ISHS Acta Horticulturae 557: VII International Symposium on Orchard and Plantation Systems
EARLY PREDICTION OF APPLE FRUIT SIZE USING ENVIRONMENTAL INDICATORS |
| Authors: | C.J. Stanley, J.R. Stokes, D.S. Tustin |
| Keywords: | fruit growth, fruit weight, growing degree days, Malus domestica, ‘Royal Gala’, temperature |
| Abstract:
Apple growers and marketers need to be able to predict mean fruit weight and time of harvest early in the season. This information could be used by growers and marketers to assist with management decisions (e.g. hand thinning at about 50-60 days after full bloom (DAFB)) to enable them to optimise fruit size for market preferences. The objective of this project was to find environmental indicators to develop robust early predictions of fruit weight and time to harvest. The influence of temperature and photosynthetically active radiation (PAR) levels on growth of ‘Royal Gala’ apples on MM.106 rootstock was studied using trees from one site in each of 3 regions (Canterbury, Hawkes Bay and Nelson) over three consecutive seasons. Crop loads were established at bloom to a very low level to minimise competition between fruit and provide a clearer response of fruit growth to environmental conditions. Additional fruit growth studies were undertaken in Gisborne, Central Otago (Clyde) and Hawkes Bay in the 1997-98 growing season to extend the environmental range. Using this extended database, accumulated growing degree days with a base of 10oC (GDD) from full bloom to 50 DAFB was significantly correlated with final fruit weight (r2= 0.79, p=0.001). Using accumulated hourly PAR did not improve the prediction of final fruit weight. Fruit weight at 50 DAFB significantly predicted fruit weight at harvest. Using non-limiting, low crop conditions, this model accounted for 89.7% of the variance in mean fruit weight at harvest. GDD from full bloom to 50 DAFB was strongly correlated to fruit weight at 50 DAFB (r2=0.90, p=0.001). Time from full bloom to harvest was predicted using GDD from full bloom to 50 DAFB (r2=0.63, p=0.002). | |
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