Study On The Plant Pesticides Screening Against Pathogens Of Ginseng

The antifungal activities of the extracts from the plants of Pheum franzeubachii , Ricinus communis, Typhonium giganteum, Macleaya cordata were tested on the four species parasitic fungi of ginseng. The effects and physical and chemical properties of the two extracts from Pheum franzeubachii, Ricinus communis were researched. The results show as the followings:1. Two kinds of solvents, water and ethanol, were applied to extract the dry powder of the four plants. The antifungal activities of the plants extracts were tested on Phytophthora cactorum , Rhizoctonia solani k(u|¨)hn, Alternaria panax Whetz, Cylindrocarpon destructans(Zinss)Scholten with the growth rate method in the laboratory. Results show that the extracts of Pheum franzeubachii , Ricinus communis are apparently able to inhibit the mycelium growth of the four pathogens when the extracts concentration is about 0.01g/mL. And the extracts with ethanol show better inhibitory effects; the antifungal rate is 100%.2. The growth rate method shows that the best ethanol concentration to extract the dry powders is 80%. And the EC50 (the extracts' concentration when the antifungal rate is 50%) of the two plant of Pheum franzeubachii, Ricinus communis are identified. The EC50 of Pheum franzeubachii, Ricinus communis to the Phytophthora cactorum are 2710 mg/L, 3910 mg/L respectively; to the Rhizoctonia solani kuhn are 3440 mg/L, 3330 mg/L; to the Alternaria panax Whetz are 1790 mg/L, 1990 mg/L; to the Cylindrocarpon destructans (Zinss) Scholten are 1740 mg/L, 2320 mg/L.3. Sterilizing effects of the ethanol extracts from Pheum franzeubachii, Ricinus communis are determined. The results showed they are no sterilizing effects to Phytophthora cactorum even they are able to show 100% inhibitory effects in 24 hours; to Cylindrocarpon destructans(Zinss)Scholten in two days could completely inhibited their mycelium growth; but to Rhizoctonia solani k(u|¨)hn., Alternaria panax Whetz they performed sterilizing effects.4. In vitro tests, two extracts from Pheum franzeubachii and Ricinus communis are tested, the results show there is no significant protective effects to Phytophthora cactorum when the ethanol extracts' concentration is 0.01g/mL, but there is a significant therapeutic effects. And the protective and therapeutic efficiency of the extracts from Pheum franzeubachii to Rhizoctonia solani kuhn are 64.29%, 73.33% respectively; the extracts of Ricinus communis are 57.14%, 66.67%. Comparing with carbendazim, the extracts from Pheum franzeubachii have the similar control effects, especially in the protective efficiency. To the Alternaria panax Whetz, the ethanol extract of Pheum franzeubachii has a 30.67% protective efficacy, which is higher than the ethanol extracts of Ricinus communis. The extract from Ricinus communis has a better therapeutic efficacy of 44.83%, which also have the therapeutic efficacy of 30% to Cylindrocarpon destructans (Zinss) Scholten. The protective and therapeutic efficiency of the extracts from Pheum franzeubachii reach 20%.5. The control effects to Phytophthora cactorum and Rhizoctonia solani k(u|¨)hn are researched with pot test, the treatments include seed soaking and soil inoculation, and the concentration of the extracts from Pheum franzeubachii and Ricinus communis is about 0.01g/mL. The results show that the preventing and controlling efficency are more than 60%, reaching to a very significant level to CK. The control effects to Rhizoctonia solani k(u|¨)hn are less than to Phytophthora cactorum. There are no significant differences between the two extracts when they treat as soil inoculation, but both better than CK. The extracts of Pheum franzeubachii have higher preventing and controlling efficency to Phytophthora cactorum and Rhizoctonia solani k(u|¨)hn, which are 72.54%, 65.47% respectively, and the extracts of Ricinus communis are 68.63%, 68.13%, both are beyond 65%.6. Studied on physical and chemical properties of extracts of Pheum franzeubachii,Ricinus communis, show that the antifungal activities decline significantly after the extracts being treated with 80℃, and they are able to keep stable at 40℃. Antifungal activity of the extracts is the strongest in pH6, it would decreased markedly in alkaline condition. With illumination, the Antifungal activity declines much...