L40 Plant Disease, Pests and Food Production

Biotic factors

Living organisms causing crop yield losses.

Crop losses

Estimated at 40% of yields globally.

Economic impact

Over $200 billion lost annually due to pathogens.

Acute Oak Decline

Bacterial disease spread by beetle larvae.

Plant Pathogens

Includes bacteria, viruses, fungi, and similar organisms.

Bacterial diseases

Responsible for over 5% annual crop losses.

Pseudomonas syringae

Widespread bacterial pathogen affecting various crops.

Bacterial speck

Disease affecting tomatoes, caused by P. syringae.

Blackleg disease

Caused by Pectobacterium spp in potatoes.

Soft rots

Potato spoilage in storage due to Pectobacterium.

Virus diseases

Major economic losses, especially in Africa and Asia.

Viral transmission

Spread by vectors like aphids and nematodes.

Cassava mosaic virus

Significant yield losses in African cassava crops.

Phytophthora infestans

Causes Late Potato Blight, linked to Irish Famine.

Irish Potato Famine

Resulted in 1 million deaths in the 1840s.

Fungicide costs

Annual losses reach $3 billion worldwide.

Necrotrophic pathogens

Grow in dead tissue, secrete degrading enzymes.

Biotrophic pathogens

Require living tissue for growth and nutrient extraction.

Halo blight

Disease affecting French beans, caused by bacteria.

Bacterial blight

Affects soybeans, causing significant crop damage.

Kiwifruit epidemic

P. syringae caused $2 billion losses in New Zealand.

Defense Mechanisms

Strategies plants use to protect against pathogens.

Preformed Structural Barriers

Physical defenses present before pathogen attack.

Innate Immunity

Inherited defense mechanism against pathogens in plants.

Pathogen Associated Molecular Patterns (PAMPs)

Molecules recognized by plant immune systems.

Basal Immunity

Initial immune response using surface proteins.

Gene-For-Gene Hypothesis

Resistance requires matching genes in host and pathogen.

Resistance Genes (R-genes)

Genes in plants that confer resistance to pathogens.

Avirulence Genes

Pathogen genes essential for successful invasion.

PAMP-triggered Immunity (PTI)

Defense response activated by recognizing PAMPs.

Effectors

Pathogen proteins that manipulate host defenses.

Flagellin

PAMP from bacterial flagella, triggers immune response.

Lipopolysaccharide (LPS)

PAMP from bacterial outer membrane, recognized by plants.

Elongation Factor Tu (EF-Tu)

Bacterial protein recognized by plant immune systems.

Ergosterol

Fungal PAMP, component of fungal cell membranes.

Chitin

Structural polysaccharide in fungal cell walls, recognized by plants.

β-glucans

Fungal cell wall components triggering immune responses.

CBEL

Oomycete PAMP, cellulose binding elicitor lectin.

Pep-13

Oomycete PAMP, triggers plant immune response.

Virulent Pathogen

Pathogen capable of causing disease in susceptible hosts.

Avirulent Pathogen

Pathogen that cannot cause disease in resistant hosts.

Pseudomonas syringae

Bacterial pathogen used in plant resistance studies.

Rx Gene

Resistance gene in potatoes against Potato Virus X.

Tobacco Resistance

Tobacco's ability to resist Pseudomonas syringae infection.

Resistance genes

Genes that recognize pathogen effectors in plants.

Type III secretion system (T3SS)

System delivering effectors into host cells.

Effectors

Molecules that suppress plant defense responses.

Avirulence genes

Genes encoding effector molecules in pathogens.

Resistance (R) genes

Plant genes triggering defense against pathogens.

Programmed Cell Death

Localized response to pathogen infection in plants.

Systemic Acquired Resistance (SAR)

Broad-spectrum resistance activated by local infection.

Salicylic acid (SA)

Signaling molecule in Systemic Acquired Resistance.

Pathogenesis-related (PR) proteins

Proteins with anti-pathogen properties synthesized during defense.

Chitinases

Enzymes targeting insect and fungal cell walls.

β1-3 glucanases

Enzymes targeting bacterial and fungal cell walls.

Genetic drift

Pathogen evolution leading to loss of resistance.

Boom or Bust

Cycle of resistance success followed by failure.

P. infestans

Pathogen causing late blight in potatoes.

Rpi-vnt1.1

Promising R gene from Solanum venturii.

Transgenic lines

Plants genetically modified for enhanced resistance.

Simplot Innate Potatoes

Potatoes engineered for multiple disease resistances.

Non-conventional resistance

Resistance strategies not based on R-genes.

Papaya Ringspot Virus

Virus causing significant agricultural losses in Hawaii.

Constitutive expression

Continuous expression of a gene under all conditions.

Field trials

Tests conducted in natural conditions to evaluate resistance.

Cultivated varieties

Domesticated plant species bred for specific traits.

Emergence of new races

Development of new pathogen strains evading existing resistance.