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Bacillus Velezensis VS Trichoderma Harzianum

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In the pursuit of sustainable agriculture, biocontrol agents have emerged as crucial components in managing plant diseases and promoting plant growth. Among these, Bacillus velezensis and Trichoderma harzianum are two prominent microorganisms, each with unique characteristics and applications. This article delves into a detailed comparison between them to help farmers and researchers make informed decisions.
Contents hide
1 1. Taxonomy and Biological Characteristics
1.1 Bacillus velezensis
1.2 Trichoderma harzianum
2 2. Antagonistic Mechanisms Against Pathogens
2.1 Bacillus velezensis
2.2 Trichoderma harzianum
3 3. Effects on Plant Growth Promotion
3.1 Bacillus velezensis
3.2 Trichoderma harzianum
4 4. Application in Disease Control
4.1 Bacillus velezensis
4.2 Trichoderma harzianum
5 5. Compatibility and Environmental Impact
5.1 Bacillus velezensis
5.2 Trichoderma harzianum
6 6. Market Availability and Future Prospects
6.1 Bacillus velezensis
6.2 Trichoderma harzianum

1. Taxonomy and Biological Characteristics

Bacillus velezensis

  • Classification: Bacillus velezensis belongs to the genus Bacillus, which is Gram – positive, aerobic, and endospore – forming. It was first isolated from a river in Spain in 2005 and named after the river.
  • Survival and Adaptability: Its endospore – forming ability allows it to survive in harsh environmental conditions, such as extreme temperatures, drought, and high salinity. This characteristic enables it to persist in the soil for extended periods, maintaining its beneficial effects.

Trichoderma harzianum

  • Classification: Trichoderma harzianum is a member of the genus Trichoderma, falling under the Ascomycota phylum. It is a filamentous fungus.
  • Growth Habits: It has a high growth rate and can quickly colonize plant roots and soil environments. It is well – adapted to a wide range of soil types and climatic conditions, including both temperate and tropical regions.

2. Antagonistic Mechanisms Against Pathogens

Bacillus velezensis

  • Production of Secondary Metabolites: Bacillus velezensis produces a diverse array of secondary metabolites with strong antimicrobial properties. Cyclic peptides like iturin A and bacillomycin L disrupt fungal cell membranes, leading to intracellular substance leakage and cell death. Antimicrobial lipopeptides such as fengycin B and plipastatin A work in synergy with cyclic peptides, enhancing membrane damage. Bacitracin – like compounds like bacillomycin D and mycosubtilin bind to sterols in fungal membranes, altering membrane fluidity and permeability. Surfactin – like compounds, including surfactin and bacilysin, have surface – active and antibiotic properties, inhibiting both Gram – positive and Gram – negative bacteria.
  • Competition for Nutrients and Space: This bacterium competes effectively with plant pathogens for essential nutrients and space in the rhizosphere. By rapidly colonizing the root surface, it limits the access of pathogens to the plant, reducing the likelihood of infection.

Trichoderma harzianum

  • Competition: Trichoderma harzianum has a high growth rate, allowing it to quickly occupy the ecological niche around plant roots, competing with pathogens for nutrients and space. It can rapidly grow and spread, forming a physical barrier that prevents pathogens from reaching the plant.
  • Mycoparasitism: It exhibits mycoparasitic behavior, where it attaches to the hyphae of pathogenic fungi. Once attached, it secretes extracellular enzymes such as chitinases, glucanases, and proteases that degrade the cell walls of the host pathogen, penetrating the hyphae and absorbing nutrients, ultimately killing the pathogen.
  • Antibiosis: Trichoderma harzianum produces a variety of antibiotics, including trichodermin, harzianic acid, and gliotoxin. These antibiotics inhibit the growth and development of pathogenic fungi and bacteria, preventing them from infecting plants.
  • Induced Systemic Resistance (ISR): It can induce systemic resistance in plants. When Trichoderma harzianum interacts with the plant, it triggers a series of physiological and biochemical responses in the plant, leading to the activation of defense mechanisms. This makes the plant more resistant to subsequent pathogen attacks.

3. Effects on Plant Growth Promotion

Bacillus velezensis

  • Hormone Secretion: Bacillus velezensis secretes plant – growth – promoting hormones such as indole – 3 – acetic acid (IAA) and gibberellins (GA). IAA promotes root growth, cell elongation, and differentiation, while GA is involved in stem elongation, seed germination, and flowering. In tomato plants treated with Bacillus velezensis, an increase in root length and biomass has been observed, attributed to IAA secretion.
  • Nutrient Solubilization: The bacterium secretes enzymes like phosphatase, which solubilizes phosphorus in the soil, making it more available for plant uptake. Nitrifying enzymes secreted by Bacillus velezensis enhance the conversion of ammonia to nitrate, improving nitrogen availability for plants, especially beneficial in nutrient – poor soils.

Trichoderma harzianum

  • Enhanced Nutrient Uptake: Trichoderma harzianum can enhance the uptake of nutrients such as nitrogen, phosphorus, and potassium by plants. It improves the root system’s efficiency in absorbing nutrients from the soil, leading to better – nourished plants.
  • Stimulation of Root Growth: It stimulates root growth and development, leading to a more extensive and efficient root system. The fungus also produces growth – promoting substances that can enhance plant growth, such as auxins and cytokinins.

4. Application in Disease Control

Bacillus velezensis

  • Spectrum of Activity: Bacillus velezensis has a broad – spectrum activity against various plant pathogens. It can effectively control soil – borne fungal diseases like Rhizoctonia solani, Fusarium oxysporum, and Penicillium spp. It also shows antibacterial activity against pathogens such as Pseudomonas spp. and Xanthomonas spp. In the case of root rot diseases caused by Fusarium oxysporum, the application of Bacillus velezensis – based biocontrol agents has been shown to reduce disease incidence.
  • Mode of Application: It can be applied through seed treatment, soil drenching, or foliar spraying. Seed treatment protects seeds from soil – borne pathogens during germination and promotes early root growth. Soil drenching controls soil – borne pests and pathogens, while foliar spraying protects above – ground parts from fungal and bacterial diseases.

Trichoderma harzianum

  • Spectrum of Activity: Trichoderma harzianum is highly effective against a wide range of fungal pathogens, including those causing root rot, damping – off, and wilt diseases. It can parasitize and inhibit the growth of fungi such as Rhizoctonia solani, Sclerotium rolfsii, and Fusarium spp. It is also effective in controlling some foliar diseases like powdery mildew.
  • Mode of Application: Common application methods include seed treatment, soil amendment, and foliar application. Seed treatment with Trichoderma harzianum can protect seeds from soil – borne pathogens and promote germination. Soil amendment with the fungus can improve soil health and suppress soil – borne diseases. Foliar application forms a protective biofilm on leaves, preventing pathogen invasion.

5. Compatibility and Environmental Impact

Bacillus velezensis

  • Compatibility: Generally, Bacillus velezensis is compatible with many fertilizers and some pesticides. However, it may not be compatible with strong chemical fungicides that could kill the bacterium.
  • Environmental Impact: As a natural bacterium, it has a low environmental impact. It does not leave harmful residues in the environment and can contribute to soil health by promoting the growth of beneficial microorganisms.

Trichoderma harzianum

  • Compatibility: Trichoderma harzianum is often compatible with other beneficial microorganisms and can be used in combination with some fertilizers. However, like Bacillus velezensis, it may not be compatible with certain broad – spectrum chemical pesticides.
  • Environmental Impact: It is considered environmentally friendly. It decomposes organic matter in the soil, contributing to nutrient cycling, and does not pose a threat to non – target organisms.

6. Market Availability and Future Prospects

Bacillus velezensis

  • Market Availability: In recent years, several commercial products containing Bacillus velezensis have been developed and registered. These include microbial fertilizers and pesticides. For example, some companies have launched products targeting specific diseases.
  • Future Prospects: With the increasing demand for sustainable agriculture, the use of Bacillus velezensis is expected to grow. Further research may lead to the development of more effective formulations and applications, expanding its use in different crops and regions.

Trichoderma harzianum

  • Market Availability: Trichoderma harzianum – based products are widely available in the market. There are numerous commercial formulations for soil amendment, seed treatment, and foliar application, targeting a variety of crops.
  • Future Prospects: Continued research on Trichoderma harzianum may lead to the discovery of new strains with enhanced properties, such as increased disease resistance or better adaptation to specific environmental conditions. This could further expand its market share and applications in agriculture.
Comparison Items
Bacillus velezensis
Trichoderma harzianum
Taxonomic Status
Firmicutes, Bacillales, Bacillaceae, Bacillus
Hypocreaceae, Trichoderma, Ascomycota
Characteristics
Gram – positive, endospore – forming rod. Aerobic, grows at 15 – 45°C, pH 5.0 – 10.0
Aerial mycelium white/gray/yellow, curly. Transparent, smooth – walled hyphae, rapid growth
Action Mechanisms
Secretes enzymes, antibiotics; hydrolyzes fungal walls, inhibits spore germination, alters membrane, promotes growth with hormones
Competition, parasitism, antibiosis, induces plant resistance
Target Pathogens
Phytophthora, Fusarium, Rhizoctonia, etc.
Pythium, Rhizoctonia, Fusarium, etc., causing root rot, mildew
Growth – Promoting
Hormones (IAA, GA), enzyme – based nutrient solubilization
Nutrient transformation, root growth stimulation
Applications
Foliar spray, irrigation; used in feed, medicine, etc.
Seed dressing, soil mixing; for various crops
Precautions
Control dosage, avoid high – temp spraying, keep dry, no strong acids
Check expiration, cool storage, no chemical/fungicide mix
 

In conclusion, both Bacillus velezensis and Trichoderma harzianum offer significant advantages in agricultural applications, including disease control and plant growth promotion. The choice between them depends on various factors such as the specific crop, the prevalent diseases in the area, and the desired mode of application. Understanding their differences and similarities can help in devising more effective and sustainable agricultural strategies.

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