Study of physiologic specialization in Plasmodiophora brassicae: Proposals for attempted rationalization through an international approach

A new set of differential hosts is described and proposed for research into physiologic specialization in Plasmodiophora brassicae , and methods are suggested for the performing of differentiation tests. The differential set comprises five hosts each of Brassica campestris, B. napus and B. oleracea . Thirty-four European P. brassicae collections were differentiated. A modification of the binary notation system of nomenclature is adopted for coding P. brassicae populations, the latter term being preferred to physiologic race. The coding system described is amenable to considerable expansion.