''Trichoderma harzianum'' is a

fungus A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately fr ...

that is also used as a

fungicide Fungicides are biocidal chemical compounds or biological organisms used to kill parasitic fungi or their spores. A fungistatic inhibits their growth. Fungi can cause serious damage in agriculture, resulting in critical losses of yield, quality ...

. It is used for

foliar A leaf ( : leaves) is any of the principal appendages of a vascular plant stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, ste ...

application, seed treatment and soil treatment for suppression of fungal pathogens causing various fungal plant diseases. Commercial biotechnological products such as 3Tac have been useful for treatment of ''

Botrytis Botrytis may refer to: * ''Botrytis'' (fungus), the anamorphs of fungi of the genus '' Botryotinia'' **''Botrytis cinerea'', a mold important in wine making *Botrytis, the cauliflower cultivar group of ''Brassica oleracea ''Brassica oleracea'' is ...

'', ''

Fusarium ''Fusarium'' is a large genus of filamentous fungi, part of a group often referred to as hyphomycetes, widely distributed in soil and associated with plants. Most species are harmless saprobes, and are relatively abundant members of the soil mi ...

'' and ''Penicillium'' sp.3Tac product page
/ref> It is also used for manufacturing

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...

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 Ascomycota is a phylum of the kingdom Fungi that, together with the Basidiomycota, forms the subkingdom Dikarya. Its members are commonly known as the sac fungi or ascomycetes. It is the largest phylum of Fungi, with over 64,000 species. The defi ...

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.

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 The genotype of an organism is its complete set of genetic material. Genotype can also be used to refer to the alleles or variants an individual carries in a particular gene or genetic location. The number of alleles an individual can have in a ...

and phenotype of wild strains. While wild strains are highly adaptable and may be

heterokaryotic A heterokaryon is a multinucleate cell that contains genetically different nuclei. Heterokaryotic and heterokaryosis are derived terms. This is a special type of syncytium. This can occur naturally, such as in the mycelium of fungi during sexual ...

(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.

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. *
W. Gams and W. Meyer. What Exactly Is ''Trichoderma harzianum''? Mycologia. Vol. 90, No. 5 (Sep. - Oct., 1998), pp. 904-915

External links

Index Fungorum

USDA ARS Fungal Database
{{Taxonbar, from=Q3003918 Fungal pest control agents harzianum Fungi described in 1930