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Keywords:

  • Cantaloupe;
  • peroxidase;
  • phenylalanine ammonia lyase;
  • pink rot;
  • scanning electron microscopy-energy dispersive X-ray;
  • silicon oxide;
  • sodium silicate;
  • Trichothecium roseum

Summary

Silicon oxide and sodium silicate were investigated as potential agents for the control of postharvest pink rot in Chinese cantaloupe (cultivar Yujingxing) caused by Trichothecium roseum. In vitro tests showed that sodium silicate, when added to potato dextrose agar, was effective in suppressing the radial growth of the pathogen on the medium, whereas silicon oxide was ineffective. The effectiveness of sodium silicate increased with concentration, and the growth of the fungus was completely inhibited at 100 mm. When melons were dipped in the solutions, both silicon oxide and sodium silicate significantly (P < 0.01) reduced the severity of pink rot of the cantaloupe with lesion diameters reduced by up to fivefold when compared with the controls. Scanning electron microscopy-energy dispersive X-ray analysis showed that silicon (Si)-treated melons had a smoother surface feature and higher Si levels in the epidermis, especially at the stomata and along the junction between the exocarp and mesocarp. Enhanced peroxidase and phenylalanine ammonia lyase activities were observed in sodium-silicate-treated melons but not in those treated with silicon oxide. The results indicate that different mechanisms might be involved in sodium silicate and silicon-oxide-initiated reduction of postharvest pink rot in Chinese cantaloupe.