The effects of 1-methylcyclopropane and ethylene on postharvest rachis browning in table grapes

• 1-MCP treatment reduced rachis browning while ethylene tended to enhance it.
• Rachis respiration was reduced by 1-MCP treatment.
• Auto-fluorescence showed that 1-MCP enhanced and ethylene decreased chlorophyll fluorescence.

The green rachis in clusters of table grapes provide an important indication of the freshness of the produce after storage. In the past rachis browning was associated mainly with dehydration but results of the current study suggest the involvement of ethylene in the process. We show that 1-methylcyclopropane (1-MCP) delayed rachis browning in three table-grape varieties whereas ethylene tended to enhance it. Respiration was reduced in 1-MCP-treated-rachis and ethylene production was reduced in one of the varieties. Berry respiration and ethylene production were not affected by the treatments. Interestingly, respiration and ethylene production in rachis of ‘Thompson Seedless’ were much lower than in the other two tested varieties. Significant differences were observed between the auto-fluorescence properties of the treated rachis and those of the untreated ones—differences that were consistent with the lower accumulation of flavonoids in the former. Berry auto-fluorescence was also affected by the treatments: ethylene enhanced auto-fluorescence associated with flavonoids in the two green varieties and 1-MCP reduced it in the black variety. Although it was shown that 1-MCP affected rachis browning, applicability of this approach requires further study.

Untreated (left) and 1-MCP-treated (right) rachis of ‘Thompson Seedless’ after cold storage.Figure optionsDownload as PowerPoint slide