Antagonistic Activity and Mechanism of Bacillus subtilis XZ16-1 Suppression of Wheat Powdery Mildew and Growth Promotion of Wheat.

Wheat powdery mildew caused by Blumeria graminis f. sp. tritici (Bgt) is one of the most serious wheat diseases in the world. Biological control is considered an environmentally safe approach to control plant diseases. Here, to develop effective biocontrol agents for controlling wheat powdery mildew, antagonistic strain XZ16-1 was isolated and identified as Bacillus subtilis based on the morphological, biochemical, and physiological characteristics and 16S rDNA sequence. The culture filtrate of B. subtilis XZ16-1 and its extracts had a significant inhibitory effect on the spore germination of Bgt. Moreover, the therapeutic and prevention efficacy of the 100% culture filtrate on wheat powdery mildew reached 81.18 and 83.72%, respectively, which was better than that of chemical fungicide triadimefon. Further antimicrobial mechanism analysis showed that the XZ16-1 culture filtrate could inhibit the development of powdery mildew spores by disrupting the cell membrane integrity, causing reductions in the mitochondrial membrane potential, and inducing the accumulation of reactive oxygen species in the spores. Biochemical detection indicated that XZ16-1 could solubilize phosphate, fix nitrogen, and produce hydrolases, lipopeptides, siderophores, and indole-3-acetic acid. Defense-related enzymes activated in wheat seedlings treated with the culture filtrate indicated that disease resistance was induced in wheat to resist pathogens. Furthermore, a 106 CFU/ml suspension of XZ16-1 increased the height, root length, fresh weight, and dry weight of wheat seedlings by 77.13, 63.46, 76.73, and 19.16%, respectively, and showed good growth-promotion properties. This study investigates the antagonistic activity and reveals the action mechanism of XZ16-1, which can provide an effective microbial agent for controlling wheat powdery mildew.

[Expression and synergistic function of ENHANCIN-like gene of Agrotis Segetum granulovirus].

ENHANCIN is an enhancing protein chiefly found in insect baculoviruses. One ENHANCIN homologue was identified, by blast method, in Agrotis Segetum granulovirus (AgseGV) genome, named enhancin-like. Sequence analysis indicated that this gene includes the conserved domains, conserved in other ENHANCIN, and it has no signal peptide or a-transmembrane helix. A proline-rich domain, which is similar to those of mammals, is present at its C-terminal. To analyze the synergistic function of AgseGV enhancin-like gene, prokaryotic expression vectors of its whole gene and the 5'-truncated fragment (1, 017bp) were constructed. Expression product of truncated fragment was purified by chromatography, and then it was used to prepare antibody. The expression product of whole gene was identified by Western blot with specific antibody and anti-His-Tag antibody. Bioassay proved that the expression product of whole gene can increase the mortality with 16.25% to 3th instar larvae of Helicoverpa armigera (HaNPV: 1.17 x 10(2) PIBS/mL), while the truncated fragment has no obvious synergistic function.