REAPPRAISAL OF SEASONAL APPLE FRUIT-GROWTH

Three apple cultivars (McIntosh, Delicious and Empire) were used in 1989 to study seasonal fruit growth. Fruit fresh weight (FW), dry weight (DW), dry matter concentration (DMC) and relative growth rate (RGR) were regressed against days after full bloom (DAFB) while partitioning the fruit growth curve into either two or three linear phases. Linear phases in fruit DW and FW development were evident throughout most of the growing season. However, cultivars differed in seasonal FW and DW accumulation totals and daily rates. Fruit RGR gradually declined until 75-80 DAFB, when it reached a low and constant rate until harvest. The DMC of fruitlets at about 30-35 DAFB was about half that at full bloom. After an additional 20-30 d during which DMC increased, fruits maintained a relatively stable DMC level to the end of the season.