Precursor and terminal metabolites in AF biosynthesis. Sterigmatocystin (ST), O- methylsterigmatocystin (OMST) and aflatoxins (AF) are synthesized as end products by numerous ascomycetes. There are four major aflatoxins: B1, B2, G1 and G2. Aflatoxins B2 and G2 are missing the double bond (indicated in red), which is present in B1 and G1. A. parasiticus produces B1, B2, G1 and G2; nonaflatoxigenic A. parasiticus strains commonly accumulate OMST. The gene aflU is required for the formation of G aflatoxins ; aflQ is required for the formation of B aflatoxins ; and aflP is required for the conversion of ST to OMST . A. flavus, A. parasiticus, A. nomius , A. pseudotamarii  and A. bombycis  belong to Aspergillus section Flavi. Emericella is a teleomorphic genus for the sexual stage of Aspergillus. Monocillium is an anamorphic name associated with a Niesslia teleomorph, also in the Phylum Ascomycota. The Ascomycota comprise highly divergent fungal lineages that span 450 million years of evolutionary history .