Mechanisms and genetics of winter dormancy in raspberry (Rubus idaeus L.)

Dormancy protects temperate plants from abiotic stress during the winter. Once it is established, plants become non-responsive to growth stimuli until they are exposed to a period of cold temperatures (‘chilling’). Climate change is threatening this mechanism by disrupting its environmental cues. Red raspberry (Rubus idaeus L.) crops are impacted by this issue, causing significant economic losses for the industry. This PhD project characterised the mechanisms and genes underpinning dormancy in two raspberry cultivars with contrasting responses, ‘Glen Ample’ and ‘Glen Dee’. Historic phenology and meteorology data were integrated in mathematical models to identify and quantify the drivers of bud break in ‘Glen Ample’ and ‘Glen Dee’. The models identified optimum and suboptimum ranges of accumulated chill and time of application in ‘Glen Ample’. Bud break in ‘Glen Dee’ was found to be independent of cold exposure. Genetic mechanisms underlying the different responses of ‘Glen Dee’ and ‘Glen Ample’ were analysed through transcriptomic profiling. The analysis produced a month-by-month overview of the processes occurring during dormancy in ‘Glen Ample’. Phenotypic and transcriptomic data suggested a misregulation of dormancy induction in ‘Glen Dee’. A VRN1-like gene, RiVRN1.1, was identified as a potential candidate. Metabolic profiling was conducted over the same tissue samples. The results identified dormancy status as the main driver of variation in ‘Glen Ample’. This variation did not occur in ‘Glen Dee’, supporting the misregulation of dormancy observed in transcriptomic and phenotypic analysis. QTL analysis identified loci associated with winter phenology traits in a population developed by crossing ‘Glen Ample’ and ‘Glen Dee’. 14 loci linked to spring vigour, duration of dormancy, time of senescence and bud break were identified. The results of this study, and the tools and datasets developed provide a framework for molecular biology studies on winter phenology in raspberry.