Effects of abscisic acid or ethephon at veraison on the maturity and quality of ‘Beidaneh Ghermez’ grapes

SummaryVitis vinifera ‘Beidaneh Ghermez’ is one of the most popular seedless table-grape cultivars grown in the Middle East, but it usually has a poor berry colour. The impact of abscisic acid (ABA) or ethephon, applied at four rates (0, 100, 200, or 300 µl l−1) at 20 – 30% of verasion, on berry quality in ‘Beidaneh Ghermez’ was studied over two seasons (2007 – 2008). Application of ethephon or ABA did not significantly affect berry yield compared to untreated controls, but berry size increased as the rate of ethephon increased. Neither treatment affected soluble solids concentrations (SSC), titratable acidity (TA), or juice pH. The highest SSC and TA values were recorded in the untreated controls. Total anthocyanin contents of berry skin increased with each incremental increase in ABA or ethephon. The relationship between anthocyanin content and berry skin colour was linear. Berries that received ABA were firmer than the untreated controls, or those treated with ethephon. Ethephon reduced berry firmness compared to control and ABA-treated grapes. All ABA-treated grapes had better overall berry quality than those which received no treatment or ethephon.