AUTHOR=Ku Yongli , Yang Nan , Pu Peng , Mei Xueli , Cao Le , Yang Xiangna , Cao Cuiling 

TITLE=Biocontrol Mechanism of Bacillus subtilis C3 Against Bulb Rot Disease in Fritillaria taipaiensis P.Y.Li

JOURNAL=Frontiers in Microbiology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2021.756329

DOI=10.3389/fmicb.2021.756329

ISSN=1664-302X

ABSTRACT=<p>Bulb rot disease has become one of the main diseases that seriously affects the yield and quality of <italic>Fritillaria taipaiensis</italic> P.Y.Li (<italic>F. taipaiensis</italic>). In this study, <italic>F. taipaiensis</italic> was used as the research object to explore the effect and mechanism of <italic>Bacillus subtilis</italic> C3 in preventing and curing bulb rot. Through isolation and verification of the pathogenic fungi, we determined for the first time that the pathogenic fungus that causes bulb rot in <italic>F. taipaiensis</italic> is <italic>Fusarium oxysporum</italic>. The results of the study showed that <italic>B. subtilis</italic> C3 inhibits the growth of pathogenic fungi, and the inhibition rate is as high as 60%. In the inhibition mechanism, strain C3 inhibits the conidiogenesis of pathogenic fungi and destroys the cell structure of its hyphae, causing protoplast exudation, chromatin concentration, DNA fragmentation, and ultimately cell death. Among the secondary metabolites of C3, antimicrobial proteins and main active components (paeonol, ethyl palmitate, and oxalic acid) inhibited the growth of <italic>F. oxysporum</italic>. The molecular weight of the antibacterial protein with the highest inhibition rate was approximately 50 kD. The results of a field experiment on the Taibai Mountain <italic>F. taipaiensis</italic> planting base showed that after the application of strain C3, the incidence of bulb rot in <italic>Fritillaria</italic> was reduced by 18.44%, and the ratio of bacteria to fungi in the soil increased to 8.21, which verified the control effect of C3 on <italic>Fritillaria</italic> bulb rot disease. This study provides a theoretical basis for the use of <italic>B. subtilis</italic> C3 to prevent and control bulb rot in <italic>Fritillaria</italic>.</p>