What is a low sugar alternative to potatoes

Radishes make a really nice potato sub, when steamed the color becomes paler and they have less "bite".

How about cauliflower florets cut approximately the same size? They kind of have the color and density of potatoes. Not exactly but a decent sub for far less carb/sugar content. You can steam or boil the florets and then add them as the recipe states.

I think this recipe could also work with sliced cucumbers (all ingredients combined just before serving). Cucumber+yogurt+dill is a common combination in many cuisines from Persia to Eastern Europe to Scandinavia. It won't be as filling but would make a lovely summer lunch or supper nonetheless.