A Preliminary Study Of The Soybean Cyst Nematode Biocontrol Strain

Cysts of soybean cyst nematode were used to screen parasitic germ. Germ colonization was determined for cysts of soybean cyst nematode on soybean roots or in rhizosphere soil from Anda city, Heilongjiang province. The soil sample was collected in the soybean field in which cyst had decayed naturally. 78 germ strains were isolated from the cysts of soybean cyst nematode by some methods, including direct isolating, cover slip isolating and filter paper disc isolating. There were 54 fungus and 24 bacteria in the 78 germ strains. The 25 fungus whose spore shape was different from others were selected for deep researches.Parasitic rate to cysts of soybean cyst nematode was investigated. The parasitic rate of 25 fungal strains were more than 80%, and all of the 25 fungal strains, the parasitic rate of 2 fungal strains were 100%, the parasitic rate of 7 fungal strains were more than 80%, the parasitic rate of 16 fungal strains were more than 80%. It indicated that all 25 fungal strains were parasitic germs. Toxic effects of 25 fungal strains on juveniles of soybean cyst nematode were determined. Mortality of 18 fungal strains to juveniles was more than 40%, so the 18 fungal strains were selected for deep researches. Infected effects of 18 fungal strains on soybean were determined. The infected rate of 7 fungal strains to soybean were less than 20%, thus the 7 fungal strains were the biocontrol fungi from soybean cyst nematode. The strain HDQ17 and the strain HDQ18 which were both better at infecting cyst and juveniles, not infesting soybeans were chosen for deep researches.The identification of the strain HDQ17 and the strain HDQ18 were done, according to strain sharp characteristics, colony feature, and ITS sequence. The strain HDQ17 was Fusarium solani, and the strain HDQ18 was Verticillium chlamydosporia.The researches on bionomics of the strain HDQ17 and the strain HDQ18 were done, including hypha growth feature, spore-produced and spore germination characteristics. Carbon source, nitrogen source, temperatures, pH and cathodolyte were researched for hypha growth feature of the strain HDQ17 and the strain HDQ18. Glucose is the optimal carbon source for the strain HDQ17 and the strain HDQ18. Ammonium nitrate is the optimal nitrogen source for the strain HDQ17, and potassium nitrate is the optimal nitrogen source for the strain HDQ18.The fungus of the strain HDQ17 and the strain HDQ18 grew well at 25℃. The favorable pH of the strain HDQ17 is 6, and the suitable pH of the strain HDQ17 is 7. Zn2+ had increased maximally the biomass of hypha of the strain HDQ17; Cu2+ had increased maximally the biomass of hypha of the strain HDQ18. Spore-produced characteristics were researched. Carbon source on which spore of the strain HDQ17 and the strain HDQ18 produced best was glucose. Nitrogen source on which spore of the strain HDQ17 grew best was ammonium nitrate, and nitrogen source on which spore of the strain HDQ18 grew best was ammonium phosphate dibasic. The favorable spore-produced temperature of the strain HDQ17 and the strain HDQ18 were 25℃. The sutiable spore-produced pH of the strain HDQ17 and the strain HDQ18 were both 6. Fe2+ was best at spore-produced of the strain HDQ17 and the strain HDQ18.Spore germination characteristics were investigated. Spore of the strain HDQ17 germinated best at soybean dip, and spore of the strain HDQ18 germinated best at cysteine liquid. The favorable spore germination temperature of the strain HDQ17 and the strain HDQ18 were 25℃. The sutiable spore germination pH of the strain HDQ17 and the strain HDQ18 were both 6.The effect of metabolite of the strain HDQ17 and the strain HDQ18 on cysts and juveniles was investigated. Metabolite stock solution of the strain HDQ17 and the strain HDQ18 was best at cyst hatching and juvenile activity. Correspondence inhibition ratio of metabolite of the strain HDQ17 depressed cyst hatching was 92.0%, and correspondence inhibition ratio of metabolite of the strain HDQ18 depressed cyst hatching was 83.3%; Correspondence mortality of metabolite of the strain HDQ17 depressed juvenile activity was 96.8%, and correspondence mortality of metabolite of the strain HDQ18 depressed juvenile activity was 93.7%.Due to deliquation multiple was raised, inhibition ratio of metabolite of the strain HDQ17 and the strain HDQ18 was lessened. When the deliquation multiple was 50, the effect of metabolite of the strain HDQ17 and the strain HDQ18 on cysts and juveniles was corresponding on sterile water. The result of the potted plant manifests that the metabolite stock solution of the strain HDQ17 and the strain HDQ18 was better than the spore suspension preparation. After the metabolite stock solution of the strain HDQ17 dealt with soybean, control effect was 92.12%; after the spore suspension preparation of the strain HDQ17 dealt with soybean, control effect was 83.29%. After the metabolite stock solution of the strain HDQ18 dealt with soybean, control effect was 89.70%; after the spore suspension preparation of the strain HDQ18 dealt with soybean, control effect was 79.57%.