Streptomyces sp. JCK-6131 Protects Plants Against Bacterial and Fungal Diseases via Two Mechanisms

Abstract

Plant bacterial and fungal diseases cause significant agricultural losses and need to be controlled. Beneficial bacteria are promising candidates for controlling these diseases. In this study, Streptomyces sp. JCK-6131 exhibited broad-spectrum antagonistic activity against various phytopathogenic bacteria and fungi. In vitro assays showed that the fermentation filtrate of JCK-6131 inhibited the growth of bacteria and fungi with minimum concentration inhibitory (MIC) values of 0.31–10% and 0.31–1.25%, respectively. In the in vivo experiments, treatment with JCK-6131 effectively suppressed the development of apple fire blight, tomato bacterial wilt, and cucumber Fusarium wilt in a dose-dependent manner. RP-HPLC and ESI-MS/MS analyses indicated that JCK-6131 can produce several antimicrobial compounds, three of which were identified as streptothricin E acid, streptothricin D, and 12-carbamoyl streptothricin D. In addition, the disease control efficacy of the foliar application of JCK-6131 against tomato bacterial wilt was similar to that of the soil drench application, indicating that JCK-6131 could enhance defense resistance in plants. Molecular studies on tomato plants showed that JCK-6131 treatment induced the expression of the pathogenesis-related (PR) genes PR1, PR3, PR5, and PR12, suggesting the simultaneous activation of the salicylate (SA) and jasmonate (JA) signaling pathways. The transcription levels of PR genes increased earlier and were higher in treated plants than in untreated plants following Ralstonia solanacearum infection. These results indicate that Streptomyces sp. JCK-6131 can effectively control various plant bacterial and fungal diseases via two distinct mechanisms of antibiosis and induced resistance.

Bioactive Metabolite Survey of Actinobacteria Showing Plant Growth Promoting Traits to Develop Novel Biofertilizers

“…The use of actinobacteria, with Streptomyces spp. being the most studied particularly as biocontrol agents to contrast various bacteria and fungi causing plant diseases [ 48 , 49 , 50 , 51 , 52 , 53 ], has been described. These studies highlighted the production of an arsenal of different bacterial volatile and non-volatile bioactive molecules that can promote plant growth by increasing tolerance against abiotic and biotic stresses and by stimulating plant development as inferred from the scientific literature describing their action mechanisms [ 51 , 54 , 55 ].…”

A potential biocontrol agent Streptomyces tauricus XF for managing wheat stripe rust

“…For example, the fermentation broths of Streptomyces sp. JCK-6131 (Le et al 2021) and Streptomyces sp. AgN23 (Vergnes et al 2020) were previously reported to induce PR1 gene expression in tomato and Arabidopsis thaliana.…”

Streptomyces‐triggered coordination between rhizosphere microbiomes and plant transcriptome enables watermelon Fusarium wilt resistance

“…These results, along with the stimulated relative abundance of plant beneficial microbes and co-occurrence network complexity, demonstrated that the application of S769 fermentation products triggered plant immune response and auxindependent signal transduction in plant roots, and thus improved the balance between plant defence and growth. Although we didn't strictly differentiate the effect of Streptomyces alive cells and its metabolites in the field, previous studies suggested that culture filtrates of Streptomyces species containing secondary metabolites exhibited strong antagonistic effects on diverse plant pathogens in vitro (Le et al, 2021;Yun et al, 2021). Further studies are needed to decipher the modes of action of antifungal compounds in S769, to deploy precise strategies for plant health and productivity (Noel et al, 2023).…”