| Tolclofos-methyl is an especial organophosphorus fungicide .The mode of action of this fungicide is still unknown. Cross-resistance has been observed with dicarboximides, aromatic hydrocarbons and phenylpyrrolcs fungicides in some reports. State with the activity of against plant pathogen, resistance and risk of.fungi, mechanism of resistance and inhibited the fungi, has been studied in this paper, 1. In vitro activity (EC~0) of tolclofos-meth晊l to against 2S fungi and bacteria of plant pathogen has been tested by measuring the diameter of colony on plates. Tolclofos-methyl is effective to most of Zygom~ycetes,Ascomycetes Basidiomycetes and Deuteromycetes Tolclofos-methyl shows a strong fungicidal activity against Rhizoctonia, Sclerotinia, Sclerotium, Botrytis, Macrophoma, Penicil(ium and Phomopsis. Fungitoxicity of tolclofos-methyl to Alternaria, Colletotrichum, Rhizopus and Fusarium gram inearum is remarkable on lower dosage and concentration too. 2~. Resistance and risk of the plant pathogen fungi to tolclofos-methyl was studied in vitro dependent on testing resistant degree, growth ratio on PSA medium, infectivity to rice. sensitivity to other fungicides, examining sclerotia. of resistant strains from lab. Result showed that resistance and risk to tolclofos methyl differ between unlike species of plant pathogen fungi It is high resistance and risk to tolclofos-meth yl appeared in Rhi:octonia solani (rice sheath blight), and low in R.cerealis (wheat sheath blight) and Scleratinta sclerotiorum (rapeseeds sc Ic rtini a blight). Resistant strains of R. solani to to I clofo s-methyl showed highly positive cross resistance to dimcthachlon. Resistance of R..cerealis to dimethachlon and iprodionc is medium. Resistance both germs are low to quintozcne. There was not any cross resistance between tolclofos methyl with diniconazolc and IBP. 3. After the myceliunt of Rhi:octonia soloni culture in liquid 3d, at 5 ug mI拻tolclofos-methyl be added in the flasks, the sample mycelium had 70 been taken out and washed by water on 20?0 mine separately, and transfer in colid. The fungi grow normally. This result show that the target microscope be inhibited by tol cia fos-methyl 1 is recersi b ii ity. 4. Adenosine triphosphoate (ATP) do not antagonism to tolclofos- methyl, show target is not in cell respiration. 5. Inhibiting effect of tolclofos-methyi to fungus can抰 be removed by pralidoxime chloride and pyraloxime iodide, two stronger nuceaphilic reagents .The mode action is not in hydroxy group of the Ser (Tht1 of protein by phosphorus acylation. 6. The growth of resistant strains of R.solani been impressed by to add over 0.075mo1 ~1 NaCI, KNO3, and KCI in PSA culture. But influence of glycerol is alike the wild and resistant strains. The fungi can us glycerol The resistant stains are sensitive to concentration of ion in culture, but no osmotic pressur. 7. 13y analyzing the variety on or in mycclium and in loquid culture medium, of organophosphorus fungicid tolclofos methyl of resistant and wild Rhi:octonia solani with gas chromatography, we have studied the action and resistant mechanism of it. Result show: tolclofos methyl he degraded by all pathogen: The be decom posed and occur q uantity on or in the mycelium of tolclofos-mthyl relate the resistance directly.
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