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The following points highlight the top eleven features of basidiomycetes.
1. The somatic phase consists of a well-developed, septate, filamentous mycelium which passes chiefly through two stages.
(a) Primary mycelium:
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It is formed by the germination of a basidiospore and contains a single haploid (n) nucleus in each cell. It bears neither sex organs nor any basidia and basidiospores. It is short-lived.
(b) Secondary or dikaryotic mycelium:
It constitutes the main food absorbing phase and consists of cells each containing two haploid nuclei (n+n). It is long-lived and plays prominent role in the life cycle.
In the Homobasidiomycetidae it may continue to grow for years producing fructifications every year by the interweaving of hyphae. The fructifications bear basidia and basidiospores.
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In the Heterobasidiomycetidae it forms teleutospores or brand spores which germinate to produce basidia bearing basidiospores.
2. Except in rusts and smuts the septal pore in the Basidiomycetes is complex. It is dolipore parenthesome type.
3. The motile cells are absent in the life cycle.
4. The clamp connections on the dikaryotic hyphae are of universal occurrence.
5. Asexual reproduction by spores plays an insignificant role in the life cycle. The Homobasidiomycetidae do not form any asexual spores. The Heterobasidiomycetidae form them in the dikaryotic mycelium. The latter produces uredospore’s and aeciospores in the rusts.
6. The sex organs are lacking in the Basidiomycetes. The sexual process is represented by plasmogamy and karyogamy. Karyogamy is immediately followed by meiosis.
7. Basidium is the characteristic reproductive organ of Basidiomycetes in which both karyogamy and meiosis take place.
8. Typically the basidium bears four basidiospores exogenously. The number, however, varies from one to many depending on the species.
9. The basidiospore germinates to produce the primary mycelium.
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The Basidiomycetes and Ascomycetes resemble each other in the following respects:
1. The Basidiomycetes and Ascomycetes are similar in their habit as both include parastitic as well as saprophytic species.
2. The purely terrestrial mycelium consists of septate, filamentous hyphae both in the Basidiomycetes and Ascomycetes.
3. The septa have each a central pore in both.
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4. The motile cells are completely lacking in the life cycle of both the classes.
5. The sex organs which are completely absent in the Basidiomycetes have gradually been eliminated from the life cycle in the advanced Ascomycetes.
6. The sexual process in both the classes comprises plasmogamy and karyogamy. The latter is immediately followed by meiosis.
7. The delayed fusion of nuclei of opposite strains after plasmogamy has resulted in the origin and establishment of a binucleate or dikaryophase in the life cycle of both Basidiomycetes and Ascomycetes.
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8. The characteristic reproductive organ, basidium of Basidiomycetes and ascus of Ascomycetes resemble each other in development and cytology till the initiation of spores.
Both arise from the binucleate cells, the basidium from the dikaryotic hyphae and ascus from the ascogenous hyphae. Karyogamy and meiosis both occur in the basidium as in the ascus.
9. The basidiospores are usually uninucleate and haploid as are the ascospores in most of the Ascomycetes.
10. The dikaryotic mycelium in the Basidiomycetes is comparable to the ascogenous hyphae of the Ascomycetes.
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11. The basidiocarps of Basidiomycetes are comparable to the ascocarps of Ascomycetes but the two are not homologous structures.
12. A clamp connection of the Basidiomycetes is considered homologous in structure and analogous in function to the hook of the Ascomycetes.
The Basidiomycetes differ from the Ascomycetes in the following respects:
1. The septal pore in most of the Basidiomycetes is not a simple hole as in Ascomycetes but is a complex structure known as a dolipore.
The actual pore is barrel-shaped. It is surrounded by a swollen rim which is a part of the annular septum. The opening of the pore on either side is guarded by a curved pore cup called parenthesome.
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2. The primary mycelium consisting of cells, each with a haploid (n) nucleus is short-lived. On the other hand the primary mycelium in the Ascomycetes is dominant and long-lived.
3. The primary mycelium in the Basidiomycetes bears neither the sex organs nor basidia or basidiospores.
4. The conidia (uredospores and aeciospores) are borne on the secondary mycelium whereas in the Ascomycetes they are borne on haplomycelium.
5. Excepting the Uredinales all traces of sexual apparatus have been lost throughout the class.
6. Presence of clamp connections is a characteristic feature of the secondary mycelium.
7. The dikaryotic (secondary) mycelium is a long-lived, independent structure whereas the ascogenous hyphae of the Ascomycetes which are homologous to the former are short-lived, dependent and occur only inside the fruit body.
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8. The dikaryotic mycelium which is the result of a single mating of compatible hyphae may produce a large number of fructifications instead of only one as in the Ascomycetes.
9. The fruit bodies in the Basidiomycetes consist entirely of dikaryotic hyphae whereas in the Ascomycetes the basal hyphae, peridia and paraphyses are haploid.
10. The basidium bears a definite number of basidiospores, which is usually four whereas the ascus of the Ascomycetes usually produces eight ascospores.
11. The basidiospores are produced externally or exogenously on the basidium whereas the ascospores are produced inside or endogenously in the ascus of the Ascomycetes.
