Non-reducing polyketide synthase that mediates the biosynthesis of alternariol (AOH), a micotoxin that seems not to be involved in virulence and oxidative stress tolerance (PubMed:26025896). PKS19 alone is sufficient for AOH synthesis which is initiated by priming with acetyl-CoA, followed by sequential condensations of 6 malonyl-CoA units (PubMed:26025896). Multidomain protein; including a starter unit:ACP transacylase (SAT) that selects the starter unit; a ketosynthase (KS) that catalyzes repeated decarboxylative condensation to elongate the polyketide backbone; a malonyl-CoA:ACP transacylase (MAT) that selects and transfers the extender unit malonyl-CoA; a product template (PT) domain that controls the immediate cyclization regioselectivity of the reactive polyketide backbone; and an acyl-carrier protein (ACP) that serves as the tether of the growing and completed polyketide via its phosphopantetheinyl arm (By similarity). Impairs the production of alternariol (PubMed:26025896).