Flower quality and fruit size of Hayward kiwifruit

Kiwifruit vines (Actinidia deliciosa cv. Hayward) growing in the warmer, northern region of New Zealand were sprayed with hydrogen cyanamide to increase flowering. When vines were at mid-bloom, flowers which had just opened were selected and flower quality was destructively assessed on a random sub-sample of these flowers. Flowers on vines sprayed with hydrogen cyanamide had larger ovaries and larger pedicels, than flowers on untreated vines. Although the number of carpels per flower was not altered, the percentage of dry matter in the ovaries was reduced on sprayed vines. Fruit growth was monitored on the remaining sub-sample of flowers. Fruit size on vines sprayed with hydrogen cyanamide was consistently larger throughout the growing season. Allowing for differences in crop load between treatments, the increase in fruit size at harvest was commensurate with the increase in newer size observed during bloom. This suggests that flower quality may be an important determinant of final fruit size.