According to Spock, "Quadrotriticale is a high-yield grain, a hybrid of wheat and rye. A perennial, also, I believe. Its root grain, triticale, can trace its ancestry back to 20th century Canada."
The implication is that quadrotriticale was created by further hybridization and selective breeding, the same kind of genetic modification we've been practicing on our crops and domesticated animals for thousands of years. Nothing new.
Genetic modification of the sort that's being done today, by manipulating individual genes and inserting genes from one species into the genetic material of another, was unknown in the 1960s.