What is Disease Resistance?
Disease resistance refers to the ability of a plant to limit the growth and development of a pathogen. There are several types of disease resistance in plants:
- Passive resistance - innate traits that make it harder for pathogens to establish an infection, like waxy layers on leaves, bark thickness, etc. These traits are always "on".
- Active resistance - plants detect pathogens and actively respond with defense mechanisms to stop infections. This induced resistance relies on the plant's immune system. There are two types of active resistance:
- Nonhost resistance - the plant is resistant to all genetic variations of a pathogen species. Most plants are nonhosts for most pathogens.
- Gene-for-gene resistance - the plant resists specific variations of a pathogen that has genes the plant recognizes. This leads to a hypersensitive response to stop the infection.
What causes disease resistance?
- Resistance can be caused by major resistance (R) genes that recognize specific pathogens. These genes encode receptors that detect pathogen proteins and trigger defense responses.
- There are also quantitative trait loci (QTLs) that provide partial disease resistance. These involve many genes, each contributing small effects.
- Epigenetic changes can also prime defenses against pathogens without altering the DNA sequence.
What are the benefits of disease resistance?
- Maintains crop yield and quality by reducing loss from infections.
- Reduces reliance on chemical pesticides.
- Slows the evolution of more aggressive pathogens.
- Important part of integrated pest management programs.
There are several methods for introducing disease resistance into crop plants:
- Traditional breeding to combine resistance genes from different varieties.
- Genetic engineering to insert R genes or silence susceptibility genes.
- Mutagenesis followed by selection of resistant mutants.
- Searching wild relatives for new resistance traits to introgress.
I hope this gives you a good overview of what disease resistance entails and why it is an important agronomic trait! Let me know if you have any other questions.