In this study, the root systems of three markedly different sugar beet varieties from Hokkaido were examined the shallow-rooted ‘Ascend’, the deep-rooted ‘Kabutomaru’, and the intermediately rooting ‘Stout’. Root system development was characterized based on the number of lateral roots branching out from the taproot, root growth angle, and root diameter. Root development over time approximated a sigmoid curve in which three growth phases could be identified a slow growth phase with few roots, followed by a sudden increase in the number of roots, and then a peak in the number of roots. ‘Kabutomaru’ had more roots than ‘Ascend’, with the difference in root number in the second and third phases clearly contributing to the final difference in root number between varieties. Despite a statistically significant difference in the growth angle of lateral roots among the three sugar beet varieties at 16 days after sowing, the root growth angle parameter is considered to fluctuate widely as a function of the branching capacity of the varieties tested however, testing this hypothesis would be both time consuming and difficult. Analysis of root diameter with a root model revealed that ‘Kabutomaru’ had wider roots in each root-diameter class than ‘Ascend’, and ‘Kabutomaru’s primary and secondary lateral roots were particularly thick. Thus, the deep-rooted ‘Kabutomaru’ had good branching capacity and a well developed root system while the shallow-rooted ‘Ascend’ had relatively thinner roots and a slower rate of root system development.

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