Biennial sugar beets capable of flowering without vernalization treatment

Abstract A biennial sugar beet (Beta vulgaris) generally takes two years to flower and complete its life cycle. In the first year, the plant grows vegetatively, and then enters a period of cold winter. In the second year, it grows reproductively and initiates flowering under long daylength conditions. Among biennial beets that grow vegetatively in outdoor field conditions, two strains were found to flower early under 24-hour daylength conditions without being exposed to cold temperatures. The hypothetical locus related to the flowering trend was named ‘BLOND’ and crossings between strains of the BLOND and normal biennials yielded hybrid derivatives of F1, F2, and BC1F1. Bolting rate was investigated both in an outdoor field under natural daylength conditions and in a greenhouse with an artificial 24-hour daylength. BLOND strains and hybrid derivatives did not bolt in the outdoor field similar to those in the biennial control strains. This enables evaluation of important agronomic traits, such as yield, which cannot be evaluated using an annual control strain in which all plants bolt. However, under 24-hour daylength conditions, BLOND strains bolted without vernalization treatment, unlike those in the biennial control strains but similar to annuals. The bolting rates of the hybrid derivatives suggested that the flowering characteristics of BLOND were mainly controlled by a single dominant gene. Because seed production in BLOND is estimated to take at least four months, similar to that of the annual beet, BLOND’s bolt rate may be applicable for speed breeding of sugar beets.