Wei Deng

BACKGROUND: Pretilachlor (PR), a pre‐emergence herbicide crucial for rice weed management, is prone to rapid degradation and poses significant environmental risks, necessitating frequent applications. This study aims to develop an environmentally friendly carboxymethyl chitosan (CMCS)/Cu ²⁺ hydrogel delivery system that provides controlled release, enhances application efficacy, and mitigates ecological impacts while utilizing biowaste‐derived materials. RESULTS: CMCS hydrogel particles crosslinked via Cu ²⁺ coordination achieved a PR loading capacity (LC) of 13.70 ± 0.32%. The system displayed pH‐responsive behavior with maximum swelling (429%) at pH 8, enabling sustained PR release (51.2% over 80 h) and rapid biodegradation (83.9% mass loss within 7 days). At an agronomically relevant dosage of 500 g a.i. (active ingredient) ha ⁻¹ , the hydrogel formulation provided effective Echinochloa crus‐galli control comparable to commercial standards while eliminating rice phytotoxicity. Ecotoxicity assessments revealed significantly reduced environmental risks, with LC ₅₀ values of 0.60 mg L ⁻¹ for Danio rerio (1.7‐fold safer than emulsifiable concentrate (EC)) and >1600 mg kg ⁻¹ for Eisenia fetida . CONCLUSION: This study demonstrates the feasibility of utilizing CMCS/Cu ²⁺ hydrogel particles as a controlled‐release delivery system for PR in rice cultivation. The developed formulation provides sustained herbicide release aligned with early weed growth stages, reduced non‐target toxicity, and enhanced biodegradability compared to conventional formulations. While further field validation is needed, this approach offers a promising foundation for developing more environmentally compatible pesticide delivery systems that could potentially reduce application frequency and environmental loading in rice production. © 2026 Society of Chemical Industry.

BACKGROUND: Various mechanisms or factors may cause the wide infestation of herbicide‐resistant weeds with different contributions, such as target‐site resistance (TSR), non‐target‐site resistance (NTSR), hormesis, and dissemination of herbicide‐resistant weeds. Here we tested this hypothesis in eastern China in Leptochloa chinensis , for which cyhalofop resistance is a major challenge to rice planting. RESULTS: Our results revealed that 30% of the total 242 populations held high (10 < RI < 100) or very high resistance (RI > 100) to cyhalofop. Resistance increased from north to south, and from transplanted rice fields to direct‐seeded rice fields. Six mutant types conferring TSR to cyhalofop were found in 89% sampled populations, with 18% carrying two types, 2% carrying three types, and another 2% carrying four types of mutations. W2027C was the most frequent TSR mutation, present in 47.3% of sampled populations, followed by I2041N (21.8%), W1999C (20%), L1818F (20%), W1999G (5.5%) and C2088R (1.8%). Non‐target‐site resistance linked with P450 monooxygenases (P450) and glutathione S‐transferases (GST) were observed in 7% and 10% cyhalofop‐resistant populations sampled. No significant correlation between genetic and geographic distances were observed among cyhalofop‐resistant populations. Hormetic effects of cyhalofop to L. chinensis were evident in 13% of overall populations. CONCLUSIONS: This study compared the contribution of different mechanisms towards herbicide resistance, revealed herbicide hormesis and revealed the distribution of resistance. Insights from this study could be important for weed management practices in other areas of the world. © 2025 Society of Chemical Industry.

BACKGROUND: Leptochloa fusca is a new dominant grass weed in paddy ecosystem of local region in China. The extensive herbicide application has selected the cyhalofop‐butyl‐resistant L. fusca populations. Here, we aimed to (i) characterize the target‐site resistance mechanisms to ACCase inhibitors, and (ii) establish an efficient and rapid method for detecting mutations.RESULTS: The L. fusca population (SFC‐R) was resistant to cyhalofop‐butyl (RF = 5.4), metamifop (RF = 5.5), and fenoxaprop‐P‐ethyl (RF = 6.8). Gene sequencing revealed that the Ile‐1781‐Val mutation was the molecular basis of resistance. A recombinase‐aided amplification (RAA) combined with CRISPR/Cas12a method was successfully developed, which could rapidly and visually detect the single nucleotide variation underling the Ile‐1781‐Val substitution in L. fusca.CONCLUSION: This study confirmed that target‐site mutation (Ile‐1781‐Val) endowed resistance to ACCase inhibitors in L. fusca, and represented the first report of applying the RAA‐CRISPR/Cas12a assay for mutation detection in resistant weeds. Considering its simplicity and specificity, this technique may be used in monitoring and early warning of resistant weeds. © 2025 Society of Chemical Industry.

The decreased or lost control efficacy of bensulfuron‐methyl in controlling Ludwigia prostrata, a troublesome weed of most rice‐growing areas in China, has been frequently observed. Hence, 24 L. prostrata populations collected from Jiangsu Province, China, were surveyed for their resistance levels and potential resistance mechanisms. Dose–response assays confirmed that 45.8% of L. prostrata populations had evolved varying degrees of resistance to bensulfuron‐methyl, with resistance factors ranging from 6.7 to 188.3. ALS sequencing revealed that five various amino acid substitutions (P197S, P197L, P197A, P197Q and D376E) in LpALS2 mainly contributed to bensulfuron‐methyl resistance in these resistant L. prostrata populations. Additionally, 11, 3, 2, 1 and 1 populations showed cross or multiple resistance to pyrazosulfuron‐ethyl, penoxsulam, bispyribac‐sodium, imazamox and carfentrazone‐ethyl, respectively. MCPA‐Na, fluroxypyr, and bentazone, commonly used in paddy fields, remained largely effective against L. prostrata, with no plants of 24 populations surviving the field‐use rates of the three herbicides. Moreover, a molecular diagnosis for the diverse Pro197 mutation in resistant plants was created using a cleaved amplified polymorphic sequence (CAPS). This finding characterises the herbicide resistance patterns of L. prostrata and will facilitate the formulation of targeted resistant weeds management systems.

BACKGROUND: Developing herbicide‐resistant (HR) crop cultivars is an efficient way to control weeds and minimize crop yield losses. However, widespread and long‐term herbicide application has led to the evolution of resistant weeds. Here, we established a resistant (R) E. indica population, collected from imidazolinone‐resistant rice cultivar fields.RESULTS: The R population evolved 4.5‐fold resistance to imazamox. Acetolactate synthase (ALS) gene sequencing and ALS activity assays excluded the effect of target‐site resistance in this population. P450 inhibitor malathion pretreatment significantly reversed resistance to imazamox. RNA sequencing showed that a P450 gene CYP81A104 was expressed higher in R versus susceptible (S) plants. Arabidopsis overexpressing CYP81A104 showed resistance to ALS inhibitors (imazamox, tribenuron‐methyl, penoxsulam and flucarbazone‐sodium), PSII inhibitor (bentazone), hydroxyphenyl pyruvate dioxygenase inhibitor (mesotrione) and auxin mimics (MCPA), which was generally consistent with the results presented in the R population.CONCLUSION: This study confirmed that the CYP81A104 gene endowed resistance to multiherbicides with different modes‐of‐action. Our findings provide an insight into the molecular characteristics of resistance and contribute to formulating an appropriate strategy for weed management in HR crops. © 2024 Society of Chemical Industry.

Digitaria ciliaris var. chrysoblephara (Fig. & De Not.) R.R. Stewart is an annual xeromorphic weed that severely infests direct-seeded rice fields in China. Herbicide resistance is emerging in D. ciliaris var. chrysoblephara owing to extensive and recurrent use of the acetyl-CoA carboxylase (ACCase)-inhibiting herbicide metamifop. In this study, a total of 53 D. ciliaris var. chrysoblephara populations randomly sampled from direct-seeded rice fields across Jiangsu Province were investigated for metamifop resistance and potential resistance-endowing mutations. Single-dose assays revealed that 17 (32.1%) populations evolved resistance to metamifop and 5 (9.4%) populations were in the process of developing resistance. The resistance index (RI) of metamifop-resistant populations ranged from 2.7 to 32.1. Amino acid substitutions (Ile-1781-Leu, Trp-2027-Cys/Ser, and Ile-2041-Asn) in ACCase genes were detected in resistant D. ciliaris var. chrysoblephara plants and caused various cross-resistance patterns to ACCase-inhibiting herbicides. All of four resistant populations (YC07, YZ09, SQ03, and HA06), with different ACCase mutations, exhibited cross-resistance to the aryloxyphenoxypropionate (APP) herbicides cyhalofop-butyl (RI values: 10.0 to 19.9), fenoxaprop-P-ethyl (RI values: 53.7 to 132.8), and haloxyfop-P-methyl (RI values: 6.2 to 62.6), and the phenylpyrazoline (DEN) pinoxaden (RI values: 2.3 to 5.4), but responded differently to the cyclohexanedione (CHD) herbicides clethodim and sethoxydim. It is noteworthy that four postemergence herbicides used for rice cropping, including bispyribac-sodium, pyraclonil, quinclorac, and anilofos, showed poor control effect against D. ciliaris var. chrysoblephara, suggesting few alternations for managing this weed in rice fields except ACCase inhibitors. In conclusion, this work demonstrated that the D. ciliaris var. chrysoblephara had developed resistance to ACCase-inhibiting herbicides in rice cultivation of China, and target-site amino acid substitutions in ACCase were primarily responsible for metamifop resistance.

Glyphosate is a non-selective herbicide and is widely used for weed control in non-cultivated land in China. One susceptible (S) and five putative glyphosate-resistant (R1, R2, R3, R4, and R5) Eleusine indica biotypes were selected to investigate their resistance levels and the potential resistance mechanisms. Based on the dose–response assays, the R3 and R5 biotypes showed a low-level (2.4 to 3.5-fold) glyphosate resistance, and the R1, R2, and R4 biotypes exhibited a moderate- to high-level (8.6 to 19.2-fold) resistance, compared with the S biotype. The analysis of the target-site resistance (TSR) mechanism revealed that the P106A mutation and the heterozygous double T102I + P106S mutation were found in the R3 and R4 biotypes, respectively. In addition, the similar EPSPS gene overexpression was observed in the R1, R2, and R5 biotypes, suggesting that additional non-target-site resistance (NTSR) mechanisms may contribute to glyphosate resistance in R1 and R2 biotypes. Subsequently, an RNA-Seq analysis was performed to identify candidate genes involved in NTSR. In total, ten differentially expressed contigs between untreated S and R1 or R2 plants, and between glyphosate-treated S and R1 or R2 plants, were identified and further verified with RT-qPCR. One ATP-binding cassette (ABC) transporter gene, one aldo-keto reductases (AKRs) gene and one cytochrome P450 monooxygenase (CytP450) gene were up-regulated in R1 or R2 plants. These results indicated that EPSPS overexpression, single or double mutation was a common TSR mechanisms in E. indica. Additional NTSR mechanisms could play an essential role in glyphosate resistance. Three genes, ABCC4, AKR4C10, and CYP88, could serve as important candidate genes and deserve further functional studies.

Ammanniaauriculata is a troublesome broadleaf weed, widely distributed in the paddy fields of southern China. In this study, 10 biotypes of A. auriculata were sampled from Yangzhou City, China, where the paddy fields were seriously infested with A. auriculata, and their resistance levels to acetolactate synthase (ALS) inhibitor bensulfuron-methyl were determined. The whole-plant response assays showed that nine A. auriculata biotypes were highly resistant (from 16.4- to 183.1-fold) to bensulfuron-methyl in comparison with a susceptible YZ-S biotype, and only one YZ-6 biotype was susceptible. ALS gene sequencing revealed that three ALS gene copies existed in A. auriculata, and four different amino acid substitutions (Pro197-Leu, -Ala, -Ser, and -His) at site 197 in the AaALS1 or 2 genes were found in eight resistant biotypes. In addition, no amino acid mutations in three ALS genes were found in the YZ-3 biotype. These results suggested that target-site mutations or non-target-site resistance mechanisms were involved in tested resistant A. auriculata biotypes. Finally, a cleaved amplified polymorphic sequence (CAPS) marker was identified to rapidly detect the Pro197 mutations in A. auriculata.

Ammannia multiflora Roxb. is a dominant broadleaf weed that is a serious problem in southern China rice fields, and acetolactate synthase (ALS)-inhibiting herbicides have been used for its control for more than 20 years. Excessive reliance on ALS-inhibiting herbicides has led to herbicide resistance in A. multiflora. In this study, 10 A. multiflora populations from the Jiangsu Province of China were collected, and the resistance levels and target site–resistance mechanisms to ALS-inhibiting herbicides bensulfuron-methyl and penoxsulam were investigated. The dose–response assays showed that eight populations evolved resistance to bensulfuron-methyl (9.1- to 90.9-fold) and penoxsulam (5.0- to 103.1-fold). Amplification of ALS genes indicated that there were three ALS genes (AmALS1, AmALS2, and AmALS3) in A. multiflora. Sequence analysis revealed amino acid mutations at Pro-197 in either AmALS1 (Pro-197-Ala, Pro-197-Ser, and Pro-197-His) or AmALS2 (Pro-197-Ser and Pro-197-Arg) in resistant populations, and no mutations were found in AmALS3. Moreover, two independent mutations (Pro-197-Ala in AmALS1 and Pro-197-Ser in AmALS2 or Pro-197-Ala in AmALS1 and Pro-197-Arg in AmALS2) coexisted in two resistant populations, respectively. In addition, the auxin mimic herbicides MCPA and florpyrauxifen-benzyl, the photosystem II inhibitor bentazon, and the protoporphyrinogen oxidase inhibitor carfentrazone-ethyl can effectively control the resistant A. multiflora populations. Our study demonstrates the wide prevalence of ALS inhibitor–resistant A. multiflora populations in Jiangsu Province and the diversity of Pro-197 mutations in ALS genes and provides alternative herbicide options for controlling resistant A. multiflora populations.