AUTHOR=Zhang Lu , Liu Ziyu , Wang Yong , Zhang Jiaqi , Wan Shujie , Huang Yating , Yun Tianyan , Xie Jianghui , Wang Wei 

TITLE=Biocontrol Potential of Endophytic Streptomyces malaysiensis 8ZJF-21 From Medicinal Plant Against Banana Fusarium Wilt Caused by Fusarium oxysporum f. sp. cubense Tropical Race 4

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.874819

DOI=10.3389/fpls.2022.874819

ISSN=1664-462X

ABSTRACT=<p>Banana (<italic>Musa</italic> spp.) is an important fruit crop cultivated in most tropical countries. Banana Fusarium wilt caused by <italic>Fusarium oxysporum</italic> f. sp. <italic>cubense</italic> tropical race 4 (<italic>Foc</italic> 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 <italic>Streptomyces.</italic> The phylogenetic tree demonstrated that strain 8ZJF-21 formed a distinct clade with <italic>Streptomyces malaysiensis</italic>. Average nucleotide identity (ANI) was 98.49% above the threshold of novel species. The pot experiment revealed that endophytic <italic>Streptomyces malaysiensis</italic> 8ZJF-21 could improve the plant resistance to <italic>Foc</italic> 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 <italic>S. malaysiensis</italic> 8ZJF-21 extract inhibited mycelial growth and spore germination of <italic>Foc</italic> TR4 <italic>in vitro.</italic> Pathogenic cells occurred cytoplasmic heterogeneity, disappeared organelles, and ruptured ultrastructure. Sequencing and annotation of genome suggested that <italic>S. malaysiensis</italic> 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 <italic>Streptomyces</italic> strains will become essential biocontrol agents of modern agricultural practice.</p>