Antifungal activity of potato glycoalkaloids and its potential to control severity of dry rot caused by Fusarium sulphureum

Identifying novel sources of antifungal agents from common food waste (i.e., green potato peel) could provide an inexpensive alternative for botanical fungicides. Identification of the potato (Solanum tuberosum L.) glycoalkaloids (PGAs) content in the green peel by high performance liquid chromatography (HPLC), and the antifungal activity of PGAs against the potato dry rot pathogen Fusarium sulphureum were evaluated using addition of PGAs to the medium in vitro and injection of it into potato tubers in vivo. The results of HPLC showed that the average content of PGAs per kilogram green potato peel was 2238.76 mg, and the alpha-chaconine content was about 1.8 times higher than that of alpha-solanine. Antifungal activity test of PGAs in vitro uncovered that mycelium growth rate of F. sulphureum was inhibited in potato dextrose agar (PDA) medium with varying concentrations of PGAs, and the inhibition rate was positively correlated with PGAs concentration. Moreover, PGAs were also capable of reducing the contents of malondialdehyde, total phenols, flavonoids as well as the activities of peroxidase and superoxide dismutase induced by F. sulphureum through inhibiting or killing part of mycelium. These findings suggest that the protective effect of PGAs against potato dry rot might be associated with the direct fungistatic effect on the pathogen. Thus, PGAs can serve as a promising botanical fungicide to substitute, at least partially, the use of synthetic fungicides in the disease management of potato.