Cytochrome P450 monooxygenase; part of the gene cluster that mediates the biosynthesis of abscisic acid (ABA), a phytohormone that acts antagonistically toward salicylic acid (SA), jasmonic acid (JA) and ethylene (ETH) signaling, to impede plant defense responses (PubMed:31034868). The first step of the pathway catalyzes the reaction from farnesyl diphosphate to alpha-ionylideneethane performed by the alpha-ionylideneethane synthase abl3 via a three-step reaction mechanism involving 2 neutral intermediates, beta-farnesene and allofarnesene (By similarity). The cytochrome P450 monooxygenase abl1 might then be involved in the conversion of alpha-ionylideneethane to alpha-ionylideneacetic acid (By similarity). Alpha-ionylideneacetic acid is further converted to abscisic acid in 2 steps involving the cytochrome P450 monooxygenase abl2 and the short-chain dehydrogenase/reductase abl4, via the intermediates 1'-deoxy-ABA or 1',4'-trans-diol-ABA, depending on the order of action of these 2 enzymes (By similarity). Abl2 is responsible for the hydroxylation of carbon atom C-1' and abl4 might be involved in the oxidation of the C-4' carbon atom (By similarity). Hormone biosynthesis. Expression is induced during the early biotrophic stage of development (PubMed:31034868). Expression is positively regulated by the ABA cluster-specific transcription regulator abl7 (PubMed:31034868). Impairs the production of abscisic acid (ABA) (PubMed:31034868). Does not affect sporulation, pycnidiospore germination nor fungal growth rates in vitro, and does not alter the pathogenicity of L.maculans (PubMed:31034868). Belongs to the cytochrome P450 family.