Abstract

Half of the UK’s sugar demand is met by domestic supply from sugar beet. Field-grown sugar beet varieties are long day biennials and have an obligate requirement for vernalization (prolonged exposure to cold temperatures) to induce reproductive development. The UK commercial crop is spring-sown, and vegetative roots, which contain up to 19% sugar, are harvested the following autumn and winter. Plants can become vernalized in cool springs, resulting in bolting (the stem extension which precedes flowering) with reduced sugar yields. One tall bolter per square metre reduces yield by up to 11% due to shading and competition. Understanding the genetic control of the beet vernalization requirement and bolting can enable development of bolting resistant varieties that can be sown earlier in spring, or in autumn, allowing flexibility of farm management and greater yields. Important sugar beet flowering genes have been identified, but the role of gibberellin (GA) in control of bolting, flowering, or both processes has not been defined. The amount of bioactive GAs at the beet shoot apex increases after vernalization, and GA deficiency causes late bolting and sterility. Exogenous GA induces bolt elongation in biennial types in non-inductive short day photoperiods, but only after vernalization. The mechanism of this block on the response to GA is unknown, but has great potential to be harnessed for bolting resistant varieties. Using transcriptomics, qRT-PCR, in-situ hybridization and morphological studies, we are investigating the role of GA in bolting and flowering in beet. The wider impact of our research is being considered by investigating how earlier spring or autumn sowing of bolting resistant varieties would change future farm practice.