Tomatograftingto managebacterialwilt(causedby Ralstonia solanacearum) in the southeastern U.S

Ralstonia solanacearum causes severe losses to tomato growers who manage infested soils in the southeastern U.S. Commercial tomato varieties offer little host resistance and fumigation has limited efficacy as primary inoculum can be re-introduced through soil water movement. Bacterial wilt (BW) is managed worldwide by grafting popular fruiting varieties onto resistant rootstocks. However, few rootstocks are available in the U.S. and little is known regarding their efficacy against native Ralstonia strains. Field trials were conducted in NC from 2007-2009 to determine the utility of grafting to manage BW and evaluate commercially-available rootstocks against endemic populations of R. solanacearum. Four rootstocks displayed effective partial resistance, and BW AUDPC values were significantly lower among all rootstocks compared to non- and self-grafted controls in all trials (P < 0.05). Fruit yield was significantly affected by grafting onto resistant rootstock (P < 0.05). Interestingly, several rootstocks showed differential efficacy across locations, suggesting that pathogen population dynamics plays a role in rootstock selection. 'RST-04-105' had complete resistance in eastern NC, but showed intermediate resistance in western NC. Similarly, 'Dai Honmei' had high resistance in western NC, but was intermediate in eastern NC. Grafting is an effective management strategy against bacterial wilt and could be an important component of a successful IPM program.