Inter‐specific transfer of clubroot resistance from <i>Brassica campestris</i> L. to B. <i>Napus</i> L.

Abstract

Abstract No varieties of Brassica napus L. have been found resistant to race E of clubroot, Plasmodiophora brassicae Wor., but several varieties of B. campestris L. are highly resistant. Crosses were made between B. campestris L. var. Debra turnip, resistant to races A–F of clubroot, and B. napus L. var. Sensation swede, which is susceptible to these races. There were no major fertility barriers between the two species. Two clubroot resistant swede‐like F 2 plants were crossed with Calder swede, which is susceptible to races B, C, and E, and with Doon Spartan swede, which is susceptible to races C and E of clubroot. F 1 progenies of these turnip×swede 2 crosses were screened for resistance to race C. There was a high level of resistance to races B, C, and E of clubroot in selected high–yielding F a progenies in the field and in glasshouse experiments. These progenies were morphologically identical to and fully inter‐fertile with swedes, B. napus , but no cytological comparisons were made.