The mode of pollination and stigma receptivity in Vitis coignetiae Pulliat

Vitis coignetiae Pulliat, a dioecious grape cultivated for wine making, exhibits fluctuations in productivity from year to year. Pollination mode and stigma receptivity were studied in an attempt to identify the factors involved in this phenomenon. Analysis of airborne pollen using Durham samplers and experiments preventing insects visitation on clusters showed that wind contributed little to cross-pollination. There was no correlation between airborne pollen and the distance from pollenizer. A high level of self-pollination was noted, and insects contributed more to cross-pollination than did wind. The amount of fertile pollen (pollen from male vines) on stigmas was little, even for open pollinated flowers. Hand-pollination carried out at 0, 2, 4, and 6 days after anthesis showed that stigmas were most receptive two days after flower opening. Year to year yield variation in Vitis coignetiae may be due to differences in pollination level.