Isolation,Identification Of Antagonistic Bacteria And The Preliminary Analysis Of The Inhibition Effect To Strawberry Root Rot Of Fusarium Oxysporum

In order to screen antagonistic bacteria against Fusarium root rot of strawberry, totally436bacterial strains were isolated from strawberry rhizosphere soils. Three strains (w-25, w-79, w-181) were found to have high antifungi activities to Fusarium root rot of strawberry using five-point confrontation method, with inhibition zone of11.0mm,5.4mm and6.4mm, respectively. In addition, the three antagonistic bacteria (w-25, w-79, w-181) also have high antagonistic effect against strawberry botrytis (Botrytis Cinerea), strawberry red column pathogens(Fragria ananassa) and strawberry gum spore anthrax (Colletotrichum gloeosporioides). Pot experiment showed that the three antagonistic bacteria (w-25, w-79, w-181) had high antagonistic effect against Fusarium root rot of strawberry. According to their physiological and biochemical characters as well as16S rDNA sequences, w-25was probablely identified as Pseudomonas fluorescens, and w-181and w-79were probablely identified as Bacillus subtilis. Antagonistic bacteria (w-25,w-79and w-181) can inhibit the mycelium growth. Their metabolic products treatment can lead fungi mycelium abnormality, bioplasm condensed and cellular vacuole increased, which was observed using light microscope and transmission electron microscopy.The characters of antagonistic metabolites of antagonistic bacteria W-25were preliminarily studied. Treated at25-40℃for30min, the antibiotic activity of strain W-25maintained unchanged. Treated at pH4-8for12h, the antibiotic activity of strain W-25maintained more than80%of its antibiotic activity. Treatment with pepsin and trypsin had no effect on its antibiotic activity. The antagonistic activity of strain W-25was largely destroyed by treated with proteinase K. Furthermore, our study results showed that strain W-25might produce siderophore and2,4-DAPG but no chitinase.