Trichoderma harzianum
This article needs additional citations for verification. (August 2009) |
Trichoderma harzianum | |
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Fungi |
Division: | Ascomycota |
Class: | Sordariomycetes |
Order: | Hypocreales |
Family: | Hypocreaceae |
Genus: | Trichoderma |
Species: | T. harzianum
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Binomial name | |
Trichoderma harzianum Rifai, (1969)
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Synonyms | |
Sporotrichum narcissi Tochinai & Shimada, (1930) |
Trichoderma harzianum is a
Taxonomy and genetics
Most Trichoderma strains have no sexual stage but instead produce only asexual spores. However, for a few strains the sexual stage is known, but not among strains that have usually been considered for biocontrol purposes. The sexual stage, when found, is within the
Genetics
Most strains are highly adapted to an asexual life cycle. In the absence of meiosis, chromosome plasticity is the norm, and different strains have different numbers and sizes of chromosomes. Most cells have numerous nuclei, with some vegetative cells possessing more than 100. Various asexual genetic factors, such as parasexual recombination, mutation and other processes contribute to variation between nuclei in a single organism (thallus). Thus, the fungi are highly adaptable and evolve rapidly. There is great diversity in the genotype and phenotype of wild strains.
While wild strains are highly adaptable and may be
Mycoparasitism
Trichoderma spp. are fungi that are present in nearly all soils. In soil, they frequently are the most prevalent culturable fungi. They also exist in many other diverse habitats.
Trichoderma readily colonizes plant roots and some strains are rhizosphere competent i.e. able to grow on roots as they develop. Trichoderma spp. also attack, parasitize and otherwise gain nutrition from other fungi. They have evolved numerous mechanisms for both attack of other fungi and for enhancing plant and root growth. Different strains of Trichoderma control almost every pathogenic fungus for which control has been sought. However, most Trichoderma strains are more efficient for control of some pathogens than others, and may be largely ineffective against some fungi.
Trichoderma spp. continue to be a major source of contamination and crop loss for mushroom farmers.
References
Bibliography
- Yedidia, I., Benhamou, N., and Chet, I. 1999. Induction of defense responses in cucumber plants (Cucumis sativus L.) by the biocontrol agent Trichoderma harzianum. Appl. Environ. Microbiol. 65: 1061–1070.
- Bissett, John (November 1991). "A revision of the genus Trichoderma. III. Section Pachybasium". Canadian Journal of Botany. 69 (11): 2373–2417. doi:10.1139/b91-298.
- W. Gams and W. Meyer. What Exactly Is Trichoderma harzianum? Mycologia. Vol. 90, No. 5 (Sep. - Oct., 1998), pp. 904-915