THE EFFECT OF ETHEPHON ON BERRY COLOUR OF CRIMSON SEEDLESS AND EBONY STAR TABLE GRAPES
The use of ethephon for improvement of colour and quality of Crimson Seedless and Ebony Star was investigated in the Hex River Valley and at Paarl in the Berg River Valley of South Africa, to determine optimal concentrations and timing of application. Ethephon concentrations ranging from 0 to 1600 mg L-1, in combination with four application times, were evaluated. The relationship between application time and certain quantifiable berry quality parameters was also investigated, to enable producers to determine optimal application time objectively. At each ethephon application time, berries were sampled and analysed for TSS, TA and pH. At harvest, 50 berries per treatment were sampled randomly and subjected to sensory colour evaluation. Berry skin anthocyanins was extracted and absorbance at 520 nm was determined. Anthocyanin absorbance levels complemented visual evaluation of berry colour in all three trials. Neither ethephon concentration, nor ethephon application time, affected anthocyanin absorbance of Crimson Seedless (Hex River Valley) significantly. Ethephon concentrations of 400 to 800 mg L-1 are considered as the optimum range for both Ebony Star (Hex River Valley) and Ebony Star (Paarl). For Ebony Star (Hex River Valley) applications later than 5% véraison resulted in higher absorbance and fewer partially coloured berries. Reaction on ethephon application time may be affected by season. Berry TA at time of ethephon application, seems to give the best relationship with berry skin anthocyanin absorbance at harvest.
Avenant, J.H. and Avenant, E. (2006). THE EFFECT OF ETHEPHON ON BERRY COLOUR OF CRIMSON SEEDLESS AND EBONY STAR TABLE GRAPES. Acta Hortic. 727, 381-388
concentration, grapevine, timing, anthocyanin