Screening and partial characterization of Bacillus with potential applications in biocontrol of cucumber Fusarium wilt

Bacullus strains are effective biocontrol agents of the cucumber wilt caused by Fusarium oxysporum f. sp. Cucumerinum. In this study, a total of 400 Bacillus samples were isolated from surface-sterilized roots of cucumber plants grown in greenhouses and fields, and were screened using a modified gnotobiotic system for their capability in controlling Fusarium wilt of cucumber. A strain designated as B068150 showed a high potential in control of the Fusarium wilt, with biocontrol effectiveness up to 50.68% in seedling stage in greenhouse experiments. Interestingly, B068150 showed no obvious antagonistic activity to F. oxysporum f. sp. Cucumerinum on potato dextrose agar plate. B068150 was identified as Bacillus subtilis by using morphological, physiological, biochemical tests, cellular fatty acids analysis, and Biolog-based substrate utilization test. In addition, 16S rRNA gene and gyrA gene-based phylogenetic analysis illustrated that B068150 exhibits high levels of similarity to known Bacillus species. Therefore B068150 was finally designated as B. subtilis B068150. The pot experiments results in greenhouse indicated that B. subtilis B068150 could be a promising agent in biocontrol of Fusarium wilt of cucumber, which might help to minimize the yield loss of cucumber caused by F oxysporum f. sp. cucumerinum in north China. (C) 2011 Elsevier Ltd. All rights reserved.