In Vitro and In Vivo Inhibitory Effects of Gaseous Chlorine Dioxide Against Diaporthe batatas Isolated from Stored Sweetpotato

Abstract

Chlorine dioxide (CIO2) can be used as an alternative disinfectant for controlling fungal contamination during postharvest storage. In this study, we tested the in vitro and in vivo inhibitory effects of gaseous CIO2 against Diaporthe batatas SP-dl, the causal agent of sweetpotato dry rot. In in vitro tests, spore suspensions of SP-d1 spread on acidified potato dextrose agar were treated with various CIO2 concentrations (1-20 ppm) for 0-60 min. Fungal growth was significantly inhibited at 1 ppm of CIO2 treatment for 30 min, and completely inhibited at 20 ppm. In in vivo tests, spore suspensions were drop-inoculated onto sweetpotato slices, followed by CIO2 treatment with different concentrations and durations. Lesion diameters were not significantly different between the tested CIO2 concentrations; however, lesion diameters significantly decreased upon increasing the exposure time. Similarly, fungal populations decreased at the tested CIO2, concentrations over time. However, the sliced tissue itself hardened after 60-min CIO2 treatments, especially at 20 ppm of CIO2. When sweetpotato roots were dip-inoculated in spore suspensions for 10 min prior to treatment with 20 and 40 ppm of CIO2 for 0-60 min, fungal populations decreased with increasing CIO2 concentrations. Taken together, these results showed that gaseous CIO2 could significantly inhibit D. batatas growth and dry rot development in sweetpotato. Overall, gaseous CIO2 could be used to control this fungal disease during the postharvest storage of sweetpotato.