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POSTERS: Chemical control

Effects of seed storage conditions and chemical disinfestation treatments on the survival of Xanthomonas vasicola pv. vasculorum on maize seed
Silvina Arias - Iowa State University. Derrick Mayfield- Iowa State University, Charles Block- Iowa State University, Gary Munkvold- Iowa State University

To evaluate the effects of seed storage conditions on the survival of Xanthomonas vasicola pv. vasculorum (Xvv), the causal agent of bacterial leaf streak on corn, artificially-contaminated seeds (soaked in bacterial suspension of 10^5 and 10^6 CFU/ml) were place in two different environments: refrigerated storage (10°C and 50% RH) and “warehouse” conditions. Seeds were sampled every two months for one year. In a second set of experiments, artificially-contaminated seeds were immersed in disinfectant solutions of sodium hypochlorite, hydrochloric acid and hydrogen peroxide. Bacterial survival was monitored by dilution plating onto semi-selective agar. Suspect colonies of Xvv were subcultured onto non-selective medium and confirmed by PCR. In addition, effects of the treatments on seed germination and seedling growth rate were evaluated. After one year, Xvv survived on maize seed storage under both storage conditions but the viability of the initial bacterial population declined in both environments, showing a marked reduction especially under warehouse conditions. In the latter, Xvv survival was noticeably reduced from an initial 4.77 to 2.68 log CFU/ml after 4 months, after which it remained generally stable. The different chemical disinfestation treatments effectively decontaminated the seeds, specifically the seed treatment with 1% sodium hypochlorite for one minute, which also did not affect germination or seedling growth.