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Resistance

Components of Variation for Quantitative Adult-Plant Resistance to Powdery Mildew in Winter Rye. T. Miedaner, State Plant Breeding Institute (720) and Institute of Plant Breeding, Seed Science and Population Genetics, University of Hohenheim (350), D-70593 Stuttgart, Germany; H. K. Schmidt, and H. H. Geiger. State Plant Breeding Institute (720) and Institute of Plant Breeding, Seed Science and Population Genetics, University of Hohenheim (350), D-70593 Stuttgart, Germany. Phytopathology 83:1071-1075. Accepted for publication 25 June 1993. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1993. DOI: 10.1094/Phyto-83-1071.

The genetics of quantitative resistance to powdery mildew (Erysiphe graminis f. sp. secalis) in winter rye (Secale cereale) was investigated by testing four sets of factorial crosses along with their parental inbred lines (53 crosses, 28 inbred lines in total) at two locations during 1988 and 1989. Genotypes were scored on a 09 scale for the percentage of infected leaf area at booting and heading stages on the upper three leaves of 10 randomly chosen main stems per plot. Estimates of heritability were high in all materials at both assessment stages (h2 = 0.650.95). High correlations were found among leaves (r = 0.750.97; P = 0.01) for all sets and between booting and heading pooled over leaves for three out of four sets (r = 0.890.98; P = 0.01). Significant quantitative variation was observed among crosses and lines. General combining ability (GCA) variances were significant for the males in all sets and for the females in three sets; specific combining ability (SCA) was negligible throughout. Strong GCA-environment interactions were found. Moderate (r = 0.68; P = 0.05) to strong (r = 0.770.87; P = 0.01) correlations existed between line and GCA effects. The resistance levels of lines and crosses were similar in two sets, whereas in the third set the inbred lines and in the fourth set the crosses were slightly more resistant. We concluded from the data that considerable progress can be expected from selection for quantitative resistance to powdery mildew in current hybrid rye breeding programs.

Additional keywords: Blumeria graminis, partial resistance.