Soutenance de thèse d'Ajithkumar Munusamy

Dans le cadre du projet européen EATFISH, Ajithkumar Munusamy soutiendra ses travaux de thèse le 25 février 2025 à 14h00 dans l'Amphithéatre Michel Crépeau du Pôle Communication, Multimédia et Réseau de l'Université de La Rochelle.

Titre de la thèse:  "Les bases génétiques des mortalités massives de moules en France"

Résumé de thèse:

France is one of the main contributors to mussel production in Europe. Since 2014, abnormal mussel mortalities (AMM) have been frequent in France, the causative agent being still unknown. This project investigates the genetic basis of resistance to MA outbreaks in two mussel species (Mytilus edulis and Mytilus galloprovincialis) and their natural hybrids grown in France. Mussel families tested at two sites from October 2017 to June 2018 revealed low to moderate heritability values for survival and significant genotype-environment interaction.

In addition, mussel families were evaluated in the context of an experimental infection in July 2018, using a pathogenic strain of Vibrio splendidus isolated during episodes of MA in 2014. The weak genetic correlation between the field infection and the experimental infection suggests that this strain of Vibrio was not the primary cause of the mortality epidemic observed at the two sites in 2018. No response to selection for MAiD has been observed in co-residential experiments using donors from MAID sites, while epidemics of high mortality have occurred for both species, indicating that without access to field conditions, it is impossible to mimic a MA in the laboratory.

Microbiota analysis revealed that Vibrio was the predominant genus in moribund mussels, followed by Colwellia, Tropicibacter, Malaciobacter and Fusibacter. In addition, the genomic architecture of resistance to a pathogenic strain of V. splendidus has shown that this trait is polygenic, suggesting that genomic selection is likely more efficient than marker-assisted selection. In addition, genomic selection can improve accuracy by up to 19% compared to pedigree-based selection.

Finally, the response to selection to increase or decrease cytogenetic quality after a generation of selection was 1.44% for M. edulis and no response to selection for M. galloprovincialis. More importantly, this trait was not correlated with survival, using a cohabitation experiment with donors sampled at a site where a massive epidemic of mortality occurs each year. The mussel industry could use all the results of this work to counter future outbreaks of MAiD, which could be more frequent and intense in the future in the context of global warming.

  

Composition du jury de thèse: 

M. Lionel DEGREMONT - Institut Français de Recherche pour l'Exploitation de la Mer, Directeur de thèse
M. Pierre BOUDRY - Institut Français de Recherche pour l'Exploitation de la Mer, Examinateur
Mme Jildou SCHOTANUS - Wageningen University, Examinatrice
Mme Marie LILLEHAMMER -  NOFIMA, Examinatrice
Mme Florence PHOCAS - INRAE, Rapporteure
M. Marc VANDEPUTTE -  INRAE, Rapporteur
M. Pierrick HAFFRAY -  Syndicat des Sélectionneurs Avicoles et Aquacoles Français, Invité
M. Tim REGAN - Roslin Institute, University of Edinburgh, Invité