Efficacy of five disinfectants against Potato spindle tuber viroid

Viroids are RNA molecules which are harmful to numerous cultivated plant species and considered, for some of them, as quarantine organisms. Because these pathogens are readily transmitted by contact, effective disinfection measures to clean the cultivating tools, machineries or facilities have to be found and approved. To this end, five disinfectants: Virkon^®, Hyprelva™ SL, Jet 5 ^®, MENNO^® clean and Virocid™, were evaluated for their effectiveness against Potato spindle tuber viroid (PSTVd). The virucids were assessed on dried droplets and in aqueous solutions of PSTVd infected tomato sap. For both experimental setups, the infectiousness of the sap and disinfectant mixtures was checked by inoculation on tomato seedlings followed by RT-PCRs. The experiments involving aqueous solutions, which allowed a discrimination of tested virucids, were carried out in 5 laboratories. In these experiments, MENNO^® clean, the only approved product for PSTVd in several European countries, was not found to be effective at the minimum manufacturer's recommended contact time or at an intermediate contact time for the minimum manufacturer's recommended concentration. Conversely, the four other commercial disinfectants: Virocid™; Hyprelva™ SL; Virkon^® and Jet 5^®, were not found to be significantly different from the bleach control. However, in the experiments performed on dried sap droplets, the effectiveness of the five commercial disinfectants decreased substantially.