introduction plant pathology, General plant pathology,
- 1. Plant pathology JRF, MSc, BSc,& Competitive Exams Introduction Of Plant Pathology Prepared by :- Abhishek sharma MSc Plant Pathology Complete Lecture Upload on Youtube Channel :- Fasal Doctor
- 2. Plant Pathology- Definition Plant Pathology, also known as Phytopathology is a branch of agricultural, biological or botanical science which deals with the study of diseases in plants - their causes, etiology, epidemiology, resulting losses and management. Relation to other Sciences ✓ Virology, ✓ Mycology, ✓ Bacteriology, ✓ Microbiology, ✓ Physiology, ✓ Chemistry, ✓ Genetics, ✓ Biotechnology
- 3. Objectives of Plant Pathology ➢To study living, non-living and environmental causes of diseases or disorders of the plants. ➢To study the mechanism of plant disease development. ➢To study interaction between host/susceptible and the pathogens. ➢To develop systems of management of plant diseases and reducing losses caused by them. Importance of Plant Diseases or Plant Pathology About 34% of the crop produce is lost annually due to diseases, insect-pests and weeds on the global basis (Cramer, 1967); out of which, 12% is lost due to diseases (caused by fungi, bacteria or viruses), 11% due to nematodes, 7% due to insect-pests and 3% due to weeds. When plant protection measures are not implemented, annual loss of 30-50% are common in major crops including horticulture (Encyclopedia Britannica, 2002)
- 4. Causes of Plant Diseases Plant diseases are caused by a variety of pathogens. The word pathogen can be broadly defined as any agent or factor that incites ‘pathos’ or disease in an organism. Thus in strict sense, the pathogens do not necessarily belong to living or animate groups. Abiotic (Inanimate) factors They include mainly the deficiency or excess of nutrients, light, moisture, aeration, abnormality in soil condition, atmospheric impunities etc. Examples • Black tip of mango (due to SO2 toxicity), • khaira disease of rice (due to Zn deficiency), • whiptail of cauliflower (Mo deficiency), • hollow and black heart of potato (due to excessive accumulations of CO2 in storage), • bitter pit of apple (due to Ca deficiency).
- 5. Mesobiotic These are the disease incitants which are neither living nor non-living. They are considered to be on the threshold of life. ➢Viruses: They are infections agents made up of one type of nucleic acid (RNA or DNA) enclosed in a protein coat. • potato leaf roll, • leaf curl of tomato and chillies, ➢ Viroids: They are naked, infectious strands of nucleic acid. They cause diseases like • potato spindle tuber, • citrus exocortis, • chrysanthemum stunt, • cadang cadang of coconut palm, • star crack of apple, etc.
- 6. Biotic (Animate) causes This category includes the pathogens which are animate or living or cellular organisms. Prokaryotes Bacteria which are unicellular prokaryotic microorganisms lacking true nucleus. • Brown rot or wilt of potato, • Soft rot of potato and vegetables, • Citrus canker, etc. Mollicutes: This group includes spiroplasmas and phytoplasmas, are wall-less prokaryotes and cause diseases • Little Leaf of Brinjal (Eggplant) • Coconut Root (Wilt) Disease • Corn Stunt Disease • Stubborn Disease of Citrus • Briittle Root of Horseradish Fastidious bacterium, Xylella fastidiosa causes almond leaf scorch, Pierce‘s disease of grapevine.
- 7. Biotic (Animate) causes This category includes the pathogens which are animate or living or cellular organisms. Eukaryotes i) Fungi: Potato wart, powdery mildew, rust, smuts, red rot of sugarcane (nearly 80% of plant diseases are caused by fungi). ii) Straminopiles (Oomycetes): Downy mildews, late blight of potato, white rust of crucifers, damping off etc. iii) Protozoa: Hart rot of coconut palm and phloem necrosis of coffee. iv) Algae: Red rust of mango or papaya or litchi v) Metazoan animals (Nematodes): Root knot of vegetables, ear cockle of wheat, citrus decline etc. vi) Parasitic flowering plants (Phanerogamic plant parasites): Dodder, Striga, Orobranche, Loranthus, Phoradendron, etc.
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