Sexuality

The wood-inhabiting Ascomycetes and Basidiomycetes are either homothallic or heterothallic (Ryvarden and Gilbertson 1993). Homothallic fungi are self-fertile, that is no second mating type is required for sexual reproduction. Fertilization takes place at the same mycelium.

Many Ascomycetes and about 10% of the Basidiomycetes belong to this type. Heterothallism includes both bipolar and tetrapolar fungi. In bipolar (uni-factorial) species, incompatibility is controlled by a series of multiple alleles at one locus. Any dikaryon has two alleles that segregate at the the basidiospores have one allele and half the other. Compatible matings occur between monokaryons with different mating type factors. The inbreeding level is 50%. The outbreeding level inpopulations of bipolar polypores is over 90%.

In tetrapolar (bifactorial) species, incompatibility is controlled by two se-ries of multiple alleles at two loci on different chromosomes. The twopairs segregate independently at meiosis. Four different mating types rise from one dikaryon. In a fruit body of an isolate, basidiospores of the mating type A,13x, AxBy, AyBx and AyBy develop. These spores germinate to monokaryons. Fully compatible matings of monokaryons (+ in Table 2.5) occur when both factors are heterozygous (A#B#): Ax13„ and AyBy as well as AxBy and AyBx. In addition, there are hemicompatible matings, in which only one factor is different: AO, and A,By as well as AyBy and AxBy.

The inbreeding level is 25%. The outbreeding level is very high. In Schizo-phyllum commune 450 A factors and 90 B factors can combine to over 40,000 mating types (Raper and Miles 1958). Many Ascomycetes and about 25% of the examined Basidiomycetes are bipolar heterothallic (e.g., Oligoporus pla-centa). About 65% Basidiomycetes are tetrapolar (Raper 1966).

Bipolar mating predominates among brown-rot fungi and tetrapolar mating among white-rot fungi (Rayner and Boddy 1988). Of 25 investigated brown-rot polypores, 17 were bipolar, three were tetrapolar, three were heterothallic with type of mating system undetermined, one was homothallic, and one was reported by different authors as bipolar and tetrapolar (Ryvarden and Gilbertson 1993). The biolog-ical significance of heterothallism is that inbreeding is limited and outbreeding is enhanced, promoting gene flow between populations and decreasing the rate of speciation.

Combination and recombination of the genetic material with plasmogamy, karyogamy, and haploidization, but without sexual organs, gamets and changes ofgenerations, can take place by parasexuality, particularly in Deuteromycetes ( Jennings and Lysek 1999). Nuclei of a hypha migrate by anastomosis into another hypha and multiply and spread there. In the case of a heterokaryon,

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Reproduction of Deuteromycetes

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What shapes the peer review landscape in ecology?

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Red Streaking

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Ecosia ; Ecology Search

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Bioenergetics

T housands of chemical reactions occur throughout the body during each minute of the day. Collec-tively, these reactions are called metabolism. Metab-olism includes chemical pathways that result in the synthesis of molecules (anabolic reactions) as well as the breakdown of molecules (catabolic reactions). Since energy is required by all cells, it is not sur-prising that cells possess chemical pathways that are capable of converting foodstuffs (i.e., fats, proteins, carbohydrates) into a biologically usable form of energy . This metabolic process is termed bioenergetics. In order for you to run, jump, or swim, skeletal muscle cells must be able to continuously extract energy from food nutrients. In fact, the inability to transform energy contained in foodstuffs into usable biological energy would limit performance in endurance activities. The explanation for this is simple. To continue to contract, muscle cells must have a continuous source of energy. When energy is not rea

White Rot

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Soft Rot

The term " soft rot " was originally used by Findlay and Savory (1954) to describe a specific type of wood decay caused by Ascomycetes and Deuteromycetes which typically produce chains of cavities within the S2 layer of soft- and hardwoods in terrestrial and aquatic environments (Liese 1955), for example when the wood-fill in cooling towers became destroyed despite water saturation, and when poles broke, although they were protected against Basidiomvcetes. About 300 species (Seehann et al. 1975) to some 1,600 examples of ascomvcete and deuteromvcete fungi (Eaton and Hale 1993) cause soft rot, e.g., Chaeromium globosurn (Takahashi 1978), Hurnicola spp., Lecythophora hoffrnannii, Monodictys putredinis, Paecilornyces spp., and Thielavia terrestris. Soft-rot fungi differ from brown-rot and white-rot Basidiomycetes by grow-ing mainly inside the woody cell wall trate, starting from the tracheidal lumina., by means of thin perforation hyphae of less than 0.5 pm thickne

Antagonists, Synergists, and Succession

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Sexual Reproduction

A specific feature of the sexual reproduction of Ascomycetes and Basid-iomycetes is that plasmogamy of haploid cells and karyogamy of two nuclei (n) to form a diploid nucleus (2n) are separated from each other temporally as well spatially by the dikaryophase (two-nuclei phase, dikaryon, n + n, ===) (Fig.1). A dikaryotic hypha is one with two nuclei that derive from two haploid hyphae, but in which the nuclei are not yet fused by karyogamy. Particularly in Basidiomycetes, the dikaryotic phase is considerably ex-tended. By conjugated division of the two nuclei (conjugated mitosis), by division of the dikaryotic hypha, and by means of a special nucleus migration connested with camp formation both daughter cells become again dikaryotic. Ascomycetes The life cycle of a typical ascomycete is shown in Fig.1 (also Muller and Loeffler 1992; Eaton and Hale 1993; Schwantes 1996; Jennings and Lysek 1999). Haploid (n) spores (A, ascospores or conidia from an anamorph) germi-nate

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