Study On Screening And Biocontrol Effect Of Endophytic Bacteria From Kochia Scoparia

Biological control, an enviroment-friendly strategy, has been a focus of recent research. Endophytic antagonists play a vital role in plant protection against soilbome pathogens and in the overall productivity of agricultural ecosystem. The aim of the study is screen anti-microorganism endophytic bacteria for plant disease control.All about108endophytic bacterial strains were isolated from Kochia scoparia. Among them,5strains exhibited extensive antagonistic activities against Botrytis cinerea and2strains exhibited antagonistic activities against Rhizoctonia solani.D-29strain showed antagonistic activity against a wide range of pathogens. It showed strong antagonistic activity against Exserohilum turcicum and Botrytis cinerea, inhibitory rate reached54.6%and50.6%respectively.The fermentation solution, suspension of bacteria and sterile filtrate showed significant control efficacies against pathogens.Among them,the D-29fermentation solution showed strongest antagonistic activity against Exserohilum turcicum and Botrytis cinerea, inhibitory rate reached64.61%and28.8%;the D-29sterile filtrate showed the strongest antagonistic activity against Monilinia fructicola and inhibitory rate reached51.62%.According to the characteristics of morphology,physiology and biochemistry tests and fatty-acid technology, the strain D-29was identified as Bacillus subtilis.Results showed that optimum fermentation medium component for strain Bacillus subtilis D-29was corn flour10g·L-1, maltose30g·L-1soybean dregs30·L-1and CaCO31.5g·L-1. The obtained best fermentation condition was described as:anount of load100mL (in a250mL,flask),amount of inoculation1%,original pH7,the fermentation temperature28℃,rotation speed170r·min-1.The results of observation under microscope illustrated that D-29could make cell material leaked and the deformity of top mycelium and spores infarction.100%D-29sterile filtrate had the most significant inhibitory effect anginst spores germination of Botrytis cinerea and its inhibiting rate reached80%.Crude protein was extracted with ammonium sulphate at80%saturation. The crude protein endured acid, heat, organic solvent and UV-irradiation, but it was sensitive to alkali.6elution peaks were isolated from crude protein by using column chromatography of DEAE fast flow.Among them,elution peak Ⅳ showed the strongest protein activity.