Fungi belonging to Phylum Basidiomycota commonly are known as basidiomycetes. They are a large and diverse group and include the mushrooms, earthstars, puffballs, bird's nest, rusts, and smuts. They are characterized by:

1. sexual spores called basidiospores that are borne on a basidium where karyogamy and meiosis take place (Fig. 1)

2. vegetative stage of the the basidiomycetes is free-living dikaryon and free-living homokaryon

3. diploid state is brief and occurs only in basidium

4. don't produce sexual structures and sexual reproduction is by somatogamy or spermatization
rusts-only basidiomycetes that have sexual structure (spermatia and spermagonia)

5. many have clamp connections on vegetative hyphae (rusts are exceptions) which is a mechanism for the perpetuation of a dikaryon

6. most have a dolipore septum.

7. their cell wall is b,1-3 and 1-6 glucans and chitins

8. most have fruiting bodies called basidiocarps except the rusts and the smuts.

9. some have anamorphs

10. they are either heterothallic or homothallic. The heterothallic are bipolar or tetrapolar, all are multiallelic which greatly enhances outbreeding.

There are two recognized "formal" classes in the Basidiomycota, the Homobasidiomycetes and Heterobasidiomycetes. There are three "informal" traditional groups referred to as Gasteromycetes, Hymenomycetes, and Teliomycetes. The following scheme shows the classes and orders we will consider in this class.

I. Class Heterobasidiomycetes

In the Heterobasidiomycetes, the basidia vary in shape but are septate or deeply divided. The basidia usually arise from a thick-walled cell. The basidiospores also germinate repetitively or by budding. The class contains both species with and without fruiting bodies. The vegetative mycelium have simple or dolipore septa.

A. Order Uredinales-The Rusts

The basidia in the Uredinales are transversely septate and arise from a thick-walled teliospore. Each basidium produces four basidiospores which are forcibly discharged. No basidiocarp is formed. Uredinales are called rust fungi because of the color of certain spore stages in their life cycle. These fungi have the most complex life cycle of all fungal species, with up to five separate spore stages. All of the rust fungi are obligate parasite of vascular plants.

1. Family Pucciniaceae-teliospores stalked, septate external basidium.

a. Puccinia-the teliospores are two-celled, pigmented, and have a pedicel, and the pycnia are globose and subepidermal. Examine prepared slides of different spore stages of Puccinia. Note the different shapes of the structures you see and compare them with each other. The life cycle of a common species of this genus is attached. Study this life cycle and relate the structures you see under the microscope. b. Uromyces-one-celled teliospores. Examine infeted leaves. c. Gymnosporangium-telia are gelatinous and appear as `horns' on dried galls. The disease caused by Gymnosporangium jupineri-virginianae, apple cedar rust, is common in the southeast and is a formidable problem for apple growers.

Examine dried materials bearing different rust spore stages of this fungus.

d. Observe the different Riker mounts of plants infected with rusts.

2.Family Melampsoraceae-one-celled teliospores, sessile, external basidium united laterally into a crust.

a. Cronartium-This genus has tall, hairlike columns of teliospores which are one-celled and are arranged in vertical chains without intercalary cells. Cronartium fusiforme is the cause of fusiform rust of pine. Look at preserved or dried aecial galls on pine.

B. Order Ustilaginales-The Smuts

The Ustilaginales produce basidia that may be transversely septate or non-septate and arise from intercalary teliospores. The basisiospores are produced in infinite numbers and are not forcibly discharged. Both haploid and dikaryotic stages occur. The haploid stage will grow in culture as a yeast-like colony, but the sori in various host tissues and are especially common in the inflorescence. There is no fruiting body and the teliospores may form singly or in balls. The large numbers of dark-colored teliospores formed on the host gives rise to the common name of smut fungi for these organisms. Look at the attached table summarizing the differences between rusts and smuts.

1. Family Ustilaginaceae-basidia septate, basidiospores produced laterally from each cell.

a. Ustilago-In this genus the mature sorus is dusty, the teliospores are small, and the sorus lacks a peridium. Examine prepared slides showing teliospores of Ustilago maydis, the causal organism of corn smut.

Examine other specimens infected with this smut fungus.

2. Family Tilletiaceae-basidium is non-septate, basidiospores are terminal on the basidium. a. Tilletia-sori are dusty at maturity but the spores are small. Examine wheat heads infected with Tilletia caries. The life cycle of Tilletia caries are also illustrated in the attached figures.

C. Order Auriculariales

basidium transversely septate and four-celled. Some species have dolipore septa. Most species are saprobic but a few are parasitic. There is a single family, the Auriculariaceae.

a. Auricularia-The basidiocarp is variable in shape, firm gelatinous, with unilateral hymenium. Put a dried Auricularia auricula in water and watch it turn jelly-like. Note the shape and consistency of the basisocarp. This fungus is referred to as wood ear. Mount a small portion of a basidiocarp in water and look for basidia under the microscope.

We will try to grow an edible oyster mushroom, Pleurotus ostreatus. We will plant our mushrooms in different substrates and will determine the best substrate for growth, based on fruiting quantity and quality. We will become acquainted with the different structures formed at each stage of its growth. We are hoping to harvest a good crop of edible mushrooms for a lab cookout. The substrates we will test are coffee grounds, grains (wheat and barley), sawdust, hay straws, and newspaper. We will also include combinations of straw and grains, grains and sawdust, and coffee grounds and grains. This will be done in pairs, with each pair testing a different substrate.

Under sterile conditions, inoculate sterilized or pasteurized substrates with P. ostreatus mycelial spawn. Mix the bag completely and inflate it by letting the air blow from the laminar flow hood into the bag and piching the side of the bag. Pack the bag by compressing the inoculated substrate. Tie the bag with a wire or make a knot. Slash the bags in several places using sterile scalpel. The bags will be incubated at 55-75 F for 3-5 days in an incubator with 95-100% RH. The RH will be lowered to 85-95% for the next 4-7 days after the first signs of fruiting primordia appear.