🧬 Biological Control and PGPR

Biological control uses beneficial microorganisms to suppress plant pathogens and is a key low-residue strategy in sustainable plant disease management.

---

Biological Control: Definition and Relevance

Biological control reduces pathogen inoculum or disease-causing activity using living antagonists and their interactions in the crop ecosystem.

Common agents include Trichoderma, Pseudomonas, and Bacillus species.

---

Main Mechanisms of Biocontrol

Mycoparasitism and Lysis

Antagonists attack pathogen hyphae and degrade cell walls using enzymes such as chitinase and glucanase.

Antibiosis

Beneficial microbes release metabolites that inhibit pathogen growth or reproduction.

Competition

Antagonists outcompete pathogens for nutrients, space, and micronutrients such as iron.

Induced Resistance

Some rhizosphere microbes prime host defense pathways and reduce disease severity after challenge.

---

Trichoderma-Based Disease Management

Trichoderma formulations are widely used against root and collar pathogens.

Benefits include:

• Rhizosphere colonization
• Antagonism against multiple fungi
• Improvement of root growth and nutrient uptake

Good field performance depends on viable formulation, proper carrier, and timely application.

---

PGPR: Plant Growth Promoting Rhizobacteria

PGPR are root-associated bacteria that promote growth and improve stress tolerance while suppressing diseases.

Important functions:

• Siderophore-mediated nutrient competition
• Production of growth-promoting metabolites
• Support to systemic resistance

---

Practical Use in IDM

Biological agents are most effective when integrated with:

• Seed treatment
• Soil application near root zone
• Compatible cultural and chemical schedules

Avoid tank-mixing with incompatible fungicides that kill beneficial microbes.

---

Summary Cheat Sheet

Mechanism Snapshot

Mechanism	What Happens	Example Outcome
Mycoparasitism	Antagonist attacks pathogen hyphae	Lower pathogen viability
Antibiosis	Inhibitory metabolites produced	Reduced pathogen growth
Competition	Nutrient/space capture by antagonist	Pathogen suppression
Induced resistance	Host defense primed	Lower disease expression

Quick Recall Points

• Biocontrol is a living system; viability matters.
• PGPR can give both disease suppression and growth benefit.
• Integration with agronomy decides field-level consistency.

Exam Traps

• Biocontrol is not instant like contact fungicide action.
• Not all strains of same species perform equally.
• Poor storage can collapse microbial population and efficacy.

References

2 sources • [1] [2]

[1]

Biological Control of Plant Pathogens

Book

[2]

PGPR and Rhizosphere Health in Crop Protection

Journal