Clubroot of the crucifers caused by Plasmodiophora brassicae is one of the most important diseases in the cultivation of Brassica species. In the Metropolitan Region of Curitiba, PR most of the soil is contaminated by the pathogen Plasmodiophora brassicae infesting agent of the clubroot of the crucifers making the cultivation of different species not feasible in many properties. Liming to increase soil pH is one of the most recommended control measures. Whereupon the objective of this work was to evaluate the effect of soil pH in different inoculums concentrations in the control of P. brassicae. Four levels of soil pH were used: 4,3; 5,5; 6,2 and 7,3 and three inoculums concentrations: 1.2 x 10(7), 2.5 x 10(7) 5 x 10(7) spores.mL-1 and non-inoculated control. The spores suspension was obtained from Chinese cabbage roots showing galls and it was added to the plant collars when the Chinese cabbage (Brassica rapa var. pekinensis) seedlings were transplanted to pots. At 45 days after inoculation the evaluations were performed. The effect of pH on the disease severity was more expressive with the average inoculums (1.2 x 10(7) to 2.5 x 10(7) spores.mL-1) With the higher inoculums concentrations the disease severity was reduced in soil pH 6,2 and 7,3. The best development of the plants assessed by the accumulation of foliar dry phytomass was obtained where the soil presented pH between 6,2 and 7,3 and with the lowest inoculum concentration.
galls; liming; supressiviness; Brassica rapa var pekinensis
