The objective of this investigation was to assign the genes for resistance to leaf rust Puccinia hordei Otth. race 4 in two varieties of barley to the correct chromosome pair by means of crossing with nine translocation stocks.

The varieties Sudan (C.I.6489) and Reka 1 (C.I.5051) were crossed with the following translocation stocks: 5051-2 (a-b), 5059-5 (a-e), 5030-2 (b-d), 5034-2 (b-f), 5062-3 (b-g), 5038-2 (c-d), 5056-2 (c-e), 5053-6 (e-f), and 5057-1 (f-g). The F₁ plants from crosses of Sudan with all translocations and Reka with all translocations were tested for rust reaction and found to be resistant. Examination of the mature pollen showed that the F₁’s were partially sterile. In the crosses involving the variety Sudan with translocation stocks having interchanges of chromosomes a with e and c with e, the F₂ data indicated complete linkage. The common chromosome e must carry the gene for resistance. This is substantiated by crosses involving translocations of a with other chromosomes and c with others, which showed independent assortment. In the crosses involving the variety Reka with translocation stocks having interchanges of chromosomes b with f and e with f, the F₂ data indicate that in Reka, the gene for resistance is linked with chromosome f. This is substantiated by crosses involving translocations of b with other chromosomes and e with others, which showed independent assortment.

The results obtained from the F₂ data of the crosses studied indicated that in the varieties Sudan and Reka reaction to leaf rust is conditioned by genes that are independent of each other.