If you are serious about feeding astronauts in space, then you need to classify what gives the highest percentage edible matter in the whole plant and needs the least mass of things like water. Leafy plants with minimal root systems seem like a good start.

Grains have loads of stalk and root that you don't eat, tend to need a lot of water and need extra equipment in preparation and are often used as powders, which easily form combustible suspensions in low gravity.