mesosulfuron-methyl and iodosulfuron

Acetolactate synthase (ALS)-inhibiting herbicides have been widely used for effective management and control of wild mustard (Sinapis arvensis) biotypes in Iran. The resistance of the ALS inhibitor to weeds is attributed to either target site alteration or enhanced herbicide degradation. Molecular and genetic characterization of the resistance mechanism is relevant to the evolution and management of herbicide resistance. The aims of this research were (a) to characterize the mechanism molecular suspected to Granstar (tribenuron methyl) and Atlantis (Mesosulfuron + Iodosulfuron) resistance in S. arvensis biotypes in the greenhouse and laboratory (b) to investigate the organization of the target-site loci in field selected S. arvensis populations and (c) instantly recognize the mutations that cause resistance to ALS inhibitors. Eighty resistant populations of S. arvensis were carefully collected from fields repeatedly treated with Granstar and Atlantis. The resistance level and pattern of the population were determined through a greenhouse dose-response experiment by applying the above-mentioned herbicides. Extraction of genomic DNA was carried out for PCR and ALS gene analysis. Our results showed that by greenhouse experiment across 80 biotypes suspected to resistance collected in the fields of whole Kermanshah Province, 30 biotypes (37.5%) conferred S. arvensis resistance species reported in the farm. Among 30 biotypes screened in a greenhouse experiment, six biotypes (20%), No. 9, 14, 17, 19, 23 and 28 revealed a mutation in the ALS gene that was detected by PCR-based method. Biotype No. 9 in the position 376 (Asp376-Gly, GAC to GGC), biotypes 14 and 19 in the position 197 (Pro197-Ala, CCT to GCT), biotypes 17, 23 and 28 in the position 574 (Trp574-Leu, TGG to TTG) and biotype No. 23 in the position 122 (Thr-122-Ala, ACA to GCA) showed herbicide resistance. The specific mutation in the position of 122 of the ALS gene in S. arvensis is the first report. Other biotypes showed resistance in the greenhouse but didn't indicate any mutation by PCR-based method. Most of the resistance to Granstar and Atlantis are genetic and are induced by mutations in the ALS gene. The resistance to herbicides may contain a non-mutagenic and non-genetic origin. The reason of herbicide resistance as non-target-site in some of the biotypes may relate to the activity of the herbicide-metabolizing enzyme(s) or transporter proteins that will naturally lead to an increase in herbici

Topics: Acetolactate Synthase; Amino Acid Substitution; Arylsulfonates; Enzyme Inhibitors; Herbicide Resistance; Herbicides; Plant Proteins; Point Mutation; Polymerase Chain Reaction; Sinapis; Sulfonamides; Sulfonylurea Compounds

The aim of this study was to determine the effect of three active substances, diflufenican, mesosulfuron-methyl and iodosulfuron-methyl-sodium, applied in combination, on soil microbial counts, the structure of soil microbial communities, activity of soil enzymes and their resistance to the tested product, the biochemical indicator of soil fertility, and spring wheat yield. Soil samples with the granulometric composition of sandy loam with pHKCl 7.0 were used in a pot experiment. The herbicide was applied to soil at seven doses: 0.057 (dose recommended by the manufacturer), 1.140, 2.280, 4.560, 9.120, 18.240 and 36.480 mg kg(-1) soil DM. Uncontaminated soil served as the control treatment. It was found that a mixture of the tested active substances increased the counts of total oligotrophic bacteria and spore-forming oligotrophic bacteria, organotrophic bacteria and actinomycetes, decreased the counts of Azotobacter and fungi, and modified the structure of soil microbial communities. The highest values of the colony development (CD) index and the ecophysiological (EP) index were observed in fungi and organotrophic bacteria, respectively. The herbicide applied in the recommended dose stimulated the activity of catalase, urease and acid phosphatase, but it had no effect on the activity of dehydrogenases, alkaline phosphatase, arylsulfatase and β-glucosidase. The highest dose of the analyzed substances (36.480 mg kg(-1)) significantly inhibited the activity of dehydrogenases, acid phosphatase, alkaline phosphatase and arylsulfatase. The values of the biochemical soil fertility indicator (BA21) decreased in response to high doses of the herbicide. Urease was most resistant and dehydrogenases were least resistant to soil contamination with a mixture of diflufenican + mesosulfuron-methyl + iodosulfuron-methyl-sodium. The analyzed herbicide had an adverse influence on spring wheat yield, and doses of 18.240 and 36.480 mg kg(-1) led to eventual death of plants.

Topics: Actinobacteria; Arylsulfatases; Bacteria; Biomass; Fungi; Herbicides; Microbial Consortia; Niacinamide; Soil; Soil Microbiology; Soil Pollutants; Sulfonamides; Sulfonylurea Compounds; Triticum; Urease

Black-grass (Alopecurus myosuroides HUDS.) is a common weed of cereal crops widely spread in Northern Europe. Even if the first Belgian case of resistance was reported in 1996, until now, Belgium was quite spared of this problem and only a few restricted areas were concerned: the Polders, the marshland of the Escaut River and the Fosses-la-Ville region. About 90 seed samples were collected trough the South part of Belgium and in the Polders during July 2006, 2007 and 2008. These populations were tested in greenhouse conditions by spraying plantlets with herbicides of three modes of action. The herbicides used were photosynthesis inhibitor, ACCase inhibitors and ALS inhibitors. Susceptible and resistant standard populations (Rothamsted and Peldon) were included in the test in order to validate it and to permit wild populations classification according to "R" rating system. Populations showed differences of susceptibility to photosynthesis inhibitor, ACCase inhibitors and ALS inhibitors. For each herbicide mode of action, it was possible to find at least one population in each resistance class of the "R" rating system. Furthermore, it appeared that resistance was not confined to restricted areas listed above anymore.

Topics: Belgium; Geography; Herbicide Resistance; Herbicides; Heterocyclic Compounds, 2-Ring; Oxazoles; Photosynthesis; Poaceae; Propionates; Seeds; Sulfonamides; Sulfonylurea Compounds

Resistance to the ALS inhibitor mesosulfuron+iodosulfuron ('Atlantis') had been identified in 293 populations of A. myosuroides in the UK by 2008. Two field trials were conducted in winter wheat crops where ALS target site resistance (Pro197Thr) occurred. Mesosulfuron+iodosulfuron (12+2.4 g a.i. ha(-1)) gave 73% - 79% reductions in head numbers in Town Mead field, but only -7% - 5% reductions in Long Covert. Mixtures and sequences improved overall control. Pre-emergence flufenacet+pendimethalin (240+1200 g a.i. ha(-1)) followed by mesosulfuron+ iodosulfuron plus pendimethalin (1320 g a.i. ha(-1)) or clodinafop+trifluralin (30+960 g a.i. ha(-1)) gave 93 - 98% reductions in Town Mead but only 60 - 73% reductions in Long Covert. A non-ALS treatment of pre-emergence flufenacet+pendimethalin followed by isoproturon+pendimethalin (1500+1320 g a.i. ha(-1)) in late October and clodinafop+trifluralin in November or February achieved 97% and 93% reductions in the two trials. Seed samples collected from surviving plants were evaluated in glasshouse assays to quantify any changes in the incidence of resistance. There was an increase in the proportion of plants resistant to mesosulfuron+iodosulfuron regardless of whether it was used alone, in mixture or sequence. No such changes occured with non-ALS treatments. The trials highlight the difficulty of achieving adequate control with alternative herbicides, especially as isoproturon and trifluralin will not be available for use in the UK after 2009.

Topics: Drug Combinations; Herbicide Resistance; Phenylurea Compounds; Poaceae; Seeds; Sulfonamides; Sulfonylurea Compounds; Triticum

Black-grass is a common grass weed, widely spread in Northern Europe and also in Belgium. For ages, it has been an increasing problem in industrial crops, especially winter cereals. Therefore, farmers started to spray herbicide intensively and soon cases of failure occurred for different molecules and different modes of action. Black-grass populations have been tested in greenhouses to assess the influence of an herbicide treatment as to the resistance level regarding three different herbicides: chlortoluron, fenoxaprop-P and mesosulfuron+iodosulfuron. Black-grass seeds were collected in field trials in six locations in Belgium, on individuals which have survived the herbicide treatment. Each population comes from trial plots, measuring 2 meters wide by 5 meters long and characterized by a single or a combination of products. Herbicides sprayed were isoproturon, flufenacet+diflufenican, ACCase inhibitors and ALS inhibitors. Seeds were also collected in the untreated plots. The population present in these last ones corresponds to the former population, before the herbicide selection pressure was applied. In the glasshouse assay, this population was used as the standard population to compare with other populations issued from the same field. The 'R' rating system was set up with this population to assess the evolution of resistance level, year in, year out. Rothamsted and Peldon populations were also included as cross-reference. Each field population presented different behaviours towards herbicide applied in greenhouses and some cases of resistance can be highlighted. Generally, a reduction of treatment efficiency between field and greenhouse results was clearly visible for the whole of studied active ingredients. Indeed, a distribution shift of the populations towards higher resistance classes could be observed. This is particularly remarkable for active ingredients sharing the same mode of action. For example, it has been found that populations already sprayed with fenoxaprop-P on the field showed a higher resistance level to fenoxaprop-P than to mesosulfuron in the greenhouse test.

Topics: Belgium; Brassica rapa; Herbicide Resistance; Herbicides; Oxazoles; Poaceae; Propionates; Quinolines; Sulfonamides; Sulfonylurea Compounds

A formulated mixture of two sulfonylurea herbicides, mesosulfuron and iodosulfuron, combined with the safener mefenpyr-diethyl ('Atlantis') is being used extensively in Europe and there is concern that resistance will evolve in Alopecurus myosuroides (black-grass). Glasshouse screening bioassays showed that the best single discriminating dose for detecting resistance is the UK field rate of 12 g mesosulfuron + 2.4 g iodosulfuron ha(-1) applied at the 3 leaf stage, with herbicidal effects recorded 4 weeks later. Using this methodology with 466 UK seed samples, resistance was confirmed on a total of 24 farms in 11 counties by 2005, 81 farms in 19 counties by 2006 and 133 farms in 21 counties by 2007. Cultural histories for 10 resistant (R) and 7 susceptible (S) fields were obtained. Winter cereals were grown in 73% R/ 71% S years and a mean of 3.0 grass-weed active ingredients applied per year in both R and S fields. Four herbicide classes dominated, comprising almost 80% of all applications: ALS inhibitors 17% R/ 21% S; ACCase inhibitors 19% R/ 17% S; substituted ureas 18% R/ 10% S; dinitroanilines 25% R/ 30% S. Consequently, ALS inhibitor use was not excessive and field histories were not a reliable indicator of resistance risk. DNA sequencing of the ALS gene from resistant and susceptible individuals of nine populations was used to identify resistance mechanisms. All highly resistant individuals from seven populations showed a single nucleotide polymorphism in the first position of the Pro197 codon of an A. myosuroides ALS gene. One population showed resistant individuals with a single nucleotide polymorphism in the second position of the Trp574 codon. Consequently ALS target site resistance was confirmed in eight of the nine populations studied in detail.

Topics: Acetolactate Synthase; Acetyl-CoA Carboxylase; Codon; Dose-Response Relationship, Drug; Herbicide Resistance; Poaceae; Polymorphism, Single Nucleotide; Sulfonamides; Sulfonylurea Compounds