Leaching of Several Pesticides in Andosol Upland Field under Natural Rain Conditions
In andosol upland field, leachate samples of six pesticides, pendimethalin, dimethoate, iprodione, linuron, acephate and prometryn were collected using the porous cup method during two years period. About 10μg/l of dimethoate was detected in the leachate from 50‐70cm depth during a short period after the application, but its dissipation was rapid. Pendimethalin was detected at the low level. The leachate concentrations of iprodione and acephate differed markedly across two years. Linuron and prometryn were not detected in the leachate.
The pesticide residues in the surface soil were analyzed for acetone soluble fraction (ASF) and water soluble fraction(WSF). The WSF/ASF ratios of dimethoate, iprodione and linuron decreased with time, and the magnitude of corresponding ratios were in the same order with the leachate concentrations; dimethoate＞iprodione＞linuron (not detected). The half-lives (t1/2) of dimethoate and iprodione in the soil were dependent on temperature, but leachate concentrations were not effected. The leachate concentrations of dimethoate and acephate were higher in moist soil condition than in dry soil condition, but the reverse was obtained for iprodione. The leachate concentrations of above three pesticides were not dependent on the accumulative amount of rainfall. The leachate concentrations and soil residues of most pesticides were approximately the same between the plots with standard treatment and amended organic materials.Key words: leaching, andosol field, porous cup method, rainfall, pesticide residues.
Hapten Design and Antibody Preparation on Immunoassay toward the Insecticide Oxamyl
To detect small amount of oxamyl, indirect competitive enzyme-linked immunosorbent assays (indirect C-ELISAs) were established. Four haptens for immunogen and three haptens for coating antigen on indirect C-ELISA were synthesized and their polyclonal (PoAbs) and monoclonal antibodies (MoAbs) were prepared. Hapten N, N-dimethyl-2-(5-carboxypentyl)carbamoyloxyimino-2-(methylthio)acetamide was the most effective to raise antibodies toward oxamyl out of haptens for immunogen. MoAbs prepared with this hapten were more highly reactive than PoAbs. In particular, MoAb OXM 6‐8 showed the highest reactivity. When N,N-dimethyl-2-(4-carboxycyclohexyl)carbamoyloxyimino-2-(methylthio)acetamide was used for coating antigen on indirect C-ELISA with OXM 6‐8, the highest sensitivity was observed and the concentration for 50% inhibition value showed 3.6ng/ml. Methanol extract of potato showed no effect on the reactivity.
Key words: oxamyl, hapten, polyclonal antibody, monoclonal antibody, indirect C-ELISA, immunoassay.
Enzymatic Activity of Protoporphyrinogen-IX Oxidase from Various Plant Species:Its Sensitivity to Peroxidizing Herbicides
Enzyme activity of protoporphyrinogen-IX oxidase (Protox) prepared from 34 kinds of plant sources, containing 18 monocotyledons and 16 dicotyledons was evaluated. Protox(es) originated in monocotyledonous plants such as Zea mays cv. Anjou and DK212, Lolium perenne and Poa annua exhibited high enzyme activity, and Protox(es) in dicotyledonous plants such as Agrostemma githago and Arabidopsis thaliana showed a little higher enzyme activity than that of the above monocotyledonous plants. Highly active Protox(es) obtained from Zea mays cv. Anjou, Lolium perenne, Agrostemma githago and Arabidopsis thaliana were selected for the Protox inhibitory assay of peroxidizing herbicides. Echinochloa utilis was also selected for control. Protox inhibition by six peroxidizing herbicides such as oxyfluorfen, chlorophthalim, BW-91, pyraflufen-ethyl, DLH-1777 and LS-82556 was investigated using highly active Protox from the above monocotyledons and dicotyledons. As a result, six peroxidizing herbicides exhibited high inhibitory activity to Protox. Pyraflufen-ethyl showed the highest inhibition. The order of Protox inhibitory activity was pyraflufen-ethyl＞oxyfluorfen＞BW-91＞chlorophthalim＞DLH-1777＞LS-82556, in experiment using four Protox(es) such as Zea mays cv. Anjou, Echinochloa utilis, Agrostemma githago and Arabidopsis thaliana except Lolium perenne. Oxyfluorfen exhibited the highest inhibitory activity to Protox of Lolium perenne. On the other hand, DLH-1777 showed a little less activity to Protox of Zea mays than that of other four weeds. DLH-1777 may become a model compound to find out new selective herbicides. Protox from four weeds will be used for peroxidizing herbicides assay, since the Protox showed high sensitivity to structually different peroxidizers.
Key words: protoporphyrinogen-IX oxidase (Protox), enzyme activity, sensitivity, peroxidizing herbicides, selectivity.
Synthesis and Fungicidal Activities of Heterocyclic Compounds Having α-Methoxyimino-2-phenoxymethylbenzyl Group
A series of (α-methoxyimino-2-phenoxymethylbenzyl)heterocycle derivatives were synthesized and their fungicidal activities were assessed. Studies of the structure-activity relationships revealed the strongest fungicidal activity when the heterocycle moiety was comprised of 1-methyl-2-imidazolyl and 1,3,4-oxadiazol-2-yl groups. When the benzene ring on the phenoxymethyl moiety was substituted with 2-methyl, 2,5-dimethyl or 4-chloro-2-methyl, good fungicidal activity was obtained. Between the two geometrical isomers at the oxime moiety, the E-isomers of imidazole and oxadiazole derivatives were more active than the Z-isomers. Among the compounds examined, (E)-2-[2-(4-chloro-2-methylphenoxy-methyl)-α-methoxyiminobenzyl]-1-methylimidazole (27) showed a potent activity against cucumber powdery mildew and cucumber gray mold.
Key words: (α-Methoxyimino-2-phenoxymethylbenzyl)heterocycle derivatives, imidazole, oxadiazole, fungicidal activity, powdery mildew, gray mold.
Sensitivity to Phenylpyrrole Fungicides and Abnormal Glycerol Accumulation in Os and Cut Mutant Strains of Neurospora crassa
Neurospora osmotic sensitive strains with os-1, os-2, os-4 and os-5 mutations showed cross-resistance to dicarboximides, aromatic hydrocarbons and fludioxonil. The os-2, os-4, and os-5 mutant strains were highly resistant to them, while the os-1 mutant strain was moderately resistant and its growth was inhibited by fludioxonil (LD50:0.087μg/ml) and iprodione (LD50:14μg/ml). Another osmotic sensitive mutation cut did not give resistance to these fungicides. The conidia of wild-type and cut strains swelled and burst without germination on the medium containing fludioxonil, and bursting of conidia was rescued by high osmotic pressure. Stimulation of glycerol biosynthesis by fludioxonil and iprodione observed in the wild-type strain was not induced in os-2, os-4 and os-5 mutant strains. The moderately resistant os-1 mutant strain accumulated substantial quantities of glycerol by 10μg/ml of fludioxonil, but produced less glycerol by 10μg/ml of iprodione. Thus it was assumed that fungal toxicity of these fungicides might be due to abnormal glycerol accumulation. However, both fludioxonil and iprodione did not induce glycerol biosynthesis in the fungicide-sensitive cut mutant strain. In response to osmotic stress, os mutant strains accumulated less amount of glycerol than the wild-type strain, whereas cut mutant strain did not produce glycerol in the medium containing 4% NaCl. Despite its lack of ability of glycerol biosynthesis in cut mutant strain, wild-type and cut strains were not distinguishable in their modes of fungal toxicity of fludioxonil. These data suggest that dicarboximides, aromatic hydrocarbons and fludioxonil interfere with the osmotic signal transduction pathway resulting in stimulation of glycerol biosynthesis, but abnormal glycerol accumulation is not essential for their fungal toxicity.
Key words: dicarboximides, aromatic hydrocarbons, phenylpyrroles, osmotic stress, Neurospora, resistance.
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