What is disease resistance?
Disease resistance refers to the ability of a plant to prevent, limit, or overcome infection by a pathogen such as a virus, bacteria, or fungus. There are several types of disease resistance in plants:
- Passive resistance involves physical or chemical barriers that prevent infection or limit pathogen growth and reproduction. Examples include waxy layers on leaves, bark on stems, or antimicrobial compounds.
- Active resistance relies on recognition of pathogen molecules to trigger defense responses. This can be race-specific, effective against strains of a pathogen, or broad-spectrum, effective against multiple pathogens. Defense responses may include:
- Hypersensitive response (HR) - programmed cell death around infection site to limit spread
- Systemic acquired resistance (SAR) - heightened defenses throughout the plant after infection
- Induced systemic resistance (ISR) - enhanced defensive capacity mediated by beneficial microbes
- Quantitative or horizontal resistance - conferred by multiple genes and effective against all strains of a pathogen, but with partial effect. Slows epidemic development.
- Vertical or qualitative resistance - complete resistance mediated by single R genes that recognize specific pathogen strains. Can be overcome by new strains.
There are several strategies for increasing disease resistance in crops:
- Traditional breeding to combine resistance genes from different plant varieties
- Molecular breeding to precisely introduce R genes using genetic engineering
- Seed treatments to coat seeds with protective microbes or chemicals
- Cultivar mixtures and multilines to deploy crops with multiple sources of resistance
The use of disease resistant crop varieties is a central pillar of integrated pest management. It provides an economical and environmentally friendly method of controlling endemic pathogens. By reducing infection, resistant plants exhibit improved growth, yield, and quality. This in turn supports productive and sustainable agriculture systems.
In summary, disease resistance refers to the innate and adaptive defenses that enable plants to thwart or mitigate invasion by the pathogens that cause infectious disease. Understanding the mechanisms, genetics, and strategies behind plant immune systems is crucial for developing resilient, healthy crops.