Evaluation of aqueous chlorine dioxide for disinfecting plant explants

Sterilization of explants while maintaining viability is a major task for those working in plant tissue culture. This task is usually accomplished through the use of mercuric chloride or sodium hypochlorite. Due to environmental and health concerns, however, new disinfectants are desired. Chlorine dioxide is an environmentally friendly disinfectant that has been used for many purposes, though its use in plant tissue culture has not been thoroughly investigated. This report describes the application of aqueous chlorine dioxide for the disinfection of yacon (Smallanthus sonchifolius) and pomegranate (Punica granatum) explants. The threshold concentration for obtaining high antimicrobial efficiency with aqueous chlorine dioxide was determined to be 1.25–2.5 mM; however, the viability of the explants from the two species differed with treatment. While the viability of yacon explants remained high at 1.25–1.67 mM aqueous chlorine dioxide, pomegranate explant viability was severely impaired at all tested concentrations. The level of explant viability was negatively correlated with high levels of endogenous polyphenol and subsequent free radical accumulation following treatment. Aqueous chlorine dioxide at concentrations of 1.25–2.5 mM was also suitable for explant disinfection in other low-polyphenol-containing plant species such as rice (Oryza sativa), Pinellia ternata, and Isodon amethystoides. This work shows that aqueous chlorine dioxide can be effectively utilized as an alternative disinfectant for low-polyphenol-containing explants in general.