Final answer:
In Basidiomycota, the primary mycelium is monokaryotic and haploid, resulting from individual basidiospores. The secondary mycelium is binucleate, containing nuclei from two mating strains, and it forms the dominant stage in the lifecycle, culminating in the creation of a basidiocarp, the mushroom's fruiting body.
Step-by-step explanation:
The primary mycelium in Basidiomycota consists of monokaryotic haploid hyphae, which are the result of germination of a basidiospore. This primary mycelium is considered a less mature phase and precedes the formation of a more advanced secondary mycelium. In contrast, the secondary mycelium arises when mycelia from different mating strains come together in a process called plasmogamy.
The secondary mycelium contains haploid nuclei from two distinct mating strains per cell. This secondary form is the dominant phase in the basidiomycete life cycle and is responsible for generating the basidiocarp, the fruiting body, which is observable as a mushroom with a stalk and cap. Inside the basidia, located on the gills of the basidiocarp, karyogamy occurs, leading to the formation of diploid cells. Subsequently, these diploid nuclei undergo meiosis to form haploid basidiospores.