Abstract: To elucidate the possible mechanism by which 6-benzylaminopurine (6-BA) regulates the senescence of broccoli, the effects of 30 mg/L 6-BA on the endogenous 6-BA content, total chlorophyll content, total bacterial account, ethylene production, the expression of senescence-related genes, the activities and gene expression of the ethylene-forming enzymes in broccoli were investigated. The results showed that 6-BA treatment could significantly alleviate the degradation of total chlorophyll and inhibit the increase in total bacterial count in broccoli. The endogenous 6-BA content of control broccoli continuously decreased with the extent of storage time, while exogenous 6-BA treatment maintained higher endogenous 6-BA content at the later stage of storage. The endogenous 6-BA content in both the control and 6-BA treatment groups decreased after cooking. Additionally, 6-BA treatment down-regulated the expressions of chlorophyllase gene (2BoCLH2), cysteine protease gene (5BoCP5), proline rich protein gene (BoLSC810), and retarded the decline in the expression of chlorophyll a/b binding protein 1 (BoCAB1). Moreover, 6-BA treatment significantly suppressed ethylene production in broccoli, which might be associated with decreased activity of ethylene synthase and down-regulated expression of BoACS1 and BoACS2. These results suggested that exogenous 6-BA maintained higher endogenous 6-BA level at the later period of storage, thereby inhibited ethylene production, and finally slowed down the senescence of broccoli.

Key words: broccoli, 6-benzylaminopurine, senescence, ethylene