- Trichoderma harzianum
name = Trichoderma harzianum
familia = "
genus = "
species = "T. harzianum"
binomial = "Trichoderma harzianum"
binomial_authority = Rifai, (1969)
synonyms = "Sporotrichum narcissi" Tochinai & Shimada, (1930)
"Trichoderma lignorum var. narcissi" (Tochinai & Shimada) Pidopl., (1953)
"Trichoderma narcissi" (Tochinai & Shimada) Tochinai & Shimada, (1931)
Trichoderma harzianum is a
fungusthat is also used as a fungicide. It is used for foliarapplication, seed treatment and soil treatment for suppression of various disease causing fungal pathogens. Commercial biotechnological products such as 3Tac have been useful for treatment of Botrytis, Fusariumand Penicillium sp. [ [http://www.avancebiotechnologies.com/3tace.html 3Tac product page] ] . It is also used for manufacturing enzymes.
* [http://www.speciesfungorum.org/Names/Names.asp Index Fungorum]
* [http://nt.ars-grin.gov/fungaldatabases USDA ARS Fungal Database]
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 Ascomycetes in the genus Hypocrea. Traditional taxonomy was based upon differences in morphology, primarily of the asexual sporulation apparatus, but more molecular approaches are now being used. Consequently, the taxa recently have gone from nine to at least thirty-three species.
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 heterokaryotic (contain nuclei of dissimilar genotype within a single organism) (and hence highly variable), strains used for biocontrol in commercial agriculture are, or should be, homokaryotic (nuclei are all genetically similar or identical). This, coupled with tight control of variation through genetic drift, allows these commercial strains to be genetically distinct and nonvariable. This is an extremely important quality control item for any company wishing to commercialize these organisms.
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