QTL detection for flowering date in sweet cherry: fine mapping and GxE effects
Résumé
Flowering and fruit production in sweet cherry (Prunus avium) are strongly environment-dependent, mainly because bud release from dormancy requires two combined processes: winter chill followed by spring heat. Climate change, by inducing elevations of temperatures in winter and spring, can lead to strong yield and economic losses. On the one hand, winter chilling requirements are not satisfied, which causes a delay in the release of dormancy. On the other hand, a rise of the temperatures in spring induces earlier blooming date and therefore a higher frost risk. Thus, increasing our knowledge about the genetic control of phenology and flowering in sweet cherry to then obtain new varieties well adapted to changing environment is a key step to ensure the production of cherry in the future.
The genetic determinsm of blooming date was investigated using two different biparental populations. The first was composed of 1400 individuals obtained from a crossing of Regina and Garnet, and planted in one location in Toulenne, France. The second mapping progeny, 122 hybrids from the crossing of Regina and Lapins, was planted in five locations across four European countries (France, Italy, Slovenia and Spain). While several genomic regions associated with flowering time were identified, genotype-by-environment interactions were also studied using this multi-environment trial.
QTL detection allowed us to confirm the presence of a major QTL on linkage group 4 (LG4), explaining up to 40% of the phenotypic variation for the flowering time. This QTL is highly significant in all environments but Murcia, the only site characterized by a mild winter. In this location, another region was identified at the end of LG1 and is the major one demonstrating the high effect of environmental conditions on the flowering process.