The answer is
potato.
Potato is a stem tuber while carrot, beetroot, and radish are true root crops and not tubers.
Tuber is a structure that provides nutrients for the next season regrowth. It is specialised for asexual reproduction. Potato is a stem tuber, for example. In one growing season, the tuber is produced and used to perennate the plant. In the autumn, when the plant structure above-ground dies, the tuber survives underground over the winter. When spring comes, tuber regenerates new shoots thanks to nutrients stored. On the other hand, true root crops (carrot, beetroot, radish) are modified roots to store energy but they are not specialised for asexual reproduction.
