Abstract
The effect of environmental temperatures on the coloration of Kyoho grapes was investigated by exposing whole vines and clusters separately to different temperature regimes during ripening stage. Young bearing vines were placed in the sunlit growth cabinets kept at 20°C and 30°C and, in each cabinet, their clusters were enclosed in acrylic cylinders whose inside temperature was regulated at 15°, 20°, 25° and 30°C, respectively. In another experiment only night temperatures around clusters of young bearing vines grown under natural conditions were regulated at 15°, 20°C and 25°, 30°C in the same manner.
Anthocyanin contents in the berries increased with lowering in temperature around clusters from 30°C to 15°C regardless of temperature in the cabinets. Low night temperature around clusters, also, increased anthocyanin levels compared to high night temperature. Sugar levels in the skin were not affected by temperature around clusters. However, ABA contents in the skin of grapes exposed to low temperatures were much greater than those of grapes exposed to high temperatures.
These results indicate that fruit temperature acts an important role on anthocyanin synthesis of Kvoho grapes, and that ABA levels in the skin may be involved in the coloration affected by the fruit temperatures.
