Journal of Pesticide Science

A quizalofop-resistant Echinochloa crus-galli biotype (RR) was collected from Geqiushan Farm in Heilongjiang Province. Gramineae acetyl-CoA carboxylase (ACCase) in plastid is the target site of quizalofop. Two full-length cDNAs of the plastid ACCase from RR and sensitive Echinochloa crusgalli (SS) were cloned. Plastid ACCase cDNA from RR encodes a protein of 2316 amino acids with an estimated isoelectric point of 5.97 and a calculated molecular mass of 256 kD. The two sequences were compared with their homologs from other plants and the deduced proteins were analyzed to identify plastid ACCase. It was found that the amino acid at position 1781 (standardized to Alopecurus myosuroides) was Leu in RR, while Ile in SS and other cereal plastid ACCases. It was suspected that the change of Ile to Leu residue related to the resistance to quizalofop of RR.

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A series of twenty substituted 3,4-dihydropyrimidine derivatives were prepared and characterized by TLC, IR, ¹H NMR, ¹³C NMR spectroscopic data and elemental analysis. These were screened for insecticidal activity by the film residue method against the pulse beetle (adzuki bean weevil, Callosobruchus chinensis). 4-(2′-Chlorophenyl)-6-phenyl-3,4-dihydropyrimidine-2(1H)-thione (LC₅₀ 0.00201 mg/cm²), 4-(2′-chlorophenyl)-6-p-tolyl-3,4-dihydropyrimidine-2(1H)-thione (LC₅₀ 0.00122 mg/cm²), 4-(4′-methoxyphenyl)-6-(4″-methylphenyl)l-3,4-dihydropyrimidine-2(1H)-thione (LC₅₀ 0.00164 mg/cm²), 4-(4′-chlorophenyl)-6-(4″-methoxyphenyl)-3,4-dihydropyrimidine-2(1H)-thione (LC₅₀ 0.00175 mg/cm²) were found to be more effective than dichlorvos (2,2-dichlorovinyl dimethyl phosphate, LC₅₀ 0.00243 mg/cm²), a commercial insecticide recommended for managing Callosobruchus chinensis.

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Octopamine (OA) is a biogenic amine that controls a variety of important physiological processes and behaviors of invertebrates. To identify the amino acid residues interacting with (R)-OA in a β-adrenergic-like OA receptor from the silkworm Bombyx mori (BmOAR2), the wild-type receptor and seven mutant receptors with an amino acid substitution at a potential orthosteric site were expressed in HEK-293 cells and examined for their ability to elevate intracellular cAMP levels ([cAMP]_i) in response to (R)-OA. The S206A mutant receptor retained the ability to increase [cAMP]_i after (R)-OA treatment. In contrast, the other six mutant receptors (D115A, S202A, Y300F, Y300N, Y300L, and Y300A) lacked the ability to elevate [cAMP]_i. These results indicate that Asp115, Ser202, and Tyr300 participate in (R)-OA binding and the activation of BmOAR2. Homology modeling studies suggest that Ser202 and Tyr300 interact with the phenolic OH group of (R)-OA, whereas Asp115 interacts with the β-OH group and the NH₂ group of (R)-OA.

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The applicability of multi-residue analytical method for 496 pesticides (including metabolites) in frozen gyoza dumplings was verified. This method involved extraction using aqueous acetonitrile (around 70% of acetonitrile content) followed by cleanup using octadecylsilyl (ODS) and primary secondary amine (PSA) mini-column solid-phase extraction (SPE). The target compounds were determined by gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS). Validation tests were performed on frozen gyoza dumplings fortified at 0.01 and 0.10 μg/g in accordance with the guideline issued by the Japanese Ministry of Health, Labour and Welfare. Among the 496 pesticides tested, 378 pesticides were found to conform to the guideline when the solvent standard was used, and 432 pesticides conformed when the matrix-matched standard was used, respectively. The limits of quantitation (S/N≥10) were set at 0.01 μg/g for all, except 20 of the pesticides that were tested. Although no significant matrix effects were observed for most of the pesticides, the use of the matrix-matched standard was preferable to the solvent standard for accurate quantitation. The method was applied to 11 commercial samples, and 14 different pesticides were detected from 8 samples at concentrations ranging from trace levels (<0.01 μg/g) to 0.11 μg/g.

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