Camille BRANCHEREAU

Team A3C

Monday, April 25, 2022 - 2 p.m. - Amphitheater Colette & Josy Bové - Campus INRAE Villenave d'Ornon

Abstract :

Flowering date is a trait of main interest in perennial fruit species including sweet cherry (Prunus avium L.). It is highly dependent on the environment and has a major impact on fruit formation: as already observed, a poor synchronization between flowering date and the environmental conditions can lead to significant economic losses. Understanding the genetic determinism of the flowering date is therefore essential to optimize selection strategies and create new varieties better adapted to future climatic conditions.
The first objective of this thesis is to study the genotype-by-environment (G × E) and QTL-by-environment (QTL × E) interactions. To do this, an intra-specific population called 'Regina' × 'Lapins' (n = 122) was planted in five locations with contrasting climates distributed in four European countries. It was thus possible to identify two major QTLs. The first one, located on linkage group 4, is found in all environments except the site located in Murcia (Spain), characterized by the highest temperatures. In the latter environment, the major QTL is localized on linkage group 1. Highly significant G×E and QTL×E interactions were assessed using different statistical models.
The second objective of this thesis is to fine-map the QTL on linkage group 4 using a second population, 'Regina' x 'Garnet' (n = 1386). This QTL, very stable across years, explains the most important part of the phenotypic variation in this plant material. This QTL was detected in a 68-kb interval, containing twelve candidate genes that were functionally characterized using the new cherry genome sequence of the cultivar 'Regina'. In addition, their expression was studied in 'Regina' and 'Garnet' cultivars during the period from dormancy to flowering, leading to the identification of a few promising candidates. Also, two KASP markers have been developed and validated on different genetic backgrounds and can be used in marker-assisted selection (MAS) for flowering date.
In the long term, these results should help breeders to create new varieties that are well adapted to their planting site and to ensure the production of sweet cherries in geographical areas covering a wide range of climates.

Jury :

• Mrs Elisabeth DIRLEWANGER
  Directrice de recherche INRAE Bordeaux - Directrice de Thèse
• Mrs Laurence MOREAU
  Directrice de Recherche INRAE Le Moulon - Université Paris-Sacla - Rapporteur
• M. Eric DUCHÊNE
  Ingénieur de Recherche -  INRAE Colmar - Université de Strasbourg - Rapporteur
• M. David POT
  Cadre scientifique des EPIC - CIRAD - Examinateur
• Mrs Valérie SCHURDI-LEVRAUD
  Professeur Université de Bordeaux - Examinateur
• M. Jean-Marc CELTON
  Professeur Associé - Université d'Angers - Examinateur