Objective Bacillus sp. isolated from Hordeum vulgare L. distiller’s grain were explored as a potential biocontrol agent against the potato dry rot disease.
Method The plate confrontation method was applied to examine the antagonistic activities of 9 Bacillus strains isolated from the barley wine distiller’s grain against 4 potato dry rot pathogens. Active strains were then identified by morphological, physiological, biochemical, and molecular biology methods. The plate transparent ring and discharge of oil ring tests were used to determine the capacity of the selected strains in secreting bacteriostatic proteins and lipopeptides. Using the potato dry rot pathogens as indicator in the Oxford cup test, the antibacterial activity and the stability under different conditions of the extracts of the fermentation broths of the active strains were determined.
Result (1) The Bacillus sp., JZ3-4-7 and JZ3-1-15 displayed significant inhibitory activities against the potato dry rot pathogens in the screening. JZ3-1-15 also exhibited a desirable stability. (2) JZ3-1-15 was subsequently identified as B. velezensis. (3) The JZ3-1-15 fermentation broth contained protease, amylase, cellulase, as well as lipopeptides. (4) The n-butanol extract of JZ3-1-15 fermentation broth had a significant inhibitory rate of 80.07% against the pathogen, Qing 9D-2-6. (5) The same extract withstood a temperature as high as 121 ℃ maintaining a strong thermal stability. It was also stable under acidic and alkaline conditions with a peak anti-pathogenicity at pH 8, and its activity not affected by ultraviolet.
Conclusion JZ3-1-15 and the n-butanol extract of its fermentation broth showed significant inhibitory activity on the potato dry rot pathogens. It appeared that they could be developed as a new biocontrol agent against the target pathogens and/or a preservative for fresh potatoes. The effective compounds or precursors might also be isolated from them for combating the potato dry rot disease and further studies.
DownLoad: