HOG MAP kinase regulation of alternariol biosynthesis in Alternaria alternata is important for substrate colonization

► Regulation of alternariol biosynthesis in Alternaria is highly dependent on aw. ► The HOG signal cascade is essential for the regulation of alternariol biosynthesis. ► Alternariol increases the colonization capacity of Alternaria on tomatoes. ► Alternaria strains from wheat seem to be less sensitive towards low aw.