Gnomoniopsis smithogilvyi is the major chestnut pathogen, responsible for economic losses and recently
described as a 3-nitropropionic acid and diplodiatoxin mycotoxin producer. Bacillus amyloliquefaciens QST 713 (Serenade®
ASO), B. amyloliquefaciens CIMO-BCA1, and the fungicide Horizon® (tebuconazole) have been shown to reduce the growth of
G. smithogilvyi. However, they enhanced mycotoxin production. Proteomics can clarify the mould's physiology and the impact
of antifungal agents on the mould's metabolism. Thus, the aim of this study was to assess the impact of Horizon®, Serenade®,
and B. amyloliquefaciens CIMO-BCA1 in the proteome of G. smithogilvyi to unveil their modes of action and decipher why the
mould responds by increasing the mycotoxin production. For this, themyceliumclose to the inhibition zone provoked by antifungals
was macroscopically and microscopically observed. Proteins were extracted and analysed using a Q-Exactive plus Orbitrap.
RESULTS: The results did not elucidate specific proteins involved in the mycotoxin biosynthesis, but these agents provoked different
kinds of stress on the mould, mainly affecting the cell wall structures and antioxidant response, which points to the
mycotoxins overproduction as a defence mechanism. The biocontrol agent CIMO-BCA1 acts similar to tebuconazole. The results
revealed different responses on the mould's metabolism when co-cultured with the two B. amyloliquefaciens, showing different
modes of action of each bacterium, which opens the possibility of combining both biocontrol strategies.
CONCLUSION: These results unveil different modes of action of the treatments that could help to reduce the use of toxic chemicals
to combat plant pathogens worldwide.
