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.

Study on sampling scheme for detecting mycotoxin during wheat storage.

BACKGROUND: Mycotoxin produced by mould is one of the most serious contamination sources in food security. Safe storage of grain has become more important to control food security. Currently, there is no officially approved or standardized sampling scheme for detecting mycotoxin in grain storage worldwide. RESULTS: In this study, deoxynivalenol (DON) was taken as a typical mycotoxin in stored wheat to be detected. Population density of corn weevil could not significantly increase wheat moisture, but wheat moisture was highly significantly and positively correlated with DON content (P < 0.01). Corn weevil density significantly increased the DON content in wheat. DON contamination degree was mainly distributed in the region of 14-20 cm below the surface layer of wheat. In the process of ventilation and dehumidification during the storage period, moisture of wheat decreased slightly with the extension of ventilation, but the DON content in wheat increased significantly. Combined with the analysis of ventilation, DON content in the upper layer and H1 position, where the wind direction is not easy to reach, increased significantly. CONCLUSION: Areas with high insect population density (14-20 cm below the surface layer of stored wheat) and low ventilation and high humidification (H1 position in the upper layer) should be taken as the key cutting sample areas for detecting mycotoxin during the period of grain storage. This study provides for the first time a scientific basis for the standardization of the wheat sampling scheme to monitor mycotoxin contamination during wheat storage. © 2022 Society of Chemical Industry.

Antagonistic Strain Bacillus amyloliquefaciens XZ34-1 for Controlling Bipolaris sorokiniana and Promoting Growth in Wheat.

Common root rot, caused by Bipolaris sorokiniana, is one of the most prevalent diseases of wheat and has led to major declines in wheat yield and quality worldwide. Here, strain XZ34-1 was isolated from soil and identified as Bacillus amyloliquefaciens based on the morphological, physiological, biochemical characteristics and 16S rDNA sequence. Culture filtrate (CF) of strain XZ34-1 showed a high inhibition rate against B.sorokiniana and had a broad antifungal spectrum. It also remarkably inhibited the mycelial growth and spore germination of B. sorokiniana. In pot control experiments, the incidence and disease index of common root rot in wheat seedlings were decreased after treatment with CF, and the biological control efficacy was significant, up to 78.24%. Further studies showed XZ34-1 could produce antifungal bioactive substances and had the potential of promoting plant growth. Lipopeptide genes detection with PCR indicated that strain XZ34-1 may produce lipopeptides. Furthermore, activities of defense-related enzymes were enhanced in wheat seedlings after inoculation with B.sorokiniana and treatment with CF, which showed induced resistance could be produced in wheat to resist pathogens. These results reveal that strain XZ34-1 is a promising candidate for application as a biological control agent against B.sorokiniana.