The Pathogen Isolation And Fungicides Screening Of Root Rot Of Ginkgo Biloba

Ginkgo biloba is often applied to urban greening. In recent years, yellow leaves of Ginkgo biloba is happened in summer at many places, which is affected its landscape. According to investigation, most yellow leaves of Ginkgo biloba has rot root. The phenomenon is more serious, more serious the degree of root rot. In order to find out the main pathogenic bacteria of root-rot of Ginkgo biloba and its effective fungicides, to relieve the phenomenon of yellow leaves of Ginkgo biloba. Using the root of Ginkgo biloba as the experimental materials, the pathogen was isolated with the method of tissue isolation and morphological characteristics was identified. The effects of fungicides to root rot of Ginkgo biloba were studied with mycelia growth rate indoors. The screening fungicides were used in field experiment. At last, studying fungicides effect on soil microbial community to determine the best fungicides.The mian finding were as follows:1. Using the root of Ginkgo biloba from 4 places as the experimental materials, the pathogen was isolated with the method of tissue isolation. 21 strains were isolated, including 19 fungis, 2 bacteriums. Pathogenicity of fungal isolates obtained from these samples was tested by verifial standard means of the Koch’s Postulation. 2 isolates named SJZ-4, SJZ-5 were obtained from the root of Ginkgo biloba. Pathogenic test indicated that the 2 separate matters had pathogenic. Based on the colony morphology, growth cha- racteristics, and macroconidium under a microscope, the pathogen of the root of Ginkgo biloba were identified as Fusarium oxysporum.2. The toxicities of 5 fungicides on pathogens of root rot of Ginkgo biloba were assayed with mycelia growth rate indoors. The result indicated that: At the test range, 5 fungicides inhibited the mycelial growth of pathogens of the root rot of Ginkgo biloba. The toxicities of difenoconazole worked effectively. On targets strain named SJZ-4 was the strongest with EC50 values of 120.2263 μg/ml, the toxicities of other fungicides with EC50 values of more than 143.7655μg/ml. On targets strain named SJZ-5 was the strongest with EC50 values of 189.0067 μg/ml, the toxicities of other fungicides with EC50 values of more than 210.3378μg/ml. Bacillus subtilis showed antagonism to SJZ-4, SJZ-5. Bacillus subtilis was diluted 9600 times, it can inhibited the mycelial growth of pathogens of the root rot of Ginkgo biloba, with the inhibition rate of more than 95%.3. By irrigation, the 5 fungicides were used in field experiment, using the degree of yellow leaves as indirect standard to reflect the effect of root rot. Using the degree of yellow leaves as standard, bacillus subtilis diluted 300 times with pure water worked effectively, difenoconazole and carbendazim followed by bacillus subtilis, benziothiazolinone and hymexazol showed less effective. Using the area percentage of yellow laeves as standard, difenoconazole and bacillus subtilis showed better effective to the yellow leaves of Ginkgo biloba, with area percentage below 20%. Those significantly higher than other fungicides. Using the mean disease index as standard, bacillus subtilis worked bestly, with control effect of 71.11%. Difenoconazole followed by bacillus subtilis, with control effect of 56.31%. Carbendazim, benziothiazolinone and hymexazol had control effect reaching 48.54%, 28.64%, 12.62%. Above all, 5 fungicides showed effective to the root rot and yellow leaves of Ginkgo biloba, bacillus subtilis worked significantly effectively.4. 5 fungicides were irrigated into soil. By determining the quantity of Fusarium, the result indicated that: After irrigation, the quantity of Fusarium was significantly lower than the control; The quantity of Fusarium showed tendency to approache control with the time extension; Bacillus subtilis continuously significantly inhibited the quantity of Fusarium. By determining the microbe quantity of rhizosphere soil, the result indicated that: Microbe quantity of rhizosphere soil nearby the roots was higher than the rhizosphere soil awayby the roots. 30 days after irrigated fungicides, the soil irrigated by benziothiazolinone, bacillus subtilis, carbendazim had higher quantity of bacterium than the soil irrigated by other fungicides, the quantity of fungi, actinomycete were inhibited. The soil irrigated by difenoconazole and hymexazol inhibited the microbe quantity of rhizosphere soil. 105 days after irrigated fungicides, the microbe quantity of rhizosphere soil irrigated fungicides showed the tendency to close the microbe quantity of soil wihout irrigated fungicides. According to analysis, bacillus subtilis continuously significantly inhibited the quantity of Fusarium. The microbe quantity of rhizosphere soil irrigated by bacillus subtilis was higher than the rhizosphere soil irrigated by difenoconazole and carbendazim. Taking into account the perspective of safety, sustainable development, bacillus subtilis was the most effectively fungicides to relieve the root rot and yellow leaves of Ginkgo biloba.