Isolation and characterization of antagonistic Paenibacillus polymyxa HX-140 and its biocontrol potential against Fusarium wilt of cucumber seedlings

Objective The aim of this study is to evaluate the efficacy of the strain Paenibacillus polymyxa HX-140, isolated from the rhizosphere soil of rape, to control Fusarium wilt of cucumber seedlings caused by Fusarium oxysporum f. sp. cucumerinum. Results Strain HX-140 was able to produce protease, cellulase, beta-1,3-glucanase and antifungal volatile organic compounds. An in vitro dual culture test showed that strain HX-140 exhibited broad spectrum antifungal activity against soil-borne plant pathogenic fungi. Strain HX-140 also reduced the infection of Fusarium wilt of cucumber seedlings by 55.6% in a greenhouse pot experiment. A field plot experiment confirmed the biocontrol effects and further revealed that antifungal activity was positively correlated with inoculum size by the root-irrigation method. Here, inoculums at 10(6) 10(7) and 10(8) cfu/mL of HX-140 bacterial suspension reduced the incidence of Fusarium wilt of cucumber seedling by 19.5, 41.1, and 50.9%, respectively. Conclusions Taken together, our results suggest that P. polymyxa HX-140 has significant potential in the control of Fusarium wilt and possibly other fungal diseases of cucumber.