Bacterial wilt of tomato caused by Ralstonia solanacearum is one of the most devastating diseases of tomato (Solanum lycopersicum) on the Eastern Shore of Virginia (ESV). Four research trials were conducted on the ESV over three growing seasons to determine the temporal and spatial distribution of bacterial wilt throughout commercial tomato fields. Individual plants were assessed at ≈1-week intervals throughout the growing seasons with the incidence of bacterial wilt for each individual plant being recorded. Bacterial wilt increased gradually during each growing season. An increase in the clustered distribution of symptomatic plants was determined to exist within rows but not across rows. There were positive correlations between disease incidence and the percentage of rows exhibiting a significantly clustered distribution in every trial. These findings suggest that as bacterial wilt incidence increases in tomato fields by either the intimate contact between roots of adjacent tomato plants or the movement of the pathogen in surface irrigation water, symptomatic plants become more clustered within rows.
Adam F. Wimer, Steven L. Rideout and Joshua H. Freeman
Theodore McAvoy, Joshua H. Freeman, Steven L. Rideout, Stephen M. Olson and Mathews L. Paret
Seven hybrid tomato rootstocks with possible resistance to bacterial wilt caused by Ralstonia solanacearum and a known resistant cultivar were tested as grafting rootstocks to impart resistance to a bacterial wilt-susceptible cultivar, BHN 602. Greenhouse studies showed resistance of all the rootstocks to bacterial wilt. The disease incidence and yield of ‘BHN 602’ grafted to these rootstocks were evaluated in open-field tomato production in Florida and Virginia over four seasons. Significant differences in bacterial wilt incidence were observed between grafted entries in three of the four trials. In these three trials, grafted entries consistently exhibited the least bacterial wilt incidence compared with the controls; the self-graft, and non-grafted entries. Over all the trials, tomato plants grafted onto ‘Cheong Gang’, ‘BHN 1054’, and ‘BHN 998’ displayed the least bacterial wilt incidence. Rootstocks had a significant effect on total marketable yield in all the trials with certain grafted entries yielding significantly greater than non-grafted ‘BHN 602’. Field studies show that grafting holds promise for decreasing the impact of bacterial wilt on tomato cultivars as well as increasing the overall productivity of tomato cultivars.
Leslie D. Hintz, Renee R. Boyer, Monica A. Ponder, Robert C. Williams and Steven L. Rideout
Tomatoes have been associated with numerous outbreaks of salmonellosis in recent years. Trace-backs suggest tomato fruits may become contaminated during preharvest. The objective of this study was to determine the potential for Salmonella enterica serotype Newport to be internalized into the roots, stems, leaves, and fruit of red round tomato plants through contaminated irrigation water at various stages of plant development. Tomato plants were irrigated with 250 or 350 mL (depending on growth stage) of 7 log CFU·mL−1 S. Newport-contaminated irrigation water every 7 days. Roots, stems, leaves, and two tomato fruit from plants irrigated with S. Newport or water (negative control) were sampled for contamination at five stages of growth. Twenty-five of the 92 total samples taken from plants irrigated with S. Newport were confirmed positive (serovar specificity was not evaluated). Sixty-five percent of confirmed samples were roots, 40% were stems, 10% were leaves, and 6% were fruit. There was a significant difference in the presence of S. enterica according to tissue sampled (roots > stems > leaves, and fruit) (P < 0.05) and no association between growth stage and contamination (P > 0.05). Contamination of tomato fruit with S. Newport introduced through irrigation water is low because a high level of persistent contamination of a plant in the agricultural setting is unlikely.