bispyribac and imazethapyr

Tausch's goatgrass (Aegilops tauschii Coss.) is one of the most troublesome weeds in winter wheat-growing regions of China. In recent years, the recommended field rate of mesosulfuron-methyl failed to control the Tausch's goatgrass population in Shanxi province (SX), China. Experiments were conducted to characterize the herbicide resistance level and investigate the basis of mesosulfuron-methyl resistance in Tausch's goatgrass. Whole-plant dose-response tests showed that the SX population exhibited 11.42-fold resistance to mesosulfuron-methyl than the susceptible HN population, and the resistance level in the SX population could be significantly reduced by malathion, a cytochrome P450 inhibitor. The SX population also exhibited cross-resistance to imazethapyr, pyroxsulam and bispyribac‑sodium. Acetohydroxyacid synthase (AHAS) sequencing and enzyme activity assays demonstrated that the mesosulfuron-methyl resistance was not conferred by target-site substitution. A sensitive AHAS, together with the malathion revisable resistance, suggested that herbicide metabolism likely plays a main role in the mechanism of mesosulfuron-methyl resistance in the SX population. To our knowledge, this is the first report elucidating the mesosulfuron-methyl resistance in Tausch's goatgrass.

Topics: Acetolactate Synthase; Aegilops; Benzoates; Herbicides; Nicotinic Acids; Pyrimidines; Sulfonylurea Compounds

Herbicides are very effective at eliminating weed and are largely used in rice paddy around the world, playing a fundamental role in maximizing yield. Therefore, considering the flooded environment of rice paddies, it is necessary to understand the side effects on non-target species. Field experiment studies were carried out during two rice growing seasons in order to address how the commonly-used herbicides imazethapyr and imazapic, bispyribac-sodium and penoxsulam, used at recommended dosage, affect water quality and the non-target zooplankton community using outdoor rice field microcosm set-up. The shortest (4.9 days) and longest (12.2 days) herbicide half-life mean, estimated of the dissipation rate (k) is shown for imazethapyr and bispyribac-sodium, respectively. Some water quality parameters (pH, conductivity, hardness, BOD5, boron, potassium, magnesium, phosphorus and chlorides) achieved slightly higher values at the herbicide treatment. Zooplankton community usually quickly recovered from the tested herbicide impact. Generally, herbicides led to an increase of cladocera, copepods and nauplius population, while rotifer population decreased, with recovery at the end of the experiment (88 days after herbicide treatment).

Topics: Agriculture; Animals; Benzoates; Biodegradation, Environmental; Herbicides; Imidazoles; Nicotinic Acids; Oryza; Pyrimidines; Sulfonamides; Uridine; Water Pollutants, Chemical; Zooplankton

Horseweed is a weed commonly found in agronomic crops, waste areas and roadsides. Resistance to ALS-inhibiting herbicides in horseweed was first reported in 1993 in a population from Israel. Resistance to ALS-inhibiting herbicides in horseweed is now widespread, but, as of now, the resistance mechanism has not been reported.. Two of three populations evaluated (P116 and P13) were found to be uniform for resistance (>98% of individuals survived 8.8 g AI ha(-1) of cloransulam), whereas a third population, P525, contained about 85% resistant individuals. Cross-resistance to cloransulam, chlorimuron, imazethapyr and bispyribac was observed in the P116 population. P525 and P13 were both sensitive to imazethapyr but resistant to chlorimuron, imazethapyr and bispyribac. Enzyme activity assays indicated that resistance in P13 was due to an altered target site. Southern blot analysis indicated that the ALS target site is encoded by a single copy gene. Overlapping ALS gene regions were amplified and sequenced from each population. Amino acid substitutions of Ser for Pro at position 197 (P197S) was detected from P13, Ala for Pro (P197A) was identified from P525 and substitution of Glu for Asp (D376E) at position 376 was found in P116. Molecular markers were developed to differentiate between wild-type and resistant codons at positions 197 and 376 of horseweed ALS.. Resistance to ALS-inhibiting herbicides in horseweed is conferred by target-site mutations that have also been identified in other weed species. Identification of the mutations within horseweed ALS gene sequence enables molecular assays for rapid detection and resistance diagnosis.

Topics: Acetolactate Synthase; Amino Acid Substitution; Benzoates; Biomarkers; Blotting, Southern; Codon; Conyza; Enzyme Activation; Enzyme Assays; Genes, Plant; Herbicide Resistance; Herbicides; Mutation; Nicotinic Acids; Plant Weeds; Pyrimidines; Species Specificity; Weed Control