Israël Tankam, a mathematician working on the practical applications of mathematical modelling in agriculture

Dr Israël Tankam is a mathematician working on optimizing the management of resistance to plant-parasitic nematodes. He implements the “NEMO” project at the IGEPP laboratory, Institut Agro-Rennes Angers.

BIENVENÜE Team : Hello Israël, what is your background?

I have a background in Applied Mathematics, specializing in mathematical modelling, ecological modelling, and their practical applications, particularly in fields such as plant epidemiology and agriculture. I’m the laureate of the Ovide Arino Outbreak Award (OAOA) 2021 for my PhD work on optimal and sustainable management of banana soil-borne pests. My previous postdoc position focused on modelling the epidemiology of transboundary cassava diseases in Central and West Africa with the Epidemiology and Modelling Group of the University of Cambridge, and the Central and West Africa Virus Epidemiology for Food Security (WAVE).
Since January 2023, I’ve been actively involved in the NEMO project (Optimizing the management of resistance to plant-parasitic nematodes), collaborating with experts like Frédéric Hamelin, Josselin Montarry, and Sylvain Fournet.

What is the project NEMO about?

The NEMO project addresses the threat posed by the potato cyst nematode (Globodera pallida) to potato crops in Brittany, France, following the ban on effective chemical nematicides. Our goal is to develop, through mathematical models, sustainable strategies for managing this pest by combining plant resistance with crop rotation and biocontrol methods.

Potato varieties resistant to cyst nematodes have been developed for several decades now. Most of this resistance acts through the masculinization of the nematode larvae that feed on it, which means that the latter cannot develop into adult females by feeding on the roots of a resistant potato, but exclusively into males. Their reproduction being sexual, a population made up only of males is destined to disappear. It’s brilliant in idea, but in practice it’s another matter.

Indeed, the principles of evolution require that resistance leads to adaptation through natural selection. Indeed, it occurs that in nematode populations there exist individuals which have characteristics allowing them to circumvent the masculinizing resistance and therefore to produce females on resistant potatoes. These individuals are then said to be virulent, not only because they are able to reproduce on resistant potatoes, but also because they are even more aggressive.

Virulence is characterized by a so-called virulence gene, that is to say a code on their DNA which causes them to develop the virulence characteristic. Furthermore, this gene is only expressed if the DNA carries two copies (we then speak of a recessive allele). Because of the existence of this virulence, the fact of systematically deploying only resistant plants will ensure that only virulent nematodes survive (as the other won’t reproduce as they can’t produce females), which has two consequences. On the one hand, resistance will become obsolete because virulent nematodes are no longer affected by plant resistance. On the other hand, virulent nematodes are even more aggressive and reproduce faster than avirulent ones.

The aim of mathematical modelling is to analyze a priori the best strategies for deployment and alternation of resistant varieties with susceptible varieties (on which avirulent nematodes can reproduce and dilute the population of virulent nematodes) and even non-host plants for cyst nematodes to plan an optimal cropping calendar in response to a nematode outbreak. The objectives are of several orders: (i) that resistance does not become obsolete, (ii) that virulence does not become the majority, (iii) that potato yields are maximum, (iv) and ultimately that cyst nematodes are definitively eliminated.

What makes this project unique is our use of mathematical modelling, including demo-genetic models, to optimize these strategies and prevent nematodes from adapting to plant resistance. We aim to identify the best crop rotation strategies and provide practical decision-making support for farmers.

This project introduces innovation by considering various factors, including diploid nematode genotypes (the state by which the nematode has two alleles for each of its genes), the absence of fitness costs for virulence, and the polyandric nature of cyst nematodes. Additionally, we aim to create decision-making tools based on economic criteria.

Our project involves international collaborations, interdisciplinary research that combines biology and mathematical modelling, and connections with private institutes and companies in the potato and carrot sectors. We anticipate that our work will have a significant impact on crop protection, promote sustainable agricultural practices, and benefit both the scientific community and growers worldwide.

Why did you choose to implement it at the IGEPP laboratory?

I chose to carry out the NEMO project in UMR 1349 IGEPP (Institute of Genetics, Environment, and Plant Protection), INRAE – L’Institut Agro Rennes-Angers due to its complementary expertise, collaborative history, experienced supervisors, interdisciplinary approach, and strong international connections.

• Complementary Expertise: This laboratory consists of two teams, Demecology and PMB, each with expertise in different but complementary areas. Demecology specializes in theoretical and mathematical models related to Ecology, Epidemiology, and Plant Protection. PMB, on the other hand, focuses on generating data related to plant-parasitic nematodes. This combination of skills allows us to take a comprehensive approach to the project, where theoretical models can be informed and validated by real-world data.
• Collaborative History: The supervisors from both teams have a history of successful collaboration, evident from their joint publications. This existing synergy between the teams provides a strong foundation for a fruitful partnership.
• Experience and Reputation: The project supervisors, have extensive experience in modelling crop diseases and pests (F. Hamelin) and studying sustainable plant resistance management (J. Montarry).
• Interdisciplinary Approach and International Collaborations: The laboratory actively engages in international collaborations with researchers from institutions such as the University of Wageningen and the University of Cambridge. These collaborations ensure that our project benefits from diverse perspectives and expertise, enriching the quality of our research.

Thank you Israël!