Corn smut ( Ustilago maydis )
The fire Fungal ( Ustilaginales ) are by far the most species-rich group of smut fungi ( Ustilaginomycotina ). The most species-rich genera Ustilago and Sporisorium. All representatives are parasitic flowering plants.
Characteristics and ecology
The smut fungus -like form their spores mostly in the flowers ( ovary or anther ) of their hosts. Fruiting bodies are not formed. You have dark-colored, thick-walled teliospores germinate and with mostly four-cell Phragmobasidien.
They parasitize on higher plants and grow intercellular.
The basidiospores are determined bipolar ( and -). They germinate into a haploid yeast-like mycelium that lives exclusively saprobiontisch, it can not parasitize on plants. If two differently determined cells meet, the result is formation of a Kopulationsschlauches. This moves the contents of one cell to another over: there is a cell fusion ( plasmogamy ), which retained the two nuclei. The result is a binucleate ( dikaryotic ) cell. From this a binucleate hypha grows from that can now infect a host plant.
The binucleate mycelium spreads in the host plant intercellular out. It grows with the Apikalmerstem without causing any symptoms. In species-specific organs, such as anthers or in the ovary, the mycelium changes to intracellular growth, destroys the host tissue and forms dense Myzellager. In these arise globular swellings, get the thick brown-black cell walls and disconnect from the mycelium: smut spores, so named after the coal dust -like appearance. The smut spores are young basidia homologous in them takes karyogamy. They are called probasidia. In most species overwinter smut spores and germinate in the spring of forming a querseptierten Hyphenschlauches. The meiosis takes place. At the end of meiosis, there are four cells, each with a haploid nucleus. This technique, known as Promyzel stage corresponds to a Phragmobasidie . From these spores are laterally constricted ( sporidia ), this can happen several times in succession. Thus, the haplo - dikaryotic cycle is complete.
The fire Fungal are economically important pests of crop plants, especially in cereals. Examples are corn smut ( Ustilago maydis ), the oat smut ( Ustilago avenae ), barley loose smut ( Ustilago hordei ) and wheat smut ( Ustilago tritici ).
The smut fungus -like form as a monophyletic group one of the two orders of Ustilaginomycetes.
In recent years, the species-rich family of the smut fungus relatives ( Ustilaginaceae ) was divided into several smaller families, regrouping is not yet complete. The fire Fungal be Begerow et al. (2006 ) can be subdivided as follows:
- Anthracoideaceae: Cyperaceae and Juncaceae hosts are. Anthracoidea
- Planet Ella
- The following genera are placed in the family Anthracoideaceae provisionally:
- Pseudozyma ( Anamorphic )
- The following genera are placed in the family Ustilaginaceae provisionally: