Abstract
The inheritance of pathogenicity in wheat stem rust was studied in selfed cultures of races 29 and 111, F1 and F2 cultures of a cross between the two races and cultures from a backcross to race 29. The various cultures were tested on Marquis and Prelude and on a series of lines of these varieties carrying single genes for stem rust resistance. Virulence on Sr 5, Sr 6, Sr 8, Sr 9a, Sr 14 and a gene in Marquis was recessive and in each case there was a single gene for virulence corresponding to each gene for resistance. Virulence on Sr 1 was possibly controlled by two dominant complementary genes. There appeared to be two alleles for virulence on Prelude, one dominant and one recessive.