Here's a breakdown:
* Primary mycelia: These are haploid mycelia, meaning they have only one set of chromosomes.
* Different mating types: Basidiomycetes have two mating types, often denoted as "+" and "-".
* Fusion: When a "+" primary mycelium meets a "-" primary mycelium, they fuse together.
* Dikaryotic mycelium: The fused mycelium is called a dikaryotic mycelium because it contains two nuclei, one from each mating type. These nuclei do not immediately fuse, but they coexist within the same cell.
This dikaryotic stage is crucial for the sexual reproduction of basidiomycetes. It allows for genetic recombination and eventually leads to the formation of basidia and spores.
