Host Range of Plasmodiophora brassicae on Cruciferous Crops and Weeds in China.

Clubroot caused by Plasmodiophora brassicae is an increasingly important soilborne disease in China. The host range of P. brassicae was investigated with 30 cruciferous plants, including 16 crop species, 9 ornamentals, and 5 weeds in field and pot-cultured conditions. In the field, 17 species from five genera produced visible galls, and these included radish, Capsella bursa-pastoris, Orychophragmus violaceus, Sinapis alba, and 13 Brassica crops. In pot-cultured conditions, an additional 13 plant species (11 genera) were determined to be hosts of P. brassicae. Five common weeds were found to be hosts of P. brassicae, including C. bursa-pastoris, Lepidium apetalum, Descurainia sophia, S. alba, and Thellungiella salsuginea. The infection of these plants was confirmed via polymerase chain reaction (PCR) with primers specific to P. brassicae. No galls were found on Matthiola incana roots in the field or in pots and no resting spores of P. brassicae were observed in M. incana roots, although P. brassicae was detected in M. incana roots via PCR. Microscopic examination revealed infection only in the root hairs of M. incana roots. These results suggested that M. incana was highly resistant to P. brassicae in China and could be developed as a bait crop. In total, 297 accessions of oilseed rape were tested in the field, and 3 accessions of Brassica napus and 1 accession of B. juncea were found to be highly resistant to clubroot disease. These resistant resources provide options for managing clubroot in P. brassicae-infested fields.