Effect of Previous Crop on Soil Populations of Burkholderia solanacearum, Bacterial Wilt, and Yield of Tomatoes in Taiwan

Three field experiments were conducted to evaluate populations of Burkholderia solanacearum and the occurrence of tomato bacterial wilt in soil left fallow, and following crops of cowpea, eggplant, and rice. Bacterial population declined after cowpea and rice, but not after eggplant. The population also declined after soil was left fallow, indicating that a suitable host plant is required to maintain the bacterial population. The area under disease progress curve (AUDPC), based on the incidence of wilted tomato plants, was significantly (P < 0.05) higher following eggplant compared with cowpea and rice for three experiments and in fallow for two of the three experiments. Yields of cowpea, eggplant, and rice were not affected by the presence of B. solanacearum in the soil; however, yields of tomato crops were significantly (P < 0.05) lower following eggplant than following rice. Under greenhouse conditions, bacterial populations decreased more when soil was cropped to rice under permanently flooded conditions.