Bioagent Trichoderma: A Hope in globally changing environment

Introduction- Over the decades, rampant use of fungicides in plant disease management has led to irreparable damage to environment and also a health hazard. Therefore, the need of the hour is to accelerate adoption of sustainable agricultural practices that have minimal adversarial effect on environment, humans and other living beings.
In this context, adoption of organic agricultural practices that excludes application of the chemicals in agriculture is suggested to reduce the cost of cultivation thereby enhancing profitability of the agricultural produce and could play a great role in doubling of farmers income in India by 2022.
Genus Trichoderma comprises of vast number of fungal isolates which colonize the roots of plants to form a symbiosis and also trigger the growth of plant for their development. Trichoderma has been used successfully for controlling wide range of the soil-borne plant pathogens for which no resistance source has been identified within the gene pool of the crop. Trichoderma can act against a broad range of pathogens including fungi, nematodes, bacteria and viruses. The biological control ability of the Trichoderma species against many plant diseases has been explored by seed or soil application.

Some important facts about Trichoderma :-
Naturally, Trichoderma present in most soils and rhizosphere root of some plants. It can be easily isolated from soil, decomposing organic matter and decaying woods. Trichoderma spp. release various compounds that can promote plant growth and also enhances availability of nitrogen, phosphorous, potassium and other mineral nutrients. Moreover, in some crop species they have been found to enhance tolerance to various abiotic stresses. There are many Trichoderma species commercially available in the market which includes T. viride, T. atrovide, T. harzianum, T. reesi, T. virens, T. Koningii etc. but T. viridiand T. harzianum are two most using species of Trichoderma as a biofertilizer.
These both the species also effective to improve plant tolerance against environmental stress and are used as a biopesticide against various plant pathogens such as Pythium, Verticillium, Fusarium, Phytopthora, Rhizoctonia, Sclerotiniaetc.

Mode of action against plant pathogen and interaction with plants :-
Trichoderma inhibits the pathogen growth by multiple modes which can be either through indirect ways such as competition for space and nutrition, promotion of plant growth mechanisms or directly by mycoparasitism mechanism. Many species of Trichoderma colonize the roots and attack on the pathogens, parasite them and take nutrition from them. The multiple mechanism used by Trichoderma spp. to inhibit pathogen growth are as follows:
1. Mycoparasitism
2. Competition for nutrients, oxygen and space
3. Antibiosis
4. By inducing systemic plant resistance
5. Synthesize various cell wall degrading enzymes etc. to degrades pathogen cell wall
6. metabolizes plant exudates that promote pathogen growth
7. Inactivation of enzymes produces by pathogens

Since the Trichoderma spp. use various combinations of aforementioned mechanisms to restrict growth of target pathogen, selection of the right Trichoderma spp is critical for achieving desired results. Further, environmental conditions, soil pH and crop species also influence the performance of the Trichoderma, so these factors should be also considered while selecting its right strain in the management of the target pest.

Uses of Trichoderma :-
Trichoderma are most useful in disease management of all types of grains, fruits, vegetables like cauliflower, cotton, tobacco, soybean, sugarcane, sugar, eggplant, red gram, Bengal gram, banana, tomato, chilli, potato, lemon, onion, peanut, peas, sunflower, eggplant, Coffee, tea, ginger, turmeric, black pepper, betel vine, cardamom etc.
The usage of a number of species of Trichoderma, T. harzianum, T. polysporum, T. virens and T. viride not only reduced the disease incidence but also increased the yield of vegetables, pulses fruits and cereal crops.

Methods of Application:
There are several ways and some of them are listed below.
a) Seed treatment – Mix 8 to 10 g of Trichoderma formulation in 1 litre of cow slurry for the treatment of 1 kg seeds of seeds before sowing.
b) Seedlings/cuttings – Mix 10 g Trichoderma formulation in one liter water. Dip the seedling/cuttings for the 10 minutes.
c) Nursey treatment – Mix 10-20 g of Trichoderma formulation per 100 m2 nursery bed. The application of organic manures before treatment can enhance the efficiency.
d) Planting Soil Treatment: Apply green Trichoderma powder per hectare after changing sun hemp or mulch in the soil for green manure. Or mix 1 kg of Trichoderma formulation in 100 kg of cultivated manure and cover it with polythene for 7-10 days. Sprinkle the pile with water. Rotate the mixture every 3-4 days and then spread it over the field.

Trichoderma Formulations :-
In market, Trichoderma formulations are available in many brand names, with minimum 2 x 109 or 3 x 106 colony forming units (cfu) per gram in carrier material (talc, vermiculite-wheat bran, pesta granules, coffee husked). The uses of formulation may vary from product to product and crop to crop.

Compatibility with other inputs :-
The Trichoderma formulations have higher efficacy when applied with organic manures such as FYM, composts and biofertilizers like Azospirillum, Rhizobium, Bacillussubtilis and Phosphobacteria. Application of Trichoderma with composts or organic manures has been shown to improved availability of nitrogen, phosphorus and potassium and also enhance the uptake of micronutrients to plants.
Further, since moisture is essential for faster growth survivability of Trichoderma it should be used with water or in moist soil. Also, as far as possible inorganic fertilizers should be avoided for 4-5 days after the application of Trichoderma formulations.

Dr. Monika Karnawat, Associate Professor, School of Agriculture Sciences, Career Point University, Kota

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