Appraisal And Biocontrol Mechanism Of Biocontrol Bacteria PFMP-5 Against Root-knot Nematodes

With the forbidden of chemical nematicide,biological methods had become a new,rapid,environmentally friendly approach to control root-knot nematodes.The study of antagonistic bacteria strains that had excellent control effects to root-knot nematodes were taken seriously.We got a bacterial strain PFMP-5 which had excellent preventing effects to root-knot nematodes.Then we studied the antagonistic mechanism of metabolites of PFMP-5 on root-knot nematodes.Solid-liquid fermentation was conducted with strain PFMP-5,At last,we know it could kill root-knot nematode and even be applied in controlling root-knot nematode in the field.The results were as follows:1.The fermentative broth of PFMP-5 could kill all root-knot nematodes within 12h.the nematicidal rates decreased with the increasing of dilute ratios.Through morphological observation,physiological and biochemical test,16S rDNA sequence analysis,strain PFMP-5 was identified to be Serratia nematodlphila.The strain PFMP-5 had a wide prospect for its significant inhibitory effect on root-knot nematodes.2.The results was that the metabolites of strain PFMP-5 could interfer the nematodes' body fluctuation remarkablely.These root-knot nematodes which were infected by metabolite died rapidly and their bodies grew red.Nevertheless,the metabolite could decompose the nematodes' bodies at the same time.the metabolite was defined as prodigiosin through LC-MS(Liquid chromatography-mass spectrometry).As a result,prodigiosin reached inside of nematodes' body and killed the host by resloving organizations quickly.3.the optimum composition of culture medium and cultivation parameters of strain PFMP-5 were studied.The result showed that the optimum condtion were as following:optimal carbon source was sucrose,optimal nitrogen source was peptone,optimal ferment time was 30 hours,best pH 7,optimal ferment temperature 28?,inoculum proportion 5%,broth volume 150 mL,,rotation speed 180r/min and the best NaCl concentration was 6%.4.The effect of PFMP-5 on the growth of melon plants and the field were studied.The results showed that compared with the CK,after the treatment with PFMP-5 bacteria solution,the plant height and stem diameter increased.The second instar larvae density,root knot index and root number of root-knot nematode were significantly decreased,and the number of free nematodes in soil was significantly increased.