[Objective] With a strain of endophytic antagonistic bacteria with good disease control efficacy in pot as trial material,the paper was to explore the antagonistic mechanism of siderophore against Fusarium oxysporum.[Method] Whether the strain produced siderophore and its fluorescent property was judged by MSA（Modified Sugar-Aspartic acid） plate.The siderophore activity of strains in liquid MSA medium was determined through the absorbance values at particular wavelength.The inhibition effects of it siderophore against F.oxysporum under different concentrations of Fe3＋ were compared.Then the strain was preliminarily identified based on morphological,physiological and biochemical characteristics [Result] The fluorescent siderophore produced by the endophytic bacteria in MSA medium had a strong inhibition effect against F.oxysporum.With the increasing concentration of Fe3＋,the inhibition effect against the pathogen weakened.The preliminary analysis showed these strains belonged to Bacillus.[Conclusion] Bacillus could compete the absorption of Fe3＋ by secreting siderophore to inhibit the growth of F.oxysporum.
[ Objective ] The paper was to study and analyze the genetic diversity of 48 endophytic bacteria isolated from Sophora alopecuroide with strong antagonis- tic effect against Fusarium oxysporum and Verticillium dahliae, and carry out sequence measurement and phylogenetic analysis on 10 representative strains. [ Meth- od] Using total DNA ERIC-PCR and 16S rRNA sequencing analysis method, a total of 48 endophytic bacteria were carried out genetic diversity and phylogenetic analysis. [Result] ERIC-PCR fingerprint map showed that 48 endophytic bacteria were divided into 6 ERIC groups and 2 strains with independent groups at Wat- son distance of 0.31. Representative strains were selected from each group to determine 16S rRNA gene for phylogenetic analysis, and the results showed that these strains belonged to Bacillus atrophaeus, Bacillus subtilis, Bacillus cereus, Bacillus megaterium, Bacillus pumilus and Serratia marcescens, respectively. [ Conclu- sion ] The genetic diversity of 48 strains of bacteria was obvious. Determination of 48 strains of bacteria on diversity and phylogenetic status could lay foundation for study on mechanism of F. oxysporum and V. dahliae, which could also provide new strain sources for biological control of diseases in cotton production.
