Dikaryon Formation (Dikaryophase): In Ascomycetes and Basidiomycetes, after plasmogamy (fusion of cytoplasm), the fusion of the nuclei (karyogamy) is delayed. This results in a stage where each cell contains two separate haploid nuclei (n+n), known as a dikaryon.

Significance: This intermediate dikaryotic phase is a hallmark of their sexual life cycle, leading to the formation of ascocarps (in ascomycetes) or basidiocarps (in basidiomycetes).

Other options: Phycomycetes do not typically exhibit a prolonged dikaryotic phase, as karyogamy occurs immediately after plasmogamy.

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