Study On Insecticdal Activity Against Nilaparvata Lugens (Stal) Of An Endophytic Fungi Of Ginkgo Biloba

Endophytic and plant have a long-term process of co-evolution with each other, so endophytic fungi can produce some active substances which sililar to some substances in the plant, endophytic fungi has been widely used in agricultural and pharmaceutical research. The experiment is designed to obtain insecticidal endophytic fungi, isolated from a traditional Chinese herbal plant Ginkgo (Ginkgo biloba), to provide materials for the further experiment:isolate and identificate the active substances from the crude extract of endophytic fungi, the main results were as follows:1.172 endophytes fungus were isolated from leaves, short shoot and roots of Ginkgo biloba. Among them, The most endophytes fungus,78 fungus,isolated from short shoot accounting for 45.35%, secondly was root, accounting for 38.37%. The least endophytes were obtained from leaf (28), accounting for 16.28%.2. Selecting Nilaparvata lugens Stal as targeted pest and using point back method to determinate the insecticidal activity against Nilaparvata lugens Stal of the 172 strains. It was showed that nine endophytic fungus exhibited higher toxicity on Nilaparvata lugens (Stal), They were FC-5-3, FP-8-1, JP-6-2, JP-5-1, JP-1-1, JP-6-5, NP-5-3, NP-2-2, NC-3-3. Among them, JP-6-2 strain had the best activity, the adjusted mortality rate was 97.69%, and it’s LC50 was 0.44 mg/ml.3. The stability of the insecticidal activity against Nilaparvata lugens Stal produced by JP-6-2 strains had been tested to determine the physical and chemical properties. The test result show that:the insecticidal activeity had good thermal stability, it was stable to high temperature; UV radiation and outdoor environmental conditions showed strong role on the stability, insecticidal activity significantly decrased.4. Based on morphology observation and ITS sequence analysis, the results show the strain JP-6-2 is belong to Altermaria tenuissima, and we constructs phylogenetic tree to research the species status.5. The optimal culture medium was determined by one factor experimental design and orthogonal experimental design. The optimization fermentation condition was 30.00 g/L sucrose,2.00 g/L urea,4.00 g/L K2HPO4,1.00g/L MgSO4, FeSO40.01 g/L, 0.50 g/L KC1,50.0/250 ml loading volume,12.0 ml/L initial inoculation,27.0℃, 200 r/min, the initial pH 8.5, fermentation time 9 d. In this conditions, the object of maximizing extraction is 0.456 g/L, increased 237.78% compared with that of basic culture broth; LC50 was 0.58mg/ml, increased 31.82%.