Effect of Ultraviolet Disinfection of Hydroponic Solutions on Pythium Root Rot and Non-target Bacteria

Dispersal of root pathogens is a major concern in closed hydroponic cultures. To limit dispersal, ultraviolet (UV) disinfection technology has been used to remove pathogens but its effect on non-target bacterial populations is largely unknown. In this study, the circulating solution was disinfected with various UV doses (i.e., 19, 38, 59, 88 mJ cm⁻²) before recirculation. At the beginning of the experiment, the hydroponic solution was inoculated with Pythium aphanidermatum at 6.7±1.5 CFU mL⁻¹. Four months later the population density of P. aphanidermatum reached 1030 CFU mL⁻¹ in the control and 1028, 970, 610, and 521 CFU mL⁻¹ in the solutions treated by the above UV doses. In all UV-treated solutions, significant (P