Isolation, identification, and biological characterization of Streptomyces strains against tomato bacterial wilt

Abstract:

Tomato bacterial wilt caused by Ralstonia solanacearum seriously affects the yield and quality of tomato and brings serious economic losses and challenges to the tomato planting industry.Objective To achieve efficient biocontrol of tomato bacterial wilt by Streptomyces, providing a solid theoretical foundation for the development of biocontrol agents.Methods Six biocontrol strains of actinomyces (AB_1 to AB_6) exhibiting potent inhibitory activities against R. solanacearum were isolated from soil samples. The morphological, physiological, biochemical, and taxonomical characteristics of these strains were determined. Additionally, the extracellular enzyme activities and rhizosphere colonization abilities of the strains were analyzed. Furthermore, a greenhouse pot experiment was conducted to evaluate the biocontrol efficacy of these strains against tomato bacterial wilt.Results The inhibitory zone diameters of the strains against R. solanacearum ranged from 1.76 cm to 6.76 cm. Comparative analysis of the 16S rRNA gene sequences revealed that all the six strains belonged to the Streptomyces. The sequence similarities between strain AB_1 and Streptomyces gardneri, AB_2 and S. pratensis, AB_3 and S. diastatochromogenes, AB_4 and S. canus, AB_5 and S. albiflavescens, and AB_6 and S. gramineus were 98.67%, 97.59%, 97.33%, 96.54%, 96.94%, and 97.34%, respectively. Pot experiments demonstrated that these six Streptomyces strains prevented tomato bacterial wilt with the efficacy ranging from 69.23% to 100.00%. All the six strains successfully colonized the tomato rhizosphere and exhibited activities of diverse extracellular enzymes including esterase, amylase, and urease. Additionally, they displayed extensive utilization of carbon and nitrogen sources along with robust tolerance towards variations in pH and salt concentrations.Conclusion The six strains of Streptomyces exhibited remarkable environmental adaptability and demonstrated efficient colonization in the tomato rhizosphere. Moreover, they displayed potent antagonistic activity against tomato bacterial wilt in pot experiments. These findings align with the principles of sustainable agriculture and provide both theoretical and experimental evidence for utilizing Streptomyces as a preventive and management strategy against tomato bacterial wilt.