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Inheritance of Resistance to Stagonospora nodorum Leaf Blotch in Kansas Winter Wheat Cultivars

Stagonospora nodorum blotch can cause serious yield and quality losses of wheat (Triticum aestivum) in many countries worldwide. Although there are other control methods, host resistance is the most desirable. Three recent Kansas winter wheat cultivars (Betty, Heyne, and 2163) have been developed with moderate levels of resistance to the leaf phase of Stagonospora nodorum blotch. To determine inheritance of resistance and allelism, these cultivars were crossed with one of three susceptible lines (Larned, KS96WGRC39, or Newton) and intercrossed in all possible combinations, including reciprocals. The parents, F₁, F₂, and F₃ generations were tested for resistance to S. nodorum in the greenhouse as 4-week-old seedlings. Cytoplasmic effects were not detected in any cross. The mean levels of infection in the F₁s of the two crosses Betty × Larned and Heyne × KS96WGRC39 indicated resistance was dominant. The observed phenotypic ratios of F₂ plants for both crosses were not significantly different from the expected ratio for a single dominant gene. The ratio observed for F₃ lines in the Betty × Larned cross fit that expected for a single dominant gene. However, the observed ratio of the F₃ lines from the cross Heyne × KS96WGRC39 did not fit the ratio expected for a single dominant gene. The allelism test for Betty and Heyne indicated that they have different resistance genes. The F₁ mean rating of the cross 2163 × Newton was intermediate between the two parents, indicating the absence of dominance for resistance in 2163. The phenotypic ratio observed in the F₂ plants from this cross did not fit the ratio expected for a single dominant gene. The simple genetic control of resistance in cv. Betty makes it a useful source of resistance for wheat breeding programs.