Comparative unravelling the antifungal activity and mechanism of oleuropein and matrine inhibiting the growth of phytopathogen Fusarium spp.

Fusarium spp. threaten both plants and animals, while traditional chemical control faces environmental risks and pesticide residue issues. Therefore, development of green and effective botanical pesticide has become an alternative. In this study, the antifungal activity and mechanism of oleuropein (OLE) and matrine (MAT) against four species of Fusarium based on the phenotypic, physio-biochemical, and transcriptome levels were investigated. The results showed that OLE and MAT exhibited obvious antifungal activities through inhibiting spore germination, damaging the microstructure of the mycelium, and thereby causing the leakage of intracellular small and macromolecular electrolytes. Moreover, MAT displayed stronger antifungal activity at lower concentrations than OLE, while F. graminearum was more sensitive to the both extracts, with IC values of 18.09 g/L and 1.99 g/L for F. graminearum inhibition by OLE and MAT, respectively. Transcriptomic analysis using F. graminearum as model strain revealed that differentially expressed genes (DEGs) after OLE treatment were enriched in 20 GO terms, including cell wall chitin metabolic and small molecule metabolic processes. While, DEGs after MAT treatment were enriched in GO terms related to endoplasmic reticulum, Golgi apparatus, and intracellular macromolecule metabolic processes. Furthermore, DEGs from the OLE treatment were annotated to 19 pathways involved in glutathione metabolism and aminoacyl-tRNA biosynthesis pathway; DEGs from the MAT treatment were annotated to 8 genetic information processing and 11 metabolism. These findings reveal the distinct antifungal mechanisms of OLE and MAT, and suggest that OLE also has the potential to be developed into a botanical fungicide for application in plant protection.