TRICHODERMA

Priority & Trillum

These products are the only fully registered Trichoderma asperellum biological fungicide for the control of Fusarium, Pythium and Rhizoctonia on maize, wheat, soybeans, bean crops, potatoes and vegetable crops in South Africa. The active ingredient, T. asperellum, is a soil borne, opportunistic plant symbiont, which forms beneficial relationships with a variety of plant species. Members of the genus Trichoderma are among the most frequently isolated soil fungi, making Priority and Trillum environmentally friendly alternatives to synthetic fungicides. T. asperellum easily adapts and survives in different soil types, under a range of environmental conditions and can even survive in the presence of certain chemical fungicides. These attributes make this microorganism one of the most practical and effective biological agents in the marketplace.

Priority and Trillum Technologies

Priority and Trillum are produced on a unique growth medium using a process called solid state fermentation (SSF). This growth medium and process allows for the production of a high amount of viable T. asperellum spores (survival structures) that ensures a high survival rate when the products are applied under harsh conditions. During SSF a high concentration of several important enzymes are produced, which play a crucial role in both the suppression of plant pathogens and the induction of plant resistance. These enzymes ensure that Priority and Trillum start to work on the pathogens in the soil even before the Trichoderma spores germinate. Priority and Trillum therefore has an immediate suppression effect as well as a long-lasting effect on the plant pathogens once the Trichoderma spreads in the soil and around the plant root.

Enzymes produced by Priority and Trillum are involved in:

• Degradation of cell wall of phytopathogenic fungi. The fungal cell wall consists mainly out of glucans, proteins and chitin (Fig. 1). T. asperellum produces enzymes that can degrade all these components. The cell wall is a layer surrounding the cell and provides the cell with both structural support and protection. Degradation of this cellular structure leads to cell death. 

• Inhibition of hydrolytic enzymes produced by pathogens. Most plant pathogens produce an array of enzymes that are capable of degrading plant cell-wall components. Therefore, to infect the host, fungal pathogens must first excrete an array of enzymes that not only helps the pathogen to gain access to the plant but also facilitates the adherence of the pathogen to the plant. Proteases produced by T. asperellum can degrade these enzymes and reduce the ability of the pathogen to infect the plant.

• Aiding in root colonization. Intimate contact between T. asperellum and the plant root is necessary to allow the plant the full benefits of biocontrol, resistance stimulation and plant growth stimulation.  Cellulase and xylanase produced by T. asperellum aid in the colonization of the root system, allowing intimate contact between the biocontrol agent and the plant.

• Triggering induced systemic resistance. Microorganism-associated molecular patterns (MAMPs) produced by T. asperellum include cellulase and xylanase. These MAMPs are known to induce different signals that are transported in the plant and lead to the expression of defence proteins.  These proteins are involved in the direct suppression of pathogens but also increase biochemical and structural barriers to protect the plant from pathogen attack. Damage-associated molecular patterns (DAMPs) that are liberated by the T. asperellum from both plants and fungal pathogens can also be recognized by plant receptors and activate the defence cascade in the plant.

Protein Defense

• β-1,3 glucanase – Degrades cell walls of phytopathogenic fungi. Inhibits mycelial growth.
• Protease – Degrades cell walls of phytopathogenic fungi. Inhibit hydrolytic enzymes produced by pathogens.
• Cellulase – Degrades cellulose during root colonization to penetrate the plant tissue. Inhibits mycelial growth. Triggers induced systemic resistance in plants by increasing the ethylene pathway.
• Xylanase – Helps Trichoderma to colonise plant roots. Xylan is the second most important structural polysaccharide in plant cell walls. Triggers induced systemic resistance in plants by increasing the ethylene pathway.
• Chitinase – Degrades mycelia and conidial walls of phytopathogenic fungi. Inhibits mycelial growth.

Priority and Trillum – Multifunctional Products

Both products control phytopathogenic fungi through several modes of action:

• Mycoparasitism. Once T. asperellum is incorporated into the soil, it recognises pathogens through the production of cell-wall degrading enzymes (CWDEs). These enzymes hydrolyze the cell wall of the host fungus, subsequently releasing oligomers from the pathogen cell wall. The low molecular weight degradation products activate the Trichoderma to grow towards the pathogen (Fig. 2).

Once the Trichoderma comes in contact with the pathogen it coils around and grow alongside the host hyphae (Fig. 3).

Structures known as appressoria develop from the Trichoderma hyphae and enable the fungus to penetrate the pathogen via an infection peg (Fig. 4).

Once the Trichoderma has penetrated the host it can spread and kill the pathogen through the production of a range of bio-active compounds.

• Competition for nutrients and space. The fact that Trichoderma species are among the most frequently isolated soil fungi proves its excellent competitive capabilities. They are aggressive biodegraders and act as competitors to fungal pathogens, especially when nutrients are limited.  Due to its high growth rate and nutrient uptake capabilities, Trichoderma easily colonizes the rhizosphere of plants and therefore exclude pathogens from this very important area.

• Siderophore production. Siderophores are small, high-affinity iron-chelating compounds secreted by certain microorganisms. Trichoderma produces these compounds to sequester iron essential for the growth and functioning of plant pathogens and thereby reduce their proliferation in the soil.

• Induce systemic resistance in the plant. T. asperellum produces a range of microorganism-associated molecular patterns (MAMPs) that are known to induce different signals that are transported in the plant and lead to the expression of defense proteins. These proteins are involved in direct suppression of pathogens but also increase biochemical and structural barriers to protect the plant from pathogen attack. Damage-associated molecular patterns (DAMPs) that are liberated by the T. asperellum from both plants and fungal pathogens can also be recognized by plant receptors and activate the defence cascade in the plant.

Priority and Trillum promote plant growth and root development through several modes of action:

1. Production of plant growth hormones (e.g Auxin) by Trichoderma.
2. Reduction in ethylene levels due to enzymatic action of Trichoderma, resulting in root elongation.
3. Release of unavailable nutrients like phosphates, iron, copper, manganese and zinc for plant uptake.
4. Production of secondary metabolites involved in plant growth promotion.
5. Improvement of water and nutrient uptake due to better root development.