Alternaria
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Conidia chain of an Alternaria mushroom |
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Alternaria is a species of mold that is widespread worldwide. Alternaria iscounted as a black fungus . There are around 40 species. The genus is one of the so-called Fungi imperfecti .
Way of life
Fungi of the genus Alternaria are widespread in nature. Most of them live among other things as decomposers ( saprophytes ) of organic matter, which makes them very important in the nutrient cycle. Their mycelium survives on dead plant material in the soil . Like other organisms that primarily feed on dead substances, they can also be harmful.
Alternaria species (especially A. alternata ) can be used as saprophytes, e.g. B. colonize and damage substrates in the contact area of humans. This affects food when it is stored appropriately moist. In addition, building and living materials (wood, wallpaper) are infested in a damp environment.
In addition, some Alternaria species can also live parasitically on plants. They preferentially attack weakened individuals, on whom they cause more or less serious fungal diseases.
Alternaria species need a relatively high amount of moisture (> 22%) to grow . With regard to the a w value, this value depends on the respective substrate.
Importance in crop production
Economically important plant diseases caused by Alternaria species are dry spot disease ( A. solani ) and the closely related spray blotch disease ( A. alternata ) on potatoes, as well as hard rot on the potato tubers (recognizable by dark, sunken spots with radial folds of the skin ).
A. helianthi causes leaf spot disease in sunflowers . In rapeseed , a plant disease caused by Alternaria species is rapeseed blackness ( A. brassicae , A. brassicola ), which also affects other cabbage and vegetable plants. Alternaria appears on cereals , in association with other genera such as Cladosporium or Epicoccum , as a so-called black fungus when it attacks ears and stalks as a weak parasite with delayed harvest, especially in damp weather.
Health relevance
Alternaria species are among the mycotoxin producers. Little is known about the harmfulness to humans. The metabolites are u. a. Tenuazonic acid (has an insecticidal effect), Altenuen, Tentoxin, Alternariol and Alternariol monoethyl ether. Alternaria is often identified as an allergen ( mold allergy )
Alternaria species can occasionally cause skin infections in animals , see also phaeohyphomycosis .
Systematics
The genus Alternaria belongs to the Fungi imperfecti , d. H. their representatives do not form asci , but only reproduce asexually through conidia . Through genetic studies, however, the genus Lewia as a teleomorph could be assigned to the genus as a whole . Species that have to be assigned to other teleomorphs are therefore no longer included in Alternaria .
Significant species
- Alternaria alternata (Fr.) Keissl .: Most common Alternaria species, important mold in building and living materials, one of the blackening fungi on cereals and the cause of spray stain on potatoes.
- Alternaria brassicae (Berk.) Sacc .: Infects mainly plants of the Brassicaceae family ( cruciferous vegetables ). Rape and various types of cabbage are of particular economic interest.
- Alternaria citri Ellis & N.Pierce: Infects citrus fruits (black spots appear; then partial maceration of the tissue). Occasionally, tomatoes are also attacked.
- Alternaria solani Sorauer: Infects nightshade family , here v. a. Potatoes (dry spot disease), tomatoes and peppers.
- Alternaria tenuissima (Kunze) Wiltshire: Species widespread in the soil ( mycotoxins ) and weak parasite on vegetables and fruit (not host-specific).
literature
- Klaus H. Domsch, Walter Gams , Traute-Heidi Anderson: Compendium of Soil fungi. 2 volumes. Academic Press, London et al. 1980, ISBN 0-12-220401-8 (Vol. 1), ISBN 0-12-220402-6 (Vol. 2).
- Patrick Joly: Le Genre Alternaria. Recherches physiologiques, biologiques et systématiques (= Encyclopedie Mycologique. 33, ISSN 0301-4290 ). P. Lechevalier, Paris 1964.
- Lutz Roth, Hanns K. Frank, Kurt Kormann: Poison mushrooms, mushroom poisons. Molds, mycotoxins; Occurrence, ingredients, fungal allergies, food poisoning. Nikol Verlagsgesellschaft, Hamburg 2001, ISBN 3-933203-42-2 .
- Bärbel Schöber-Butin, Volker Garbe, Gerhard Bartels: Color atlas diseases and pests on agricultural crops. Potato, sugar beet, rapeseed, grain, corn, sunflower, hemp. Eugen Ulmer, Stuttgart 1999, ISBN 3-8001-4133-7 .
Individual evidence
- ^ Opinion of the Federal Institute for Risk Assessment (BfR) from 2003; accessed in June 2015
- ↑ Alternaria species in the Fungorum index