Due to climate change, many plants need to adapt to changing conditions worldwide, and there are increasing incidences of pests, diseases, and infestations. Boosting plant immunity is necessary to relieve the shocks of global warming and the complex chain of side effects it triggers.

Here, we’ll explore plant immune systems and how climate change impacts them, and what Open Access researchers are doing to strengthen them in response.

Plant immune system

Plants, unlike mammals, lack an adaptive immune system that learns and responds to microbes in specific ways. Instead, they rely on their innate immune systems, which involves surveillance and then response.

Members of every class of pathogen (like bacteria, fungi, viruses, and insects) that infect humans also infect plants. To do so, they need to affect the plant’s structure and disrupt its defence, promote nutrient leakage or pathogen dispersal, or even produce molecules that mimic plant hormones, controlling its response.

Pathogens can enter a plant in different ways. Pathogenic bacteria can enter through gas or water pores, or even wounds. Insects feed by inserting a stylet directly into a plant’s cells. And fungi can directly enter plants’ epidermis, their skin-like exterior.

Plants and microbes have evolved antagonistically for hundreds of millions of years, meaning they have evolved in response to each other. As such, plants have evolved diverse strategies to combat infection. But how is climate change affecting them?

Climate change and pathogen growth

Global warming due to the excessive human-driven burning of fossil fuels and environmental destruction is threatening the survival of all living species, both plant and animal. New infectious plant pathogens and diseases are emerging due to changing conditions. Here’s why:

• Temperature: Higher average temperatures can increase the virulence, reproduction rate, and more of pathogens.
• Humidity: High humidity conditions (rainfall, high atmospheric humidity, and high soil moisture) are favourable for plant infections, especially bacterial diseases.
• Carbon dioxide: High rates of carbon dioxide can alter plants’ stomatal control, which refers to its guard cells that regulate the entry of water/gas. This can give pathogens entry into plants.

All these factors combine to create environments that can trigger rapid pathogen growth and spread. Therefore, finding effective ways of boosting plant immunity is integral.

Thankfully, scientists are tackling this issue across the world. Let’s explore some of the research.

Plant microbiome

The plant microbiome is an assembly of microorganisms that live in and near a plant, all interacting to form a microbial ecosystem. An article in Microorganisms looks at plant microbiomes as a potential avenue for disease resistance.

Plants in nature coexist with diverse microbial communities that can be beneficial or even damaging. These interactions are complex and dynamic. Microbiomes can be beneficial in a variety of ways. These include protecting the plant from harmful stresses, improving tolerance to various stresses, and increasing growth, health, and production.

Furthermore, the plant microbiome triggers “induced systemic resistance”, which involves shielding the plant’s organs against attacks from pathogens.

Microbiome engineering

Shared signalling pathways in both plants and microorganisms lead to the theory that plants experiencing stress actively recruit specific microorganisms from the microbiome. This helps protect them from any detrimental effects by boosting plant immunity.

Accordingly, the authors discuss developing disease-resistant microbial communities for disease resistance. This would involve beneficial microbiome engineering and editing plant genes to encourage productive interactions.

Of course, this is challenging due to the intricate nature of the interaction between plants and microbiomes. But this represents an exciting avenue for supporting plants in climate change-affected regions.

Light signalling

Light is essential for the life of plants. It varies depending on the time of day, latitude, cloud cover, neighbouring plants, etc. In response, plants respond dynamically and appropriately depending on their environment. An article in IJMS investigates how manipulating light signalling could be used for boosting plant immunity.

Allocating resources between growth and defence is a key process determining a plant’s survival. Given light perception plays a major role in the control of a plant’s growth, it can also influence plants’ defences too. Moreover, pathogens also perceive and react to light in complex ways to regulate their own growth, development, and virulence.

Accordingly, the author suggests using light as a weapon to reduce plant infection or even kill pathogens.

Boost plant immunity using light

UV light applications have a positive effect on plant disease resistance. This occurs primarily by boosting metabolites, strengthening the plant’s defence. In some cases, UV radiation can be used to directly damage pathogen species that are susceptible to it.

The author describes how robots have been used to deliver light in horticultural crops to control fungal pathogens. As automated environmental control and light technology improve, studies like this point to the potential of harnessing light to control plant responses and increase resistance.

This could also help in cases where reducing pesticides is necessary.

Pesticides and fungicides

Bread wheat is one of the most cultivated cereals worldwide and is an important source of protein and nutrients for humans. But it is very vulnerable to Fusarium diseases. These are fungal infections that can drastically reduce yields by up to 70% and make ingestion of the wheat toxic to humans and animals. An article in Plants looks at sustainable methods to manage fungus in plants.

Fungicides are used in response. However, these negatively affect all plant life surrounding crops. And resistant fungus strains are emerging too. As such, the European Commission has set the target of reducing the use of fungicides and pesticides by 50% by 2030. But climate change is causing warmer temperatures, which encourages fungal disease diffusion.

We need to fight fungus without fungicides. So, these authors turned to nanotechnology.

Nanotechnology and circular economy

Building on circular economy principles, which involve reusing materials, the authors promote using nanotechnology. This refers to manipulating matter on an atomic scale for industrial purposes.

So, from wheat waste, the authors extracted cellular nanocrystals and high-amylase starch. The nanocrystals serve as a carrier and the starch as a releaser to essentially create a nanotechnology-based delivery system. The nanotechnology will deliver chitosan and gallic acid, which are organic-derived molecules from the shells of shrimps and different plant tissues. These molecules have antimicrobial properties, meaning they can fight the fungus.

Instead of using fungicides, which damage the surrounding environment and are toxic for consumption, the authors propose this all-natural, recycled fungicide for boosting plant immunity in bread wheat.

Climate change and plant immunity

The planet is threatened by global warming. And it’s changing faster than plants can adapt naturally. As such, we need to work on effective ways to bolster plant immunity in response, including against pathogens.

The highlighted research is all Open Access, which is a key value for MDPI. MDPI makes all its research immediately available worldwide, giving readers free and unlimited access to the full text of all published articles. If you’re interested in joining in and helping boost plant immunity, why not submit to one of our journals? See the full list here.