Isolation and identification of endophytic bacterial strains from Ginkgo biloba and their antimicrobial activities

Abstract:

[Objective] To isolate and identify biocontrol bacterial strains from Ginkgo biloba and evaluate their inhibition to Phytophthora capsici in vitro and control efficacy against fruit phytophthora blight of pepper. [Methods] The method of dual culture on agar plate was used for screening the antagonistic endophytic bacteria against P. capsici, and the inhibition effect of the volatile substances from a better control effect strain on P. capsici was tested by two-sealed-base-plates method. Control efficacy against pepper phytophthora blight was evaluated by spraying bacterial cultures on capsicum fruits. The identification of bacterial strains was based on morphological, physiological, biochemical characteristics and phylogenetic analysis of 16S rDNA and gyrA gene sequences. [Results] Nine endophytic bacterial strains were isolated from healthy stems and leaves of Ginkgo biloba. Among them strain W5 was selected for further study, which had antagonistic action against P. capsici, Pyricularia grisea, Rhizoctonia solani, Fusarium oxysporum, Peronophythora litchii, Geotrichum candidum on agar plates, especially to P. capsici, P. grisea and P. litchi, the inhibitory rates were prominent with 88.9%, 86.3% and 90.2%, respectively. The volatile substances produced by strain W5 could significantly inhibit the mycelia growth of P. capsici. The control results of fruit phytophthora blight of pepper by strain W5 showed that it could get better protective efficacy when the spore suspension of the pathogen was inoculated 24 h after spraying inoculation with strain W5. And spraying strain W5 could also prolong the fresh period of pepper fruits to 2?3 d than the control. The strain W5 was identified as Bacillus amyloliquefaciens. [Conclusion] An antagonistic B. amyloliquefaciens strain W5 was obtained, and it had potential for the biological control of fruit phytophthora blight of pepper and other pathogenic fungal diseases.