Study on Pathogenicity Difference of Plasmodiophora brassicae Under Different Temperature and pH Conditions.

[Objective] This study was conducted to investigate the pathogenicity of Plasmodiophora brassicae on cabbage grown under different temperature and soil pH conditions. [Method] The pathogenicity of P. brassicae were tested at seven different temperatures and at six different soil pH values with the resting spore concentration of 1×10⁸ (spores/g) in the soil. The plant survival rate and incidence rate of clubroot were investigated after 90 d. [Result] The incidence rate of clubroot on cabbage among the different temperature sets varied in a descending order as follows: 30 °C>25 °C>20 °C>35 °C>15 °C>10 °C>5 °C at soil pH value of 6, indicating that the pathogenicity of P. brassicae was weak at 5 and 10 °C. The incidence rate increased with soil temperature increasing from 15 to 30 °C, but decreased at 35 °C. The incidence rates of clubroot were 80.36%, 100%, 65%, 10.77%, 3.23% and 0% at soil pH 4, 5, 6, 7, 8 and 9 at 25 °C, respectively. The growth of cabbage was inhibited and the survival rate was reduced at pH 4The incidence rates of clubroot were low at pH value of 7 and 8, and was 0% at pH 9. The Chinese cabbage grew better at pH value of 5 and 6, but had high incidence rates of clubroot. [Conclusion] The results revealed that the incidence rate of clubroot on cabbage was closely related to the temperature and soil pH. [ABSTRACT FROM AUTHOR]