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Full project title and acronym: Responses of local populations of Mycosphaerella graminicola to spatial variations of two major agro-environmental factors - temperature and varietal resistance - and inference of their potential to adapt to global changes - SEPTOVAR Type and date of project: emergence 2014-2016
Project leader: Frédéric Suffert (BIOGER) Other people from BIOGER in the project: Henriette Goyeau, Thierry Marcel, Sandrine Gélisse, Nathalie Retout, Ghislain Delestre (CDD AI), Jean Legeay (M2 intern), Ivan Sache, Florence Carpentier Anne-Lise Boixel (PhD student)
Partners:

•     in BASC: ECOSYS: (Michaël Chelle, Alain Fortineau) CIRAD, BGPI: (Virginie Ravigné)
•     academic outside BASC: CNRS, IRBI: (Sylvain Pincebourde)
•     non academic: ARVALIS - Institut du Végétal: (Romain Valade)

==> The researcher presents in VIDEO the latest RESULTS of the project

(LabEx Scientific Days, January 2021)

The SEPTOVAR project has initiated an ambitious research program on the adaptive potential of Zymoseptoria tritici populations (fungus responsible for wheat septoria) to global changes (climate). This program aims to characterize the heterogeneity of the responses of pathogen populations to temperature variations at different spatial and temporal scales and to estimate their potential for adaptation to seasonal temperature variations as well as to global warming. The SEPTOVAR project led to the development of a thesis project that started in the fall of 2015, led by Anne-Lise Boixel (PhD student AgroParisTech / ED ABIES). As a preliminary step, the analysis of a dataset acquired in 2011 highlighted a local adaptation pattern suggesting that an intra-population selection takes place at the annual scale in Z.tritici and is influenced by host (physiological stage) and climate (seasonal temperature variations) characteristics. One of the main objectives of the project was to establish experimentally, in a first step without interaction with the host plant, the temperature response curves (TPCs) of different French populations of Z. tritici. For this, a miniaturized in vitro method coupled with modeling work (choice of models to be fitted) was developed and validated in 2015 during an M2 internship. This method allowed to follow the cell multiplication rate of Z. tritici (in liquid medium on microplates) by optical density measurement using a spectrophotometer. It was optimized by Anne-Lise Boixel in 2016 as part of her thesis and is now used routinely. To date, CPTs of more than 350 isolates have been established. The analysis of how climatic conditions can explain intra- and inter-population variability at different spatio-temporal scales is ongoing and focuses on several sampling scales: French spatial scale (isolates collected along a North-South and West-East transect; non-significant differences between populations), pan-European spatial scale (isolates collected in about ten countries; probably¹ significant differences between populations), temporal scale (probably¹ significant differences between local subpopulations, which seasonal fluctuations contribute to structure). The question of temperature variability at the canopy scale was also addressed. Thermographic measurements to characterize the thermal heterogeneity of a wheat canopy were performed with a thermal camera by Alain Fortineau and Sylvain Pincebourde in 2014 at Grignon. Interpretation of the data is in progress; these data (leaf temperature,air temperature and radiation) can be linked to the problem addressed by Anne-Lise Boixel in her thesis to estimate whether the thermal heterogeneity of the canopy can also explain the small-scale spatial variability of Z. tritici performance.

¹ analyses in progress at the time of the final project report (2017)

Publications (not exhaustif)

> Boixel A-L, Chelle M, Suffert F (2020) Patterns of thermal adaptation in a worldwide plant pathogen: local diversity and plasticity reveal two-tier dynamics. bioRxiv. https://doi.org/10.1101/867572

> Boixel, A.-L., Delestre, G., Legeay, J., Chelle, M., Suffert, F. (2019) Phenotyping Thermal Responses of Yeasts and Yeast-like Microorganisms at the Individual and Population Levels: Proof-of-Concept, Development and Application of an Experimental Framework to a Plant Pathogen. Microb. Ecol. 78, 42–56. https://doi.org/10.1007/s00248-018-1253-6

> Suffert F., Goyeau H., Sache I., Carpentier F., Gélisse S.,  Morais D., Delestre G. (2018). Epidemiological trade-off between intra- and inter annual scales in the evolution of aggressiveness in a local plant pathogen population. Evolutionary Applications.doi: 10.1111/eva.12588** 

> Suffert F, Ravign. V, Sache I, 2015. Seasonal changes drive short-term selection for fitness traits in the wheat pathogen Zymoseptoria tritici. Applied and Environmental Microbiology 81: 6367-6379.

> Boixel A-L, Gélisse S, Marcel T, Suffert F (2019) Differential tolerance to changes in high moisture regime during early infection stages in the fungal pathogen Zymoseptoria tritici. bioRxiv https://doi.org/10.1101/2019.12.16.877696

Thesis

> Environmental heterogeneity, a driver of temperature adaptation in foliar plant pathogen populations? - Anne-Lise BOIXEL (ABIES graduate school) defended in June 2020