Isolation and characterization of the antagonistic bacterium YN-2-2 against potato common scab

Abstract:

[Background] The potato common scab is a highly destructive disease caused by Streptomyces scabies, which leads to severe economic loss in the main producing areas of China. Due to the increasing disease risk and lack of efficient control means, identification of antagonistic microorganisms is becoming a hotspot in the relevant research field. [Objective] This study is aimed to screen antagonistic bacterial strains against Streptomyces scabies, ultimately providing candidates for developing applicable microbial agents. [Methods] The near-rhizosphere soil was collected from potato fields in Zhaotong, Yunnan, where severe scab disease raged, and strains with antagonistic effects were isolated. Morphological observation, physiological and biochemical analyses, and 16S rRNA gene sequence determination were performed to characterize the strains isolated. The stability and bacteriostatic function of their metabolites were further examined. [Results] A strain with high antagonistic capacity was obtained and named YN-2-2. The bacterial cells were rod-shaped and gram-positive with a size range of (2.51?4.09) μm×(1.09?1.68) μm. Its 16S rRNA gene sequence had 99.79% identity to Bacillus thuringiensis ATCC 10792T (ACNF01000156). The secondary metabolites of YN-2-2 showed good thermal stability, a wide pH tolerance between pH 3.0 and pH 13.0, and low sensitivity to proteinase K. The diameter of the largest inhibition zone against Streptomyces scabies was 22.8 mm. Pot experiments indicated that the disease index of common scab decreased significantly when potato plants were inoculated with 100 mL YN-2-2 culture with a final concentration of 1×107 CFU/mL, and the control effect was 36.11%. [Conclusion] Strain YN-2-2 was identified as Bacillus thuringiensis, it can be included into compound microbial agent against potato common scab.

Key words:Potato common scab, Antagonistic strain, Bacillus thuringiensis, Identification, Biological control