Biodegradables-Plant-diseases-triangle-and-common-symptoms

Disease Definition

  • Disease: Any physiological abnormality or significant disruption in the "normal" health of a plant.

    • Caused by:

      • Living (Biotic) agents: fungi, bacteria

      • Environmental (Abiotic) factors: nutrient deficiency, drought, lack of oxygen, excessive temperature, UV radiation, pollution.

Plant Disease Categories

  • Abiotic Diseases:

    • Non-contagious and non-infectious.

    • Do not spread from plant to plant.

    • Examples include:

      • Damages from air and soil pollutants.

      • Suboptimal conditions: light, moisture, temperature.

  • Biotic Diseases:

    • Infectious and contagious.

    • Spread from plant to plant.

    • Primarily caused by pathogens:

      • Viruses

      • Fungi

      • Bacteria

    • Damage caused to plant tissues:

      • Leaves, shoots, stems, roots, flowers.

      • Economically important parts: fruits and seeds.

Disease Triangle

  • A model to analyze the occurrence of plant diseases.

    • Three essential components must intersect:

      • Pathogen: Disease-causing agent.

      • Host: The plant that gets infected.

      • Environment: Conditions necessary for disease occurrence.

Plant Defenses

  • Constitutive Defenses:

    • Physical barriers such as:

      • Cell walls

      • Waxy epidermal cuticles

      • Bark

  • Inducible Defenses:

    • Detected by living plant cells in response to pathogens. Includes:

      • Production of toxic chemicals.

      • Production of pathogen-degrading enzymes.

      • Deliberate cell suicide (programmed cell death).

Symptoms of Plant Disease

  • A visible effect on the plant indicating disease. Common symptoms include:

    • Changes in color, shape, or function due to pathogen response.

Types of Plant Diseases

  • Spots (Lesions): Localized diseased area.

  • Blight: Affects large amounts of tissue.

  • Galls/Tumors: Masses of undifferentiated tissue growth found in stems, roots, leaves.

  • Cankers: Sunken lesions on stems or tree trunks.

  • Wilts and Rots:

    • Rots indicate tissue degradation by pathogens.

    • Wilt associated with pathogen affecting vascular tissues, often appears dark.

    • Damping off: Rots seedlings as they emerge from soil.

  • Mottling: Visible symptoms of viral disease include:

    • Yellowing, crinkling of leaves.

    • Misshapen leaves.

    • Yellow or necrotic rings on leaves/fruits.

    • Dwarfed plant appearance.