A marker-assisted analysis of bolting tendency in sugar beet (Beta vulgaris L)

Bolting tendency in sugar beet varies among breeding lines and cultivars. Four crosses were made between breeding lines susceptible and resistant to bolting in order to study the genetic basis of bolting tendency. Bolting percentage in F-2, after 8 weeks of low temperature treatment, varied among the crosses, suggesting a complicated genetic control of bolting tendency. Different segregation ratios were observed, in particular, between families derived from the bolting F-1 plants and those from their non-bolting siblings, the former families showing a significantly higher bolting percentage than the latter. A marker-assisted analysis with seven isozyme loci, Ak1, Gdh2, Idh1, Lap, Mdh1, Pgi2 and Pgm1, revealed that a locus with marked effect on bolting tendency was located near Idh1. Because of a close linkage of Idh1 with B for annuality, the gene tagged by Idh1 appeared to be equivalent or similar to B' for easy bolting allelic to B as reported by Owen et al. (1940). The results obtained suggest that the B locus may not only have an important role in determining growth habits but also control various degrees of bolting tendency in individual sugar beet plants. A linked pair, Ak1-Lap, and Pgi2 also were found to affect bolting tendency, although their effects varied depending on the crosses and families tested.