"Trichoderma"

By Alfredo Norte
General Index

1.  Preceding
2.  What is Trichoderma?
3.  Limitations, Myths and False Expectations of the Use of Trichoderma
4.  Mechanisms of Action of Trichoderma sp. as Bio pesticide
5.  Other Properties of Trichoderma sp. 
6.  Biotech applications

1.  Preceding

During the last 25 years comes it self investigating intensively in the utility of diverse micro organisms such as Trichoderma sp.  Bacillus sp.  Aspergillus sp.  Pseudomonas sp. to enlarge the efficacy of the processing, reducing the dangerous counter-indications by-products of the control of different vegetable pathologies such as:  Armillaria spp., Botrytis cinerea, Colletotrichum gloeosporioides, Cylindrocladium scoparium, Fusarium oxysporum (Fusariosis), Macrophomina phaseolina.  (Mildiu), (Oidio), Phytophthora infestans, Phytophthora spp., Pythium spp., Rhizoctonia sunny spot, Rosellinia necatrix, Verticillium dahliae (Verticiliosis).  With this new strategy they would be reduced sensitively the abusive employment of chemical pesticides, and with it the great environmental impact that these products cause, and the dangerous consequences for the human health by the exposition to these substances.

Of all the micro organisms mentioned, is the kind Trichoderma the more extensively utilized due to the following motives: 

1.  Great versatility, thanks to its triple action:  Biopesticide, Biofertilizer and Bio stimulating. 
2.  Great adaptation and survival to the diverse conditions of the soil of destiny. 
3.  Simplicity in its manipulation and biotech multiplication. 

2.  What is Trichoderma?

Trichoderma sp. is a mushroom belonging to the subdivision Deuteromicete that are characterized for present not a sexual state determined.  It is found represented in an important number of so much, natural floors of forest origin, as of other organic substrata whose main component be the lignin or the cellulose.  Trichoderma sp. has evolved in the nature toward this nutritious strategy where the competence with other micro organisms is very scarce, though has its limitations in punctual moments, where many present nutrients exist on the ground, since can be seen displaced by them called opportunistic micro organisms, with a faster capacity of multiplication with regard to Trichoderma sp.  Its development is seen favoured by the presence of high densities of roots, which, they are colonized quickly by these micro organisms.  The utilization of Trichoderma sp., provided that this is done of correct form, involves a clear decrease of the need to treat with insecticides, fertilizing or composed of whose, chemical origin negative effects on the environmental quality and the human health; they are extensively shown by diverse scientific studies.
The kind Trichoderma counts on more than 30 different species, more than 100 subspecies, of which more than 400 stumps, they are placed in official agencies as the CECT (Spanish Collection of Cultivations Type); in Europe, the ECCO (European Cultivate Collection Organization) or in US the ATCC (American Type Cultivation Collection).  The species of Trichoderma more extensively represented, given its qualities are:  Trichoderma hamatum, Trichoderma harzianum, Trichoderma koningii, Trichoderma pubescens, Trichoderma reesei, Trichoderma virens and Trichoderma viride.  Trichoderma sp. is a microbiotic kind characterized by being extensively adapted to all kinds of habitats, being found stumps or cut off from Trichoderma sp. in very diverse environments.  Though it has some optimum conditions of growth that when itself they are not given has the capacity to create you form latent or of resistance called clamidosporas.  The present genetic changeability in this kind does difficult the establishment of some conditions of optimum growth, varying this in function of the species and even of the subspecies in study.  The adequate conditions for the kind Trichoderma are the following: 

1.  The temperature of optimum growth is of 25ºC, though the rank of growth is among 15º and 35ºC.  By underneath or over this temperature, Trichoderma sp. is characterized for producing forms of resistance. 
2.  The conditions of adequate humidity are environment al 70% of the capacity of water retention, though is capable of growing among the 20% the 80%. 
3.  It is a micro organism anaerobic optional. What confers him the capacity to act so much in conditions of aerobics (very porous floors), whose conditions are optimum for his growth, though can also grow in media with high punctually deficient, microbiotic activity in I oxygenate. 
4.  The pH adequate for the development of Trichoderma sp. is situated between 6 and 6, 5, though they can live in upper ranks, therefore most of the species of Trichoderma they have the capacity of increase the pH of their environment by means of the liberation of organic acids. 
5.  The source of main carbon for its metabolic development is the cellulose or lignocelluloses. 
6.  The content in nitrogen in floor is a factor constraint, being the adequate dose that of 100 mg.  N by kg. of floor, being able to survive in smaller concentrations.  The form that better assimilates the nitrogen is in organic form, although also tolerates the mineral form as is the amoniacal, not tolerating the presence of nitric nitrogen. 
7.  The content in match varies according to the species, being environment to 2 mg.  by kg. of soil.  This micro organism has the mineral capacity to assimilate nitrogen in the shape of phosphate, though can also mineralize it of organic forms, facilitating its absorption on the part of the plant.  
8.  The content in microcomputer nutrients and trace elements are necessary for the growth of Trichoderma sp., though does not need contribute additional therefore these they are found sufficiently represented on the ground. 
9.  In general Trichoderma sp. is tolerant to the application of chemical pesticides, although its growth is seen reduced by the present heavy metals in them cited pesticides. 

3.  Myths and False Expectations of the Use of Trichoderma

The main causes that limit the efficacy of Trichoderma sp. are: 

1.  Incorrect information in the recommendations of the prepared commercial.  (On appraisal of the extensive spectrum) Alteration of the conditions of the prepared commercial by a deficient manipulation of the distribution, commercial personnel or end user. (Alteration of the physical conditions or by Mixing unduly with phytosanitary products)
2.  Bad application of the prepared commercial by the end user.  (Variation of the conditions "in vitro-in I live", Low percentage of concentration or by Application to a sick tree)

3. Mechanisms of Action of Trichoderma sp. as Bio-pesticide

The utilization of Trichoderma sp. as a bio-pesticide, emphasizing its properties like biological fungicide (Photo 1). Its way of variable action depending on the species and the conditions, being these: antibiosis, micoparasitism, competence, and hipovirulence.

  The efficacy of these stumps to act as bio-pesticide, depends on multitude of variables such like place of isolation, place of application, end for the ones that be destined, etc.  The research team headed by the Dr. José Antonio Paschal (BAIT-CSIC) figure the viability of action set against plants pathogen in around al 10-20%, data obtained from trials "in vitro" set against different pathogenic micro organisms.

Various mechanisms shown of action exist of Trichoderma sp. set against pathogenic micro organisms, like they are: 
MICOPARASISTISMO: due to stimuli quimiotrópicos, produced by the pathogen, the hyphae of Trichoderma sp. grow to being put in contact with the pathogen.  Once both micro organisms have themselves placed in contact, the hyphae of Trichoderma sp. are rolled up around those of the pathogen or they adhere him themselves through structures specialized.  Subsequently to these interactions the micro-parasitoid penetrates in the mycelium of the pathogen, degrading, apparently, in a partial way its cell wall (Photo 2). 

In the micro-parasitism they are several the enzymes produced by Trichoderma sp. capable to hydrolyze the cell walls of numerous mushrooms.  These enzymes are induced for the different polymers components of the wall of the mushrooms objective.  This process can be divided into four main phases: 
1.  Growth:  Them they exuded of the pathogen they attract to Trichoderma sp. 
2.  Recognition:  Some isolations of Trichoderma sp. are specific to some plants pathogen, and are in this phase where the attack specificity phenomenon is defined. 
3.  Penetration:  Once Trichoderma sp. has recognized al pathogenic wraps it and adheres to the hyphae covering it totally.  The hyphae of Trichoderma sp. penetrate in those of the pathogen swelling them and producing haustoria’s; at the same time that causes the disorganization of the cell content. 
4.  Degradation:  The final step is the degradation of the cell wall of the mushroom plants pathogen through the production and excretion of enzymes. 
5. Disintegration:  Some results that support this hypothesis have shown that Trichoderma sp. produces a series of substances that give rise to the separation of the cell wall of the guest in the points of interaction with the antagonist, at the same time, causing their fast disintegration.

B. ANTIBIOSIS:  This occurs when there is production of metabolites toxic or antibiotic, of an agency with direct action on another.  Nevertheless for this mushroom particularly the production of metabolites is hardly connected with the production of own enzymes of the process of micro-parasitism.  On the other hand, is well established that the enzymes hydrolytic of the cell wall has an effect synergic with the antibiotics, being the action anti-fungal of both composed very superior to that of any of them by separated (Photo 3).  Some of the species of Trichoderma sp. they are characterized for presenting a high origin carbonated waters substances production with a pronounced fragrance to coconut. 

C. COMPETENCE:  An essential factor so that exist competence is the shortage or limitation of some essential element.  Mainly a direct competence by the space is produced and the nutrients between the micro organism antagonist and the pathogen.  In some cases Trichoderma sp. acts on some pathogens due to its capacity to colonize quickly the substrate.  The zone colonized by Trichoderma sp. will be able to be occupied by no pathogen. 

D. RESISTANCE INDUCED:  When Trichoderma sp. enters contact with the active plant its system of defence, fundamentally by induction of its enzymatic system oxidative, preparing to the plant set against the possible attack of pathogens.  The mechanisms of action previously exposed are not exclusive, but they act of form synergic in the control of pathogens.  The relative importance of each one of them depends on the antagonist-pathogenic system that is being studied, since not all the stumps of Trichoderma sp. present the same antagonistic capacity set against a specific pathogen, for which at the moment of to create a biotech product from Trichoderma sp. should be known set against that pathogenic or group of pathogens wants to be utilized, choosing those more. 

5.  Other Properties of Trichoderma sp. 

As we have commented previously, the main biotech use of Trichoderma sp. is the biological control of illnesses, though they exist other that also they can be of utility and that subsequently they are commented: 

6.  Biotech applications

Trichoderma sp. groups diverse species and each one of them presents a different affinity set against you determined mushrooms plants pathogen, of equal form, they require different environmental conditions.  When the antagonistic mushroom is found in a favourable middle can act of efficient and fast form, in cases where the conditions are not the optimum, Trichoderma sp. requires a period of adaptation to show its potential as the controller.  Therefore, it seems logical and necessary, the to know the species, subspecies and even the stump that intends to inoculate, in order to knowing, to priori, if this is going to meet the conditions for the end that intends him itself to require.  On this point, fits to impact that is very important that the manipulator biotechnologist know exactly the specifications of its stump and recommend its use for that that have been tested.  The research team of the BAIT-CSIC, has identifying this as one of the basic problems that has the commercialization of prepared based on Trichoderma, which intends that be the solution for all the problems of the cultivation, can be given the case that the stump that markets do not be efficient, given the not alone existing genetic changeability inside the kind, but to level of species, It has been verified in numerous investigations.  Trichoderma sp. possesses innate resistance to the majority of the phytosanitary products, including the fungicides.  Nevertheless, the level of resistance differs among stumps.  Trichoderma sp. also is utilized frequently for the control of pathogenic roots, through its application in combination with organic amendments.  With what, besides improving the quality of the soil, due to its nutritious, organic load and microbiological.  Different formulations in the market exist of Trichoderma sp. that is presented in granules, dust or as covering of seeds.  This type of formulations they are carried out with isolations of Trichoderma sp. competent, which they are capable of colonizing totally the roots of the cultivation, conferring him to the plant a greater resistance before the attack of you determined mushrooms.  For commercial use, the dry material is the preferred by the importance of the weight and the easy manipulation of the products during the commercialization.  These products are presented in: 

1.  SOLID FORMULATIONS:  They utilize as adhesive substances inoculation backup, like the arabic gum or carboximetilcelulosys especially recommended for the inoculation of seeds, also clays can be utilized or you mix composed by nutrients.  In the market the following formulations can be found: 
WET DUST:  That they can apply for sprinkling to the air part of the plant or through the system of irrigation.  -Advantages: easy storage, transportation and management, less danger of absorption by the skin and the eyes at the moment of application.  -Inconvenient: they require of a constant agitation.  A potential risk by inhalation exists. 
DRY DUST:  -Advantages:  Does not it need to be diluted before utilizing it.  -Inconvenient: risk of inhalation or adhesion to the skin. 
CAPSULAE:  One of the most they utilized substances is the alginate sodium, since due to its characteristics permits to generate granules of alginate with a high content of units creators of colonies of Trichoderma sp. 
-Advantages: a gradual liberation of the micro organism is produced. 
-Inconvenient: the agitation of the product before its application should be constant.  GRANULES:  They apply directly to the substrate. 
-Advantages: easier dosage, reduction of the quantity of product adhered to the containers and less risks for the operatives that take charge of their application.  -Inconvenient: slow liberation of the micro organism.