Shifting paradigm in plant pathology to tackle present and future challenges in plant health

On the onset of agriculture in the Neolithic age ca. 8000 BC, over 10’000 plant species were used to feed humanity. The adoption of modern agriculture practices and breeding, starting from the 19^th century, have drastically reduced that number from 10’000 to 150. Of these, 9 plants account for 66% of all human diet globally: wheat, rice, maize, potatoes, soyabeans, sugarcane, oil-palm fruit, sugar beet, and cassava.

According to the United Nations Food and Agriculture Organization (FAO), every year, 20-40% of all crops produced on the planet are lost because of plant pests and diseases. Considering that (i) recent gains in global crop production fall short of the projected increase in the world population (i.e. food demand), and (ii) that yields are projected to stagnate or collapse in many areas where major crops are produced, this lecture will discuss the central role of plant pathology in closing that gap.

The first part will address the paramount importance of agricultural biodiversity (i.e. the sum of all plant varieties available for cultivation) for the future of a pesticide-free, environmentally sustainable, and healthy agriculture. I will present specific examples from my ongoing and planned work (and the work of others) on major cereal crops, with a particular focus on how to leverage next-generation resistance breeding in wheat, as a case study.

In nature, disease is an exception. Most plants are totally immune to almost all microbes, that is in striking contrast with the crops we cultivate in the field. Research in plant pathology (including plant immunity and resistance breeding) has been historically and consistently based on studies of individual pairs of one-pathogen-one-host.

A major setback of such approach is that crops are never attacked by one pathogen at a time. Actually, plants are attacked by a large diversity of pathogen populations and interact with an even larger diversity of microbes. Altogether, these interactions are controlled by the plant immune system which they can in turn affect positively (beneficial microbes) or negatively (pathogens) in a way that strikingly resembles the way our gut microbiome interacts with our immune system and affects our health.

Thus, the second part of my lecture will address the importance of understanding the diversity and complexity of the plant ‘pathobiome’ (i.e. the sum of microbes that cause disease), and address the central question of the resilience of our farming systems to diseases and pandemics. I will introduce a new paradigm in plant pathology defining plant health as a ‘homeostasis’ (i.e. an equilibrium) between the plant immune system (i.e. the capacity of the host to defend) and the plant microbiome (i.e. all microbes engaging in an interaction with a plant host).

I will discuss why this is absolutely central to future disease management and resistance breeding. I will also highlight specific gaps of knowledge in the field, provide practical examples on why it is so difficult to develop crops that ‘do not need pesticides’ to stay healthy, and explain how my research will address this issue.

In the third and last part of the lecture, I will touch upon the importance of educating (sensu lato) the public, students, and the industry to plant health from a ‘one health’ perspective, and why this has become a pre-requisite to best serve the expectation of society and support/accompany change in the industry. I will conclude by explaining my strategy to tie together scientific excellence in research and education at SLU in a coherent vision that contributes to SLU’s long-term strategy in light of the UN Sustainable Development Goals.