A four-lobed hybrid of wheat and rye stored aboard Deep Space Station K-7, whose poisoning by a Klingon agent was exposed when the tribbles that ate it began to die.
Quadrotriticale is a perennial, high-yield grain developed from triticale, itself a cross of wheat and rye. In the episode The Trouble with Tribbles it is the only Earth grain that will grow on Sherman's Planet, a world claimed by both the Federation and the Klingon Empire, and whichever side develops the planet best will win it.
A large shipment waits in the storage compartments of Deep Space Station K-7 under the anxious eye of Nilz Baris, who has the Enterprise summoned to guard it. Tribbles get into the bins and devour the lot, and Kirk is buried in them when he opens an overhead hatch.
Many of the animals are dead: the grain had been laced with a virus by Arne Darvin, a surgically altered Klingon. The events are revisited in the Deep Space Nine episode Trials and Tribble-ations.