EndophyticBacillus subtilisStrain E1R-J Is a Promising Biocontrol Agent for Wheat Powdery Mildew

In this study, the biocontrol efficacies of 14 endophytic bacterial strains were tested against Blumeria graminis f. sp. tritici ( Bgt ) in pot experiments under greenhouse conditions. Bacillus subtilis strain E1R-j significantly reduced disease index and exhibited the best control (90.97%). When different formulations of E1R-j were sprayed 24 h before Bgt inoculation, fermentation liquid without bacterial cell and crude protein suspension displayed the similar effects; and they reduced disease index more than bacterial cell suspension (10 9 cfu mL −1 ) and fermentation liquid without protein. The control effects were not significantly different between 10 11 and 10 9 cfu mL −1 of bacterial cell suspension but were higher than 10 7 cfu mL −1 . Further observations showed that conidial germination and appressorial formation of Bgt were retarded by spraying E1R-j 24 h before Bgt inoculation. Compared with the water check, conidial germination and appressorial formation were decreased by 43.3% and 42.7%, respectively. In the treatment with E1R-j, the number of houstoria significantly reduced and the speed of mycelial extension was slowed down in the wheat leaves. Scanning electron microscopy observation revealed that E1R-j significantly suppressed the conidial germination and caused rupture and deformation of germ tubes. On the surface of wheat leaves, mycelia and conidiophores became shrinking.