Leveraging Management Strategies for Seedborne Plant Diseases To Reduce Salmonella enterica Serovar Typhimurium Incidence on Tomato Seed and Seedlings

Tomatoes have been linked to many outbreaks of salmonellosis over the last decade, but the routes of contamination have yet to be discerned. Many phytopathogens of tomato are seedborne and are effectively managed using seed sanitizers. Seed sanitizers effective against bacterial phytopathogens were evaluated for their efficacy in killing bioluminescent Salmonella enterica serovar Typhimurium strain SeT-A14 on tomato seed infested with moderately high and high levels of pathogen. SeT-A14 incidence on seedlings produced from contaminated seed following sanitation was also determined. At a moderately high infestation rate (40%), SeT-A14 was eradicated on seed sanitized with 1.2% sodium hypochlorite (NaClO) mixed with 0.03% surfactant for 2 min, hydrochloric acid (HCl) for 30 min, and trichloromelamine for 2 min. At a higher infestation rate (94%), only NaClO and HCl were effective in eradicating SeT-A14 from the seed. At both infestation rates, 2% Virkon-S for 15 min significantly reduced SeT-A14 incidence compared with the nontreated infested controls but did not eradicate the pathogen. Hot water, a commonly used sanitizer for managing seedborne bacterial plant diseases, significantly reduced SeT-A14 on heavily infested seed, but incidence was still moderate at 17.5%. On seedlings produced from moderately highly infested seed, SeT-A14 was not detected using RapidChek Salmonella test strips. Using heavily infested seed, SeT-A14 was detected with the test strips in one of four pooled samples of 14-day-old seedlings produced from nonsanitized seed and from seed sanitized with hot water and trichloromelamine. However, bioluminescence was not observed on 14-day-old seedlings. To our knowledge, this is the first report that provides evidence that S. enterica serovar Typhimurium can be seed transmitted and can lead to the contamination of tomato seedlings. In addition to eliminating important bacterial phytopathogens from tomato seed, NaClO or HCl may mitigate the risk of Salmonella seedling contamination.