‘Gaucho’ (CI 15323) is an octoploidTriticaledeveloped from a cross between susceptible ‘Chinese Spring’ common wheat and an Argentine rye (Insave F. A.) that is resistant to the greenbug,Schizaphis graminum(Rondani). (Insave F. A. is the only greenbug-resistant rye known at present.) Arriaga and Ree (1963) reported that a single dominant gene controlled the overall resistance in this rye to the greenbug. The transfer of resistance to common wheat would be of great importance to wheat production since no practical level of resistance is present in commercial varieties. However, the chromosomes of rye rarely pair with those of wheat in the intergeneric hybrid, so the transfer of desirable characteristics from rye to wheat by conventional breeding methods is impossible (Riley and Chapman 1958). However, a number of workers have used an irradiation technique to obtain transfer of genetic material carrying genes for disease resistance via alien chromosomes to wheat (Sears 1967). Therefore, the transfer of greenbug resistance from the Argentine rye via Gaucho to wheat should be possible since only one of the pairs of rye chromosomes bears the genes for resistance.