Selection Of Endophytie Antagonistic Bacteria Against Soybean Cyst Nematode From Nodules And The Biological Characters Of Strains With Antinematodal Activity

From June 2007 to September 2008, 496 soil samples had been collected from 81 regions of Liaoning, Jilin, Heilongjiang, Hebei, Shaanxi, Chongqing, Jiangxi, Gansu, Jiangsu, Guangdong, Hubei, Shanxi and Shandong province,and so on. Soybean root nodules had been obtained from the soil samples adopting traping method. The 518 strains of endophytie bacterias had been isolated from soybean root nodules. The biocontrol rhizobium antagonistic against soybean cyst nematode had been screened from them. Research had been conducted on the ability of tolerance to stresses of soybean rhizobia resourses isolated from Liaoning province,Moreover,the two biocontrol endophytie bacteria had been identified and effect of their fermented broth on chemotaxis and incubation of soybean cyst nematode had been studied. Some experiments were studied on Sneb183 such as fermentation optimization and green-house control effect. The results were as following:1.Sneb183 and Sneb241 which had prevention rate of 82.99% and 70.10% deal with J₂ for 72h was gained through bacteria susppension preliminary screening and fermentation further screening.Sneb183 was indentified as Sinorhizobium fredii, and Sneb241 was indentified as Bradyrhizobium japonicum through physiology and biochemistry and molecular biology method.2.Through the study of the effect of Sneb183 and Sneb241 on chemotaxis and incubation of soybean cyst nematode, the results were as follows: the fermentation of Sneb183 and Sneb241 was able to inhibit incubation of soybean cyst nematode independently,but when the fermentation of the two strains mixed with root exudates,only Sneb183 inhibited incubation of cyst in effect ,Sneb241 showed synergistic action on cyst incubation. Both Sneb183 and Sneb241 zymotic fluid interfered with chemotaxis of J₂ to the root exudates,and the approach-avoidance effect to J₂ of Sneb183 was better than Sneb241.So the Sneb183 was selected as the final biocontrol strain in this test.3.The major nutrient substance of the culture medium was optimized consider cell growth and toxicity to nematode. The results showed that the nutritional requirements between cell growth and nematicidal metabolite production was different .The research took the nematicidal acivities of metabolites as measure,choosen the best nutritional combination as follows: Mannitol 1.5% yeast powder 0.05% MgSO₄ 0.005% NaCl 0.01% CaCl₂ 0.005%.Since primary metabolites production Parallel to cell growth , it estimates that the nematicidal ingredient is the secondary metabolites of Sneb183.4.In sterilized soil, the prevention rate of the stock fermentation solution of Snebl83 was 47.92%,and the prevention rate of 5xdilution reached at 41.67%. The fermentation broth dilution had growth promotion effect on the plant.5.Soybean rhizobium sppreaded widely in Liaoning province, slow-growing rhizobium was the dominate sppecies among them. There were also fast-growing rhizobium which had strong resistibility distributed in Liaoning province. The stress resistance ability of rhizobium in Liaoning province was diversity as the ecology and environment of the region was different, meanwhile,the strains were ammonia intolerance in general.