Unité de Recherches de Pathologie Végétale INRAE PACA cm Domaine St Maurice BP 94 67, allée des chênes CS 60094 F84143 Montfavet cedex France Tel : 33 (0) 4.32.72.28.67 christel.leyronas(a)inrae.fr

My publications in the open archive HAL INRAE         https://orcid.org/0000-0002-2693-1140

My research projects cover fundamental questions about disease epidemics all while being rooted in concerns with direct importance for production in the field. I collaborate with horticultural sectors that encounter fungal diseases. With the overall objective of optimizing the reasoned protection of crops, my work aims to 1) -identify and characterize pathogens, 2) - identify reservoirs of inoculum and 3) - evaluate the aerial dissemination at local to global scales. To accomplish this, I design experimental set-ups and develop sampling strategies and methodologies for the quantification of airborne inoculum and its phenotypic and genetic characterization.

I work mostly on diseases caused by fungi with broad host ranges including Botrytis cinerea (grey mold), Sclerotinia sclerotiorum (white mold), and Fusarium proliferatum. Whereas B. cinerea and S. sclerotiorum have caused recurrent epidemics for decades on various horticultural crops in France – importantly on tomato and lettuce, respectively – F. proliferatum has only recently emerged as a pathogen on garlic (Leyronas, C., et al. (2018). First report of Fusarium proliferatum causing garlic clove rot in France. Plant Disease, 102 (12), 2658. DOI: 10.1094/PDIS-06-18-0962-PDN)

Identify and characterize pathogens

Clarifying the etiology of a disease is an essential first step toward an effective and lasting control method against this disease. This involves identifying the species responsible for the symptoms as well as a detailed characterization of the individuals within the species.

Strains of Sclerotinia sclerotiorum collected from a range of plant hosts (carrot, rapeseed, witloof chicory, beans, lettuce, and cantaloupe) grouped according to their haplotype

Research on the etiology of garlic brown rot, a newly emerging disease in France

Identify reservoirs of inoculum

Identifying the sources of inoculum is essential for understanding the epidemiology of disease and ultimately predicting epidemic risks. Locating them is all the more difficult when a pathogen has a broad host range, a saprophytic phase on various substrates in and outside of cropped fields and can survive during aerial transport - as is the case for the organisms that I study. It is becoming increasingly evident that we must take into account the diversity of what is outside the agricultural plots (that is to say expand beyond a solely agro-centered vision) to fully understand epidemiological phenomena.

Phylogenetic tree indicating the relationships and genetic distance among strains of Botrytis cinerea collected from within and outside of agricultural habitats. (click on the image to enlarge)

Evaluate aerial spread from local to global scales

Unlike the spread of pathogens with human activities, aerial spread is difficult to control because air masses know few borders. Although we cannot stop the movement of pathogens in the atmosphere, we can try to elucidate their pathways in order to anticipate them and predict epidemic risks in different areas. To predict the arrival of spores in areas where susceptible crops are grown, it is necessary to identify the sources of spores, local and distant, and to model the trajectories of air masses. For polyphagous fungi with important saprophytic phases such as B. cinerea and S. sclerotiorum, predicting the arrival of spores is particularly difficult because there are many possible sources of inoculum and they cannot be all easily identified.

Identifying the path of microorganisms in the air is accomplished by indirect means: observation of the development of a disease in an area distant from the source area, comparison of the genetic profiles of individuals at the source and at the sink, capture of particles suspended in the air using specialized equipment, and modeling air mass trajectories.

Characteristic air masses that typically arrive in the region of Avignon
Relationship between the haplotype profiles of strains of B. cinerea and the origin of air masses that potentially transported them to the collection site (Avignon)
Relationship between aerial connectivity (colored arrows) that links different regions of France (North, Northwest, Southwest, Central-west) and haplotype profiles (colored rectangles) for strains of S. sclerotiorum collected in these same regions

I am strongly interested in the managerial aspects of research and in particular the management of human resources where staff work in teams. From 2016 to 2022 I was the deputy director of the Plant Pathology unit (42 permanent staff) in charge of human resources. Managing human resources is a real balancing act (between kindness and high standards, between the interests of the collective and that of the individual, ...). It is also a continuous and iterative process of questioning and adjustment (of oneself and of the group) for an optimal functioning, so that everyone finds their place, a meaning and satisfaction in their activities, while keeping the common goal in sight.

In addition to the direct experience I have acquired, I have followed training in personnel management, communication, conflict management, personal development (transactional analysis, resilience ...) in order to acquire and implement tools encouraging the coherence and cohesion of groups and teams. Within my unit, I have created groups promoting the integration of newcomers (AIMIE workshops: discovery of the unit's experimental facilities through a visit and practical activities), providing support to colleagues who are candidates for internal evaluations and promotion (career support group), and optimizing the quality of life at work (AQuaViT: organization of occasional internal cohesion events). My motto is the African proverb that says "alone we go faster, but together we go further"