Trichoderma: A bio-control agent for management soil born diseases
Trichoderma is a very effective biological mean for plant disease management especially the soil born. It is a free-living fungus which is common in soil and root ecosystems. It is highly interactive in root, soil and foliar environments. It reduces growth, survival or infections caused by pathogens by different mechanisms like competition, antibiosis, mycoparasitism, hyphal interactions, and enzyme secretion.
Colonies, at first transparent on media such as cornmeal dextrose agar (CMD) or white on richer media such as potato dextrose agar (PDA). Mycelium typically not obvious on CMD, conidia typically forming within one week in compact or loose tufts in shades of green or yellow or less frequently white. Yellow pigment may be secreted into the agar, especially on PDA. A characteristic sweet or 'coconut' odor is produced by some species.
Conidiophores are highly branched and thus difficult to define or measure, loosely or compactly tufted, 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. The branches may rebranch, with the secondary branches often paired and longest secondary branches being closest to the main axis. All primary and secondary branches arise at or near 90° with respect to the main axis. The typical Trichoderma conidiophores with paired branches assumes a pyramidal aspect.
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 (gliocladium-like). Phialides may be densely clustered on wide main axis (e.g. T. polysporum, T. hamatum) or they may be solitary (e.g. T. longibrachiatum).
Conidia typically appear dry but in some species they may be held in drops of clear green or yellow liquid (e.g. T. virens, T. flavofuscum). Conidia of most species are ellipsoidal, 3-5 x 2-4 µm. Conidia are typically smooth but tuberculate to finely warted conidia are known in a few species.
Synanamorphs are formed by some species that also have typical Trichoderma pustules. Synanamorphs are recognized by their solitary conidiophores that are verticillately branched and that bear conidia in a drop of clear green liquid at the tip of each phialide.
Chlamydospores may be produced by all species, but not all species produce chlamydospores on CMD at 20° C within 10 days. Chlamydospores are typically unicellular subglobose and terminate short hyphae; they may also be formed within hyphal cells. Chlamydospores of some species are multicellular (e.g. T. stromaticum).
Teleomorphs of Trichoderma are species of the ascomycete genus Hypocrea Fr. These are characterized by the formation of fleshy, stromata in shades of light or dark brown, yellow or orange. Typically the stroma is discoidal to pulvinate and limited in extent but stromata of some species are effused, sometimes covering extensive areas. Stromata of some species (Podostroma) are clavate or turbinate. Perithecia are completely immersed. Ascospores are bicellular but disarticulate at the septum early in development into 16 part-ascospores so that the ascus appears to contain 16 ascospores. Ascospores are hyaline or green and typically spinulose. More than 200 species of Hypocrea have been described but only few have been grown in pure culture and fewer have been redescribed in modern terms.
Benefits of Trichoderma
- Disease Control: 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, viz. Fusarium, Phytopthara, Scelerotia etc.
- Plant Growth Promoter: Trichoderma strains solubilize phosphates and micronutrients. The application of Trichoderma strains with plants increases the number of deep roots, thereby increasing the plant's ability to resist drought.
- Biochemical Elicitors of Disease: Trichoderma strains are known to induce resistance in plants. Three classes of compounds that are produced by Trichoderma and induce resistance in plants are now known. These compounds induce ethylene production, hypersensitive responses and other defense related reactions in plant cultivars.
- Transgenic Plants: Introduction of endochitinase gene from Trichoderma into plants such as tobacco and potato plants has increased their resistance to fungal growth. Selected transgenic lines are highly tolerant to foliar pathogens such as Alternaria alternata, A. solani, and Botrytis cirerea as well as to the soil-borne pathogen, Rhizectonia spp.
- Bioremediation: Trichoderma strains play an important role in the bioremediation of soil that are contaminated with pesticides and herbicides. They have the ability to degrade a wide range of insecticides: organochlorines, organophosphates and carbonates.
Biocontrol mechanisms of Trichoderma:
The Trichoderma may suppress the growth of the pathogen population in the rhizosphere through competition and thus reduce disease development. It produces antibiotics and toxins such as trichothecin and a sesquiterpine, Trichodermin, which have a direct effect on other organisms. The antagonist (Trichoderma) hyphae either grow along the host hyphae or coil around it and secrete different lytic enzymes such as chitinase, glucanase and pectinase that are involved in the process of mycoparasitism. Examples of such interactions are T. harzianum acting against Fusarium oxyporum, F. roseum, F. solani, Phytophthara colocaciae and Sclerotium rolfsii. In addition, Trichoderma Enhances yield along with quality of produce. Boost germination rate. Increase in shoot & Root length Solubilizing various insoluble forms of Phosphates Augment Nitrogen fixing. Promote healthy growth in early stages of crop. Increase Dry matter Production substantially. Provide natural long term immunity to crops and soil.
Method of application:
- Seed treatment: Mix 6 - 10 g of Trichoderma powder per Kg of seed before sowing.
- Nursery treatment: Apply 10 - 25 g of Trichoderma powder per 100 m2 of nursery bed. Application of neem cake and FYM before treatment increases the efficacy.
- Cutting and seedling root dip: Mix 10g of Trichoderma powder along with 100g of well rotten FYM per liter of water and dip the cuttings and seedlings for 10 minutes before planting.
- Soil treatment: Apply 5 Kg of Trichoderma powder per hector after turning of sun hemp or dhainch into the soil for green manuring. Or Mix 1kg of Trichoderma formulation in 100 kg of farmyard manure and cover it for 7 days with polythene. Sprinkle the heap with water intermittently. Turn the mixture in every 3-4 days interval and then broadcast in the field.
- Plant Treatment: Drench the soil near stem region with 10g Trichoderma powder mixed in a liter of water
Important commercial formulations are available in the name of Sanjibani, Guard, Niprot and Bioderma. These formulations contain 3x106 cfu per 1 g of carrier material. Talc is used as carrier for making powder formulation.
Used in Damping off caused by Pythium sp. Phytophthora sp., Root rot caused by Pellicularis filamentosa, Seedling blight caused by Pythium, Collar rot caused by Pellicularia rolfsii, Dry rot caused by Macrophomina phaseoli, Charcoal rot caused by Macrophomina phaseoli, Loose smut caused by Ustilago segetum, Karnal bunt diseases, Black scurf caused by Rhizoctonia solani, Foot rots of Pepper and betel vine and Capsule rot of several crops. Effective against silver leaf on plum, peach & nectarine, Dutch elm disease on elm's honey fungus (Armillaria mellea) on a range of tree species, Botrytis caused by Botrytis cinerea, Effective against rots on a wide range of crops, caused by fusarium, Rhizoctonia, and pythium, and sclerotium forming pathogens such as Sclerotinia & Sclerotium
Trichoderma is most useful for all types of Plants and Vegetables such as cauliflower, cotton, tobacco, soybean, sugarcane, sugarbeet, eggplant, red gram, Bengal gram, banana, tomato, chillies, potato, citrus, onion, groundnut, peas, sunflower, brinjal, coffee, tea, ginger, turmeric, pepper, betel vine, cardamom etc.
- Don't use chemical fungicide after application of Trichoderma for 4-5 days.
- Don't use trichoderma in dry soil. Moisture is a essential factor for its growth and survivability.
- Don't put the treated seeds in direct sun rays.
- Don't keep the treated FYM for longer duration.
Trichoderma is compatible with Organic manure Trichoderma is compatible with biofertilizers like Rhizobium, Azospirillum, Bacillus Subtilis and Phosphobacteria.
Trichoderma can be applied to seeds treated with metalaxyl or thiram but not mercurials. It can be mixed with chemical fungicides as tank mix.
Trichoderma's mycelium parasitising to mycelium of Pythium
Submitted by Rakesh Kumar Singh on Tue, 06/07/2010 - 15:59