Isolation and selection of Streptomyces strains with antagonistic activity against the Ralstonia pseudosolanacearum T2C-Rasto causing bacterial wilt disease in cucumber plants

Abstract

Cucumbers are short-term fruit vegetables that are widely cultivated in the Mekong delta, providing a stable income for many farming households. Bacterial wilt disease caused by Ralstonia pseudosolanacearum is a common and severely damaging disease in cucumber plants. This study was conducted to isolate and select some Streptomyces strains capable of resisting pathogenic bacteria under laboratory conditions. In this study, 125 Streptomyces strains were isolated from soil samples collected in the Mekong delta and used to test the antibacterial ability against R. pseudosolanacearum. By direct and indirect antagonism methods on agar dish, three Streptomyces strains, including DS18.2, DS30.6, and DS32.8, exhibited to be highly effective against R. Pseudosolanacearum T2C-Rasto, which causes bacterial wilt disease in cucumber plants, with inhibition zone diameters of 22.67, 24.44, and 21.56 mm, respectively. Among them, the Streptomyces DS30.6 strain with the best antagonistic activity was identified to be Streptomyces noursei by 16S rRNA gene sequencing. Strain DS30.6 is a potential microorganism for research and production of biological products to prevent and treat bacterial wilt disease in cucumber plants.