The Epidemic Dynamics of Tobacco Bacterial Wilt and Analysis of Related Climate Factors

The population of Ralstonia solanacearum and disease index of tobacco bacterial wilt in Nanping were investigated with systematic survey method. The correlations between tobacco bacterial wilt and climate factors were also analyzed. The results showed that semi selective cultures and fluorescent quantitative PCR were both effective in detecting R. solanacearum in soil. However the correlation between the pathogen population and disease index by the method of semi selective cultures (R²=0.8191) was higher than that by fluorescent quantitative PCR (R²=0.7464). The temperature was the key factor among precipitation, temperature sunlight and humidity which contribute to pathogen population and disease index. In late May to early June when the 7 d average of temperature was higher than 22℃, tobacco bacterial wilt entered initial stage with the amount of pathogen population higher than 5.0×10⁵ cfu/mL. Then disease entered a stable period of development from the first ten days to the second ten days of June, At this stage, the average temperature of 7 d ranged from 22 to 25℃, the pathogen population varied between 1.0×10⁵ and 2.2×10⁶ cfu/g. The epidemic outbreak of tobacco bacterial wilt was in the middle and the last ten-day period of June when the average of temperature was higher than 25℃. At this stage, the pathogen population was higher than 2.2×10⁶ cfu/g. Therefore, the temperature is important in forecasting and prevention of tobacco bacterial wilt in Nanping.