Efficacy and Antifungal Mechanism of Rosemary Essential Oil against Colletotrichum gloeosporioides

The antifungal activity and mechanism of rosemary essential oil against Colletotrichum gloeosporioides, the walnut anthracnose pathogen, were investigated using scanning electron microscopy (SEM), index determination and transcriptome technique. The results showed that rosemary essential oil could inhibit the growth of C. gloeosporioides with minimum inhibitory (MIC) and fungicidal (MFC) concentrations of 15.625 μL/mL and 31.25 μL/mL, respectively. Scanning electron microscopy revealed that the mycelium morphology became shriveled, twisted, and severely deformed after being treated with rosemary essential oil. The activity of chitinase, which decomposes fungal cell wall components in C. gloeosporioides, increased. The ergosterol content in the plasma membrane decreased, while the cell contents including nucleic acids, soluble protein and soluble reducing sugar were released resulting in the extracellular electrical conductivity being changed. For metabolic activity, the enzymes succinate dehydrogenase (SDH), malate dehydrogenase (MDH), ATPase and ATP decreased, whereas phosphofructokinase (PFK) increased. Transcriptome sequencing results showed that the antifungal mechanism of rosemary essential oil involves the destruction of the cell wall and membrane, inhibition of genetic material synthesis, and cell division and differentiation. The results are helpful to understand the efficacy and antifungal mechanism of rosemary essential oil against C. gloeosporioides and provide a theoretical basis for the development of rosemary essential oil as a biological control agent.