Basidiomycota

general account, basidiomycota fungi, life cycle, basidia, basidiospores

1. General account of Basidiomycota Dr. H arwinder Kaur Akal University Talwandi S abo Bathinda .

2. According to Kirk et al. (2001), the Basidiomycota contains about 30,000 described species, which is 37% of the described species of true fungi. Although the most familiar examples of this group are the mushrooms and toadstools , there is an enormous diversity of species, including basidiomycetous yeasts, many important plant pathogens, and some serious human pathogens. The one single feature that characterizes the group is the basidium in which meiosis occurs, leading to the production of sexual spores ( basidiospores ) that usually are produced externally on short stalks termed sterigmata Basidiomycota

3. Basidiomycota Several other features are found in the Basidiomycota . The hyphae often have a complex dolipore septum that prevents nuclei from moving between different hyphal compartments. The cell wall typically is composed of chitin and glucans (but chitin and mannans in the yeast forms). The nuclei typically are haploid, but throughout most of the life of a colony each hyphal compartment contains two nuclei, representing two different mating compatibility groups. A mycelium of this type is termed a dikaryon .

4. Taxonomy and relationships The Basidiomycota is a monophyletic group (all of its members having a common ancestry) and is a sister group to the Ascomycota . In other words, both of these groups have a common ancestor. Three major sub-groups are recognized within the Phylum Basidiomycota : 1 Urediniomycetes , including the rust fungi ( Uredinales ) which are economically significant plant pathogens of many crops and wild plants . 2 Ustilaginomycetes , including the smut fungi ( Ustilaginales ) some of which again are significant plant pathogens, and gain their name from their black, sooty spores . 3 Hymenomycetes , including mushrooms, puffballs, and jelly fungi.

5. L ife-cycle of Basidiomycota Basidiospores , each containing a single haploid nucleus, germinate and grow into hyphal colonies that have a single nucleus in each hyphal compartment. This phase is termed a monokaryon (meaning that it has one nuclear type in each hyphal compartment). The monokaryon can produce small oidia that either act as fertilizing elements or they can germinate to produce further monokaryotic colonies . The next stage of development occurs when the hyphae of two monokaryons of different mating compatibility groups fuse with one another, or when an oidium of one mating compatibility group attracts a hypha of a different mating compatibility group. This causes a strong “homing response” but the chemical attractants causing it have not been identified. Once the two compatible strains have fused by the process termed plasmogamy , all subsequent growth occurs by dikaryotic hyphae (with two nuclei – one of each compatibility group – in each hyphal compartment).

6. Cross section through mushroom basidiocarp

7. BASIDIOSPORES

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