Trchoderma Spp.: Their Impact in Crops Diseases Management

Abstract

Trichoderma species, a cosmopolitan fungi, present in all types of soil, manure, and decaying plant tissues that can degrade domestic waste relatively quickly without emitting bad odors. Trichoderma is recognized worldwide as potential fungal bio-control agents for the management of various foliar and soil-borne plant pathogens, highly compatible with sustainable agriculture and play major role as a component of integrated pest management. Bio-control agents are an antagonism and eco-friendly approach for managing plant diseases. Trichoderma as bioagent area effective not only against soil-borne plant pathogens, but also against nematodes without any adverse effect on beneficial microbes. Trichoderma is capable of growth promotions in crops. There are two major mass production methods of Trichoderma spp. viz., solid state fermentation and liquid state fermentation. In solid, fungus is grown on various cereal grains, agricultural wastes, and byproducts, and these products are used mainly for direct soil application to suppress the soil-borne inoculums. In a liquid state, Trichoderma is grown on media such as molasses and yeast in deep tanks and fermentation can be made into different formulations such as dusts, granules, pellets, wettable powders. As seed-treating agents or bio-priming agents, Trichoderma formulations can be successfully used against several soil-borne diseases caused by Pythium, Phytophthora, Rhizoctonia, Fusarium and Sclerotium, spp. in several crops.

1. Introduction

The genus Trichoderma strains are versatile, highly competent, root colonizers, cosmopolitan in nature, fast growing in culture; produce numerous green spores and chlamydospores as used for eco-friendly disease management which is important in organic agriculture. Trichoderma species have been used as a biological control, biofertilizers, source of enzymes and protein producers. Trichoderma increase the fertility of soils and improved plant growth beyond disease control [1, 2]. Trichoderma strains colonization on root and enhances root growth, root area, root length, increases in dry weight, shoot length and leaf area [3]. Plant growth promotion is due to the production of plant hormones and the uptake of nutrients by the plant [4]. They promote root growth, nutrient availability and release plant growth regulators [5]. Application in plants and can prevent the infection of diseases through induced resistance, competition for nutrients and space, antibiosis, hyperparasitism. Induced resistance may be local or systemic. Trichoderma species are cosmopolitan fungi, frequently present in all types of soil, manure and decaying plant tissues [6]. Trichoderma species are a well known bio-control agent, utilize chitinolytic enzymes to disintegrate and degrade the pathogen’s cell walls and colonize on the root, soil and foliar environments suppressing phytopathogens [7, 8, 9]. Trichoderma spp. is highly interactive in root, soil and foliar in the environment, parasitize other fungi [10]. Trichoderma was first described in 1794 and its perfect stage (Hypocrea). Morphological characters and an online identification tool are available for identification of species within the genus Trichoderma and recognized from long back as biological agents, control of plant disease and also their ability to increase root growth and development, crop productivity, resistance to abiotic stresses, and uptake and use of nutrients. Application of Trichoderma harzianum to plants resulted in improved seed germination, increased plant size, and augment of leaf area and weight [11]. Trichoderma spp. is well documented and effective biological control agent of soil-borne diseases by secreting several cell wall degrading enzymes, antibiotics [12, 13]. They have produced extracellular proteins and fungi toxic substances for understanding the role in antagonistic as playing in biological interactions [14]. Trichoderma reesei and Trichoderma harzianum are capable of producing proteinase, mananase, laminarinase and chitinase that the nature of antagonism by mycoparasitism [15]. Trichoderma, a soil-borne mycoparasitic fungus has been shown effective against many.soil borne phytopathogens [16, 17, 18, 19]. Trichoderma viride and Trichoderma harzianum found to highly antagonistic against Sclerotium rolfsii and management of diseases in vegetables and legumes [20, 21, 22, 23, 24, 25, 26, 27, 28, 29]. Trichoderma harzianum is an antagonist probably their ability to fight for cellulose in the mucilage layer at the root surface [30]. Trichoderma spp. have been reported to control soil-borne plant pathogens viz., Rhizoctonia solani Khun., Sclerotium rolfsii (Sacc.) Curzi., Pythium and Fusarium spp. [31, 32, 33, 34, 35, 36] and Botrytis rot of fruits on grape. Trichoderma harzianum, widely tested as potential biological control agents many soil-borne plant pathogens [10, 37, 38, 39]. Trichoderma hamatum produced inhibitory volatiles compounds that reduced the gray mold of snap bean pods and blossom [40, 41]. Trichoderma harzianum T39 less effective in cucumber fruit and stem gray mold under wet and below 20°C compare to elevated temperatures [42]. Trichoderma harzianum inoculated in root increased peroxidase and chitinase activities in leaves of cucumber seedlings [43]. Trichoderma harzianum T39 effectively controlled Botrytis diseases, white mold (Sclerotinia sclerotiorum), leaf mold (Cladosporium fulvum) and powdery mildew (Sphaerotheca fusca) [42, 44, 45, 46, 47]. Trichoderma bio-control agents are used against fungal phyto-pathogens such as Phythium, Phytophthora, Macrophomina, Aspergillus, Rhizoctonia and Fusarium through the mechanism of mycoparasitism, antibiotics and competition for food and space [5, 48]. Induced resistance is an important mode of bio-control in vegetative tissues [49, 50]. T. harzianum induced systemic resistance in the plant against fungal and bacterial pathogens [8, 9]. Induced systemic resistance caused by various micro-organisms and protects plants against the soil or foliar pathogens [51]. Trichoderma, Gliocladium and Pythium spp. are known as mycoparasites [46]. Pythium spp. is non specific mycoparasites and interact with many soil borne fungi [52]. Trichoderma virens produces two major antifungal antibiotics- gliotoxin (toxic to Rhizoctonia solani and Pythium ultimum) and gliovirin (toxic to Pythium spp.) [53]. Trichoderma virens, produce the antibiotics gliovirin and gliotoxin as mycoparasite. Trichoderma harzianum T39 is competition for nutrients and interference with the production of pectolytic enzymes against the pathogen, and also prevents the penetration of the host tissue and is shown to induce resistance [54, 55, 56]. Trichoderma harzianum T39 produces protease on leaves against Botrytis cinerea disease development [57]. Secretion of proteolytic enzymes that deactivate pathogenicity related hydrolytic enzymes of pathogenic fungi [58]. Trichoderma viride is involved in bio-control management Sclerotium rolfsii through the proteolytic activity as reported [59]. Trichoderma species can degrade domestic waste quickly without emitting bad odors [60]. The genus Trichoderma has the potential to control plant-parasitic nematodes [7, 61]. Trichoderma harzianum is associated with a reduction in nematode population by parasitizing and killing in the rhizosphere [62]. T. harzianum has a rich source of chitinolytic enzymes which might degrade the eggshell during parasitism of eggs and juveniles [39, 62]. Trichoderma promotes crop productivity, resistance to abiotic stresses and uptake of nutrients [63]. Trichoderma colonization in the roots and soil helps insolubilization of minerals viz.; rock phosphate, Fe, Mn, Cu and Zn and also enhances N-used efficiency [1]. Trichoderma based commercial products are manufactured and marketed worldwide for the management of plant diseases [10, 17].

2. Characters and isolation techniques

Trichoderma is a good bio-control agent as well as a fertility promoter. Trichoderma fungi can produce antibiotics, enzymes that antagonize plant pathogens and hormones that regulate root architecture and promote plant growth. Trichoderma protects a wide range of foliar pathogens. Trichoderma strains have numerous mechanisms for attacking other fungi and enhancing plant and root growth [1]. Trichoderma is colonizing in the rhizosphere and resulted in the increased root, aerial systems and crop yields [64, 65]. Trichoderma has a strong capacity to mobilize and take up soil nutrients and making it more efficient and competitive. Competition for nutrients is the major mechanism used by Trichoderma harzianum to control Fusarium oxysporum f. sp. melonis. Trichoderma spp. produces three kinds of propagules; hyphae, chlamydospores, and conidia [18]. The main propagules of Trichoderma spp. is hyphae and during the drying process losing viability. Chlamydospores and conidia have been used as the active ingredients of Trichoderma spp. based production [66, 67, 68]. Trichoderma fungal conidiophores are highly branched, not verticilate, 1-celled, ovoid, borne in small terminal clusters, loosely or compactly tufted, and often formed in distinct concentric rings (Figure 1). The conidiophore branches with paired and assume a pyramidal feature, chlamydospores produced by all species. Trichoderma strains produce only asexual spores, the sexual stage of Trichoderma belong to the ascomycete genus Hypocrea [69]. Trichoderma is one of the common fungal bio-control agents used worldwide for the management of various foliar and soil borne plant pathogens. Trichoderma fungi are present in most of all types of soils can be isolated from forest and agriculture soils and wood. Several species are beneficial in agriculture. The fungus grows a range between 25 and 30°C of optimal. The most suitable culture media for its cultivation are cornmeal dextrose agar whereas colonies appear transparent, and on potato dextrose agar the colonies appear initially white and then green (Figure 2). Trichoderma can be produced in a liquid or solid fermentation medium.

Figure 1.

Phialid showing production of conidia in highly branched conidiophore (photo credit: Dr. Pranab Dutta & Lipa deb, CPGSAS, CAU (Imphal), Umiam, Meghalaya.

Figure 2.

Pure culture of Trichoderma harzianum in PDA plate (photo credit: Dr. Pranab Dutta, CPGSAS, CAU (Imphal), Umiam, Meghalaya.

3. Mass multiplication

The mass production of Trchoderma for field application and commercial use. There are two methods of production as (i) Solid-state fermentation (ii) Liquid-state fermentation.

3.1 Solid-state fermentation

It is a common method for mass production of Trichoderma. The Trichoderma spp. have been widely grown on solid substrates like sorghum grain, wheat straw, wheat bran, spent tea leaf waste, coffee husk, rice husk, banana leaves, sawdust etc. and their mass multiplication [70, 71, 72]. The commonly used for mass culturing of Trichoderma spp. on the solid substrate as sorghum grain [73], wheat bran-saw dust [74] and other agro-based waste products. Cereal grains like, sorghum, millets, ragi are used as substrates [75]. The grains are moistened, sterilized and inoculated with Trichoderma and incubated for 10–15 days. The dark green spore coating on the grains of Trichoderma produces. These grains can be powdered and used as a seed treatment or grains may use as it is for enhancing FYM for soil application. Wastage substrate potato peel, brinjal, spinach, sugarcane, banana, papaya, guava, tea leaves and pea husk used for the multiplication of Trichoderma harzianum and Trichoderma viride. Trichoderma harzianum multiplied on presoaked and autoclaved Jhangora seeds for 12 days at 28°C, air dried, ground and passed through 50 and 80 mesh sieves simultaneously to obtain the powder of spores [76]. The commercial formulation was prepared by diluting this powder with the talcum powder containing 1% carboxymethyl-cellulose to get the desired concentration of biocontrol agent.

3.2 Liquid fermentation

Trichoderma is grown in a liquid fermentation system on media in stationary/shaker/fermentor and used for field application. The production of Trichoderma in liquid state fermentation includes molasses and brewer’s yeast [77], and Jaggery-soy medium [32, 33]. Viable propagules of Trichoderma harzianum and Trichoderma viride can be obtained within 96 h of fermentation in a fermentor with aeration, agitation, temperature controls [78]. Maximum biomass of Trichoderma spp. in short-time by using the appropriate medium in a fermentor with aeration, agitation, temperature, pH with antifoam controls than in shake-flask cultures and more suitable for industrial production. The liquid fermentation can be separated of biomass with medium and incorporated into dust, granules, pellets, wettable powders or emulsifiable liquids. The carrier is inert as the food base of Trichoderma spp. can be formulated as pellets [79], dust and powders [40, 41] and fluid drill gels [21]. Molasses yeast medium is used for mother culture; it’s prepared by adding of molasses 30 g, yeast 5 g and distiller water 1000 ml. The medium hand out into conical flasks and sterilized at 15 lb. pressure for 15 minutes in an autoclave. After the cooled medium is inoculated with 10 days old fungal disc of Trichoderma viride and then incubated for 10 days for fungal growth, serves as a mother culture. The mother culture was added to the fermentor at the rate of 1.5 lit/50 lit of the medium and incubated at room temperature for 10 days. Then the incubated fungal culture is used for commercial formulation preparation using talc powder.

4. Formulations and application

The formulation depends on the type of application, its combination of active ingredients, such as fungal spores with the inert material as diluents of the desirable form. The formulation developed through standard air dried mats and mixed with the carrier contain 10⁸–10⁹ propagules per gram [80]. Trichoderma is grown in the liquid medium is mixed with talc powder in the ratio of 1: 2 and dried to 8% moisture under shade. Bio-control formulation, distribution and execlution of microbial antagonists [81]. Talc based formulations of Trichoderma viride developed for seed treatment of pulse and rice crops [82]. The commercial formulations of Trichoderma spp. based on carriers are available for controlling plant diseases [83]. Trichoderma formulation prepared based on coffee husk which is a waste from the coffee curing industry [84]. Trichoderma was formulated on press mud to farmers and value-added organic manure by sugar factory [75]. Oil-based formulations are suitable for foliar sprays under dry weather conditions with prolonged shelf life. T. harzianum is an emulsion based formulation with a shelf life of 8 months use for the control of post -harvest decay of apple caused by Botrytis cinerea [37]. The application of Trichoderma is very important for successful diseases management. Das et al. [24] tested three different media amended with and without osmoticant (Mnaitol) viz., potato dextrose broth (PDB), modified Richard’s broth (MRB) and Czapek dox broth (CDB) were tested for biomass production of Trichoderma harzianum. Osmoticant amended MRB was found best for production of maximum sporulation, cfu and dry weight of biomass of the antagonist.

The common methods are seed treatment, seed bio-priming, seedling root dip, and soil application and wound dressing.

4.1 Seed treatment

Seed coating with dry powder of Trichoderma just before sowing is an effective method of antagonist for the management of soil-borne diseases. Seeds coated with a commercial dry powder of Trichoderma just before sowing at 3 to 10 g/kg seed based on seed size [85]. Seed treatment with talc-based and wheat bran based formulations use at 4 g/kg of seed have been recommended [74]. Trichoderma germinates on treated seed surface as they are sown in the soil; on germinating propagules colonize the seedlings roots and rhizosphere [86]. Trichoderma harzianum, Trichoderma virens and Trichoderma viride were found to be effective seed protectants against Pythium spp. and Rhizoctonia solani [87]. Seed treatments are effective against the sheath blight of rice [25], loose smut of wheat [88]. Das et al. [24] reported that seed treatment with osmoticant amended talc based bioformulation of Trichoderma harzianum was best in reduction per cent disease index of soybean rot caused by Rhizoctonia solani. Seed treatment with Trichoderma harzianum was found has most effective in improving seed germination (18.43%), reducing 90.46% infection by Rhizoctonia solani in soybean and increasing yield (69.51%) over control plot [89].

4.2 Seed bio-priming

Treated seeds with Trichoderma incubate until radical emergence is referred to as bio-primming. This technique is a simple coating of seeds and results in rapid and uniform seedling emergence and also reduces the amount of bio-control agents. Trichoderma conidia germinate on the seed surface and form a layer around seeds. Such seeds tolerate adverse conditions of the soil better than the non-primed seeds. Seed bio-priming was successfully used in tomato, brinjal, soybean and chickpea [90]. It results in rapid and uniform seedling emergence and reduces the amount of bio-control agents [91].

4.3 Seedling root dip treatment

It is suitable for transplanting rice and vegetable crops. The seedlings can be treated with the spore suspension by mixing 10 g of Trichoderma powder with 100 g of well rotten FYM per liter of water and dipping roots for 10 minutes before transplanting/drenching in nursery beds. This method is generally used for vegetable crops, rice where transplanting is practiced [92]. Root dipping in antagonist’s suspension reduces disease severity and enhances seedling growth in rice, tomato, brinjal, chili and capsicum as reported [92]. The reduction of sheath blight disease of rice by root dipping in spore suspension of seedlings before transplantation [93]. Root dipping of tomato seedlings reduces the severity of root- knot nematode (Meloidogyne incognita).

4.4 Soil treatment

Trichoderma is capable of colonizing on farmyard manure (FYM) and then applied to the soil is the most effective method for the management of soil-borne diseases. The application of bio-control agents to the soil before or at the time of planting for control of soil- borne fungal pathogens [94]. Soil application of Trichoderma viride alone and in combination reduced red rot caused by Colletotrichum falcatum [95] and seedling blight, stem rot, color rot and root rot disease of Jute [14, 96]. Soil treatment with 5 Kg of Trichoderma powder per hector mixed after turning of sun hemp/dhaincha into the soil for green manuring or 1 kg of Trichoderma formulation in 100 kg of FYM. Some species of Trichoderma are reported to cause green mold disease of mushrooms [97]. Soil application (2%) of Trichoderma harzianum enriched enriched farm yard manure showed excellent result in reduction of stem rot disease incidence caused by Rhizoctonia solani and collarot of disease of tomato caused by Sclerotium rolfsii with increased seed germination (%), plant growth parameters and yield of the crop [38, 98].

4.5 Aerial spraying/wound dressing

Trichoderma can reduce the severity of diseases under field conditions. Trichoderma has been successfully applied to the aerial plant parts and on wounds of shrubs and trees [18]. Suspension of Trichoderma has been successfully applied to the aerial plant parts infected with Alternaria leaf spot of Vicia faba [99]. Trichoderma harzianum and Trichoderma virens talc-based formulations use for foliar sprays that reduce disease incidence of sheath blight of rice [100, 101]. Affects the efficacy and survival of antagonist in phylloplane [102]. The dosage and application have to be standardized based on the crop value. Foliar spraying of consortial formulation of Trichoderma harzianum + two entomopathogeic fungi along with seed treatment, seedling root treatment showed significant reduction of three important diseases of brinjal viz., Phomopsis leaf blight and fruit rot, Alternaria leaf spot, and Fusarium wilt [103].

5. Viability in the storage and field

One of the critical problems in the commercialization of bio-agents is the loss of viability of the propagules over time. The shelf life of the bio-control product is dependent on the storage temperature and carriers as used in the formulation of bio control agents. The shelf life of bio- control agent plays a significant role in successful marketing. Trichoderma spp. are multiplied on bio-degradable substrates for long shelf-life and is also beneficial for field application. Bio-control agents are a biomass product, maintaining their viability at the end of the course [104]. Talc based Trichoderma virens conidia keep 82% viability at 5°C in refrigerator after 6 months, while at room temperature was observed for 3 months [105]. The viable propagule of Trichoderma in talc formulation was reduced by 50% after 120 days of storage [77]. Increasing shelf life of talc formulations of Trichoderma using various ingredients (chitin and glycerol) in production medium fermentation was carried out the shelf of talc formulation of Trichoderma up to 1 year [106, 107]. Trichoderma on coffee husk has a shelf life of more than 18 months. Talc, peat, lignite and kaolin based formulations of Trichoderma, have a shelf life of 3–4 months. In the storage polypropylene bags use of various colors, Trichoderma viride showed maximum shelf life in milky white bags of 100-micron thickness. The Trichoderma fungus in the storage temperatures is less than 4°C.

6. Mode of action

Bio-control agents are playing an important role in controlling of plant pathogens, especially soil borne fungal pathogens. Biological control agents reduce the disease of the target crop usually by one or more of the modes of action manly antibiosis, competition, mycoparasitism, cell wall degrading enzymes and induced resistance. The indirect interaction with pathogens is competition for nutrients and space and directly with the pathogen by hyperparasitism or antibiosis [108]. Bio-control agents might directly interact with the pathogens by hyperparasitism [109], and antibiosis [110]. Bio-agents induce resistance enhanced in plants against pathogens, competitions for nutrients and spaces [111]. Various chemical compounds such as lectins during the initial contact, recognition and cell wall-degrading enzymes such as β-1,3-glucanases, chitinases, proteinases, and lipases, during the penetration [112]. In hyper-parasitism growth of bio control agent towards the target organism, coiling, final attack and dissolution of target pathogens cell wall by the activity of enzymes [86].

Mycoparasitism is one of the most important direct antagonism mechanisms that attack one fungus on another [113]. and causes complete death of fungal propagules or destruction and lysis [114]. Mycoparasitism is a complex process which involves chemotrophic growth, recognition and coiling, the interaction of hyphae and secretion of specific lytic enzymes [113]. Trichoderma hyphae, initial recognition and wind around the pathogen’s hyphae by forming a hook, the appressorium permeates into the pathogen cell, and chitin is broken down by enzymes such as chitinase and glucanase [109]. The fungal cell walls contain chitin and glucan are the major constituents of many fungal cells [115]. Trichoderma strains have antagonistic potential and are mainly characterized by their ability to secrete enzymes such as chitinases, glucanases, and proteases that hydrolyze the cell walls of pathogens [116]. Chemotrophic response fungus induces the released the cell wall degrading enzymes from Trichoderma viz. β-1, 3 glucanase, proteases, lipases and chitinases [117]. The role of proteases in biocontrol of Botrytis cinerea by T. harzianum [57]. In mycoparasitism has been attributed to the role of chitinases [118]. The proteases reduced the activities of the pathogen enzymes exo- and endo polygalacturonase, pectin methylesterase, pectate lyase, chitinase, cutinase, and β-1,3-glucanase that are essential during host infection. Trichoderma hyphae contact and start coiling around the attachment of hyphae [119]. The hyphae grow along the host hyphae and secrete different lytic enzymes such as glucanase, chitinase and pectinase that are involved in mycoparasitism and ultimately degeneration of the target fungus [119]. Trichoderma produces low molecular weight compounds that have antifungal and antibacterial properties, these substances inhibit cell wall synthesis [118]. Trichoderma hyphae release antibiotic compounds which penetrate the pathogen’s hyphae and inhibition of host cell wall synthesis [59, 120]. The mycoparasitism of Trichoderma spp. towards Pythium ultimum and Sclerotium rolfsii [18]. The parasitism of Rhizoctonia solani hyphae by the Trichoderma virens in controlling citrus seedling disease [121, 122]. Trichoderma species such as T. atroviride, T. virens, and T. reesei have ability of mycoparasitism [7, 123]. Trichoderma harzianum is excellent mycoparasitic activity against Rhizoctonia solsni [11] and also involve chitinase and β-1, 3 glucanase [1]. Trichoderma spp. is known to produce antimicrobial metabolites that act via hyperparasitism [10].

Antibiosisis is the condition of antagonistic to the suppression of pathogenic microorganisms due to toxic compounds (antibiotics). Antibiotic is a secondary metabolite with a low molecular weight that is harmful to the other microorganisms at a low concentration [124]. The antibiotic is produced by bio-control agents and is the main contributing mechanism under soil conditions [125]. Soil-borne microorganisms have different strains of Trichoderma species [5]. Secondary metabolites secreted in situ and effects against pathogens at low amounts [110].

Competition is the form of microbial in soils and living plant surfaces for nutrient limited environments [126]. Bio- control agents and pathogens compete with one another for the nutrients and space in the environment. The competition is considered to be an indirect interaction between the pathogen and bio control agent [127]. The competition for nutrients of bio-control agents fights for the essential micronutrients such as iron and manganese in soils. The bio control agents have more efficient for utilizing micro-nutrient uptake for the substances than the pathogens [128]. Iron competition is a limiting factor in alkaline soils for microbial growth and development [129]. Siderophore is low-molecular weight chelators with is a very high and specific affinity for Fe called siderophores [130]. Trichoderma spp. produces highly efficient low molecular weight ferric iron chelators termed siderophores that stop the growth of other fungi [131]. Siderophore is a chealate of the Fe ions that bind and take up the Siderophore-Fe-complex and making iron unavailable to the pathogen [132]. Trichoderma species as bio-control antagonists release siderophores that chelate iron (Fe3+) prevent the growth and development of fungal pathogens [90]. Trichoderma asperellum producing iron-binding siderophores controls Fusarium wilt [133].

Induce resistance is indirect mechanism in host physio-biochemical pathways that trigger defense cascades inside the plants and lead to suppression of disease development. Induced defense mechanisms involve the production of reactive oxygen species, phytoalexins, phenolic compounds, pathogenesis-related proteins, physical barriers [134]. The role of Trichoderma in plants defense as involved in induced immunity. Concept of induces resistance on cucumber seedling disease with T. harzianum [43]. The roots are recognized fungal-derived molecules that changes occur locally and systemically in gene expression, increasing salicylic acid, jasmonic acid, and phytoalexin levels in plants. The induced resistance is enhanced against infections by a pathogen in the plant without direct antagonistic interaction with the pathogen [135, 136]. Trichoderma application cause induces resistance against the diseases in plants and provides long-term protection [137]. Trichoderma in the rhizosphere can protect plants against aerial pathogen infections, through the induction of resistance via a hypersensitive response (HR), systemic acquired resistance (SAR) and induced systemic resistance (ISR) in plants [10]. Induced resistance was demonstrated through the induction of Trichoderma against foliage disease of beans caused by Colletotrichum lindemuthianum and Botrytis cinerea [138]. Trichoderma produces several metabolites that act as elicitors of plant results in the synthesis of phytoalexins, PR proteins that increase in resistance against several plant pathogens [139] and in abiotic conditions [10].

7. Diseases management

Trichoderma spp. and Gliocladium spp. were the first bio-control agents that effectively manage plant pathogens such as Sclerotium rolfsii, Rhizoctonia solani, and Fusarium solani, cause diseases on groundnut, bean, and apple, respectively [94, 138, 140]. Trichoderma viride, Trichoderma harzianum and Trichoderma virens are being successfully used for the control of diseases such as foot rots, root rots, damping off, collar rots and Fusarium wilts of horticultural crops. Trchoderma are effective against foliar and soil borne plant pathogens [141]. The talc based formulations of Trichoderma manage several soil-borne diseases of various crops by seed treatment at 4 g–5 g/kg seed. Soil borne plant pathogens are successfully manage through seed coating, furrow application and root dip of seedlings. Successfully managed S. rolfsii and Pythium spp. on radish and pea by seed coating of T. hamatum as reported [142]. Trichoderma harzianum application in the field with wheat bran colonized rapidly in the soil and inhibits the Rhizoctonia solani and S. rolfsii in beans [26, 143]. Trichoderma spp. has potential in controlling wilt and damping-off diseases caused by Fusarium sp. and Rhizoctonia solani [28, 121]. Pythium, and Phytophthora, Rhizoctonia, Fusarium and Sclerotium, spp. are soil borne plant pathogens causing diseases in several crops, the diseases manage through Trichoderma spp. as reported [22]. Trchoderma has the potential to manage fungal and nematode diseases as well as host defense inducing ability in plants [64]. Nano-particles (Ag and Au) of Trichoderma asperellum showed antifungal activity at different concentrations, the maximum radial growth inhibition was observed at 200 ppm against Rhizoctonia solani as compared with the chemical [23].

8. Conclusion

Trichoderma is an excellent bio-control agent and also plant growth promotion. Trichoderma spp. serves as a bio-control agent due to effective against a large number of soil-borne plant pathogenic fungi and effects on some root nematodes. Trichoderma isolates improved the growth of root length, plant height, roots and shoots fresh weight and dry weight of plants. Trichoderma is effective against abiotic stresses and provides tolerance to the abiotic stresses and increases fertilizer used efficiencies. Trichoderma species have the potential to produce several enzymes that can degrade the cell wall and release several fungi toxic substances that can inhibit the growth of the fungal pathogens. A single application of Trichoderma give the long term efficacy as induces resistance against plants diseases. Applications of Trichoderma in nurseries and fields to suppress the soil-borne inoculums. The bio-efficacy is the quality of Trchoderma products to ensure the betterment. Trichoderma formulations can be applied to dry seed treatment or seed biopriming for the control of several soil-borne diseases. Trichoderma has high efficiency and aggressiveness against Macreophomina phaseolina, Aspergillus niger and Meloidogyne incognita. Trichoderma harzianum has the best antagonism to Macrophomina phaseolina and Aspergillu. niger, while the Trichoderma asperellum is efficient in the reduction of nematode. Trichoderma has no harmful effects on the environment and non-target organisms and can be applied to most food crops. Bio-control technologies have disease control of the crops and these technologies minimize the usage of harmful chemical pesticides. Trichoderma strains play an important role in the bioremediation of soil that is contaminated with pesticides and herbicides having the ability to degrade.

Conflict of interest

“The authors declare no conflict of interest.”