Reproduction in the dikarya: basidiomycota

This group of fungi is characterized by the most complex and large structures found in the fungi. They are also distinctive in which they very rarely produce asexual spores. Many of the life cycles are spent as vegetative mycelium exploiting complex substrates. The preliminary requisite for the onset of sexual reproduction is the acquisition of two mating types of nuclei by the fusion of compatible hyphae. The Single representatives of the two mating- type nuclei are held within every hyphal compartment for extended to the time. This is termed a dikaryotic state and its maintenance requires elaborate septum formation during growth and nuclear division.

Onset of sexual spore formation is triggered by environmental conditions and begins with the formation of a fruit body primordium. The Dikaryotic mycelium expands and differentiates to form the large fruit bodies we recognize as mushrooms and toadstools. The Diploid formation and meiosis occur within a modified hyphal tip called a basidium.

Four spores are budded from the basidium. The Basidia form together to create a hymenium which is highly sensitive to the presence of free water. The hymenium is distributed

                                                        Figure  6.  Basidium  formation.
over sterile, dikaryotic-supporting tissues that protect it from  rain.  Hymenium can be exposed on gills or pores beneath the fruit body seen in the toadstools and bracket fungi or enclosed within chambers as in the puffballs and truffles.