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Resistance

A New Gene for Resistance to Bremia lactucae. J. E. Yuen, Graduate research assistant, Department of Plant Pathology, New York State College of Agriculture and Life Sciences, Cornell University, Ithaca 14853; J. W. Lorbeer, professor, Department of Plant Pathology, New York State College of Agriculture and Life Sciences, Cornell University, Ithaca 14853. Phytopathology 73:159-162. Accepted for publication 14 June 1982. Copyright 1983 The American Phytopathological Society. DOI: 10.1094/Phyto-73-159.

The lettuce cultivar Vanguard 75 was free of downy mildew caused by Bremia lactucae in a lettuce cultivar evaluation trial during 1980 in Oswego County, NY, while other cultivars of lettuce in the trial had various amounts of mildew. Vanguard and Vanguard 75 were resistant when inoculated with a number of isolates of B. lactucae, but they were completely susceptible when inoculated with other isolates, indicating that the resistance in these cultivars is race specific. Analysis of resistance and susceptibility patterns indicates that this is a new resistance factor, different from the 12 previously described. By testing F₁, F₂, and testcross families from crosses of Vanguard 75 and susceptible cultivars, it was determined that the resistance factor in Vanguard 75 is conditioned by a single dominant gene.