Effect of cultivar resistance and rotation crops on clubroot (Plasmodiophora brassicae) in canola and brassica vegetables
Clubroot, caused by Plasmodiophora brassicae Woronin, can dramatically reduce yields of brassica crops. Once present in a field, eradication is difficult, but resistant cultivars can provide effective management. The reactions of selected canola and brassica vegetable cultivars to pathotypes 2 and 6, the prevalent pathotypes in Ontario, were assessed. The canola cultivars marketed as resistant were resistant to both pathotypes. The vegetable cultivars marketed as resistant were resistant to both pathotypes except for putative resistant cultivars of cabbage and broccoli which were resistant to pathotype 6 but susceptible to pathotype 2. The effect of selected field and cover crops on spore concentrations in soil and the combined effect of planting a cereal crop and liming and were also assessed. Wheat reduced spores compared to a no-plant control. Spore concentrations decreased as the lime rate increased and there was no interaction between wheat and lime. Therefore, growers can use both strategies.