Regreein wheat was a type of food grain.

In 2370, Drofo Awa, the captain of a Xepolite Free Trader suspected to deliver weapons to the Cardassians, pretended that his ship was carrying five kilotons of Regrean wheat husks. (DS9: "The Maquis, Part II")

The Star Trek Encyclopedia entry incorrectly talks about "Regrean wheat husks", in contradiction with the spelling in the script.