II. Asexual reproduction.
    The majority of ascomycetes utilize conidiospores or conidia.

III. Sexual reproduction.
    The usual sexual spores are ascospores. These are contained in a sac called an ascus, and are produced following meiosis and usually a mitotic division.
    Haploid mycelium of two mating types occur. These will produce antheridia and ascogonia. Following contact between an antheridium and ascogonium, or an ascogonium and a conidiospore of opposite mating types, plasmogamy will occur, so that a male nucleus will be found in the same cell as the female nucleus. This establishes the dikaryotic state - i.e. n+n ploidy. Dikaryotic hyphae will now be stimulated to grow from this ascogonium, in a coordinated manner with haploid hyphae to form the fruiting body known as an ascocarp. The dikaryotic hyphae which will actually form the asci are known as ascogenous hyphae.
    The ascus forms from the penultimate cell of an ascogenous hypha where it forms a crozier hook. This cell undergoes karyogamy, followed by meiosis and usually a mitotic division, producing 8 ascospores in an ascus. The arrangement may be ordinate or inordinate, depending on the species. Within the ascocarp, there is usually a layer containing the asci, and sterile cells known as paraphyses. This layer is the hymenial layer.
    The form of the ascocarp may be one of three types.

A. Apothecium - this is a more or less cup-shaped structure, varying from quite flat to distinctly cup-like. Peziza is a good example of this type.
B. Perithecium - this is almost closed, with a small ostiole or opening at the tip. Ex. Claviceps. (Note - some authors include closed ordinate ascocarps as perithecia.)
C. Cleistothecium - this is a closed ascocarp, such as Microsphaera or Sphaerotheca. (Some authors insist that this type of ascocarp be inordinate - see note above.)

A. Yeasts
    These cellular organisms reproduce asexually by budding - i.e. blastospores - and sexually by ascospores (1-8/ascus). They show an interesting variation in the amount of life cycle spent in diploid and haploid states. There are three genera of interest.
1. Saccharomyces cerevisiae
    The familiar brewers or bakers yeast. This is one of the oldest and most important domesticated organisms. The products of its metabolism include alcohol, used in brewing, and CO2 which is important in baking, causing the bread to rise. This group reproduce asexually in both the haplophase and the diplophase. Sexual reproduction involves syngamy and meiosis to produce 4 ascospores per ascus.
2. Schizosaccharomyces
    This form is haploid, except for the brief time following karyogamy and prior to meiosis. In this group, 8 ascospores are formed.
3. Saccharomycodes
    This for is primarily in the diplophase, and also forms pseudohyphae. Certain cells undergo meiosis, forming 4 ascospores/ascus. Within the ascus, two spores undergo plasmogamy and karyogamy, forming a diploid zygote, which exits the ascus and continues as a pseudohypha.
B. Taphrinia deformans - Leaf curl fungus.
    This fungus causes the crinkled leaf condition frequently seen in peaches and other trees.
C. Powdery mildews
    This group of fungi are obligate parasites, usually occurring on the leaves of plants, where they rarely kill their hosts, but usually slow or impair the growth of the plants. Most of them show appendaged cleistothecia as their fruiting bodies, and produce aerial conidia extending from the surface of the leaf. Genera include the following:
1. Erysiphe spp.
2. Sphaerotheca
3. Microsphaera
D. Endothia parasitica - Chestnut blight
    From Japanese chestnut trees, where it is a hypovirulent strain with virus-like properties. 25 years after entering the U.S., most of the mature chestnuts were dead.
E. Ceratocystis ulmi - Dutch Elm Disease
    Named by a Dutchman, but comes from Asia, where the Chinese Elm is resistant. Carried by bark beetles, and introduced into their passageways where the young develop. The beetle larvae use the fungus as a food source.
F. Penicillium (= Talaromyces) - Blue mold
    This genus contains species important in production of antibiotics and in the aging of cheese. Conidia are borne on branched conidiophores. Development of asci is a relatively recently discovered phenomenon, and resulted in the movement from the form genus Penicillium to the current genus Talaromyces.
1. P. notatum - the source of penicillin. Discovered by Alexander Fleming, and developed by Florey and Chain.
2. P. camemberti and P. roquefortii - age and give the distinctive flavors to the respective cheeses bearing their names. Originated from caves in those regions of France, where cheeses were stored in caves to age.
G. Aspergillus - Green mold
    This genus has phialides radiating from a head-like end to the conidiophores. It can be a serious pathogen in immune-compromised individuals, should it enter the lungs and become systemic. It also can produce toxic and carcinogenic byproducts (aflatoxins) if it should grow in stored products such as peanuts. Affects humans and chickens. Generally, however, it is a harmless saprophyte.
H. Monilinia fructicola - Brown rot fungus. Infects peaches, plums, etc.
I. Claviceps purpurea - Ergot.
    Grows on rye and other cereals. The sclerotia contain some 20 different alkaloids, some of which cause very violent reactions if ingested. The hallucinogen lysergic acid, vasoconstrictors, and other substances are included. "Pit", a stimulant for childbirth is a derivative, as are vasoconstrictors used in medicine.
    Ingestion usually occurs when sclerotia are harvested and milled with the normal grain. Violent hallucinations, gangrene and limb loss, a burning sensation known as St. Anthony's Fire, and death, are some of the results of ingestion. Two percent ergot in flour will cause ergotism. Tens of thousands have died in a season. Peter the Great's campaign against Turkey was aborted because of ergotism, and Napoleon's defeat in Russia was partly attributable to ergotism in the ranks. There is indication that the Salem "witches" were ergotized, thus accounting for their unusual behavior.
    The life cycle begins in the spring with the infection of cereal flowers by ascospores. These germinate and grow into the developing grain. The hyphae mass together and form a sclerotium which actually replaces the grain. It is this sclerotium which may be harvested and ingested. If it is not harvested, it will fall to the ground, and after over-wintering perithecial stroma or heads will grow from it. Embedded in the surface of these stromas are many perithecia, where ascospores will eventually form. The ascospores are long and slender, being arranged in a bundle, rather than in a row, or a cluster.
J. Neurospora - Pink mold
    This mold is very important as a genetic tool, with its ordered array of ascospores.
K. Peziza - Cup fungus
L. Tuber - Truffles
    Highly desirable underground fungi, being one of the most expensive of mycophagists delights.
M. Morchella - morels
    Another very tasty mushroom.
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