Use of Tagging to Trace Capfall and Development of Individual Vitis vinifera L. cv. Pinot noir Flowers

Abstract

Although grape yield is a direct consequence of flower development, few studies have examined the characteristics of flowers and their impact on berry development. A novel tagging technique has been developed to trace the development of flowers into berries and to investigate the relationship between ovary diameter at flowering and the date of capfall. Thirty flowers on the basal inflorescence on each of two shoots per vine were tagged using color-coded lengths of waxed dental floss. Flowers were of different diameters and selected from different positions across the inflorescences. At the onset of flowering, one shoot per vine was girdled, between nodes two and three, to increase percentage fruit set. Shoot girdling had no effect on the date of capfall of flowers but did increase the proportion of flowers that developed into seedless berries, with a corresponding decrease in the proportion of flowers forming shot berries. Calculations of percent fruit set, including and excluding shot berries, suggest that shot berries may be considered an initial phase of berry development in Pinot noir and confirm that the increase in the number of seedless berries results from the development of flowers that would otherwise form shot berries. No acropetal progression of capfall was observed within inflorescences. Smaller flowers tended to undergo capfall after larger flowers, which may have implications for fruit set. Pollen tube growth is time and temperature dependent. Variable temperatures during an extended period of capfall may result in a greater proportion of smaller flowers setting fruit than larger flowers. Implications for berry development are unknown. Tag retention of 94.3% suggests that dental floss tagging is a suitable technique for collecting data and tracking the development of individual grape flowers.