The effect of inter-fruit competition, type of fruiting lateral and time of anthesis on the fruit growth of kiwifruit(Actinidia deliciosa)

The final fruit size of kiwifruit was dependent on seed number, but fruit with few seeds were proportionally smaller if in close proximity to fruit with many seeds. Fruit on the same lateral with equal seed numbers developed to similar final fruit sizes. The final size of a fruit was also partly determined by pre-anthesis factors. Late opening flowers tended to produce small fruit. A predominance (74.3%) of late flowers were found on short (terminating) laterals, while 85.4% of early flowers were carried on long (non-terminating) laterals. Differences in mean fruit size at harvest between fruit developing from early or late flowers on uniform, short laterals were as much as 31 g. This was equivalent to a reduction of about 2 g per day as anthesis was delayed. This difference was independent of fruit seed number, but a significant difference between the size of the ovary of early and late flowers was present at the beginning of fruit development. In addition, fruit produced on long laterals were bigger (101 cm3) than those on short laterals (89 cm3), even though they developed from flowers with the same date of anthesis. This effect was likely to be related to undefined factors associated with the vigour of the long laterals, which produced more viable seeds per fruit (1052) than did short laterals (819). An understanding of the factors that control flowering, ovary growth and the production of vigorous fruiting laterals within a vine is important for the design of training and pruning systems for increased yield.