Hydrogen Sulfide Acts as a Fungicide to Alleviate Senescence and Decay in Fresh-cut Sweetpotato

Abstract

Hydrogen sulfide (H 2 S) has been shown to be a gaseous molecule in the regulation of many processes in plants such as abiotic stress tolerance, root organogenesis, stomatal movement, and postharvest fruit senescence. We studied the role of H 2 S in the regulation of senescence and fungal decay in fresh-cut sweetpotato ( Ipomoea batatas L., cv. Xushu 18) roots. H 2 S donor sodium hydrosulfide (NaHS) alleviated senescence in fresh-cut sweetpotato root tissue in a dose-dependent manner with the optimal concentration of 2.0 mmol·L −1 NaHS solution. At the optimal concentration of 2.0 mmol·L −1 NaHS, H 2 S fumigation maintained higher levels of reducing sugar in sweetpotato fresh-cut root. H 2 S treatment also significantly increased the activities of guaiacol peroxidase (POD) and decreased those of polyphenol oxidase (PPO) in sweetpotato during storage. Further investigation showed that H 2 S treatment maintained a lower level of lipoxygenase (LOX) activity compared with water control. Consistently, the accumulation of malondialdehyde (MDA) was reduced in H 2 S-treated groups. Three fungal pathogens, Rhizopus nigricans , Mucor rouxianus, and Geotrichum candidum , were isolated from sweetpotato tissue infected with black rot or soft rot. H 2 S fumigation at 1 to 2.5 mmol·L −1 NaHS resulted in effective inhibition of the three fungi when grown on medium. When the three fungi were inoculated on the surface of sweetpotato slices, H 2 S fumigation greatly reduced the percentage of fungal infection. In conclusion, these data suggest that H 2 S effectively alleviated the senescence and decay in sweetpotato slices and might be developed into a novel fungicide for reduction of black rot or soft rot in sweetpotato.