AY Honors/Fungi/Answer Key

1. Give the name of five classes of fungi and examples of each.

Chytridiomycota

The phylum Chytridiomycota, the chytrids, represents a group of primitive aquatic fungi. They are characterized by having gametes that are motile by means of flagella.

Zygomycota

The zygomycetes, in phylum Zygomycota, are characterized by the formation of sexual spores called zygospores. The zygospores are not contained within a specialized fruiting body or sac. Zygospores form when the haploid nuclei at the ends of two hyphae fuse together in a process of fertilization to form a diploid zygote. The zygote immediately undergoes meiosis to form haploid cells that develop into zygospores. The zygospores are unenclosed, or “naked,” between the parental hyphae. An example of a zygomycete is the common black bread mold, Rhizopus nigricans.

Glomeromycota

Ascomycota- The ascomycetes are members of the phylum Ascomycota. They are also called the “sac fungi” because their sexual spores (ascospores) are enclosed in tube-like sacs known as asci. The formation of ascospores is similar to that of zygospores, except that the ascospores formed by meiosis are enclosed in the asci. Neurospora crassa is an ascomycete mold that was important in studies of genetic linkage.

Basidiomycota

Basidiomycetes, also known as the “club fungi,” are classified in phylum Basidiomycota. Their sexual spores, or basidiospores, are formed on complex fruiting body structures called basidia. Basidiomycetes include some of the most complex fungi, including mushrooms and puffballs.

3. Name three important fungi and tell what their value is.

Saccharomyces cerevisiae: This fungus is used both in many ethanol (beer) fermentation processes and in baker's yeast, which utilizes the carbon dioxide byproduct of the same fermentation.

Aspergillus niger: This fungus is used to make citric acid commercially, and it also can be used to make gluconic acid. Both are important food additives.

Penicillium chrysogenum: This is the organism that makes penicillin, from which the majority of the large class of beta-lactam antibiotics are derived. Penicillin and its derivatives have saved countless lives since they were discovered and isolated, starting in the 1940s.

5. Identify five fungus plant diseases.

Pinkroot

Pinkroot, Phoma terrestris.

Downy mildew

Downy mildew, Peronospora destructor.

Botrytis leaf blight

Botrytis leaf blight, Botrytis squamosa.

Neck rot

Neck rot, Botrytis allii.

Smut

Smut, Urocystis cepulae.

Smudge

Smudge, Colletotrichum circinans.

White rot

White rot, Sclerotium cepivorum.

References

• http://www.caes.state.ct.us/PlantPestHandbookFiles/pphO/pphonio.htm