Suppression on postharvest juice sac granulation and cell wall modification by chitosan treatment in harvested pummelo (Citrus grandis L. Osbeck) stored at room temperature.

• 1.5% chitosan coating suppressed juicy sac granulation of harvested pummelo through maintaining cell wall modification. • Chitosan reduced the deposition of lignin and cellulose in pummelo fruit. • Chitosan reduced the activities and down-regulated the expression levels of lignin synthesis-related enzyme. • Chitosan increased the activities and up-regulated the expression levels of cell wall degrading enzymes. Deposition of both lignin and cellulose accompanied by juice sac granulation is widespread in harvested citrus fruit. Hence, measures to suppress postharvest granulation of 'Majiayou' pummelo is of great importance. The fruit was treated with 1.5% chitosan and then stored at room temperature (20 ± 2 °C) for 150 d. As compared to the control fruits, chitosan coating significantly suppressed granulation index and maintained good quality. Chitosan coating inhibited lignification by suppressing the activities and expression levels of lignin synthesis-related enzymes (PAL, CAD and POD). By contrast, chitosan treatment enhanced the activities and expression levels of cell wall degrading enzymes, including PME, PG, Cx, XTH and β-Gal, which might contribute to the decrease in cellulose. In a nutshell, chitosan coating can effectively suppress juice sac granulation and fruit senescence of pummelo fruits, and play a crucial role in maintaining the cell wall modification. [ABSTRACT FROM AUTHOR]