What properties of a species of plant would make it the ideal choice for taking it on a year-long trip through space as both an oxygen source and food source?
We should assume that the amount of pressurized volume and payload mass is limited on the spaceship and that we only have technology which is plausible to exist in the near future according to the current state of science.
In an answer to another question I tried to describe some desirable properties for such a plant, but I don't know much about botany or biology, so I believe I might be talking a bit out of my ass there.