Biocontrol Effect And Acute Toxicity Of Paenibacillus Polymyxa KM2501-1 And Virgibacillus Dokdonensis 1A00493

Root-knot nematode is one kind of extremely harmful plant parasitic nematodes,which causes serious damage to the agricultural production all over the world.In the present research,we studied the bioactivity of Paenibacillus polymyxa KM2501-1 and Virgibacillus dokdonensis 1 A00493 on root-knot nematode,Meloidogyne incognita under in vitro conditions.Then the nematicidal volatile organic compounds(VOC)from P.polymyxa KM2501-1 was extracted by headspace solid-phase micro-extraction(SPME)and their structures was identified by gas chromatography-mass spectrometry(GC-MS).In addition,the control efficiency of KM2501-1 and 1A00493 on Meloidogyne incognita was studied in potted experiment.What's more,the acute oral toxicity,acute respiratory toxicity and acute injected toxicity test were made in mice to evaluate the safety of them..The results showed as followed:1.Exposure of Meloidogyne incognita to different concentration of culture filtrate(CF)of P.polymyxa KM2501-1 and V.dokdonensis 1A00493 under in vitro conditions caused substantial mortality of J2 juveniles and significantly reduced their egg hatch.The increase in the concentrations of CF and treatment time increased the antagonistic efficiency.Also,CF of the two strains showed chemotaxis effect to J2 juveniles of Meloidogyne incognita.More specifically,high concentrations repelled nematodes,low concentration attracted nematodes on the contrary.What's more,volatile organic compounds emited by KM2501-1 and 1A00493 exhibited high mortality of J2 juveniles.The volatile organic compounds from P.polymyxa strain KM2501-1 was identificated using the method of SPME-GC-MS.Together,10 compounds were found.The detected volatile compounds included ketones,alcohols,phenols,acids and pyrazines.Among them,4 compounds had been reported for their nematicidal acitivities against Meloidogyne incognita.Another 6 compounds should be checked whether they are nematicidal VOC agents2.In the green house experiment,application of various concentrations of bacterial suspension(BS)or culture filtrate(CF)of two strains into plants1 root,reduced the root galling and increased tomato plant growth compared with control(P<0.05).The increase in the concentrations of BS or CF increased the control effect and growth promoting effects.P.polymyxa KM2501-1 was more effective compared with 1A00493,although the later also goes very well.Root gall index was reduced from 4.6 to 0.8(control efficacy was 82.81%)when plant was treated with 1×CF of KM2501-1,and was reduced from 4.6 to 2.0(control efficacy was 56.52%)when treated with 1×BS of 1A00493.3.The acute oral toxicity,acute respiratory toxicity and acute injected toxicity test were made to evaluate the safety of P.polymyxa KM2501-1 and V.dokdonensis 1A00493.The mice were treated with the fermentation liquid of each strains in various concentration by single-dose intragastric,nasal drip or intravenous administration,then the physical signs,body weight and visceral index were observed and recorded.The results showed that,there were no evident poisoning symptom and death in treated groups,also,no adverse effect on the growth and development of mice was observed.Neither the body weight of mice nor visceral index measured results had significant differences with the control group(P>0.05).The viscera showed no any pathological changes while gross dissection.It indicated that the fermentation liquid of two strains had no significant toxic and side effects on mice,and it could be safely applied in diseases control during agricultural production.