About this time every year, health professionals encourage people of all ages to get the flu vaccine. The flu vaccine—like many other vaccines—contains small or inactivated doses of the disease-causing organism. Introducing it into a person’s body at such a small dose provokes the person’s immune system into mounting a response, without making them sick. Then, if and when they encounter the “real” disease-causing organism, the immune system is already prepared.
In a new review article, a multi-national group of researchers has suggested mimicking this strategy in plants. In crops, it is called induced resistance. Like a vaccination, it deliberately triggers a plant’s immune system, so that when the plant encounters a similar stress in the future, it fights back better.
Induced resistance is not without its complexities; however. And while it is a long-lasting solution, it is not a solo one—additional strategies are necessary to make it work. Still, the idea is sustainable and resilient amid a growing and changing world.
Current growing practices
Currently, crops are mostly protected through the use of pesticides and breeding for resistance genes. While these strategies are effective, they do come with downsides. Pesticides can have harmful environmental effects—they have been blamed for the colony collapse disorder that wiped out millions of bees, and they are known to make their way into bodies of water via runoff. Additionally, much like the problem of antibiotic-resistance for humans, crops and pests can and have become resistant to some pesticides.
In recent years, consumers have put much more value into “organic” food, negatively affecting crops grown on farms that use pesticides as well as those genetically modified for resistance and other genes.
The potential
Induced resistance enhances abilities a plant already has to provide more sustainable and potentially broader-spectrum protection: defending against several pathogens and pests, not just one. While there are several types, defense priming is the most popular type of induced resistance.
Like a human vaccine, defense priming occurs when part of a plant experiences stress. This weakly activates defense mechanisms that then fully come to life when the plant undergoes a real attack. According to research, defense priming can actually appear in the next generation of plants—potentially transmitted via epigenetic mechanisms.
Once implemented, induced resistance could do more than just ward off pests. Some of the defense compounds that plants produce in response to induced resistance are linked to health benefits or higher-quality nutrition—meaning humans could avoid pesticides as well as grow healthier food from the start. Induced resistance is also faster than traditional breeding, offering a quicker way to adapt to changing climatic conditions.
Roadblocks ahead
Unfortunately, induced resistance doesn’t offer complete protection, so must be combined with other measures. It also needs to be carefully calibrated to ensure that it doesn’t leave a plant open to other threats and doesn’t compromise growth by causing the plant to allocate too many resources to defense.
“Induced resistance is the result of a complex network of developmental and environmental pathways in the plant, so safe and efficient exploitation is not as straightforward as the introgression of a single gene or spraying a single pesticide,” said lead author Brigitte Mauch-Mani, professor at the University of Neuchâtel. “We will need case-by-case evaluation of the optimal growth conditions, crop germplasm, and agricultural practices to capitalize on induced resistance’s multifaceted benefits.”
In their article published in Frontiers in Science, Mauch-Mani and her team call for more research that covers more real-world circumstances. For example, they say we need to understand how induced resistance performs under less controlled conditions by developing methods that can be scaled up to field trials and, eventually, full-scale agriculture.
The researchers also call for more collaboration and legislative support to establish quality standards, protecting producers and consumers.
“We strongly believe that fundamental research into induced resistance will be critical for the transition toward a truly sustainable food supply,” said Mauch-Mani. “However, there is an urgent need for better communication between discovery-focused research and other stakeholders who have the expertise to translate discovery into application. Governments need to create a research environment and funding climate that allows for more efficient knowledge exchange between scientists, policymakers and industry. Like the biology underpinning it, successful exploitation of induced resistance relies on a multifaceted effort.”