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C4 mic319

  1. 1. MIC 319 FUNDAMENTALS OF AGRICULTURAL MICROBIOLOGY Chapter 4 Diagnosis of Plant disease By Siti Norazura Jamal (Miss Azura) 03 006/ 06 483 2132
  2. 2. Objective Identify common plant diseases cause by microorganism Observing the symptoms and sign developed Capable to relate Koch’s Postulate principles
  3. 3. Outline • Definition of symptoms and signs • Categories of symptoms     Changes of colour Death of cell necrosis Hyperplastic formation Hypoplasia • Principle of Koch’s Postulates
  4. 4. Symptoms and Signs Symptoms : The visible response of a plant to a causal agent over time. Dead spot in leaves or bark Unnatural colour or shape Swelling on root or branches
  5. 5. Dead Spot on Leaves Swelling on Branches
  6. 6. Symptoms and Signs Signs : The pathogen or its parts that seen on a host plant Observable structure of agent that cause the disease Fungal spores Insects on plant
  7. 7. Fungal Spores Aphids on Plant
  8. 8. Categories of Symptoms Symptom changes of colour Symptom death of cell Hypertrophy & Hyperplasia Hypotrophy & Hypoplasia
  9. 9. Example of Plant Disease Symptoms Symptom Changes of Colour Chlorosis Etiolation Mosaic
  10. 10. Chlorosis Yellowing of leaves due to: Loss of chlorophyll pigment/lack of active chlorophyll Nutrient deficiencies Toxicity of material (pesticide)
  11. 11. Etiolation Symptom of yellowing & elongation of stems/leaves Due to the lack of light (under dark condition)
  12. 12. Mosaic Formation of light and dark green/yellow mosaic pattern on leaves
  13. 13. Symptom Death of Cell Necrosis General necrosis Local necrosis Soft rot Leaf spots Dry rot Anthracnose Vascular wilt Downy mildew Powdery mildew Blight Canker
  14. 14. General Necrosis Occur in the whole plant that causes rot of plant / tissue Local Necrosis The necrosis sites are limited Only involved a part or few plant cells / tissues
  15. 15. General Necrosis – Soft Rot Occur to the fruit &vegetable that cause by the bacteria (Erwinia carotovora) The infected part become rot and watery
  16. 16. General Necrosis - Blight The fast and overall death of plant tissue such as shoot or leaves Pathogens kill the cells / tissues with which they are in close contact and become generally distributed. Example - Potato late blight (Phytophthora infestans)-fungus
  17. 17. Local Necrosis – Leaf Spots Spot of death cell or the presence of small necrotic areas on leaves Might caused by virus, fungal, bacteria, insect bites, etc. Example : Bacteria leaf spot – Xanthomonas campestris pv. vesicatoria Septoria leaf spots - fungus
  18. 18. Bacteria Leaf Spot on Pepper Septoria Leaf Spot
  19. 19. Local Necrosis Anthracnose Normally infected by imperfect fungi or Ascomycetes Produces blackish lesions on fruits, stem & leaf Blackness being due to the presence of dark spores, mycelium or both Example – Mango : Colletotrichum gloeosporioides Cucurbit : Colletotrichum lagenarium
  20. 20. Necrosis – Cankers Sunken areas in wood Death of plant parts Most are caused by fungi (Ascomycetes), but - a few bacterial cankers Example – Durian cankers = Phytophthora palmivora (fungus)
  21. 21. NecrosisPowdery Mildew The appearance of powdery spots on the leaves Example - Powdery mildew on cucurbit =Erysiphe cichoracearum (fungus)
  22. 22. Local Necrosis – Downey Mildew The occurrence of yellowish rectangular spot on the leaves Example – Downey mildew on cucurbit Pseudoperonospora cubensis, (fungus)
  23. 23. Symptom of Hyperplastic Deformation Hypertrophy Hyperplasia Gall
  24. 24. Hyperplastic Deformation : Abnormal outgrowths of the plant host Hypertrophy : Overgrowth of plant organ or plant size because the increasing of cell sizes Hyperplasia : Overgrowth of plant organ or plant size because the increasing of cell numbers or cell multiply rapidly. Both gave the same results to the plant where the size of plant tissue or plant organs increased than usual (abnormal size)
  25. 25. Gall Localized swellings of plant organ May caused by various pathogens such as bacteria, fungi, nematodes and insects. Examples – Crown gall = Agrobacterium tumefaciens (bacteria) Root knot = Meloidogyne spp (nematodes)
  26. 26. Bacteria Crown Gallaffect root & stem Root Knot – attack root
  27. 27. Witches' Broom Appear as a cluster of small shoots
  28. 28. Curls The leaves become twisted and curled
  29. 29. Symptom of Hypoplasia Retardation Dwarfing One or more members of a plant are significantly smaller than standard members of their species
  30. 30. Hypoplasia The underdevelopment of plant tissue and organs due to the smaller production than normal cells
  31. 31. Hypotrophy : the under-development of plant organ or plant size because the reducing of cell sizes Hypoplasia : the under-development of plant organ or plant size because the reducing of cell numbers
  32. 32. Principle of Koch’s Postulates
  33. 33. Principle of Koch’s Postulates 4 criteria designed to verify that the microorganism is the causal agent for the disease. 4 rules / steps: The suspected pathogen must be consistently associated with the diseased plant The microorganism must be isolated from the diseased organism and grown in pure culture. The cultured microorganism should cause disease when inoculated into a healthy organism. The microorganism must be reisolated from the inoculated plant and grown in a pure culture. The microorganism should have the same characteristic with the original culture.