Genetics and genomics of flowering time regulation in sugar beet

Abstract

Leaves from beets have been used since ancient times for nutrition and the swollen roots were one of the first sweeteners in the Middle Ages that could be stored through the winter. Breeding of beets to increase sugar content began only in the 18th century, after it was uncovered that the nature of the sweet taste of sugar cane and that of beet roots relies on the same sugar molecule. The major breakthrough in breeding sugar beet was the selection of beet progenies that, unlike their wild ancestors, did not flower in the first year of growth, correlating to a high root and thus sugar yield. This was the birth of the sugar beet that became a major crop in Europe and later on worldwide. Genetics has shown that the switch from annual to biennial beets relies mainly on one gene: the 'bolting gene' B. However, research from model plants has shown that the regulation of flowering is complex and involves many regulatory pathways, which perceive, transduce and integrate both endogenous and environmental cues for the fine tuning of flowering. Therefore, broad approaches to study flowering time in beets have been initiated, including both forward and reverse genetic studies to elucidate the molecular nature of B as well as other components of what is likely an intricate regulatory network also in beet. This chapter will give a short history of beet use and breeding as well as strategies and results from recent and current efforts to understand the regulation of flowering time in sugar beet.