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What is Disease Resistance?
Disease resistance refers to the ability of a plant to limit the growth and development of a pathogen. It is an important trait that allows crops to avoid infections that could otherwise cause major yield losses.
There are two main types of disease resistance in plants:
- Horizontal resistance - Also called field resistance, this provides resistance to multiple strains of a pathogen at a level that limits epidemic development and economic losses. It is generally controlled by multiple genes and is long-lasting.
- Vertical resistance - Also called race-specific resistance, this protects the plant from some but not all strains of a pathogen. It is controlled by one or a few major genes and can be easier to breed into crops, but resistance is often overcome by new strains of the pathogen over time.
How does disease resistance work biologically?
Plants have evolved complex mechanisms to recognize and respond to pathogens in order to resist infections. When a pathogen infects a plant, the plant can recognize conserved molecules, known as elicitors, produced by the pathogen. This recognition triggers defense responses such as:
- Production of reactive oxygen species and antimicrobial compounds to kill the pathogen
- Reinforcement of plant cell walls to act as a physical barrier
- Hypersensitive response - programmed death of infected cells to limit pathogen growth
If these defenses are strong enough, the plant displays resistance and prohibits significant colonization by the pathogen.
Why is breeding for disease resistance important?
Incorporating genetic resistance into commonly grown crop varieties provides an economical, environmentally friendly, and effective method to control diseases. Relying solely on fungicides and bactericides to manage diseases can select for pathogen strains that become resistant to the chemicals.
Breeding resistant crop varieties helps:
- Reduce yield losses from diseases, improving food security
- Lower chemical inputs needed for disease control
- Develop more sustainable agricultural practices less reliant on agrochemicals
What challenges exist in developing resistant varieties?
While genetic disease resistance can greatly benefit agriculture, some key challenges exist:
- Identifying effective resistance genes and incorporating them into well-adapted varieties
- Monitoring pathogen evolution and staying ahead of new virulent strains that defeat resistant varieties
- Balancing disease resistance with maintenance of key agricultural traits like yield potential and end-use quality
Ongoing research that continues enhancing our understanding of plant-pathogen interactions and explores diverse germplasm sources for resistance traits will enable continued development of resistant varieties and effective disease management strategies.