Non-reducing polyketide synthase; part of the gene cluster that mediates the biosynthesis of the selective antifungal agent ascochitine, an o-quinone methide that plays a possible protective role against other microbial competitors in nature and is considered to be important for pathogenicity of legume-associated Didymella species (PubMed:31554725). The pathway probably begins with the synthesis of a keto-aldehyde intermediate by the ascochitine non-reducing polyketide synthase pksAC from successive condensations of 4 malonyl-CoA units, presumably with a simple acetyl-CoA starter unit (Probable). Release of the keto-aldehyde intermediate is consistent with the presence of the C-terminal reductive release domain (Probable). The HR-PKS (orf7) probably makes a diketide starter unit which is passed to the non-reducing polyketide synthase pksAC for further extension, producing ascochital and ascochitine (Probable). The aldehyde dehydrogenase (orf1), the 2-oxoglutarate-dependent dioxygenase (orf3) and the dehydrogenase (orf9) are probably involved in subsequent oxidations of methyl groups to the carboxylic acid of the heterocyclic ring (Probable). The ascochitine gene cluster also includes a gene encoding a short peptide (orf2) that is often found in secondary metabolite gene clusters and which function has still to be determined (Probable). Mycotoxin biosynthesis. Multidomain protein; including an N-terminal starter unit:ACP transacylase (SAT) domain, a beta-ketoacyl synthase (KS) domain, a malonyl-CoA:ACP transacylase (MAT) domain, a product template domain, a acyl carrier protein (ACP) domain, a methyltransferase domain (CMeT) and a reductive NADPH-binding domain that is required for NADPH-dependent product release (Probable). The CMet adds methyl groups as check-point tags, which are recognized by KS, such that a lack of methylation causes release of immature products at the triketide stage (By similarity). Blocks the production of ascochitine and its derivatives.