Disinfection of Tomato chlorotic dwarf viroid by chemical and biological agents

We investigated the effectiveness of various chemical or biological agents in disinfecting Tomato chlorotic dwarf viroid (TCDVd), which causes extensive damage to tomato crops. Among seven tested chemicals, sodium hypochlorite (NaOCl) was the most effective in disinfecting TCDVd-contaminated scalpels with a 15-s dipping. TCDVd-contaminated scalpels were effectively disinfected by sodium hypochlorite solution at a concentration of 0.5% or more. Sodium hypochlorite at 0.25% and 0.125% could also reduce rates of infection via contaminated scalpels, suggesting that solutions of more than about 0.2% could also be used to suppress infection via TCDVd-contaminated tools. Low-pH sodium hypochlorite solution, which has powerful oxidizing activity, was found to degrade TCDVd dramatically even at low concentrations (below 0.1%). However, the effectiveness of such low-pH solutions in disinfecting TCDVd decreased to a level similar to that of high-pH solutions in the presence of plant tissue residues on tool surfaces, probably because of a reduction in cleaning activity. Although trisodium phosphate (Na3PO4) at a concentration of 5% was effective against TCDVd, a 2.5% solution of this chemical was not sufficiently effective against the viroid. Among the biological agents tested, crude sap of pepper plants significantly suppressed TCDVd infection.