Silicon induces resistance to postharvest rot of carrot caused by Sclerotinia sclerotiorum and the possible of defense mechanisms

The inhibitory potential of silicon (Si) against Sclerotinia sclerotiorum, the causal agent of postharvest carrot rot was investigated under in vitro and in vivo conditions, and possible modes of action were evaluated. Silicon at the concentration of 10 mM strongly decreased the mycelial growth of S. sclerotiorum by 92.2% with inhibition of sclerotia formation by 76.3%. Myceliogenic and carpogenic germination of S. sclerotiorum sclerotia were inhibited by 89.1 and 78.9%, respectively, at the same concentration. The minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) values were 12 and 30 mM, respectively. Cell membrane permeability and lipid peroxidation of S. sclerotiorum mycelia were increased with Si treatment. Silicon at 10 mM significantly decrease the content of oxalic acid in S. sclerotiorum mycelia compared to the control. Application of silicon at 10 mM reduced the incidence of sclerotinia rot in carrot roots by 60.6% with 40 mm lesion length. Silicon treatment enhanced the activities of peroxidase (POD), polyphenoloxidase (PPO) and phenylalanine ammonia-lyase (PAL) in carrot roots inoculated with S. sclerotiorum. These results confirm that silicon might applied as an alternative tool to chemical fungicides for controlling sclerotinia rot of carrot during storage and to promote the defense response in carrot.