Biocontrol of Fusarium Oxysporum-Infested Gastrodia Elata Bl. By Lactobacillus Curvatus 2768-Vocs and Mechanism of Inhibition

The volatile organic compounds (VOCs) produced by Lactobacillus curvatus 2768 against Fusarium oxysporum infestation on G. elata Bl. and its mechanism of inhibition were investigated experimentally. The test of plate fumigation showed the growth inhibition of F. oxysporum mycelium by L. curvatus 2768-VOCs was 63.37%. The direct fumigation of L. curvatus 2768-VOCs inhibited the infestation of F. oxysporum and slowed down the expansion of the spots of F. oxysporum, while the pre-fumigation of L. curvatus2768-VOCs prevented the infestation of F. oxysporum and inhibited the disease by 44.4%, which was more effective than direct fumigation. Further investigation of the inhibitory mechanism of VOCs revealed that the primarily target site was the cell membrane of F. oxysporum. The study showed that L. curvatus 2768-VOCs altered the permeability of the F. oxysporum cell membrane, and damaged the integrity of the cell membrane, leading to the leakage of the cell contents. After fumigation, the total lipid content of mycelium was reduced to 48.7%, the content of ergosterol was also significantly reduced, the maximum reduction was 21%, and the content of MDA was significantly increased, the maximum reached 9.51%. VOCs also caused damage to the structure of mycelium, and mycelium fracture phenomenon. Additionally, the fumigation of VOCs significantly reduced the activities of ATPase and mitochondrial dehydrogenase, interfered with the respiration of F. oxysporum, and affected the material synthesis and energy metabolism. The study provides a theoretical basis for the application of L. curvatus 2768-VOCs in the post-harvest industry of G. elata and other agricultural products.