Pumping up grapes

CSIRO researchers have unravelled one of the secrets of grape ripening.

Recent research by the CRC for Viticulture at CSIRO Plant Industry in Adelaide has demonstrated that steroidal hormones essential for plant growth and development, known as Brassinosteroids (BRs), have an important role in the ripening process in grapes.

An increased understanding of ripening has direct implications for improved grape production and downstream processing but little is known about the ripening mechanisms of grapes.

The research team used gas chromatography and mass spectrometry to analyse hormone levels in Cabernet Sauvignon grapevine flowers and grape berry samples from 2 to 16 weeks post flowering.

The data revealed a dramatic increase in the levels of a bioactive BR at the onset of berry ripening. Changes in the activities of grape genes associated with producing and responding to BR were consistent with the increased levels.

Field trials showed that applying BR to individual berries promoted ripening, while applying an inhibitor of BR synthesis significantly delayed ripening.

While more work is needed to find out the mechanism by which BR influences ripening, researchers believe BR may promote increased berry size, an important part of the ripening process. Further work may eventually lead to control of ripening through the application of BRs or inhibition of their action.

This research was supported by the Cooperative Research Centre for Viticulture, the Grape and Wine Research and Development Corporation and the Australian Research Council.

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