Synergistic mechanism of Bacillus subtilis Czk1 combined with propiconazole and tebuconazole mixtures against Pyrrhoderma noxium

Abstract Background Brown root rot disease is one of the devastating diseases in the rubber production process. It is not easy to be detected in the early stage of the disease. Our early research revealed that the rubber tree brown root rot fungus Pyrrhoderma noxium Pn006 was effectively inhibited by Bacillus subtilis Czk1 and 25% propiconazole–tebuconazole, and that the two agents might work in synergy. Therefore, in this investigation, we used non-targeted metabolomic method to evaluate the synergistic mechanism of B. subtilis Czk1 and 25% propiconazole–tebuconazole on Pyrrhoderma noxium Pn006. Results Metabolomics analysis identified 708 unique metabolic markers, including mainly lipids and lipid-like molecules, organic acids, alcohols, ketones, alkaloids and their derivatives, nucleotides and their analogues, benzene ring compounds and amino acids and their derivatives. Further screening identified 105 key metabolic markers that could be potential biomarkers to reveal the mechanism of biocontrol bacteria and chemical fungicides combination synergy. Three key metabolic pathways were found in pathway enrichment, including linolenic acid metabolism, benzoic acid degradation, and valine, leucine and isoleucine degradation. Conclusions The mechanism might be related to the influence of the energy supply and cell functional integrity of pathogenic fungal cells. Critical relevance statement A metabolomic method was utilized to investigate the synergistic effects of B. subtilis Czk1 and 25% propiconazole–tebuconazole use on Pyrrhoderma noxium Pn006. Graphical Abstract