Abstract: In order to study the effect of combined postharvest treatment with a low concentration of ethephon and 1-methylcyclopropene (1-MCP) on the aroma synthesis pathway of banana fruits during storage, the contents of characteristic aroma substances, key synthase activities and related gene expression in banana (Musa spp. cv. ‘Brazil’) fruits at different ripening stages were determined by gas chromatography-mass spectrometry (GC-MS), enzymatic assays and real-time fluorescence quantitative polymerase chain reaction (qPCR). The results showed that 1-MCP treatment (400 nL/L) alone and combined with ethephon (50 μL/L) significantly delayed and inhibited the formation of the characteristic aroma compounds: isobutyl acetate, isoamyl acetate, butyl butyrate, and isoamyl butyrate in fully ripe banana fruits; ethanol and ethyl acetate in over-ripe fruits; and hexanal and trans-2-hexenal in green ripe fruits, and the contents of components above were close to those in the control group. Both single and combined treatments significantly inhibited the activities of alcohol acyltransferase (AAT) and alcohol dehydrogenase (ADH) involved in the metabolic pathways of aroma compounds, and the activities of AAT and ADH in the combined treatment were close to those in the control group, but significantly higher than those in the single 1-MCP treatment. Both treatments first increased and then inhibited the activity of lipoxygenase (LOX) during the storage process, attenuated the expression of the ADH1 and pyruvate decarboxylase (PDC) genes, delayed their expression peaks, and delayed but did not reduce the expression peaks of the branched-chain amino acid transferase (BCAT), LOX and AAT genes. 1-MCP treatment alone significantly inhibited ADH2 expression, but the combined treatment had little effect on ADH2 expression. In the present study, it was confirmed that combined ethephon and 1-MCP treatment can effectively relieve ripening disorder caused by inappropriate 1-MCP treatment, and maintain the aroma quality of banana fruits, which provides a theoretical basis for the application of 1-MCP for the post-harvest quality maintenance of banana fruits.

Key words: banana; ripening; 1-methylcyclopropene; volatile compounds; enzyme activity; gene expression