Synergistic antifungal effect and potential mechanism of Dimethomorph combined with Pyrimethanil against Phytophthora capsici.

Synergistic effect of dimethomorph (DIM) and pyrimethanil (PYM) was evaluated using the Wadley method and the molecular mechanism of the antifungal effects of the combined treatment was systematically investigated. DIM+PYM had a synergistic effect on Phytophthora capsici, with the synergistic effect being observed at 5:1, at which the synergy coefficient was 1.8536. The mycelia of the pathogen treated with DIM+PYM were branched, uneven in thickness, and swollen. Moreover, scanning electron microscopy (SEM) revealed that DIM+PYM caused mycelium breaks, swelling, and apex enlargement, while transmission electron microscopy (TEM) revealed structural damage, cavities, and cell membrane morphological abnormalities. DIM+PYM inhibited the growth of mycelia, destroyed the cell membrane, interfered with energy metabolism, reduced protein and sugar content. Additionally, the transcriptome and metabolome of fungi treated with DIM+PYM changed significantly; specifically, there were 1571 differentially expressed genes and 802 differential metabolites. DIM+PYM may mainly damage the cell membrane, energy, protein, soluble sugar pathways.