Genetic Determinism and Candidate Genes for Flowering Date - A Phenological Trait Highly Affected by Climate Change in Sweet Cherry

In the context of global climate change, flowering phenology of deciduous tree species is crucial as it may affect their productivity. In fruit tree orchards, flowering phenology has an indirect influence on spring frost damage, pollination, dormancy and maturity. In a warming scenario, the  risk of frost damage may be increased due to advanced flowering time and increased temperature fluctuations. Moreover, new risks are emerging as disruptions in floral phenology synchronization, which may disturb pollination for varieties that necessitate cross pollination. Sweet cherry (Prunus avium) has a high chilling requirement compared to other Prunus species like peach or apricot. Consequently, if temperature increases in the following years, part of the regions where sweet cherry are currently produced will become critical for a competitive fruit production. Flowering and maturity dates were evaluated on a F1 sweet cherry progeny population from the cross between Regina and Lapins, during four and three years, respectively. Saturated linkage maps were constructed for each parent using a Illumina Infinium Cherry BeadChip of 6000 SNP developed within the RosBREED project. Quantitative trait locus (QTL) mapping was performed separately for each year and combined for all years together. A high heritability and stability between years of evaluation were obtained for flowering and maturity dates. For flowering date, QTLs were detected on all linkage groups (G), except G8. For maturity date, QTLs were detected on G2, G3, G4, G6, G7. For both traits, major QTLs were detected on G4. Using the peach genome sequence data, candidate genes underlying the major QTLs on G4 were investigated and key genes were identified. Our results provide a basis for the identification of genes involved in flowering and maturity dates that could be used to develop cultivar ideotypes adapted to future climatic conditions.