Plant Pathology Cheat Sheet
The core ideas of Plant Pathology distilled into a single, scannable reference — perfect for review or quick lookup.
Quick Reference
Koch's Postulates
A set of four criteria established by Robert Koch to prove that a specific microorganism causes a specific disease: the pathogen must be found in all diseased organisms, isolated from the host, cause disease when introduced to a healthy host, and be re-isolated from the newly diseased host.
Disease Triangle
A foundational concept in plant pathology stating that plant disease results from the interaction of three factors: a susceptible host, a virulent pathogen, and a favorable environment. All three must be present simultaneously for disease to occur.
Hypersensitive Response (HR)
A rapid, localized cell death reaction at the site of pathogen invasion that restricts pathogen growth. It is a key component of plant innate immunity, often triggered by the recognition of pathogen effector molecules by plant resistance (R) proteins.
Systemic Acquired Resistance (SAR)
A whole-plant immune response triggered after a localized pathogen attack that provides broad-spectrum, long-lasting protection against subsequent infections. SAR is mediated by the signaling molecule salicylic acid and the expression of pathogenesis-related (PR) proteins.
Gene-for-Gene Hypothesis
Proposed by Harold Flor in the 1940s based on studies of flax rust, this model states that for each resistance (R) gene in the host plant, there is a corresponding avirulence (Avr) gene in the pathogen. Disease occurs only when the pathogen lacks the recognized Avr gene or the host lacks the corresponding R gene.
Integrated Pest Management (IPM)
A holistic approach to disease and pest management that combines biological, cultural, physical, and chemical methods to minimize economic, health, and environmental risks. IPM emphasizes monitoring, threshold-based decision-making, and preventive strategies over routine chemical applications.
Pathogen Effectors
Molecules, typically proteins, secreted by pathogens into host cells to suppress plant immune responses, manipulate host cell processes, and promote colonization. Effectors are key determinants of pathogen virulence and host specificity.
Mycotoxins
Toxic secondary metabolites produced by certain fungi that contaminate food and feed crops, posing serious risks to human and animal health. Major mycotoxins include aflatoxins, fumonisins, deoxynivalenol, and ochratoxins.
Plant Quarantine
Regulatory measures designed to prevent the introduction and spread of plant pathogens, pests, and invasive species across geographic boundaries. Quarantine involves inspection, certification, treatment, and sometimes destruction of infected plant material.
Biological Control (Biocontrol)
The use of living organisms or their products to suppress plant diseases. Biocontrol agents include antagonistic fungi, bacteria, and viruses that compete with, parasitize, or induce resistance against pathogens.
Key Terms at a Glance
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