Late Watergrass ( Echinochloa phyllopogon ): Mechanisms Involved in the Resistance to Fenoxaprop- p -ethyl (original) (raw)
Related papers
Pesticide Biochemistry and Physiology, 1997
The mechanisms of AOPP herbicide resistance in two Alopecurus myosuroides biotypes were investigated. Resistant biotype Peldon A1, which is highly resistant to the phenyl-urea chlorotoluron, is moderately resistant to the AOPP herbicides diclofop-methyl, fenoxaprop-ethyl, fluazifop-P-butyl, and the CHD tralkoxydim. Resistant biotype Lincs. E1, which is only moderately resistant to chlorotoluron, is highly resistant to the AOPP herbicide fenoxaprop-ethyl, and moderately resistant to diclofop-methyl, fluazifop-P-butyl, and the CHD tralkoxydim. There is no clear evidence of resistance to the CHD sethoxydim in either biotype. Both Peldon A1 and Lincs. E1 exhibited moderately enhanced metabolism of diclofop-methyl. The approximate half life of diclofop was 8 and 9 HAT, respectively, compared to 17 HAT for the susceptible Rothamsted biotype. Peldon A1 showed moderately enhanced metabolism of fenoxaprop-P-ethyl. However, in the highly resistant Lincs. E1, fenoxaprop-P-ethyl metabolism rates were intermediate between Peldon A1 and the susceptible biotype. Fenoxaprop-P-ethyl metabolism in A. myosuroides was not significantly reduced by inhibitors of cytochrome P450: PBO, tetcyclasis, or ABT. While enhanced herbicide metabolism can account for the moderate AOPP/CHD resistance observed in Peldon A1 in vivo, it cannot account in total for fenoxapropethyl resistance in Lincs. E1. Lincs. E1 may possess one or more additional resistance mechanism. ᭧1997 Academic Press 1 Current address: Agronomy Unit, Agricultural, Food and thio) propyl]-3-hydroxy-2-cyclohexen-1-one; tralkoxydim, Rural Development,
Biochemical Markers and Enzyme Assays for Herbicide Mode of Action and Resistance Studies
Weed Science, 2015
Herbicides inhibit biochemical and physiological processes or both with lethal consequences. The target sites of these small molecules are usually enzymes involved in primary metabolic pathways or proteins carrying out essential physiological functions. Herbicides tend to be highly specific for their respective target sites and have served as tools to study these physiological and biochemical processes in plants (Dayan et al. 2010b).
Journal of Agricultural Science and Technology A, 2015
The good understanding of the mechanisms of resistance to herbicides in weeds is a necessity to implement sustainable weed management strategies. Here, a study was conducted to characterize the molecular bases of resistance to acetyl coenzyme A carboxylase (ACCase) and acetolactate synthase (ALS) inhibiting herbicides in Lolium rigidum populations from Tunisia. Nine Lolium rigidum (ryegrass) populations collected in wheat fields from Northern Tunisia were investigated for their resistance to two ACCase-inhibiting herbicides and an ALS-inhibiting herbicide. All populations were tested in the greenhouse in pots using the commercial dose to determine resistance status. Survival plants were also tested for the presence of two ACCase (L1781 and N2041) and two ALS (P197 and W574) mutant resistant alleles using molecular markers. Resistance to ACCase-inhibiting herbicides was found in all tested populations. Comparison of the results from herbicide sensitivity bioassays with genotyping indicated that more than 80% of the plants resistant to ACC-inhibiting herbicides would be resistant via increased herbicide metabolism. However, ALS-inhibiting herbicides are still more or less controlling ACCase resistant populations, so indicating that the selection process of resistance is ongoing. Target-site resistance appears to be the major mechanism for these early cases of ALS inhibitor resistance. This study reported the first case of resistance to ALS-inhibiting herbicides in ryegrass in Tunisia, and investigated the molecular bases of this resistance. It establishes the clear importance of non target-site resistance to ACCase-and/or ALS-inhibiting herbicides.
Biochemical mechanisms of resistance in Daphnia magna exposed to the insecticide fenitrothion
Chemosphere, 2007
Resistance to fenitrothion and enzyme activities associated with the toxicity and metabolism of organophosphorus insecticides were measured in three genetically unique Daphnia magna clones collected from rice fields of Delta del Ebro (NE Spain) during the growing season and a lab sensitive clone. The studied clones showed up to sixfold differences in resistance to fenitrothion. The lack of correlation between in vitro sensitivity of acetylcholinesterase (AChE) to fenitrooxon and resistance to fenitrothion indicated that insensitivity of AChE to the most active oxon metabolite was not involved in the observed differences in resistance. Inhibition of mixed-function oxidases (MFOs) by piperonyl butoxide (PBO) increased the tolerance to fenitrothion by almost 20-fold in all clones without altering their relative ranking of resistance. Conversely, when exposed to fenitrooxon, the studied clones showed similar levels of tolerance, thus indicating that clonal differences in the conversion of fenitrothion to fenitrooxon by MFOs were involved in the observed resistance patterns. Despite that resistant clones showed over 1.5 higher activities of carboxilesterase (CbE) than sensitive ones, toxicity tests with 2-(O-cresyl)-4H-1,3,2-benzodioxaphosphorin-2 oxide, which is a specific inhibitor of these enzymes, evidenced that this system only contributed marginally to the observed clonal differences in tolerance. Glutathione-S-transferases activity (GST) varied across clones but not under exposure to fenitrothion, and was only related with tolerance levels in the field clones. In summary, our results indicate that MFO mediated differences on the bio-activation of the phosphorotionate OP pesticide to its active oxon metabolite contributed mostly in explaining the observed moderate levels of resistance, whereas the activities of CbE and GST had only a marginal role.
Pesticide Biochemistry and Physiology, 2004
Vulpia bromoides is a grass species naturally tolerant to acetolactate synthase (ALS) and acetyl-coenzyme A carboxylase (ACCase) inhibiting herbicides. The mechanism of tolerance to ALS herbicides was determined as cytochrome P450-monooxygenase mediated metabolic detoxification. The ALS enzyme extract partially purified from V. bromoides shoot tissue was found to be as sensitive as that of herbicide susceptible Lolium rigidum to ALS-inhibiting sulfonylurea (SU), triazolopyrimidine (TP), and imidazolinone (IM) herbicides. Furthermore, phytotoxicity of the wheat-selective SU herbicide chlorsulfuron was significantly enhanced in vivo in the presence of the known P450 inhibitor malathion. In contract, the biochemical basis of tolerance to ACCase inhibiting herbicides was established as an insensitive AC-Case. In vitro ACCase inhibition assays showed that, compared to a herbicide susceptible L. rigidum, the V. bromoides ACCase was moderately (4.5-to 9.5-fold) insensitive to the aryloxyphenoxypropionate (APP) herbicides diclofop, fluazifop, and haloxyfop and highly insensitive (20-to >71-fold) to the cyclohexanedione (CHD) herbicides sethoxydim and tralkoxydim. No differential absorption or de-esterification of fluazifop-P-butyl was observed between the two species at 48 h after herbicide application, and furthermore V. bromoides did not detoxify fluazifop acid as rapidly as susceptible L. rigidum. It is concluded that two co-existing resistance mechanisms, i.e., an enhanced metabolism of ALS herbicides and an insensitive target ACCase, endow natural tolerance to ALS and ACCase inhibiting herbicides in V. bromoides.
Resistance of barnyardgrass (Echinochloa crus-galli) to atrazine and quinclorac
Pesticide Science, 1997
Two populations of Echinochloa crus-galli (R and I) exhibited resistance to quinclorac. Another population (X) exhibited resistance to quinclorac and atrazine. The R and I populations were collected from monocultures of rice in southern Spain. The X population was collected from maize Ðelds subjected to the application of atrazine over several years. The susceptible (S) population of the same genus was collected from locations which had never been treated with herbicides. The quinclorac value (dose causing 50% reduction in shoot ED 50 fresh weight) for the R and I biotypes were 26-and 6-fold greater than for the S biotype. The X biotype was 10 times more tolerant to quinclorac than the S biotype and also showed cross-resistance to atrazine, being 82-fold more resistant to atrazine than the R, I and S biotypes. Chlorophyll Ñuorescence and Hill reaction analysis supported the view that the mechanism of resistance to atrazine in the X biotype was modiÐcation of the target site, the DI protein. Quinclorac at 20 mg litre~1 did not inhibit photosynthetic electron transport in any of the test biotypes. The quinclorac values (herbicide dose needed for 50% Hill I 50 reaction reduction) of the S population was over 50 000-fold higher than the atrazine value for the same S population, indicating that quinclorac is not a I 50 PS II inhibiting herbicide. Propanil at doses greater than 0É5 kg ha~1 controlled all the biotypes.
Pesticide Biochemistry and Physiology, 1996
A biotype of Lolium rigidum Gaudin (VLR 69) shows multiple resistance to at least nine dissimilar herbicide chemistries. This biotype has enhanced metabolism to herbicides that inhibit Photosystem II, acetolactate synthase, and acetyl-coenzyme A carboxylase. The potential for malathion and piperonyl butoxide (PBO) to act as synergists for herbicides from five different chemical classes was investigated in potted plants. Of the herbicide/synergist combinations examined, PBO only synergized chlorotoluron, and malathion only synergized chlorsulfuron in this resistant biotype. The ability of PBO, malathion, 1-aminobenzotriazole (ABT), and tetcyclacis to inhibit metabolism of herbicides in vivo was also examined. ABT, PBO, and tetcyclacis inhibited metabolism of simazine and chlorotoluron, but malathion did not. Malathion alone inhibited metabolism of chlorsulfuron, ABT inhibited metabolism of diclofop, and none of these compounds affected tralkoxydim metabolism. These results suggest that at least four different herbicide-metabolizing enzymes have increased activity in this resistant biotype. In addition to enhanced metabolism, this biotype also contains a resistant form of acetyl-coenzyme A carboxylase which shows 31-, 4-, and 20-fold resistance to diclofop acid, fluazifop acid, and haloxyfop acid, respectively, but which shows no resistance to sethoxydim or tralkoxydim. Multiple resistance in this biotype of L. rigidum is clearly the result of the accumulation of several resistance mechanisms.
Altered target sites as a mechanism of herbicide resistance
Crop Protection, 2000
Over 200 distinct herbicide resistant weed biotypes have evolved worldwide. In most of these, resistance is conferred by an altered target site, i.e. a modi"ed target protein with reduced a$nity for the herbicide(s) in question. This has been documented for herbicides that target most major known sites of action, including those that inhibit photosynthetic electron transfer at photosystem II, acetyl-CoA carboxylase, acetolactate synthase, and tubulin polymerization. Patterns of cross-resistance to structurally similar herbicides and those from other chemical classes that target the same site vary, depending on the mutation and its e!ect on protein steric and electronic properties. Mechanisms of target site-based herbicide resistance are reviewed, with emphasis on the biochemical and molecular basis for resistance.