What is plant immune-priming and can it be used in sustainable agriculture?

Most of us know that humans have an immune system that helps our bodies to fight disease, allows us to recover from illness, and can even stop us from getting sick in the first place. But did you know that plants also have immune systems? When plants are challenged by a pest or disease, a cascade of reactions are triggered. This is the immune response, which leads to a defense mechanism being actioned so that hopefully, the plant doesn’t become sick and die. Priming the plant immune system is similar to giving a plant a vaccine - it boosts its immune system to protect it from pests and diseases through applying different treatments that mimic pathogen attack. Recently, CHAP’s Dr Jemma Taylor and Dr Victoria Woolley attended the ‘Priming the Future for Healthy Plants’ conference at the University of Sheffield, organised by the International Organization for Biological Control, to understand more about new research in plant immune priming.

Fundamental research

In plants, the immune system is controlled at many different levels including through the expression of different genes and the production of hormones. Understanding these fundamental mechanisms is achieved through model organisms, such as Arabidopsis thaliana, and is important, as they can inform and direct future applied research to benefit crop protection.

An example of this, which was the focus of many conference talks, is the role of beta-amino butyric acid (BABA) in immunity. This small molecule plays a key role in immune signaling in plants, but it can also be applied to plants to make them more resistant to diseases and stresses such as cold or heat by stimulating the immune response mechanism.

Translating research into crops

Whilst it is important to understand how and why immune priming works, one of the main themes of the conference was whether this research can be used to improve the resistance of crop plants to disease, pests and stresses. This, in turn, could reduce crop yield losses and reduce the need for inputs such as fungicides and insecticides.

Numerous researchers, including those at Lancaster University, the Swedish University of Agricultural Sciences and the University of Birmingham investigated the impact of BABA on crop plants such as potato and tomato. Katie Stevens of the University of Birmingham found that application of BABA can protect tomato plants from fungal infection by increasing the expression of immune-related genes. While Murilo Sandroni of the Swedish University of Agricultural Sciences found that the beneficial effects of BABA in potato were highly depended on the cultivar tested. These controlled-environment and laboratory studies highlight the potential of immune priming of crops plants, but more research needs to be done to translate this into the field.

Microbe-induced resistance

Another theme arising from the conference was that beneficial microorganisms, such as some species of bacteria and fungi, can provide protection to plants against pests and diseases. Mycorrhizal fungi are known to form associations with plant roots, where the fungi receive sugars from the plant, and the host plant receives more water and nutrients from the fungi. This beneficial association has been well understood, but more recently this fungi-plant association has also been found to prime the host plant’s immune system.

Dr Francisco Ruiz, Consejo Superior de Investigaciones Científicas (CSIC), presented that an association with mycorrhizal fungi can trigger a plant’s immune response, which increases the mortality of caterpillar pests feeding on the plant whilst attracting beneficial insects. Additionally, this boost to the plant’s immune system can protect against bacterial infection, as discussed by Dr Paola Bonfante of the University of Torino.

However, although the use of beneficial microorganisms to increase plant defense is a promising area of research and results are good in controlled environment/laboratory studies, there remains much work to be done before these can be effective in the field.

Dr Maria Pozo of CSIC highlighted that multiple factors influence the plant’s immune response to beneficial microbes in the field including light, temperature, water availability, other control methods and the presence of other microorganisms. More work needs to be conducted to understand how all of these factors will affect the immune response of plants in the field, and how these tools could be an effective part of integrated pest management (IPM) strategies, before immune priming can be considered a tool for sustainable agriculture.

How can CHAP help?

CHAP acts as a nexus, bringing together scientists, farmers and businesses to drive innovation in agriculture. CHAP is particularly focused on five main research priorities, advancing intelligent agronomy, controlled environment agriculture, crop and protein diversification, innovative crop health strategies and soil and crop health systems.

Through connecting different stakeholders within and between research areas, CHAP can facilitate the development of fundamental scientific ideas into practical solutions in agriculture. This can be through involvement in grants, supporting commercial projects and facilitating use of CHAP’s capabilities. Examples of this include the development of a handheld imaging device to detect crop diseases by Fotenix and development of a tool to detect potato cyst nematode in Kenya.

Please note, the opinions expressed in this article are the author’s own and do not necessarily reflect the views or opinions of CHAP.