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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., (Copyright © 2020. Published by Elsevier Inc.)

Recently, due to the widespread use of the acetolactate synthase (ALS)-inhibiting herbicide penoxsulam in paddy fields in China, Echinochloa crus-galli (L.) P. Beauv. has become a problematic grass weed that is frequently not controlled, posing a threat to weed management and rice yield. There are many reports on target-site mutations of ALS inhibiting herbicides; however, the detailed penoxsulam resistance mechanism in E. crus-galli remains to be determined. Greenhouse and laboratory studies were conducted to characterize target-site resistance mechanisms in JL-R, AH-R, and HLJ-R suspected resistant populations of E. crus-galli survived the field-recommended dose of penoxsulam. The whole-plant dose–response testing of E. crus-galli to penoxsulam confirmed the evolution of moderate-level resistance in two populations, JL-R (9.88-fold) and HLJ-R (8.66-fold), and a high-level resistance in AH-R (59.71-fold) population. ALS gene sequencing identified specific mutations in resistant populations, including Pro-197-His in ALS1 for JL-R, Trp-574-Leu in ALS1 for AH-R, and Pro-197-Leu in ALS2 for HLJ-R. In vitro ALS activity assays demonstrated a significantly higher activity in AH-R compared to the susceptible population (YN-S). Molecular docking studies revealed that Trp-574-Leu mutation primarily reduced the enzyme's ability to bind to the triazole-pyrimidine ring of penoxsulam due to decreased π–π stacking interactions, while Pro-197-His/Leu mutations impaired binding to the benzene ring by altering hydrogen bonds and hydrophobic interactions. Additionally, the Pro-197-His/Leu amino acid residue changes resulted in alterations in the shape of the active channel, impeding the efficient entry of penoxsulam into the binding site in the ALS protein. The three mutant ALS proteins expressed via the Bac-to-Bac baculovirus system exhibited notably lower activity inhibition rates than the non-mutant ALS proteins to penoxsulam, indicating all three ALS mutations reduce sensitivity to penoxsulam. This study elucidated the distinct impacts of the Pro-197-His/Leu and Trp-574-Leu mutations in E. crus-galli to penoxsulam resistance. Notably, the Trp-574-Leu mutation conferred stronger resistance to penoxsulam compared to the Pro-197-His/Leu mutations in E. crus-galli. The Pro-197-His/Leu mutations were first detected in E. crus-galli conferring penoxsulam resistance. These findings provide deeper insights into the molecular mechanisms underlying target-site resistance to penoxsulam in E. crus-galli. [ABSTRACT FROM AUTHOR]

Weeds significantly impact paddy yields, and herbicides offer a cost-effective, rapid, and efficient solution compared to manual weeding, ensuring agricultural productivity. Tripyrasulfone, a novel 4-hydroxyphenylpyruvate dioxygenase (HPPD) inhibitor developed by Qingdao Kingagroot Chemicals Co., Ltd., has demonstrated high efficacy when applied post-emergence, causing characteristic foliar bleaching in susceptible weed species, distinct from conventional acetolactate synthase, acetyl-CoA carboxylase, and synthetic auxin herbicides. This study investigates the impact of tripyrasulfone on the activity of key soil enzymes (urease (UE), acid phosphatase (ACP), sucrase (SC), catalase (CAT), and dehydrogenase (DHA)) in paddy soils from Jilin Province and Shandong Province. Different doses of tripyrasulfone (0.1, 1.0, and 2.5 mg kg−1) were applied, and the enzymatic activities were measured. Results indicated that tripyrasulfone initially inhibited UE and ACP activities before activating them. On the 20th day after treatment, UE activity had returned to control levels, whereas ACP activity remained significantly higher, showing long-lasting activation. SC and CAT activities were inhibited but gradually recovered to control levels. Furthermore, DHA activity was activated with a sustained effect, remaining significantly higher than the control group even 20 days after treatment. Overall, the impact of tripyrasulfone on soil enzyme activities diminished over time, suggesting that tripyrasulfone posed minimal long-term ecological risk to soil health. [ABSTRACT FROM AUTHOR]