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C4 mic319
This document discusses plant disease diagnosis and summarizes key points from Chapter 4 of the textbook "Fundamentals of Agricultural Microbiology". It defines symptoms as visible responses in plants over time while signs are observable structures of the causal agent. Common symptoms include changes in color, necrosis, hyperplasia, and hypoplasia. Koch's postulates are described as four criteria to verify a microorganism as the causal agent of a disease.
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C4 mic319
- 1. MIC 319 FUNDAMENTALS OF AGRICULTURAL MICROBIOLOGY Chapter4 Diagnosis of Plant disease By Siti Norazura Jamal (Miss Azura) 03 006/ 06 483 2132 norazura6775@ns.uitm.edu.my
- 2. Objective Identify common plantdiseases cause by microorganism Observing the symptoms and sign developed Capable to relate Koch’s Postulate principles
- 3. Outline • Definition ofsymptoms and signs • Categories of symptoms Changes of colour Death of cell necrosis Hyperplastic formation Hypoplasia • Principle of Koch’s Postulates
- 5. 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
- 6. Dead Spot onLeaves Swelling on Branches
- 7. 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
- 8.
- 10. Categories of Symptoms Symptom changesof colour Symptom death of cell Hypertrophy & Hyperplasia Hypotrophy & Hypoplasia
- 11. Example of Plant DiseaseSymptoms Symptom Changes of Colour Chlorosis Etiolation Mosaic
- 12. Chlorosis Yellowing of leavesdue to: Loss of chlorophyll pigment/lack of active chlorophyll Nutrient deficiencies Toxicity of material (pesticide)
- 13. Etiolation Symptom of yellowing &elongation of stems/leaves Due to the lack of light (under dark condition)
- 14. Mosaic Formation of light anddark green/yellow mosaic pattern on leaves
- 15. Symptom Death ofCell Necrosis General necrosis Local necrosis Soft rot Leaf spots Dry rot Anthracnose Vascular wilt Downy mildew Powdery mildew Blight Canker
- 16. General Necrosis Occur in thewhole plant that causes rot of plant / tissue Local Necrosis The necrosis sites are limited Only involved a part or few plant cells / tissues
- 17. General Necrosis – SoftRot Occur to the fruit &vegetable that cause by the bacteria (Erwinia carotovora) The infected part become rot and watery
- 18. General Necrosis - Blight Thefast 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
- 19. Local Necrosis – LeafSpots 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
- 20. Bacteria Leaf Spoton Pepper Septoria Leaf Spot
- 21. Local Necrosis Anthracnose Normallyinfected 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
- 22. Necrosis – Cankers Sunken areasin wood Death of plant parts Most are caused by fungi (Ascomycetes), but - a few bacterial cankers Example – Durian cankers = Phytophthora palmivora (fungus)
- 23. NecrosisPowdery Mildew The appearanceof powdery spots on the leaves Example - Powdery mildew on cucurbit =Erysiphe cichoracearum (fungus)
- 24. Local Necrosis – DowneyMildew The occurrence of yellowish rectangular spot on the leaves Example – Downey mildew on cucurbit Pseudoperonospora cubensis, (fungus)
- 25.
- 26. 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)
- 27. Gall Localized swellings ofplant organ May caused by various pathogens such as bacteria, fungi, nematodes and insects. Examples – Crown gall = Agrobacterium tumefaciens (bacteria) Root knot = Meloidogyne spp (nematodes)
- 28. Bacteria Crown Gallaffectroot & stem Root Knot – attack root
- 29. Witches' Broom Appear asa cluster of small shoots
- 30. Curls The leaves become twistedand curled
- 31. Symptom of Hypoplasia Retardation Dwarfing Oneor more members of a plant are significantly smaller than standard members of their species
- 32. Hypoplasia The underdevelopment ofplant tissue and organs due to the smaller production than normal cells
- 33. Hypotrophy : theunder-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
- 34. Principle of Koch’sPostulates
- 35. Principle of Koch’s Postulates 4criteria 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.