Identification, colonization and disease prevention capacity of a antagonistic bacteria against Ralstonia Solanacearum

Abstract:

Abstract: [Objective] To isolated a bacterial strain YPP-9, dominantly colonizing the rhizosphere of tomato using root exudate medium. In this study, we investigated the antagnism and disease-controling effect against Ralstonia solanacearum, evaluated the ability to colonize the rhizosphere of tomato, and further analyzed the phylogeny of YPP-9. [Methods] To evaluate the antagnism against R. solanacearum and the biocontrol on tomato bacterial wilt by YPP-9 respectively employing plate culture method and pot experiment in green house. We analyzed the rhizosphere colonization of YPP-9 by PCR-denaturing gradient gel electrophoresis, and also identified the taxonomic position of YPP-9 using morphological and chemotaxonomic characteristics together with 16S rRNA gene phylogenetic analysis. [Results] YPP-9 suppressed the growth of R. solanacearum (strains SSF-4) in vitro with the inhibition zone of 5 mm. The disease-control efficiency against tomato bacterial wilt in pot was 63.4%. YPP-9 also colonized the rhizosphere of tomato well. The colonies were cream in colour after 24 h culture. Cells were gram-positive, rods (1.8-4.1 μm × 0.9-1.1 μm) and formed endospores. Endospores were mainly ellipsoidal to cylindrical and lied in subterminal, and occasionally paracentral, positions in no swollen sporangia. No crystal protein. The pH range for YPP-9 growth was 5.5-8.5 with the optimum at pH 6.0, and the temperature for YPP-9 growth was 20 to 45 degrees with the optimum at 30 degrees. The results of BIOLOG GP2 showed that YPP-9 was Bacillus. Phylogenetic analysis of the 16S rRNA gene sequence revealed that YPP-9 was the most closely related to Bacillus fumarioli, with the sequence similarity of 97.7%. The sequence number was FJ231500. The DNA G+C content was 41.9%. The major menaquinone was MK-7. The dominant fatty acids in cell wall were C14:0 iso, C15:0 iso, C16:0 iso and C16:1ω7c alcohol, with the contents of 28.27%, 19.59%, 12.93% and 10.88%, respectively. [Conclusion] Bacterium YPP-9 strongly inhibited R. Solanacearum in vitro and efficientlyly suppressed the disease development in pot experiment. YPP-9 also colonized the tomato rhizosphere well. Taxonomically, YPP-9 is affiliated to Bacillus, and probably a novel species.