Anti-Foc RT4 Activity of a Newly Isolated Streptomyces sp. 5–10 From a Medicinal Plant (Curculigo capitulata)

Abstract

Fusarium wilt of banana caused by <i>Fusarium oxysporum</i> f. sp. <i>cubense</i> (Foc) is a disastrous soil-borne fungal disease. Foc tropical race 4 (Foc TR4) can infect almost all banana cultivars. Until now, there is a shortage of safety and effective control methods and commercial banana cultivars with a resistance against Foc TR4. Biocontrol using environmentally friendly microbes is a promising strategy for the management of Foc TR4. Here, a strain 5-10, newly isolated from a medicinal plant (<i>Curculigo capitulata</i>), exhibited a high antifungal activity against Foc TR4. Combing the morphological characteristics and molecular identification, strain 5-10 was classified as a <i>Streptomyces</i> genus. The sequenced genome revealed that more than 39 gene clusters were involved in the biosynthesis of secondary metabolites. Some multidrug resistance gene clusters were also identified such as <i>mdtD</i>, <i>vatB</i>, and <i>vgaE</i>. To improve the anti-Foc TR4 activity of the strain 5-10 extracts, an optimization method of fermentation broth was established. Antifungal activity increased by 72.13% under the fermentation system containing 2.86 g/L of NaCl and 11.57% of inoculation amount. After being treated with the strain 5-10 extracts, the Foc TR4 hyphae shrinked, deformed, and ruptured. The membrane integrity and cell ultrastructure incurred irreversible damage. <i>Streptomyces</i> sp. 5-10 extracts play a fungicidal role in Foc TR4. Hence, <i>Streptomyces</i> sp. 5-10 will be a potential biocontrol agent to manage fungal diseases by exploring the microbial fertilizer.