Screening and identification of antagonistic bacteria from vermicompost against Fusarium oxysporum f. sp. cucumerinum

Fusarium oxysporum f. sp. cucumerinum (FOC) is one of the most destructive pathogens in many cucumber-growing countries around the globe. There is still lack of high-resistant cucumber cultivars against this pathogen, and the use of fungicides is threatening the environmental conditions. However, biocontrol is an environment-friendly technique in plant protection. In this regard, the present work was aimed to screen antagonistic bacterial strains from vermicompost to against FOC in cucumber. Using the dilution-plate method, 374 bacterial strains were isolated from fresh vermicompost. A total of 28 bacterial strains showed antagonistic activity against FOC, among which strain D2 exhibited the best inhibitory effect on the growth of FOC, with the diameter of the growth inhibition zone of 28.28 mm. Then strain D2 was classified and identified based on the morphology and colony characteristics, physiological and biochemical characteristics, and 16S ribosomal DNA (rDNA) sequence homology. For molecular identification, a 1,462-bp fragment of 16S rDNA of strain D2 was obtained. Based on its morphological, physiological, and biochemical characteristics, strain D2 was identified as Burkholderia cenocepacia.