GTN3733 Chapter 5 Pathogenic Microbes in Agriculture PDF

C H A P T E R : 5 P A T H O G E N I C M I C R O B E S I N A G R I C U L T U R E B Y: DR. SUH AIZAN LOB I N TR O DU CT IO N TO PAT H OGE N I C MI CR O B ES Pathogenic microbes harm Types of pathogens: Major issues in agriculture: crops...

C H A P T E R : 5 P A T H O G E N I C M I C R O B E S I N A G R I C U L T U R E B Y: DR. SUH AIZAN LOB I N TR O DU CT IO N TO PAT H OGE N I C MI CR O B ES Pathogenic microbes harm Types of pathogens: Major issues in agriculture: crops by causing diseases that reduce yield and quality. Bacteria Yield loss. Fungi Increased production costs. Viruses Threats to food security. Nematodes Oomycetes PAT H O G E N I C B A C T E R I A Xanthomonas campestris: Black rot in crucifers. Examples of Plant Pseudomonas syringae: Bacterial blight in many crops. Pathogenic Bacteria: Ralstonia solanacearum: Bacterial wilt in tomatoes. Symptoms: Wilting, leaf spots, necrosis, and cankers. Spread: Via water, tools, insects, and infected seeds. SY MPTOMS ON CROP Xanthomonas campestris: Black rot in crucifers. SY MPTOMS ON CROP Pseudomonas syringae bacterial blight on soybean  Ralstonia solanacearum: Bacterial wilt in tomatoes. SYMPTOM ON CROP PATHOG EN LIF E CYCLE PAT HO GE NI C F U N GI Examples of Plant Pathogenic Fungi: Fusarium oxysporum: Causes wilts. Alternaria solani: Early blight in potatoes. Magnaporthe oryzae: Rice blast. Symptoms: Leaf spots, root rots, stem cankers, grain infections. Fungal Growth Conditions: High humidity, poor air circulation, wet soils. Control Strategies: Use fungicides, resistant varieties, and proper irrigation. SYMPTOMS ON CROP FU SARIU M OX YSP O RUM : CAUS ES W ILTS. ON TOMATOES SYMPTOMS ON CROP: A LT E R NA R IA S OLA NI: E A R LY B L I G H T I N P OTATOES. SYMPTOM ON CROP MAGN AP ORTHE O RYZAE: RICE BL AST. PATHOGEN LIFE CYCLE PAT HO GE NI C O O M YC E T E S Examples: Symptoms: Spread: Management: Improve soil Phytophthora Prefers waterlogged drainage, use Root and crown rots, infestans: Late blight and poorly drained fungicides, and seedling death. in potatoes. soils. plant resistant varieties. Pythium spp.: Damping-off in seedlings. SY MPTOM ON CROP Phytophthora infestans SY MPTOM ON CROP Phytium spp. PATHOG EN LIF E CYCLE VI RAL PATH OG ENS(V IRU SES ) Examples of Plant Viruses: Tomato mosaic virus (ToMV). Banana bunchy top virus (BBTV). Rice tungro virus (RTV). Symptoms: Leaf curling, mosaic patterns, stunted growth. Spread: Through insect vectors (e.g., aphids, whiteflies) or contaminated tools. SYMPTOM ON CROP Tomato mosaic virus PATHOGEN LIFE CYCLE N E M ATO D E S Types of Pathogenic Symptoms: Control: Nematodes: Meloidogyne spp. Root deformities, Heterodera spp. Soil fumigation, (Root-knot reduced water and (Cyst nematodes): crop rotation, nematodes): nutrient uptake, Impact cereals. resistant varieties. Cause root galls. stunted growth.  Meloidogyne spp. (Root-knot nematodes): Cause root galls. PATHOG EN LIF E CYCLE  Key Steps in Pathogen Life Cycle: o Survival in soil, seeds, or residues. o Spread via water, wind, insects, or tools. o Infection through stomata, wounds, or root tips. o Reproduction within the host. DISEASE CYCLES  CONTROL MEASURES Cultural Chemical Biological Genetic Methods Controls Controls Resistance Crop rotation. Fungicides, Use of Develop and Sanitation bactericides, beneficial use resistant (removal of and microbes to crop varieties. infected plant nematicides. suppress material). Focus on safe pathogens. Proper and targeted irrigation application. practices. CONCLUSION Pathogenic microbes pose significant challenges to agriculture. Understanding their biology and control methods is essential for sustainable crop production. Integrating cultural, biological, and chemical practices ensures effective management and food security.