Research Article Endophytic Bacillus subtilis Strain E1R-J Is a Promising Biocontrol Agent for Wheat Powdery Mildew

which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 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 (109 cfumL−1) and fermentation liquid without protein. The control effects were not significantly different between 1011 and 109 cfumL−1 of bacterial cell suspension but were higher than 107 cfumL−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 electronmicroscopy 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. 1