Effect of Controlled Day and Night Temperatures on Grape Coloration

Fruit coloration was investigated in several cultivars of Vitis vinifera L. grown in pots in sunlit phototron rooms held at various day and night temperatures. Mature 9Cardinal9, 9Pinot noir9, and 9Tokay9 fruits ripened at cool-day (15°C) and cool-night (15°C) temperatures had much greater coloration than fruits ripened at hot-day (35°C) and cool-night (15°C), hot-day (35°C) and warm-night (25°C), or cool-day (15°C) and warm-night (25°C) temperatures. Fruits grown at cool-day warm-night temperatures, however, had significantly greater levels of anthocyanins than fruits ripened at hot day temperatures, regardless of the night temperature. On the other hand, 9Cardinal9 and 9Pinot noir9 berries grown at hot-day (35°C) and warm-night (25 or 30°C) had a higher level of anthocyanins than fruit ripened at hot-day cool-night (15 or 10°C). A day temperature of 35°C completely inhibited anthocyanin synthesis in 9Tokay9 berries, regardless of night temperature. Also, a 30°C night temperature (day temperature 25°C) prevented anthocyanin formation in 9Tokay9 and greatly reduced the coloration of 9Cabernet Sauvignon9 compared with fruits ripened at 15 and 20°C night temperatures. On the basis of fruit coloration, 9Tokay9 was least tolerant to hot temperature, and 9Pinot noir, and 9Cabernet Sauvignon9 were most tolerant.