Integrated Analysis of Risk Factors Influencing Tobacco Black Shank Disease in Yuxi Tobacco-growing Region

In order to explore the factors associated with the risk of tobacco black shank(TBS) disease in Yuxi tobacco-growing area of Yunnan Province, 27 TBS disease risk monitoring sites were established based on the data of local altitude, topography and main layout of cultivated varieties. Field samples were collected for 3 consecutive years to detect the number of copies of Phytophthora nicotianae and soil physicochemical indexes, whereas meteorological factors and other related information were detected. The related factors affecting the risk of TBS disease in the area were analyzed. Results showed that, with large-scale pest control, no significant relationship occurred between the disease index and the amount of P. nicotianae in field, for K326, Yunyan87 and KRK26, the main cultivars in Yuxi. While without control measures against TBS, the disease index of Yunyan 87 was significantly positively correlated with the amount of P. nicotianae in pot experiment. When the concentration of P. nicotianae spores applied in the pot soil was 1×10⁴~1×10⁶ spores/mL, the disease index was significantly positively correlated with the amount of P. nicotianae in rhizosphere soil. Meanwhile, soil pH and organic matter content were negatively correlated with TBS. Soil electrical conductivity, available nitrogen, available potassium, soil type, the quantity of antagonistic bacteria, cropping patterns and succeeding crops exhibited minimal correlation with the disease risk, and could also lead to disease epidemics either individually or in combination. This study analysed the factors affecting the occurrence of TBS disease in Yuxi tobacco area, and may also provided theoretical basis for the risk prediction and regional layout of disease-susceptible varieties.