Figure 3.

The mitogen‐activated protein kinases (MAPKs) Fmk1, Mpk1 and Hog1 regulate different virulence‐associated traits. (A) Hyphal aggregates forming after 36 h of growth in potato dextrose broth (PDB) diluted 1 : 50 with water and supplemented with 25 mm of the indicated nitrogen source. Fungal cultures were vortexed to dissociate weakly adhered hyphae, transferred to a multiwell plate and observed using a binocular microscope. (B) Invasive growth on apple fruit inoculated with microconidia of the indicated strains and incubated at 28 °C for 4 days. (C) The production of extracellular polygalacturonase activity was determined by the inoculating plates containing polygalacturonic acid (PGA) with microconidia of the indicated strains. Enzymatic activity was visualized as a contrasting halo underneath the fungal colony after 3 days of growth at 28 °C.