quinclorac stress further mediated the accumulation of acetaldehyde in rice, while SA enhanced the expression of OsALDH2B5 and OsALDH7 to accelerate the metabolism of herbicide quinclorac for the protection of rice. Correlation analysis between transcriptome and proteomics demonstrated that, under quinclorac stress, correlated proteins/genes were mainly involved in the inhibition of intermediate steps in the biosynthesis of chlorophyll. Other interesting proteins/genes and pathways regulated by herbicide quinclorac and modulated by SA pre-treatment were also discussed, based on the transcriptome and proteomics results.

Salicylic acid mediates antioxidant defense system and ABA pathway related gene expression in Oryza sativa against quinclorac toxicity.

The auxin herbicide quinclorac is widely used for controlling weeds in transplanted and direct-seeded rice fields. However, its phytotoxic responses on rice are still unknown. Therefore, in the present investigation we studied the effects of different concentrations (0, 0.1 and 0.5g/L) of quinclorac herbicide on the physiological and biochemical changes of two rice cultivars (XS 134 and ZJ 88) and further analyzed the ameliorating role of salicylic acid (SA) on quinclorac toxicity in rice plants. The results revealed that exogenous application of SA significantly increased plant biomass and total chlorophyll contents in herbicide stressed plants. The lipid peroxidation and ROS (H2O2, O2(-.), (-)OH) production were significantly increased in roots and leaves of both rice cultivars under quinclorac stress, demonstrating an oxidative burst in rice plants. Whereas, application of SA significantly lowered ROS contents under quinclorac stress. Further, exogenous SA treatment significantly modulated antioxidant enzymes and enhanced GSH concentration in stress plants. Anatomical observations of leaf and root revealed that herbicide affected internal structures, while SA played a vital role in protection from toxic effects. Expression analysis of stress hormone ABA genes (OsABA8oxs, OsNCEDs) revealed that quinclorac application enhanced stress condition in cultivar ZJ 88, while SA treatment downregulated ABA genes more in cultivar XS 134, which correlated with the enhanced tolerance to quinclorac induced oxidative stress in this cultivar. The present study delineated that SA played a critical role under quinclorac stress in both rice cultivars by regulating antioxidant defense system, reducing ROS formation and preventing the degradation of internal cell organelles.

Determination of quinclorac and quinclorac methyl ester in honey by online SPE-UPLC-MS/MS.

A method employing online solid phase extraction (SPE) coupled to UPLC-MS/MS was developed for the determination of residues of the acid herbicide quinclorac plus its transformation product, quinclorac methyl ester, in honey. The analytical method involved dissolving the honey in a mixture of methanol:water followed by direct injection into a two-dimensional UPLC system which is used to perform an automated SPE cleanup on a reusable phenyl cartridge prior to the target analytes being transferred onto an analytical UPLC column for subsequent chromatographic separation followed by MS/MS detection. The limits of quantitation for quinclorac and quinclorac methyl ester in honey were both set at 0.5 µg kg-1 and the method detection limit was estimated to be 0.012 µg kg-1 for each compound. The working analytical range (0.5-100 µg kg-1) was validated by analysing a series of spiked replicate honey samples. The method was applied to the analysis of various honeys obtained from numerous different commercial sources. Quinclorac was detected in 9 out of 30 samples at concentrations ranging from 0.6 to 31.5 µg kg-1. Quinclorac methyl ester, which is estimated to be significantly more toxic than the parent herbicide itself, was not detected in any honey sample.

Response of conventional sunflower cultivars to drift rates of synthetic auxin herbicides.

The agrochemical industry has launched several new synthetic auxin herbicides in rice to combat increasing numbers of herbicide resistant weeds to other modes of action. Excessive or inappropriate use of these herbicides has resulted in unintended consequences near the sites of application, such as herbicide drift. This study was conducted to determine the impact of drift of quinclorac and florpyrauxifen-benzyl+penoxsulam (FBP) on the yield and yield components of two sunflower cultivars. In a growth chamber experiment, quinclorac and FBP were applied to 2-4 true leaf stages at rates ranging from 2.93 to 93.75 and from 0.51 to 16.25 g ai ha-1, respectively. Nonlinear regression analyses indicated that the cultivar Bosfora was more sensitive to quinclorac and FBP than the cultivar Tunca. In field experiments, these sunflower cultivars were treated with drift rates of quinclorac (<375 g ai ha-1) and FBP (<65 g ai ha-1) when they were at the 8-10 true leaf stage. Quinclorac and FBP drift rates resulted in up to 52-61% and 85-100% injury and 82-88% and 100% yield loss, respectively. Crop injury and yield data clearly showed that cultivar Bosfora was more sensitive to FBP and quinclorac rates than cultivar Tunca, and both cultivars were more sensitive to FBP than quinclorac. In our work, we also found that plant height reduction caused by quinclorac at early growth stages may be a valuable indicator to evaluate crop injury and yield loss.

Establishment of highly sensitive lateral flow immunochromatographic strips for quinclorac detection utilizing signal amplification nanoparticles.

Highly selective herbicide quinclorac (Qui) is a type of quinoline carboxylic acid hormone herbicide, which has the characteristics of long half-life and difficulty for degradation, causing high risk to the environmental safety. In this study, anti-Qui 8A3 monoclonal antibody (mAb) with good specificity and high affinity (3.89 × 109 L/mol) was prepared, and two kinds of lateral flow immunochromatographic strips (LFICS) including nano-flower nanoparticles (AuNF) - and latex microsphere (LM)- based LFICS were established based on the antibody and signal amplification. The linear range of the AuNF- and LM- based LFICS were 5.31-345.48 ng/mL and 2.52-257.92 ng/mL, respectively. The limit of detection (LOD) of the AuNF- and LM- based LFICS were determined to be 5.31 ng/mL and 2.52 ng/mL, respectively. In summary, the developed LFICS using AuNF and LM as signal amplification reporters exhibited excellent sensitivity and provided the rapid on-site screening of Qui and other analytes in food safety field.

Efficient delivery of the herbicide quinclorac by nanosuspension for enhancing deposition, uptake and herbicidal activity.

BACKGROUND: The presence of barnyardgrass poses a threat to global food security by reducing rice yields. Currently, herbicides are primarily applied for weed management. However, the effectiveness of herbicide deposition and uptake on barnyardgrass is limited as a consequence of the high wax content on leaves, low water solubility and extreme lipophilicity of herbicides. Therefore, it is imperative to develop novel formulations for efficient delivery of herbicides to improve herbicidal activity and reduce dosage. RESULTS: We successfully prepared nanosuspension(s) (NS) of quinclorac through the wet media milling technique. This NS demonstrates excellent physical stability and maintains nanoscale during dose transfer. The deposition concentration and uptake concentration of NS on barnyardgrass were 3.84-4.47- and 2.11-2.58-fold greater than those traditional formulations, respectively. Moreover, the NS exhibited enhanced herbicidal activity against barnyardgrass at half the dosage required by conventional formulations without compromising rice safety. CONCLUSIONS: These findings suggest that NS can effectively facilitate the delivery of hydrophobic and poorly water-soluble herbicide active ingredients, thereby enhancing their deposition, uptake and bioactivity. This study expands the potential application of NS in pesticide delivery, which can provide valuable support for optimizing pesticide utilization, improving economic efficiency and mitigating environmental risks. © 2024 Society of Chemical Industry.

Effect of humus on photodegradation of quinclorac under different fertilization modes.

Humus is a specific kind of organic matter widely distributed in soils. The characteristics of humus have significant impacts on the fate of pollutants in the environment. In this study, we examined the effects of fertilization modes from rice rotation systems on the contents, spectral properties, photochemical activity, and photosensitization of quinclorac (QNC) of humic (HA) and fulvic acids (FA). The results showed that under the rice-vegetable rotation system, organic fertilizer treatment decreased the humification degree and molecular weight of HA, but increased the number of oxygen-containing functional groups and the abilities of photoproducing hydroxyl radical (HO·), singlet oxygen (1O2) and photosensitizing QNC, compared with chemical fertilizer treatment. Under organic fertilization mode, the molecular weight of FA was increased, but the number of redox functional groups and the abilities of photoinducing HO· and 1O2 and photosensitizing QNC were decreased. Under rice-shrimp cultivation system, organic-inorganic fertilizer treatment increased the humification degree, molecular weight, number of redox functional groups and oxygen-containing functional groups, and 1O2 photogeneration of HA, but decreased the abilities of photoproducing HO· and photosensitizing QNC, as compared with chemical fertilizer treatment. The humification degree and molecular weight of FA under organic-inorganic fertilization mode were increased, while the abilities of photoproducing HO· and 1O2 and photosensitizing QNC were decreased. In conclusion, organic fertilization could enhance the photochemical activity and photosensitizing efficiency of humus, and further promote the photodegradation of QNC in the environment.

High aquaporin expression correlates with increased translocation of quinclorac from shoots to roots in resistant Echinochloa crus-galli var. zelayensis.

BACKGROUND: Echinochloa crus-galli var. zelayensis is a troublesome weed in rice fields and can be controlled by using quinclorac. However, over-reliance on quinclorac has resulted in resistant (R) barnyardgrass, which differs significantly in its ability to transport quinclorac compared to susceptible (S) barnyardgrass. This study aimed to investigate the underlying mechanisms for this different translocation between R and S barnyardgrass. RESULTS: Larger amount of quinclorac was transferred from shoots to roots in R compared to S barnyardgrass. After 1 day of quinclorac [300 g active ingredient (a.i.) ha-1 ] foliar treatment, its content in shoots of R was 81.92% of that in S barnyardgrass; correspondingly, in roots of R was 1.17 fold of that in S barnyardgrass. RNA-sequencing and quantitative real-time polymerase chain reaction (qRT-PCR) confirmed the expression levels of PIPs belonging to aquaporins (AQPs) in R were higher than in S barnyardgrass, with or without quinclorac treatment. With co-application of quinclorac and AQPs inhibitors [mercury(II) chloride (HgCl2 )] treatment, even though the expression levels of PIPs and the transport rates of quinclorac were both suppressed in R and S barnyardgrass, this process was less pronounced in R than in S barnyardgrass. CONCLUSION: This report provides clear evidence that higher PIPs expression results in rapid quinclorac translocation from shoots to roots and reduces the quinclorac accumulation in the shoot meristems in R barnyardgrass, thus reducing the control efficacy of quinclorac. © 2022 Society of Chemical Industry.

Proteomic Analysis Comparison on the Ecological Adaptability of Quinclorac-Resistant Echinochloa crus-galli.

Barnyardgrass (Echinochloa crus-galli L.) is the most serious weed threatening rice production, and its effects are aggravated by resistance to the quinclorac herbicide in the Chinese rice fields. This study conducted a comparative proteomic characterization of the quinclorac-treated and non-treated resistant and susceptible E. crus-galli using isobaric tags for relative and absolute quantification (iTRAQ). The results indicated that the quinclorac-resistant E. crus-galli had weaker photosynthesis and a weaker capacity to mitigate abiotic stress, which suggested its lower environmental adaptability. Quinclorac treatment significantly increased the number and expression of the photosynthesis-related proteins in the resistant E. crus-galli and elevated its photosynthetic parameters, indicating a higher photosynthetic rate compared to those of the susceptible E. crus-galli. The improved adaptability of the resistant E. crus-galli to quinclorac stress could be attributed to the observed up-regulated expression of eight herbicide resistance-related proteins and the down-regulation of two proteins associated with abscisic acid biosynthesis. In addition, high photosynthetic parameters and low glutathione thiotransferase (GST) activity were observed in the quinclorac-resistant E. crus-galli compared with the susceptible biotype, which was consistent with the proteomic sequencing results. Overall, this study demonstrated that the resistant E. crus-galli enhanced its adaptability to quinclorac by improving the photosynthetic efficiency and GST activity.