The Preliminary Screening And Identification Of Insecticidal And Bactericidal Activity Entomopathogenic Nematode Symbiotic Bacterium In Five Place Of Shaanxi' Soil Sample

The symbiotic bacteria associated with insect pathogenic nematodes belong to the family Enterobacteriaceae and Gram negative. At present, these symbiotic bacteria were divided into two genera: Xenorhabdus and Photorhabdus. Xenorhabdus coexist with Steinernematidae and Photorhabdus coexist with Heterorhabditidae. According to the reports, nematodes pathogenic symbiotic bacteria produce many secondary metabolites. These metabolites not only have diverse chemical structures, but also a wide range of medicine and agriculture bioactivities, such as antibiotic, antimycotic, insecticidal, nematicidal, antiulcer, antineoplastic and antiviral. In China, in the fields of nematodes pathogenic symbiotic bacteria is relative backwardness, mainly focus on introduction and conservation. In this paper, 500 soil samples were isolated from Yangling, Taibai, Hanzhong, Louguantai and Weinan in Shaanxi province, select the symbiotic bacteria, study its bioactivity, and make sure its taxonomic position. The primary results should as follows:1. Nematodes were isolated from 500 soil samples, which collected from Yangling, Taibai, Hanzhong, Louguantai and Weinan in Shaanxi province. The population of nematode in soil samples was 95.6%.At last, two symbiotic bacteria were separated, one wasⅠphase and the other wasⅡphase and as the object named TB. The results suggested that nematode distribution was connected with soil texture, soil moisture, soil fertility, ground cover, native host and the season.2. The inhibitory activity results demonstrated that the growth rate of hypha of the 11 species of plant pathogenic fungi were inhibited at different level by fermented liquid of the symbiontic bacteria, above all, the inhibited rate of Phytophthora capsici, Botrytis cinerea and Ceratobasidium cornigerum Rogers was 99.99﹪, 99.99﹪and99.11﹪respectively. Moreover, the fermented liquid of TB had the function to put off the germination of sporran-gia of Botrytis cinerea.The protective effect of concentration 5 times of fermented liquid to Erysiphe gram inis DC is 43.8﹪, and the therapeutic effect is 30.6﹪.The fermented liquid had no stomach and contact toxicity to Plutella xylostella and Mythimna separata, only had 90﹪injectable toxicity for the fifth instar of Mythimna separata.3. In this paper, the biochemical and physiological characteristics and 16SrDNA...