GENETICS OF STEM RUST RESISTANCE IN WHEAT CVS. PASQUA AND AC TABER

Canadian wheat cvs. Pasqua and AC Taber were examined genetically to d etermine the number and identity of stem rust resistance genes in both . The two cultivars were crossed with stem rust susceptible line RL607 1, and sets of random F-6 lines were developed from each cross. The F- 6 lines, parents, and tester lines with single stem rust resistance ge nes were grown in a field rust nursery, inoculated with a mixture of s tem and leaf rust races, and evaluated for rust resistance. The same w heat lines were tested by inoculation with specific stem rust races in seedling tests to postulate which Sr genes were segregating in the F- 6 lines. Segregation of F-6 lines indicated that Pasqua had three gene s that conditioned field resistance to stem rust and had seedling gene s Sr5, Sr6, Sr7a, Sr9b, and Sr12. Leaf rust resistance gene Lr34, whic h is in Pasqua, was associated with adult-plant stem rust resistance i n the segregating Fh lines. Adult-plant gene Sr2 was postulated to con dition field resistance in AC Taber, and seedling genes Sr9b, Sr11, an d Sr12 also were postulated to be in AC Taber.