Rye was a grass from Earth, which was often cultivated as a grain. Rye was commonly used in many products such as flour, bread, whiskey (used to make the cocktail known as rye and ginger), and many others. (TAS: "The Practical Joker", TNG: "Manhunt")
The perennial grains quadrotriticale and quintotriticale were hybrids of wheat and rye. (TOS: "The Trouble with Tribbles", TAS: "More Tribbles, More Troubles")
In 2270, Montgomery Scott ordered a grilled cheese sandwich on rye (bread) from the USS Enterprise's food synthesizer, but wound up getting all sorts of food thrown at him instead. (TAS: "The Practical Joker")