Genetic studies on the resistance of winter wheat to speckled snow mould

Speckled snow mould (caused by Typhula ishikariensis) is a potential threat to winter wheat (Triticum aestivum L.) production in eastern Canada. Information on the inheritance of snow mould resistance is needed to develop an effective breeding strategy. In this study, the inheritance of resistance to the speckled snow mould was examined using crosses of a resistant genotype, PI 173438, and four susceptible cultivars, Lennox, Kitami-2, Norin-8 and Ena. The parental lines, and the F1 and F2 populations from each of the four crosses were grown in the field and in an unheated plastic greenhouse and scored for snow mould resistance. Biomass yield, survival, plant height and number of tillers/plant, all expressed as percentage of check plants, were used as indices of snow mould resistance. Generation means analysis, combining data from the field and greenhouse experiments, indicated that snow mould resistance was largely influenced by environmental conditions, and that additive genetic effects were more important than epistatic effects in controlling the expression of the disease. Dominance effects oriented towards susceptibility were detected in only one of the four crosses. Estimates of broad sense heritability in the four F2 populations ranged from 0.62 to 0.96 and from 0.34 to 0.79, respectively, when biomass yield and number of tillers/plant were used as indices of snow mould resistance. When plant height was used as an index of snow mould resistance, the heritability estimates ranged from 0.10 to 0.53. Key words: Wheat (winter), Triticum aestivum, speckled snow mould, Typhula ishikariensis, heritability