Screening Of The Antagonistic Bacteria Against CMV And Study On Its Mechanism

Characteristic of biological control was efficient,low toxicity and environmental.The anti-viral activity of microorganism was few studied,much less their activity on plant virus.In this study CMV(Cucumber Mosaic Virus )was be used as target,the anti-CMV bacterial strains had been isolated and screened,which will provide some information for the research of microbial pesticide.In this study,87 bacterial strains was be isolatied from sick tobacco.After zymolysis,from the fermented broth a bacteria strain was be isolatied which has strong antagonist activity to Cucumber Mosaic Virus(CMV).This bacteria strain was identified as Bacillus subtilis based on physiological and biochemical characteristics and in 16S rDNA methods and named B6.The anti-virus rate of B6 is up to 98.87%.In order to identified bacteria strain,showed the ability to inhibit multiplication of CMV and studied partial physical and chemical characteristics of B6,used real-time reverse transcription PCR assay,cation exchange chromatography,molecular sieve chromatography,SDS-PAGE electrophoresis and electron microscopy to identify,and study on acid and alkali stability,temperature stability,light stability and proteinase stability,The main results are as follows:(1) The antivirus substance is protein named B6p,the relative molecular mass of subunit is 40.6kD.(2) B6 has the ability to inhibit multiplication of CMV in tobacco,and the high rejection ability was at 48 hours.(3) active protein B6p has good stability and is sensitive to acid and alkali but not to temperature completely.So it can't suffer from durative high temperature for long time.It is not sensitive to light, but its activity will decay along with prolonging the photoperiod.It is not sensitive to proteinase K or trypsin but it can keep activity.(4)B6p has the ability to inhibit multiplication of CMV in tobacco.Experiment result in round leaf method showed that the quantity of rot spots on round leaf suspending in B6p crude extracts reduced 95.9%compared with that in distilled water after abrading and inoculating.The result showed that B6p has the ability to inhibit multiplication of virus in tobacco.(5)B6p has the ability to induce host to cause systemic resistance to CMV.The lower and upper leaves of Chenopodium amaranticolor were treated with B6p and CMV respectively and lower leaves treated with water as CK.The results showed that B6p has the ability to induce Chenopodium amaranticolor to cause systemic resistance to CMV,of which the resistance rate to rot spots in the 4^th day is up to 80.002%.(6)Nicotiana tabacum var.samsun NN was inoculated with CMV,B6p,CMV,B6p and distilled water.The activities of PPO,PAL and POD content of treated leaves were tested in 12h,24h,36h,48h,60h,72h respectively.Antiviral protein can enhance the activity of cytophylaxis enzyme such as PPO,POD and PAL.The result of scanning electron microscopy indicated that B6p can break regular arrangement of CMV virion by its combining irreversibly with CMV virion and weaken infection ability of CMV.