Biocontrol Potential of Endophytic 8ZJF-21 From Medicinal Plant Against Banana Fusarium Wilt Caused by f. sp. Tropical Race 4.

Banana ( spp.) is an important fruit crop cultivated in most tropical countries. Banana Fusarium wilt caused by f. sp. tropical race 4 ( TR4) is the most destructive fungal disease. Biocontrol using endophytic microorganisms is considered as a safety and sustainable strategy. Actinomycetes have a potential for the production of diverse metabolites. Isolation of endophytic actinomycetes with high efficiency and broad-spectrum antagonism is key for exploring biocontrol agents. Our previous study showed that a total of 144 endophytic actinomycetes were isolated from different tissues of medicinal plants in Hainan, China. Especially, strain 8ZJF-21 exhibited a broad-spectrum antifungal activity. Its morphological, physiological, and biochemical characteristics were consistent with the genus The phylogenetic tree demonstrated that strain 8ZJF-21 formed a distinct clade with . Average nucleotide identity (ANI) was 98.49% above the threshold of novel species. The pot experiment revealed that endophytic 8ZJF-21 could improve the plant resistance to TR4 by enhancing the expression levels of defense-related and antioxidant enzyme genes. It also promoted the plant growth by producing several extracellular enzymes and metabolites. Antifungal mechanism assays showed that 8ZJF-21 extract inhibited mycelial growth and spore germination of TR4 Pathogenic cells occurred cytoplasmic heterogeneity, disappeared organelles, and ruptured ultrastructure. Sequencing and annotation of genome suggested that 8ZJF-21 had a potential of producing novel metabolites. Nineteen volatile organic compounds were obtained from the extract by Gas Chromatography-Mass Spectrometry (GC-MS). Hence, endophytic strains will become essential biocontrol agents of modern agricultural practice.