What is disease resistance?
Disease resistance refers to the ability of a plant to limit the growth and development of a pathogen that could otherwise cause disease. There are several ways plants can have resistance:
- Passive resistance means the plant has physical or chemical barriers that make it harder for pathogens to enter or damage the plant. Examples are waxy layers on leaves, bark on stems and branches, or toxic chemicals.
- Active resistance relies on the plant recognizing pathogens and mounting defense responses like:
- Hypersensitive response - plant cells self-destruct to deny nutrients to pathogens
- Systemic acquired resistance - whole plant goes on high alert and boosts defensive chemicals
- There are also R genes - these are plant genes that recognize specific pathogen proteins and trigger strong defenses. New strains of pathogens can overcome R genes.
Breeding for disease resistance is key for food security. Traditional breeding and biotech methods are used to introgress resistance genes from wild relatives into domesticated crop varieties. This allows farmers to reduce pesticide use while maintaining high yields. Some common examples:
- Blight-resistant potatoes
- Fusarium wilt-resistant bananas
- Papaya ringspot virus-resistant papaya
- Corn and soybeans resistant to various fungi and viruses
New biotech methods like CRISPR gene editing can precisely modify susceptibility genes to generate resistant crops faster than traditional breeding. However, genetically engineered crops are controversial and face regulatory burdens in many countries.
Climate change is reducing the durability of disease resistance. Warmer weather enables pathogens to grow faster and may make plants more susceptible if drought stressed. It also changes geographic ranges of pathogens and vectors like insects. This makes breeding for durable resistance an ongoing struggle.
In the future, integrated solutions with resistant varieties, reduced pesticide, biocontrol agents and smarter agricultural practices will all be needed. But the molecular genetics revolution keeps unlocking new tools in the breeder's toolkit. So long as they have access and incentive, plant breeders can continue raising the bar on durable disease resistance.