Biological control of Fusarium oxysporum f. sp. cubense Tropical Race 4 in banana plantlets using newly isolated Streptomyces sp. WHL7 from marine soft coral.

Banana Fusarium wilt caused by Fusarium oxysporum f. sp. cubense (Foc) is a disastrous fungal disease. Foc tropical race 4 (Foc TR4) infects almost all banana cultivars. Use of chemical fungicides caused seriously environment pollution. Biological control with antagonistic microbes is a promising strategy for controlling Foc TR4. Here, strain WHL7 isolated from marine soft coral exhibited a high antifungal activity against Foc TR4. Based on the morphological and physicochemical profiles as well as the phylogenetic tree, the strain was assigned to Streptomyces sp.. Fermentation broth of Streptomyces sp. WHL7 significantly increased the resistance of banana plantlets to Foc TR4 in the pot experiment. Analysis of antifungal mechanism showed that strain WHL7 extracts inhibited spore germination and mycelial growth of Foc TR4, and destroyed cell integrity and ultrastructure. Hence, Streptomyces sp. WHL7 is an important bioresource for exploring novel natural products and biofertilizer to manage Foc TR4.