8th INTERNATIONAL WHEAT CONFERENCE

to that of Sr36 cultivars. The powdery mildew resistance of the cultivars was tested during
the same period, and the resistance of 1BL.1RS (Pm8) cultivars was not found to be
significantly better than that of cultivars without Pm8 or Pm6. However, cultivars carrying
the Pm6 gene exhibited a significantly higher level of resistance compared to those
lacking Pm8 and Pm6.
Effect of stem rust on grain yield. To evaluate the effect of Sr31 and Sr36 genes on yield
under stem rust infection, 6-years yield trial (1993-1998) in a twin-plot design (4 replications
were inoculated with stem rust race mix and 4 replications were protected by
fungicide) was performed including 2 Sr31, 5 Sr36 and 2 non-Sr31/Sr36 cultivars. In inoculated
plots average infection level of Sr36 cultivars (1-4%) was very low; it was significantly
higher in Sr31 cultivars (10%), while in the susceptible two cultivars the infection
reached 33-38%. Grain losses due to infections were: 1-5% for Sr36, 5-9% for Sr31 cultivars
while the 2 non-Sr31/Sr36 cultivars suffered a heavy (35-36%) yield reduction. These
results sow the efficiency and differences of the two resistance genes both on infection
and yield.
Although the 1BL.1RS translocation and the Sr36/Pm6 resistance gene cluster had a major
impact on Hungarian wheat breeding programs, appearance of the Ug99 and its derivatives,
which are virulent to these genes, means that there is an urgent need to find new
genetic sources of stem rust resistance. To accelerate this process the use of molecular
markers closely linked to effective genes against stem rust seems to be an appropriate
solution.
This work was supported by grants National Office for Research and Technology (NKTH),
projects ID: GVOP-3.1.1.-2004-05-0206/3.0, DTR_2007, and OMFB 00950/2005, as well
as by trans-border co-operation grants from the European Union: INTERREG IIIA (HU-
RO-SCG-1/206) and HURO/0801/133.
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