Abstract: The effect of preharvest forchlorfenuron (1-(2-chloropyridin-4-yl)-3-phenylurea, CPPU) treatment on fruit firmness and cell wall degrading enzyme activities in ‘Qinmei’ kiwifruit during cold storage was studied by dipping young fruits with 0, 5, 10 or 20 mg/L CPPU solution 28 days after flowering. Control fruits were dipped in water. All fruits were dipped for 3–5 s. The results showed that CPPU treatment accelerated the decline in fruit firmness and the contents of protopectin and cellulose and increased the content of soluble pectin and cell wall degrading enzyme activities, including polygalacturonase (PG), pectin methylesterase (PME), cellulase (Cx) and beta galactosidase (β-Gal). For all treatment groups, fruit firmness was significantly negatively correlated with soluble pectin content and PG and Cx activity (P < 0.01), and was significantly positively correlated with protopectin and cellulose contents (P < 0.01). The firmness of 20 mg/L CPPU treated fruits was significantly negatively correlated with β-Gal activity (P < 0.05). CPPU treatment enhanced the activity of cell wall degrading enzymes, sped up the degradation of cell wall components, accelerated fruit softening during storage, and reduced storability. In order to maintain the firmness of post-harvest kiwifruit and prolong the storage period, CPPU should not be used or used at a concentration at a concentration not exceeding 5 mg/L.

Key words: ‘Qinmei’ kiwifruit, 1-(2-chloropyridin-4-yl)-3-phenylurea, fruit firmness, cell wall degradation, cell wall degrading enzyme activities