Application of a preliminary screen to select locally adapted resistant rootstock and soil amendment for integrated management of tomato bacterial wilt in Taiwan

Host plant resistance and soil amendment (SA) have not been used extensively to manage tomato bacterial wilt caused by Ralstonia solanacearum due to their variable effects over locations. A preliminary screen was developed to increase the chances of identifying successful control measures under diverse conditions. Isolates from three production areas in Taiwan were collected and their virulence evaluated on tomato. Soil samples from four field sites were collected to evaluate ability to suppress the pathogen of SAs consisting of urea or staked lime alone or combined at 30 degrees C. The mixture of urea and slaked lime showed the best suppressive effect in three tested soils and was used in subsequent field experiments. Resistant eggplant (EG203) and tomato (Hawaii 7996) rootstocks, selected based on stable resistance against representative strains at the seedling stage, significantly reduced disease incidence in field experiments. EG203 grafted plants exhibited 0 to 2.8% wilted plants compared with 24.4 to 92.9% wilted nongrafted plants. Integrated use of Hawaii 7996 as the rootstock and SA provided significantly greater control of wilt than use of Hawaii 7996 as rootstock alone in only one of the four locations, whereas SA did not provide significant control effect when EG203 was used as the rootstock.