Antagonistic ability and genome mining of soil Streptomyces spp. against Fusarium oxysporum f. sp. lycopersici

Eighty-six isolates of Streptomyces-like colonies were isolated from soil, and their antagonistic activity was assessed against Fusarium oxysporum f. sp. lycopersici (Fol) as well as their plant growth-promoting (PGP) activity. The results showed that five isolates could inhibit the mycelial growth of the fungal pathogen by producing extracellular hydrolytic enzymes for cellulose and amylase. The enzyme activities cause rough cell walls, irregular swelling, membrane collapse, and nuclear membrane and chromatin fiber degradation. In the pot experiment, the culture filtrates and cell suspensions from all isolates could inhibit fungal pathogens in tomato plants. Among them, isolate S.PNR29 had the best ability to protect the tomato plants from fungal pathogens with low disease severity scores, lowest disease severity index, and highest disease control efficacy. Moreover, these isolates had IAA production, phosphate solubilization, and siderophore production to enhance the tomato growth under pot experiments, especially isolate S.PNR29, which enhanced tomato growth and seed germination rate. These potential antagonistic strains were preliminarily identified using 16S rRNA gene sequencing. The 16S rRNA gene sequences confirmed these strains as bacteria of the genus Streptomyces. The best antagonistic and plant-growth-promoting isolate S.PNR29 was identified by multi-locus sequence analysis (MLSA) and whole genome sequencing. Interestingly, biosynthetic gene clusters (BGCs) related to antibiotics and gene clusters related to plant-growth-promoting and antagonistic properties were found in the genome of Streptomyces sp. isolate S.PNR29. These data may be valuable and used to support the antagonistic activity of Streptomyces sp. isolate S.PNR29 against the Fusarium wilt pathogen and PGP abilities in tomatoes.