GENETIC-ANALYSIS OF RESISTANCE TO PUCCINIA-STRIIFORMIS IN THE WHEAT DIFFERENTIAL CULTIVARS HEINES-VII, HEINES-PEKO AND STRUBES-DICKKOPF

One major gene for resistance to isolate WYR 85-22 of race 6EO of Pucc inia struformis was identified by genetic analysis of the differential cultivars Heines Peko, Strubes Dickkopf and Heines VII. This gene was different from Yr2 and Yr6 already identified in Heines Peko (Yr2, Yr 6) and Heines VII (Yr2), was allelic in the three cultivars and also t o a gene expressed in the other differentials Reichersberg 42 (Yr7) an d Clement (Yr9). In Heines Peko, Strubes Dickkopf and Heines VII, a mi nor gene was also postulated, which, it is proposed, gave only a low l evel of resistance by itself but strengthened the expression of the ma jor gene when the latter was homozygous or heterozygous. The genetics of the resistance was analysed using six resistance classes and applyi ng multidimensional analyses. The number of resistance genes was hypot hesized using data from F3 families from crosses between the three dif ferentials and the cultivar Heines Kolben, which is susceptible to thi s race.