बायोएजेंट ट्राइकोडर्मा: वैश्विक बदलते परिवेश में एक उम्मीद
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.
Among the available disease management strategies, microbial fungicides are considered safe as they are not harmful to beneficial insects, animals, humans and are also free from any environmental hazard. A free-living fungus Trichoderma seems to be the first biocontrol agent available commercially for management in plant diseases.
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.
Besides, the diseases controlling agent, it also has plant growth promoting ability, so it is considered a preferred input in Integrated Disease Management (IDM) systems. The biological control ability of the Trichoderma species against large number of diseases has been explored by seed or soil application.
Some important facts about Trichoderma
Naturally, Trichodermais present in most soils and rhizospheric 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. Koningiietc. 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:
- Mycoparasitism
- Competition for nutrients, oxygen and space
- Antibiosis
- By inducing systemic plant resistance
- Synthesize various cell wall degrading enzymes etc. to degrades pathogen cell wall
- metabolizes plant exudates that promote pathogen growth
- 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 Trichodermaspp 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.
Efficacy of Trichoderma against several diseases in various crop plants:
Vegetable crops
Tomato (Solanumlycopersicum):
The crop is susceptibleto a wide range of diseases like late blight caused by P. infestans, early blight by A. solani, wilt caused by F. oxysporumf. sp. lycopersici, damping off by P. aphanidermatum, collar rot by S. rolfsii, bacterial leaf spot by Xanthomonascampestrispv. vesicatoria, and bacterial wilt by Ralstoniasolanacearum.
Among them, the diseases caused by soil-borne fungi or fungal like pathogens remained a challenging task to manage. The usage of a number of species of Trichoderma not only reduced the disease incidence but also increased the yield of tomato.
Onion (Alliumcepa):
Six major diseases Alternaria alternate causing foliar blight of onion, Alternariaporri causingpurple blotch of onion, damping-off and basal rot by F. oxysporumf. sp. cepae and Pythiumsp, white rot by S. rolfsii and black mould by A. niger were found to be associated withthe crop.
The usage of a number of species of Trichoderma not only reduced the disease incidence but also increased the yield of onion.
Eggplant or brinjal (Solanummelongena L. ):
Fungi like A. solani, F. solani, C. gloeosporioides, B. cinerea, Penicillium sp. , Rhizopusniger, Curvularialunata and Botryodiplodiatheobromae are important pathogens which cause damage to the fruit through out the year.
The usage of a number of species of Trichoderma not only reduced the disease incidence but also increased the yield of brinjal.
Chilli (Capsicum annum):
Among the fungal diseases, damping off caused by S. rolfsii, F. oxysporum, Pythium spp. , R. solani and Phytophthorasp. are widely prevalent in the country. The usage of a number of species of Trichoderma not only reduced the disease incidence but also increased the yield of chilli.
Cauliflower (Brassicaoleracea L. var. botrytis) and cabbage (Brassica oleracea L. var. capitata):
Major pathogens which cause crop losses are club root caused by Plasmodiophorabrassicae, black rot by Xanthomonascampestris, wire stem by Rhizoctoniasolani, leaf spot by A. brassicae, leaf blight by A. brassiciola, dampingoff by R. solani, Pythium, Phytophthora, CorticiumandFusarium.
The usage of a number of species of Trichoderma not only reduced the disease incidence but also increased the yield of cauliflower.
Potato (Solanumtuberosum):
There are manythreatening diseases which reduce the yield of the crop such as late blight (Phythophthorainfestans), commonscab (Streptomyces scabies), dry rot (Fusarium spp. ), black scurf and bacterial wilt (Ralstoniasolanacearum). The usage of a number of species of Trichoderma not only reduced the disease incidence but also increased the yield of potato.
The usage of a number of species of Trichoderma not only reduced the disease incidence but also increased the yield of tomato, onion, brinjal, chilli, cauliflower and potato.
Pulse crops
Chickpea (Cicer arietinum L. ):
It frequently attacked mainly by a wilt caused by Fusariumoxysporum f. sp. ciceri, stem rot by Sclerotiniasclerotiorum and damping off caused by R. solani which are worldwide in distribution.
Blackgram (Vigna mungo L. ) and Green gram (Viginaradiata L. ):
R. solani, S. rolfsii, M. phaseolina, Alternariaalternata, FusariumsolaniandColletotrichumcapsici of Mung bean are some fungal pathogens which causes diseases in both these fungi.
Lentil (Lensculinaris):
It frequently attacked mainly by a wilt caused by Fusariumoxysporum f. sp. Lentis, stem rot by Sclerotiniasclerotiorum and damping off caused by R. solaniwhich cause severe loss in lentil yield every season.
The usage of a number of species of Trichoderma not only reduced the disease incidence but also increased the yield of chickpea, blackgram and lentil.
Fruit crops
Guava (Psidiumguajava):
Pre-harvest diseases like canker, die back, declineetc. affect the plant growth and production, while post-harvest diseases such as Phytophthora, Macrophominaand several others spoil the fruits in field, storage and intransit. Gliocladiumroseum is also identified as a most potent pathogen besides F. oxysporumf. sp. psidii and F. solani.
Mango (Mangiferaindica):
It suffers from greateconomic loss due to many pathogens e. g. F. moniliformevar. subglutinanscausing mango malformation. Biocontrol was used by some groups against different pathogens and found successful by many of them. The usage of a number of species of Trichoderma not only reduced the disease incidence but also increased the yield of guava and mango.
Uses of Trichoderma
Trichodermaare 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 Trichodermaformulation in oneliter 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 etc. ) . The uses of formulation may vary from product to product and crop to crop.
Compatibility with other inputs
The Trichodermaformulations 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 manureshas 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 Trichodermaitshould 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.
Authors
1*ShaiyJaveria, and 2 Dr Amit Kumar Singh
1 JRF, SERB, Division of Seed science and Technology, ICAR-IARI, New Delhi
2 Senior scientist, National Bureau of plant Genetic Resources, New Delhi,
*Email: