In dual culture antagonism test, six of eight cyanogenic bacteria were able to reduce the growth of Sclerotium cepivorum. The strains Glocoacetobacter diazotrophicus and Paenibacillus. polymyxa GQ375783.1were the most effective bacteria that recorded the highest inhibition of S. cepivorum mycelial growth by 75% and 70% respectively. Based on HCN production, two strains recorded complete inhibition of fungal growth. Moreover, the ground tissues of the nasturtium plant were able to inhibit the mycelium growth of S. cepivorum by 100%. Results of the greenhouse experiment emphasized that white-rot incidence percentage recorded the lowest values in onion cultivated in soil amended with nasturtium plant and inoculated with G. diazotrophicus plus P. polymyxa GQ375783.1. This treatment recorded the highest values of onion vegetative growth and their yield. Under field conditions, the soil treated with investigated two methods of biofumigation led to suppress white rot disease by the rate of 100% while using each one individually, it reduced disease by the rate of 94.4 and 94.9 % respectively. All onion treatments that inoculated with cyanogenic bacteria showed higher records of DH and N₂-ase activity than uninoculated ones. The highest values DH and N₂-ase were recorded with soil amended with nasturtium and inoculated with cyanogenic bacterial strains. Additionally, the same treatment gave the highest values of peroxidase and polyphenoloxidase activity, onion NPK content, and the plant's vegetative growth as well as their yield. Therefore, the biofumigation using nasturtium and investigated bacterial strains can be recommended in controlling White-rot disease in onions and increasing their productivity.