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Biology and Biotechnological applications of Trichoderma
Transcript of Biology and Biotechnological applications of Trichoderma
Bio-pesticides can be living organisms which can destroy agricultural pests. Their most important advantages are that they are target specific, they don’t destroy beneficial organisms and they don’t leave harmful residues.
Some of the most important microbial bio-pesticides include Trichoderma. The use of this genus to control plant pests has become common for a number of years. Trichoderma is effective against root pathogens and is used for seed treatment. It has been one of the oldest and most widely used fungi-based pesticides in the world
Biology of Trichoderma
They are favoured by the presence of high levels of plant roots, which they colonize readily. Some strains are highly rhizosphere competent, able to colonize and grow on roots as they develop
Conidiophores are often formed in distinct concentric rings or borne along the scant aerial hyphae.
Main branches of the conidiophores produce lateral side branches that may be paired or not, the longest branches distant from the tip and often phialides arising directly from the main axis near the tip.
Phialides are typically enlarged in the middle but may be cylindrical or nearly subglobose.
Phialides may be held in whorls, at an angle of 90° with respect to other members of the whorl, or they may be variously penicillate. Phialides may be densely clustered on wide main axis or they may be solitary.
Fungi species belonging to Trichoderma are present in nearly all soils and other diverse habitats. They are frequently the most prevalent culturable fungi from soil.
Many species in this genus can be characterized as opportunistic avirulent plant symbionts. This refers to the ability of several Trichoderma species to form mutualistic endophytic relationships with several plant species
Taxonomy and Genetics
Traditional taxonomy was based on differences in morphology, primarily of the asexual sporulation apparatus; however molecular approaches are now being used.
Most Trichoderma strains have no sexual stage but instead produce only asexual spores.
Different Trichoderma 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).
By: Souhir BETTAIBI
The organism grows and ramifies as typical fungal hyphae, 5 to 10 µm in diameter. Asexual sporulation occurs as single-celled, usually green, conidia that are released in large numbers. Intercalary resting chlamydospores are also formed, these also are single celled, although two or more chlamydospores may be fused together.
Trichoderma's strategies for combat
Trichoderma has the ability to attack pathogens via different modes of action:
• Solubilisation and sequestration of inorganic nutrients
• Inactivation of the pathogens enzymes
• Competition for nutrients or space
• Tolerance to stress
Trichoderma as a protector of plant health
Trichoderma fungi have been shown:
-to be opportunistic plant symbionts
-to enhance systemic resistance of plants and a response which is improved by ceratoplatanin family proteins.
-to enhanced root proliferation
- better growth and protection of the plants against toxic chemicals.
- be applied for remediation of polluted soil and water by treatment of appropriate plants with spores.
-more than 100 metabolites with antibiotic activity including polyketides, pyrones, terpenes
- metabolites derived from amino acids, and polypeptides
- volatile organic compounds
-A wide variety of peptaibols
Plant growth promoter
Trichoderma strains solubilize phosphates and micronutrients.
It increases the number of deep roots, thereby increasing the plant's ability to resist drought. corn whose roots are colonized by Trichoderma strain T-22 (harzianum,viride,koningii,hamatum) require about 40% less nitrogen
fertilizer than corn whose roots
lack the fungus.
Biochemical elicitors of plant disease resistance
Trichoderma strains are known to induce resistance in plants. It produces compounds that induce:
other defense related reactions in plant cultivars
Trichoderma is a potent biocontrol agent and used extensively for soil born diseases.
It has been used successfully against pathogenic fungi belonging to various genera
Introduction of endochitinase gene from Trichoderma into plants such as tobacco and potato plants has increased their resistance to fungal growth.
Several genes have been cloned from Trichoderma that offer great promise to produce transgenic crops that are resistant to plant diseases.
These genes, which are contained in Trichoderma and many other beneficial microbes, are the basis for much of "natural" organic crop protection and production
Trichoderma strains play an important role in the bioremediation of soil that are contaminated by pesticides and herbicides.
They have the ability to degrade a wide range of insecticides:
Production of cellulases and plant cell-degrading enzymes
Research is nowadays particularly focused on improvement of efficiency of the enzyme cocktail produced by trichoderma in order :
-to decrease overall costs of production of bioethanol from cellulosic waste material
-applications in the pulp and paper industry
High levels of cellulase and hemicellulase gene expression can be achieved all used on agricultural or industrial byproducts.
Trichoderma's heterologous protein production
Nowadays, Trichoderma is one of the most commonly used filamentous fungi for heterologous protein production:
immunologically active antibody fragments
feed, food and textile
Trichoderma species are used commercially for production of cellulases and other enzymes that
-degrade complex polysaccharides (used in the food and textile industries)
-are used in poultry feed to increase the digestibility of hemicelluloses from barley or other crops.
-are applied to improve the brewing process (B-glucanases), as macerating enzymes in fruit juice production (pectinases, cellulases, hemicellulases)
-are used as feed additive in livestock farming (xylanases) and for pet food.
There are 89 species in the Trichoderma genus
As opportunistic plant symbionts and effective mycoparasites, numerous species of the genus Trichoderma have the potential to become commercial biofungicides.
Besides this major application, Trichoderma become increasingly important for environmentally safe production of enzymes and antibiotics used in many industrial process.