The fungal life cycle of the fungi has two main types of reproduction: Some fungi show only one known reproduction type. Asexual forms anamorph were often described separately and given different names than the sexual form teleomoph. The complete form having both reproductive forms is called a holomorph.
Fungi known only as anamorphs were previously grouped into the form-group Deuteromycetes Fungi Imperfecti.
Explain asexual reproduction in fungi group is not used anymore, because with molecular phylogenetic techniques the systematic position of a fungus can be determined even if the sexual structures are not known. Explain asexual reproduction in fungi development of haploid nuclei, their fusion, and the emerging diploid nuclei or zygote are the key-steps of sexual reproduction.
A life cycle is considered as haplo-diploid if both phases exist. Generally a phase exists if mitotic cell divisions happen in that nuclear-state. Both Ascomycota Explain asexual reproduction in fungi Basidiomycota have a special phase in their life cycle, the dikaryotic phase, when two haploid nuclei are in one hyphal segment.
These dikaryotic hyphae develop when two monokaryotic cells or hyphae fuse somatogamy or plasmogamy but their nuclei do not. When a monokaryotic haploid stage is represented by distinct cells that fuse, we term them gametes and the fusion is called gametogamy. The gametes can develop in special structures termed a gametangium.
The differences necessary for successful sexual reproduction of fungi are represented
Explain asexual reproduction in fungi mating types. Mating types are determined by mating loci MAT loci. The main modes of heterothallism are grouped according to the number of MAT loci. This type is the bipolar heterothallism. In tetrapolar heterothallism two MAT loci with at least two alleles determine the mating type.
Several genes can function as MAT loci; often they code pheromones and their receptors or regulate genes coding such products.
Names of the main groups of fungi were coined according to the structures developed during their sexual reproduction. Sexual reproduction of the main fungal groups differs significantly between each other and even within those groups.
The oogonium contains haploid oocytes produced by meioses. Beside the oogonium, antheridia develop and produce haploid nuclei via meioses. These nuclei migrate to oogonia across a fertilization
Explain asexual reproduction in fungi developed by the oogonium to fertilize an oocyte. Their fusion produces diploid oospores that germinate and produce coenocytic non-septate hyphae with
Explain asexual reproduction in fungi nuclei.
This life cycle is diploid. Differences in lifecycles occur within the group: Both the oogonia and the antheridia can produce hormones that reciprocally stimulate and regulate their development. Chytrids have several different types of sexual reproduction.
Some have gametes which fuse gametogamy. They can be similar in size izogamy or different anyzogamy. Moreover, a bigger, non-motile oocyte sometimes develops and is fertilized by a motile gamete oogamy. In some chytrids the gametangia fuse gametangiogamy and in others gametes fertilize gametangia.
Somatogamy can also happen when thalli of chitrids fuse. Gametangia develop during the sexual reproduction of zygomycetes. Compatible coenocytic hyphae with haploid nuclei develop gametangia, opposite to each other, and these gametangia fuse real gametangiogamy. Afterwards, the nuclei also fuse karyogamy and a thick walled, generally spherical zygospore develops.
Homothallic zygomycetes do not need two gametangia for sexual reproduction and consequently could produce azygospores. Zygospores are held by suspensors which develop from the remaining parts of the two opposing hyphal outgrowths. The zygospore, strictly speaking, is not a spore but a resting zygote. After karyogamy the diploid nucleus undergoes meiosis, in some cases during spore development, in during germination of the zygospores.
This life cycle is haploid. When the zygospore germinates, a sporangium developed from the hypha produces endogenous haploid mitospores. The name of the Ascomycota refers to the sac-like structure ascus in which the meiospores ascospores develop.
The reproductive features discussed below refer to the hyphal taxa of the Pezizomycotina. An ascogonium develops with haploid nuclei and produces a trichogyn, a fertilization tube to the antheridium developed from a compatible monokaryotic hypha nearby. The haploid nucleus migrates from the antheridium to the ascogonium, from which dikaryotic hyphae with two nuclei of different origin will develop in each segment.
The dikaryotic hyphae form crosiers which enable proper segregation of the two different nuclei after mitotic cell division. Development of an ascus. These dikariotic hyphae can participate in ascoma development. During ascus development the two Explain asexual reproduction in fungi of the terminal cell of an ascogenous hypha fuse karyogamy. The diploid nucleus undergoes meiosis, and a post meiotic mitosis of the haploid nuclei will result the general eight nuclei of the eight ascospores.
The life cycle of hyphal ascomycetes is dominated by the haploid phase; the dikaryotic phase is relatively short and a diploid nucleus Explain asexual reproduction in fungi present only during karyogamy, followed immediately by a meiosis.
The characteristics of the asci shape, number of ascospores, organization of spores, chemical reactions of ascus wall, ascus wall layers etc. Ascospores vary in shape and in size from a few microns to a couple of hundred microns. Both unicellular and septate spores can be found with few e. Lewia or many e. The numbers of nuclei
Explain asexual reproduction in fungi ascospores can differ, e. Ornamentation of spores can serve as an important taxonomic character.
The asci are surrounded by a loose hyphal net in gymnothecia. In
Explain asexual reproduction in fungi the asci develop in a closed spherical ascoma with no definite operculum. A chasmothecium is a special type of cleistothecium wherein the asci form in a single basal fascicle; this ascoma is characteristic of the powdery mildews Erysiphales.
The perithecium is a flask-shaped ascoma in which the asci form in a palisade termed a hymenium. The perithecium has an aperture ostiolum where the spores can emerge. Perithecia can develop singly e.
Sordaria or sometimes are embedded in a compact mycelial structure called a perithecial stroma e. In a pseudothecium the asci develop in cavities of a compact hyphal aggregate ascostroma. The apothecium is a cup-like open ascoma and the asci with sterile cells parahpyses among them develop in a layer hymenium on the open side. The apothecia could have stipes as do the mushroom-form morels or can form closed hypogeous ascomata characteristic of the truffles.
In the general life cycle of hyphal basidiomycetes the monokaryotic phase is relatively short, the hyphae developing from haploid basidiospores fuse somatogamy and produce dikarytic hyphae. This dikaryotic phase dominates the life cycle of the basidiomycetes.
During the sexual reproductive phase the final cells of generative hyphae develop into a basidium. The nuclei fuse karyogamyand the diploid nucleus undergoes meiotic division. The four haploid nuclei migrate into the developing across the spore-holding sterigma.
Development of a holobasidium and basidiospores. In chiastobasidia the second division of the meiosis is parallel with the axis of the basidium, in stichobasidia this division is perpendicular with the axis. A Explain asexual reproduction in fungi is where karyogamy happens, and a metabasidium is the place of the meiosis. In some species where a postmeiotic mitosis happens, the faith of the four additional nuclei is characteristic of the species.
Explain asexual reproduction in fungi may be grouped by several features.
Holobasidia are not divided by walls, whereas fragmobasidia are segmented. When a fungus has heterobasidia, its basidiospores can produce secondary spores, while the basidiospores of fungi with homobasidia germinate with hyphae. Basidia generally produce four exogenous basidiospores, but Explain asexual reproduction in fungi species with less e. Agaricus bisporus or more e. Phallus spores per basidium. The size, shape, and ornamentation of the basidiospores can be characteristic of the taxa, as are the number of nuclei in the spores or the dispersal type active vs.
The dikaryotic hyphae of hyphal Agaricomycotina Explain asexual reproduction in fungi sporocarps basidiocarps or basidiomata where basidia and basidiospores develop. To expand the surface for spore production the trama employ variable anatomies gills, pores, etc.
Basidiomata have two main types according to the spore producing tissue. In the hymenial type the basidia develop in a layer hymenium. Mushrooms with cap pileus and stem stipe generally produce the basidia in a hymenium. The basidioma can develop with its exposed throughout its development gymnocarpic. In hemiangiocarpic basidiomycetes the young basidioma is completely covered by a sheath universal veil which breaks during development of the basidioma, and its remnants form a cup volva at the base of the stem and often leave fragments on the cap surface.
Explain asexual reproduction in fungi veil covers the hymenium partial veil which also breaks, the remaining parts form web-like structures or flaps at the margin of the cap and a ring annulus on the stem. In other taxa basidia can form not only in a hymenium but in a tissue mass called the gleba, that is enclosed by an outer skin or peridium.
Many gastroid fungi e. Rust fungi belonging to the subphylum Puccioniomycotina Basidiomycota illustrate well the potential complexity of a fungal life cycle. The rusts include several important plant pathogens, such as the stem rust Puccinia graministhe crown rust coronata or the coffee rust Hemileia vastatrix.
Rusts are obligate intracellular biotrophic pathogens that develop haustoria in the host cells. Rust life cycles vary in complexity, stem rust being the most complex type. How Fungi Reproduce Asexually? Different types of Spores in Fungi. Methods of Asexual Reproduction in Fungi? Difference between Zoospores and. Asexual reproduction of fungi may take place by a variety of ways. The unicellular forms may multiply by cell division, fission or budding.
Yeasts multiply either by. Spores may be produced either directly by asexual methods or indirectly by sexual reproduction. Sexual reproduction in fungi, as in other living organisms.