🌿 Host Plant Resistance
Concept, types, and utility of host plant resistance in disease management.
Host plant resistance is one of the most economical and durable approaches to disease management because it reduces disease pressure directly at the host level.
Resistance: Basic Concepts
Resistance is the inherited ability of a plant to restrict pathogen infection, colonization, or symptom development.
It can range from partial to near-complete and may be controlled by major genes, minor genes, or both.
Gene-for-Gene Relationship
The gene-for-gene model explains that for each host resistance gene, a corresponding pathogen virulence/avirulence interaction determines compatibility.
This interaction governs whether disease develops or resistance is expressed.
IMPORTANT
Disease outcome depends on both host genotype and pathogen genotype.
Vertical vs Horizontal Resistance
Vertical Resistance
- Race-specific
- Often controlled by one or few major genes
- Can be highly effective but vulnerable to new pathotypes
Horizontal Resistance
- Broadly race-nonspecific
- Usually polygenic
- Often partial but comparatively durable in field conditions
Boom-and-Bust Phenomenon
When a single major resistance gene is deployed widely, new matching pathogen races may emerge, causing resistance breakdown.
This cycle is called boom and bust and is common in rapidly evolving airborne pathogen systems.
Durable Resistance and Breeding Strategy
Durability improves when breeders combine multiple resistance sources and integrate major plus minor gene effects.
Practical strategies include:
- Gene pyramiding
- Multi-line or varietal diversification
- Resistance deployment with IDM support
Summary Cheat Sheet
Resistance Types at a Glance
| Feature | Vertical Resistance | Horizontal Resistance |
|---|---|---|
| Specificity | Race-specific | Broad/race-nonspecific |
| Genetic basis | Major genes (few) | Polygenic (many) |
| Field durability | Lower (often) | Higher (often) |
| Disease suppression | Usually strong initially | Moderate but stable |
Quick Recall Points
- Host resistance reduces dependence on repeated chemical sprays.
- Durable resistance is generally built through gene combinations.
- Pathogen evolution pressure must be considered in deployment.
Exam Traps
- Complete immunity is rare; most resistance is relative.
- Vertical resistance is not always durable.
- Horizontal resistance may look weaker initially but can be more stable over years.
References
2 sources • [1] [2]
References
Host-Pathogen Genetics in Plant Disease Resistance
BookBreeding for Durable Disease Resistance
BookLesson Doubts
Ask questions, get expert answers