Objective As an antagonistic microbe of the devastating soil-borne pathogen of watermelon Fusarium wilt, Streptomyces goshikiensis BCSPG1 was studied for the application as a biocontrol agent.

Method BCSPG1 was isolated from rhizosphere soil of healthy plants to determine its phylogenetic position based on colony and sporophore morphology as well as 16S rDNA sequence. Its optimal culture conditions and in vitro inhibition on the wilt-causing pathogen, Fusarium oxysporum f.sp. niveum (Fon), as shown of the mycelial morphology observed under SEM were investigated. Varied concentrations of cell-free BCSPG1 filtrate were administrated to examine the physical alternations occurred to the pathogen isolates, and extracellular enzymes analyzed to understand the underline inhibition mechanism. Furthermore, a pot experiment was conducted to evaluate wilt control efficacy.

Result BCSPG1 was identified to be a strain of S. goshikiensis that grew optimally on a pH 7 medium containing tryptone for nitrogen and yeast extract for carbon at 30℃. It was a salt-tolerant siderophore capable of fixing nitrogen, solubilizing potassium, and secreting protease, amylase, and cellulase. In a plate confrontation assay, the isolate showed an F. oxysporum-inhibition rate of 64.86%, while its 20% cell-free filtrate delivered a rate of 90.78% with deformed hyphae and damaged cell membranes on the pathogen. In the pot experiment, it rendered a 63.88% control efficacy against watermelon Fusarium wilt.

Conclusion S. goshikiensis BCSPG1 was shown in vitro to be significantly effective in inhibiting the growth of F. oxysporum. It could be an applicable biocontrol agent to combat the Fusarium wilt on watermelon.