Discuss the biological control practices for direct protection of plants from pathogens before or after infection takes place?

Biological control practices for direct protection of plants from pathogens can be implemented before or after infection takes place. These practices involve the use of beneficial organisms to suppress or eliminate plant pathogens.

Before infection takes place, biological control can be achieved through the use of biopesticides, which are naturally occurring substances derived from living organisms that can control pests and pathogens. These biopesticides can be applied preventatively to plants to protect them from potential infections. Examples of biopesticides include bacteria, fungi, viruses, and nematodes that are specifically targeted towards certain plant pathogens.

Another method of biological control before infection is the use of beneficial microorganisms, such as mycorrhizal fungi and rhizobacteria, which can colonize plant roots and enhance the plant's natural defense mechanisms against pathogens. These beneficial microorganisms can also outcompete harmful pathogens for resources, preventing them from establishing infections.

After infection takes place, biological control practices can involve the use of antagonistic microorganisms that can directly attack and suppress the plant pathogens. For example, certain bacteria and fungi produce antibiotics or enzymes that can inhibit the growth of pathogens. These antagonistic microorganisms can be applied as biocontrol agents to infected plants to help them recover from the infection.

Overall, biological control practices for direct protection of plants from pathogens can be effective both before and after infection takes place. By harnessing the power of beneficial organisms, farmers and gardeners can reduce the reliance on chemical pesticides and promote sustainable and environmentally friendly methods of plant protection.

Biological Control Practices for Direct Protection of Plants from Pathogens

Before Infection:

- Cultural Practices:
- Crop rotation: Planting different crops in the same area in sequential years to disrupt the pathogen's life cycle.
- Resistant cultivars: Selecting varieties of plants with genetic resistance to specific pathogens.
- Sanitation: Removing infected plant material and debris to reduce pathogen inoculum.

- Biopesticides:
- Trichoderma species: Fungi that colonize plant roots and suppress soilborne pathogens.
- Bacillus subtilis: Bacteria that produce antimicrobial compounds against pathogens.
- Streptomyces griseus: Bacteria that produce antibiotics to control fungal diseases.

After Infection:

- Biocontrol Agents:
- Hyperparasites: Parasites that attack and kill pathogens.
- Mycoparasites: Fungi that parasitize other fungi, including plant pathogens.
- Bacteriophages: Viruses that target and destroy specific bacteria, including plant pathogens.

- Induced Systemic Resistance (ISR):
- Using beneficial microbes or chemical elicitors to trigger defense responses in plants, making them less susceptible to infections.
- Examples: Pseudomonas fluorescens, Rhizobium spp., salicylic acid.

- Antimicrobial Peptides and Proteins:
- Plant-derived or microbial peptides and proteins that have antimicrobial activity against pathogens.
- Examples: Defensins, thionins, chitinases.

Mechanisms of Action:

- Competition for resources (e.g., nutrients, space)
- Production of antimicrobial compounds (e.g., antibiotics, enzymes)
- Induced systemic resistance
- Direct parasitism and predation
- Nutrient immobilization

Advantages of Biological Control:

- Environmentally friendly and sustainable
- Relatively low cost and easy to implement
- Can target specific pathogens
- May reduce reliance on chemical pesticides

Considerations:

- Careful selection of biocontrol agents to avoid potential negative effects
- Timing and method of application are crucial
- Requires an understanding of pathogen-host interactions
- May not be effective in all situations or against all pathogens