**2. History and journey of** *Trichoderma* **species**

Before touching its actual uses in agriculture, it becomes imperative to focus on some important aspects related to it. For the first time, Persoon introduced the name *Trichoderma* [12]. In 1865, the Tulasne brothers reported teleomorph (sexual stage) of *T. viride* Pers as *Hypocrea rufa* [13]. Till 1969, there were only one species, i.e., *T. viride* of genus *Trichoderma* [14].

In 1969, Rifai made out nine 'aggregate species' namely, (1) *T. harzianum* Rifai, (2) *T. viride,* (3) *T. hamatum* (Bonord.) Bainier, (4) *T. koningii* (Oudem.) Duché & R. Heim, (5) *T. polysporum* (Link) Rifai, (6) *T. piluliferum* J. Webster & Rifai, (7) *T. aureoviride* Rifai, (8) *T. longibrachiatum* Rifai, and (9) *T. pseudokoningii* Rifai. In the early 1990s, [15–17] identified five sections and 27 biological species within the genus *Trichoderma.* The introduction of molecular techniques contributed to the greater extent in identifying the species comparatively more precisely and hence from the late 1990s up to the year 2002, the number of *Trichoderma* species increased to 47 [18].

Till 2005, the International sub-commission on *Trichoderma/Hypocrea* listed 104 species on the basis of phylogenetic analyses [19]. Till the year 2015, there are 252 species one variety and one form. In addition, *T. neocrassum* Samuel (syn. *Hypocrea crassa* P. Chaverri & Samuels) and *T. patellotropicum* Samuels (syn. *Hypocrea patella* f. tropicaYoshim.Doi) were proposed as two new names [20].

### **3. Interaction of** *Trichoderma* **with phytopathogens of agricultural crops**

Hyperparasitism, competition, and antibiosis are the important mechanisms of this genus through which it interacts with phytopathogenic fungi. This antagonist is well efficient to colonise in variable ecological niches [21–23].

#### **3.1 Hyperparasitism**

In Hyperparasitism, the *Trichoderma* directly contact with a pathogen and finally cause the death of pathogen cells death [23]. For this purpose, the *Trichoderma* synthesise cell wall degrading enzymes (CWDE) namely, cellulase, xylanase, pectinase, glucanase, lipase, amylase, arabinase, protease [24], and lytic enzymes. These enzymes degrade the pathogen cell walls, composed of chitin and glucan polysaccharides. Among the chitinolytic enzymes β-N-acetyl glucosaminidase, endochitinase, and chitobiosidase are of key importance responsible for the degradation of the cell wall of other plants pathogenic fungi, which are produced by *T. harzianum*, *T. atroviride* P. Karst, and *T. asperellum* Samuels, Lieckf. & Nirenberg [25]. Several volatile metabolites, such as 6-n-pentyl-2H- -pyran-2-one (6-PAP), are produced by *Trichoderma* for plant protection [26]. The β-1,3- and β-1,6-glucanases enzymes determine the hyperparasitic capability of *Trichoderma* to react on species of *Phytophthora* sp. and *Pythium* [27, 28]. Proteolytic enzymes, namely, endo- and exoproteases of *Trichoderma* responsible for enzyme secretion for the control of *Botrytis cinerea*, *Rhizoctonia solani,* and *Fusarium culmorum* [29, 30]. Ceratin cellulase enzymes, such as exo-β-1,4-glucanases, endo-β-1,4 glucanases, and β-glucosidases, produced by antagonists also play a significant role in hyperparasitism [31].

#### **3.2 Competition**

Competition of *Trichoderma* spp. with plant pathogens is another mode of interaction that helps in the control of plant diseases. This phenomenon takes place for utilisation of nutrients, occupying ecological position or infection sites on plant roots. Certain *Trichoderma* strains produce siderophores, i.e., iron-chelating compounds. Through siderophores, antagonist traps iron from the associated environment and creates nutrient deficiency due to which the growth of pathogenic fungi, such as *B. cinerea,* is hampered. The *Trichoderma* creates an acidic environment that has a negative effect on the growth and development of pathogenic fungi and aggressively colonises the host plant's roots due to the enhanced activity of the hydrophobins [9].

#### **3.3 Antibiosis**

It is a biological interaction between two or more organisms that is unfavourable to at least one of them; it can also be an antagonistic association between an organism and the metabolic substances produced by another. Antibiosis in relation to *Trichoderma* fungi is a specific mechanism of antagonistic interactions with other plant pathogenic fungi. This phenomenon is based on the generation of secondary metabolites, which exhibit an inhibitory or lethal effect on a parasitic fungus. From the genus *Trichoderma*, over 180 secondary metabolites have been characterised so far, representing different classes of chemical compounds [32, 33]. Such compounds can be divided into volatile antibiotics, water-soluble compounds, and peptaibols. Volatile antibiotic, (6PAP (6-pentyl-α-pyrone) produced by *T. viride*, *T. harzianum*, and *T. koningii*, plays a major role in the biocontrol of *Botrytis cinerea*, *R. solani*, and *Fusarium oxysporum.*

Another category of antibiotics is Peptaibols. They are polypeptide antibiotics comprising of 500–2200 Da, rich in non-proteinogenic amino acids, specifically alfa-aminoisobutyric acid, and their characteristic attributes include the presence of N-acetylated ends and C-end amino alcohols. Peptaibols exhibit potent activity against a number of fungi (**Table 1**).


#### **Table 1.**

*Peptibols antibiotics of* Trichoderma *spp. to control phytopathogens.*

*Can Genus* Trichoderma *Manage Plant Diseases under Organic Agriculture? DOI: http://dx.doi.org/10.5772/intechopen.103762*

In *Trichoderma* fungi, the activity of antibiotics is enhanced with the activity of lytic enzymes. Their joint activity provides a higher level of antagonism compared to the activity of either enzymes or antibiotics alone [36]. Researchers found preliminary degradation of the cell walls in *B. cinerea* and *F. oxysporum* by lytic enzymes; it facilitated easier penetration of antibiotics to pathogen cells [8].

#### **4. Role of** *Trichoderma* **spp. as a biological control agent**

*Trichoderma* spp. are the ideal option for safer management of phytopathogens. *T. harzianum* and *T. viride* have been occupied the prime position and its highly exploited biological control agent for controlling soil-borne fungal diseases.

#### **5. Current status of** *Trichoderma* **formulations**

There is a list of about 970 registered manufacturers with the Central Insecticide Board & Registration Committee (CIB & RC) for the manufacturing and marketing of biopesticides in India, out of which 558 are involved in *Trichoderma* spp. (**Figure 1**). The different formulations of this antagonist comprised of wettable powder (WP), wettable suspension (WS), aqueous suspension (AS), and liquid. The *Trichoderma* spp. formulations have been manufactured and marketed by private companies, government organisations, and NGOs. Presently, wettable powder (WP) and liquid formulations are available for use by end-users; however, WP formulation in different concentrations (0.5 to 6.0%) is dominant (**Figure 2**). The liquid formulations contribute nearly 2% of the formulations.

#### **6. Management through seed treatment with** *Trichoderma* **spp.**

Seed treatment is an important and economical practice to manage the seed-borne phytopathogens at the initial stage with the minimum cost. For this purpose, a small quantity of desired input is required and this practice is very easy in handling. For seed treatment, the formulation of *T. harzianum* and *T. viride* can be used. Seedlings of vegetable crops can be treated with *T. viride* and *T. harzianum* just before transplanting into the main field (**Table 2**).

#### **7. Management through soil treatment with** *Trichoderma* **spp.**

Soil residential phytopathogens, such as *Pythium*, *Phytophthora*, *Fusarium*, *Rhizoctonia*, *Sclerotinia*, *Macrophomina,* play an important role in the development of various soil-borne diseases, such as root rot, wilt, and seedling rot of various crops. Management of such fungal phytopathogens can be achieved through the application of *T. harzianum* and *T. viride* through soil drenching with water, enriched farmyard manure, and vermicompost. There are several species of *Trichoderma*, however *T. harzianum*, *H. lixii*, *T. atroviride*, *H. atroviridis*, *T. asperellum,* and *T. virens* are potential biocontrol agents against phytopathogens [37]. Application of *T. viride* enriched FYM (5 kg/plant) to two-year guava saplings at the basin near the root zone resulted in decreased wilt incidence and better plant

**Figure 1.** *Number of manufacturers of different* Trichoderma *formulations.*

#### **Figure 2.**

*Status of* Trichoderma *WP and liquid formulation manufacturers.*

growth in terms of stem girth [38]. *T. harzianum* when applied (50 g/vine) in black pepper field it had effectively managed the foot rot disease. For the management of pomegranate wilt bio-formulation of *T. viride* (0.1 and 0.2%) was found significantly superior over the control. Soil application of *T. harzianum* plus *T. virens* is efficient in managing stem bleeding disease of coconut [39]. Five monthly applications of *T. harzianum* (50 g/plant) in bananas reduced 50% of the vascular discoloration index of *Fusarium* wilt disease and increased the yield [40]. *T. asperellum* found inhibitory against *Pythiumaph anidermatum*, *Pythium debaryanum*, *Sclerotium rolfsii,* and *S. rolfsii*, *Fusarium oxysporum* f.sp. *lycopersici* and *Alternaria solani*. Application of *Trichoderma* (@20 kg/ha) along with 2.0 tonnes castor cake/ ha reduced nematode population and increased yield in pomegranate.

Soil application of silver nanoparticles synthesised from *T. asperellum* resulted in complete control of *Fusarium* wilt in cv. Grand Nain [41]. *T. harzianum* talc

*Can Genus* Trichoderma *Manage Plant Diseases under Organic Agriculture? DOI: http://dx.doi.org/10.5772/intechopen.103762*


#### **Table 2.**

*Seed treatment with promising* Trichoderma *spp. for organic agriculture.*

formulation could control root rot disease of citrus up to 80%, and under field conditions [42]. Some strains of *Pseudomonas* spp. and *Trichoderma* spp. found effective in controlling wilt of banana, caused by *F. oxysporum* f.sp. *cubense* (Foc) race 1 under field conditions [43]. Isolates of *Trichoderma* and *Aspergillus,* when applied in the field for the control of guava wilt disease caused by *F. oxysporum* f. sp. *psidii* and *F. solani*, could reduce disease incidence and promoted plant growth [38]. Antagonistic fungi *Aspergillus niger*, *T. harzianum,* and *Penicillium citrinum* were found effective for the management of the wilt disease of guava [44].

### **8. Management through foliar application of** *Trichoderma* **spp.**

Foliar application of *Trichoderma* spp. is advisable for the management of airborne fungal and bacterial phytopathogens, such as species of *Alternaria*, *Curvularia*, *Fusarium*, *Colletotrichum*, *Pestalotiopsis*, *Pyricularia*, *Puccinia*, powdery and downy mildew pathogens of cereal, vegetable and other crops (**Table 3**). The potent candidates include *T. viride* and *T. harzianum*. Post-prune foliar application of *T. harzianum* and *T. viride* is a common practice in tea (*Camellia* sp) crop production in Darjeeling and the North East region of India [45, 46]. When a combination of *T. harzianum* and *Pseudomonas fluorescens* was sprayed before harvesting mango fruits, it had suppressed post-harvest fruit rot in dasheri mango [47]. Banana hands (cv. Grand Nain) when dipped in *T. asperellum* suspension and packed without ethylene absorbent


#### **Table 3.**

*Foliar spray of* Trichoderma *spp. in organic agriculture.*

extended its shelf life up to 75 days at 13.5°C. There was no incidence of anthracnose and crown rot [41]. It was noted that *T. viride*, *T. harzianum,* and *T*. *asperellum* were potential antagonists for the management of *F. solani* and *Pestalotiopsis theae* causing dieback and grey leaf spot disease of tea [48, 49]. Foliar spray of *T. asperellum* and *T. atroviride* could manage the dieback disease of tea (*Camellia*sp) and enhance the vegetative growth in terms of more number of pluckable shoots [50].

### **9. Management through paste application of** *Trichoderma* **spp.**

Application of *Trichoderma* paste (20% w/v) is generally done after severe pruning operations (rejuvenation prune and medium prune) in tea plantations to protect the plants from airborne pathogens. Such an application can be useful in horticultural crops in which pruning is done.

#### **10. Important considerations for better performance of** *Trichoderma* **spp.**

There are certain issues/concerns which should be taken into consideration for achieving desired benefits from the use of *Trichoderma* spp. Important concerns are—(1) reliable source of procurement, (2) assurance of fresh formulations, (3) avoidance of tank mixing with agrochemicals, (4) tank mixing with compatible bio formulations, (5) repeated application at the proper interval, (6) use of neat and clean separate sprayers for such formulations, (7) seeking technical advice from experts, (8) application during early morning and late evening hours, (9) procurement in well-ventilated store under lock and the key, and (10) quality assurance through certified agencies, such as IMO, Ecocert, Lecon, or any other approved agency.

#### **11. Conclusion**

*T. harzianum* and *T. viride* are efficient in controlling several plant diseases safely. When considering the interactions of *Trichoderma* fungi, it was found that these antagonistic fungi have an advantageous effect on plants. Stimulation of plant growth and yield takes place in this interaction and the advantageous effects are seen in the production of vitamins, the increased availability of biogenic elements

*Can Genus* Trichoderma *Manage Plant Diseases under Organic Agriculture? DOI: http://dx.doi.org/10.5772/intechopen.103762*

(nitrogen, phosphorus), the mobilisation of nutrients from the soil and organic matter, and the enhanced intensity of mineral uptake and transport. Furthermore, *Trichoderma* fungi are capable of producing zeaxanthin and gibberellin, i.e., compounds accelerating seed germination. Managing plant diseases through these approaches could be safer for the agroecosystem, overall environment, soil health, and human health and would be the right step in sustaining crop production to meet the demand of the growing population.
