Flowering Time Regulation and Crop Improvement

Shifting the seasonal timing of reproduction is a major goal in plant breeding to produce new varieties that are better adapted to local environments and changing climate conditions. Floral transition is a major developmental switch that is tightly controlled by regulatory pathways that integrate endogenous and environmental cues to ensure flowering under favorable conditions. The key regulators of floral transition have been studied extensively in model species, and in recent years a growing number of related genes have been identified in crop species. Evidently, these genes can have functions beyond flowering time regulation, such as biomass production and heterosis. These sequences can be used as selectable markers and for targeted genetic modification of agronomically important traits. I will review the major floral regulatory pathways and strategies to identify flowering time genes from crop plant genomes. Furthermore,  I will discusses current and novel strategies for altering bolting and flowering behavior in two crops, sugar beet (Beta vulgaris) and oilseed rape (Brassica napus). Sugar beet is a biennial crop which bolts and flowers after a period of cold temperatures over winter. We have cloned the central bolting time regulator (BvBTC1) from its position on chromosome 2 and demonstrated its pivotal role in bolting control. Molecular markers derived from its sequence are used for selecting bolting genotypes. Ectopic expression of BvBTC1 resulted in beets with drastically altered bolting behaviors. This opens the path for breeding a winter beet with complete bolting resistance. Because those beets are sown before winter they are expected to have a >20% higher yielding potential as traditionally grown spring beets.