GENETICS OF RESISTANCE IN RUTABAGA TO TWO RACES OF <i>PLASMODIOPHORA BRASSICAE</i>

Abstract

The York and Wilhelmsburger rutabaga cultivars, both resistant to races 2 and 3 of the clubroot pathogen, were crossed with the race 2- and 3-susceptible Laurentian cultivar. Race 2-resistant Ditmars S2 rutabaga selection was also crossed with susceptible Laurentian. Race exposure of F 1 seedlings of resistant × susceptible crosses showed that resistance to races 2 and 3 was dominant. Susceptibility studies of F 2 and backcross progenies showed that resistance to race 2 in York was controlled by a single major gene, whereas resistance to this race in Wilhemsburger was controlled by two major genes. Single major gene resistance to race 2 was indicated for the Ditmars S2 selection. This crucifer line is susceptible to race 3. F 2 progeny exposures to race 3 showed that resistance was controlled by one major gene in both the York and Wilhelmsburger rutabaga cultivars.