91Ó°ÊÓ

The kingdom Fungi contains five major phyla that were established according to their mode of sexual reproduction or using molecular data.

The five true phyla of fungi are the Chytridiomycota (Chytrids), the Zygomycota (conjugated fungi), the Ascomycota (sac fungi), the Basidiomycota (club fungi) and the Glomeromycota.

a. Chytridiomycota

The only class in the Phylum Chytridiomycota is the Chytridiomycetes. The chytrids are the simplest and most primitive Eumycota, or true fungi.

Chytrids have chitin in their cell walls, but one group of chytrids has both cellulose and chitin in the cell wall. Most chytrids are unicellular; a few form multicellular organisms and hyphae, which have no septa between cells (coenocytic). They produce gametes and diploid zoospores that swim with the help of a single flagellum.

b. Zygomycota

The zygomycetes are a relatively small group of fungi belonging to the Phylum Zygomycota. They include the familiar bread mold, Rhizopus stolonifer, which rapidly propagates on the surfaces of breads, fruits, and vegetables.

Zygomycetes have a thallus of coenocytic hyphae in which the nuclei are haploid when the organism is in the vegetative stage.

c. Glomeromycota

The Glomeromycota is a newly established phylum which comprises about 230 species that all live in close association with the roots of trees.

The glomeromycetes do not reproduce sexually and do not survive without the presence of plant roots.

d. Ascomycota

The majority of known fungi belong to the Phylum Ascomycota, which is characterized by the formation of an ascus (plural, asci), a sac-like structure that contains haploid ascospores. Many ascomycetes are of commercial importance. Some play a beneficial role, such as the yeasts used in baking, brewing, and wine fermentation, plus truffles and morels, which are held as gourmet delicacies.