Inheritance and Linkage of Turnip Mosaic Virus and Downy Mildew (Bremia lactucae) Reaction in Lactuca serriola1

Data for resistance in Lactuca serriola L. to turnip mosaic virus (TuMV) and downy mildew were obtained from 5 F 2 progenies of crosses between TuMV-susceptible, mildew-resistant, and TuMV-resistant, mildew-susceptible parents. The F 1 progeny were TuMV and mildew-resistant. Of 1,103 F 2 plants assayed 823 were TuMV-resistant and 280 TuMV-susceptible. A total of 834 mildew-resistant plants were observed, and 269 mildew-susceptible. Resistance to TuMV and mildew are each controlled by a single dominant allele, designated Tu and Dm , respectively. The TuMV gene, Tu tu , is linked with the mildew gene, Dm dm. In the repulsion phase, the crossover value was 12.0% ± 2.9. F 2 progenies of crosses between TuMV-susceptible, mildew-resistant L. serriola and TuMV-susceptible, mildew-resistant L. sativa cv. ‘Calmar’ or ‘Imperial 410’, and crosses among cv. ‘Calmar’, ‘Imperial 410’, and ‘E-4’, indicated they possessed the same dominant allele for mildew-resistance, and the same recessive allele for TuMV-susceptibility.