Potential Biological Control of Endophytic sp. 5-4 Against Fusarium Wilt of Banana Caused by f. sp. Tropical Race 4.

Fusarium wilt of banana caused by f. sp. tropical race 4 (Foc TR4) is one of the most disastrous fungal diseases. Biological control is a promising strategy for controlling Fusarium wilt of banana. To explore endophytic actinomycetes as biocontrol resources against Foc TR4, antagonistic strains were isolated from different tissues of medicinal plants. Here, a total of 144 actinomycetes were isolated and belonged to , , and . Forty-three isolates exhibited antifungal activities against Foc TR4. The strain labeled with 5-4 isolated from roots of had a broad-spectrum antifungal activity by the production of chitinase and β-1,3-glucanase and was identified as subsp. 5-4. Furthermore, disease index of banana wilt was significantly reduced by application of strain 5-4 in comparison with application of Foc TR4 alone. Exogenous application of strain 5-4 increased the expression levels of defense genes such as (), peroxidase (), pathogenesis-related protein 1 (), hydrolytic enzymes (), lysin motif receptor kinase 1 (), and mitogen-activated protein kinase 1 (). The antifungal mechanism assay demonstrated that extracts of strain 5-4 inhibited spore gemination and hyphal growth of Foc TR4, and caused abnormally swollen, deformity, and rupture of Foc TR4 hypha. Thus, subsp. 5-4 could be used as a potential biological agent for controlling Fusarium wilt of banana.