
The idea itself is stupid.
It will cost more to move potatoes to and from mars.
The money can be used to feed people.
Stupidity at its zenith.
You are stupid

Everything technology that has been used to explore the space has in turn benefited man kind in his daily life someway or the other. If potatoes can be grown on martian conditions think how easy it would be for us to grow them in harsh condition right here on earth.
How stupid can people get?
Except for the fact that focusing on growing potatoes on Mars takes your focus off the fact that you will never eat any of those potatoes. Why not. You'll die of old age before they grow any there that can be eaten.