Prediction of final weight for Actinidia chinensis 'Hort16A' fruit

Growth of the fruit of Actinidia chinensis 'Hort16A', a new yellow-fleshed cultivar commercially produced in New Zealand, was monitored non-destructively over five seasons at two sites. Fruit were destructively harvested at various times during the season to obtain measurements of individual fruit fresh weight and three linear measurements of fruit size, from which a regression relation was derived to enable estimation of fruit fresh weight from the fruit measurements (R-2 > 0.99). This enabled growth of cohorts of tagged fruit to be followed by non-destructive measurements of the fruit dimensions, A mathematical function was fitted to each growth curve, to estimate the maximum mean fruit weight and to interpolate between observations at various times during fruit growth. These interpolated data were used to obtain a simple relationship between mean fruit weights at different times during fruit growth. From c. 80 days after mid bloom (DAMB), prediction of fruit weights was found to be independent of season and site. Earlier than this, there was a marked increase in prediction uncertainty, which was independent of site. Average fresh weight at 200 DAMB could be predicted from an estimate of average fresh weight 50 DAMB with a standard deviation of 10.2 g, whereas at 100 DAMB this reduced to 5.5 g. The prediction method was validated using data collected over two seasons and the same two sites used to create the prediction method, as well as data over the same two seasons collected at two more southern sites.