Which crop is primarily harvested for its edible root?

The crop that is primarily harvested for its edible root is beets. Beets, specifically sugar beets and garden beets, are cultivated mainly for their thickened roots, which are rich in sugar and nutrients. The edible root of the beet can be consumed directly or processed to produce sugar, making them an important agricultural product.

In contrast, corn, barley, and wheat are primarily grown for their grains or seeds, which serve different purposes such as feed for livestock, food for humans, or industrial use. These grains do not have an edible root comparable to beets, emphasizing the distinctive nature of beets in this context. Thus, beets are the correct answer as they are specifically recognized for their edible root.