Characterization of the suppressor gene of powdery mildew resistance gene Pm8 in common wheat (Triticum aestivum L.) cv. Regina

The Czech winter wheat cv. Regina which does not possess specific genes for powdery mildew resistance except Pm5 was crossed with the cvs. Florida, Tjelvar, Agra, Olymp and Sabina, all possessing T1BL-1RS and the dominant suppressor SuPm8, with Riebesel 47/51 possessing substitution 1R-1B and SuPm8 and with the T1BL-1RS cvs. Sparta, Iris, Mona without SuPm8. Powdery mildew isolates avirulent on Pm8 and virulent on other Pm genes were used in the trials. Tests for resistance were carried out either on seedlings at the first leaf stage or on detached leaves cultured on benzimidazolagar. No segregation for resistant plants in F₂ of all crosses of the cv. Regina with cultivars possessing T1BL-1RS and SuPm8 indicates that Regina has SuPm8. The segregation ratio 3 resistant : 13 susceptible in the F₂ population of crosses between the cv. Regina and cultivars possessing T1BL-1RS and no SuPm8 also confirms the presence of SuPm8 in the cv. Regina. The obtained results also indicate that expression of Pm2 and Pm4b is not affected by SuPm8 and that SuPm8 does not affect stem rust resistance gene Sr31 located on 1RS segment.