Disease resistance refers to the ability of a plant to prevent, tolerate, or overcome infection by a pathogen such as a virus, bacteria, or fungus. It is an important trait in agriculture and crop breeding because it reduces or prevents crop losses from diseases without requiring pesticides or other control methods.
There are two main types of disease resistance in plants:
- Passive resistance involves physical or chemical barriers present in the plant at all times that prevent infection or spread of the pathogen. Examples include waxy layers on leaves, chemical compounds in tissues, and lignification of cell walls. These barriers are part of the innate immune system of plants.
- Active resistance occurs after a plant detects a pathogen and mounts cellular defenses to block spread or kill infected cells through programmed cell death. This induced immune response involves complex signaling pathways that activate production of antimicrobial compounds and proteins to fight the infection. Active resistance often leads to a hypersensitive response - rapid death of infected plant cells.
Disease resistance traits in modern crops derive from resistance (
R) genes that plants have evolved in their populations and are bred into elite crop varieties. These
R genes enable the plant to recognize specific pathogens and trigger defense responses. However, pathogens can adapt to overcome specific
R genes, so breeding for durable, broad-spectrum resistance is an ongoing challenge.
Some key methods used to improve disease resistance in crops include:
- Introgressing major R genes from wild crop relatives through breeding
- Pyramiding multiple R genes together for more durable resistance
- Molecular breeding assisted by genetic markers and genomic selection
- Genetic engineering to insert resistance genes or modulate defense pathways
Improving disease resistance allows farmers to reduce fungicides and pesticides, lowering costs and environmental impact. It also leads to higher, more consistent yields and quality in crop production. Overcoming diseases like rusts, mildews, blights, and viral pathogens has been key to preventing major crop failures and feeding the growing global population.