Abstract:

To investigate the evolution process and stability of fruit quality of apple trees in major growing areas to the
north of the Weihe River in Shaanxi province, mature fruits of Fuji apple trees at different ages (0-10, 11–15, 16–20, 21–25,
and > 25 years old) at orchards located in two major growing counties, Luochuan and Baishui, were analyzed for single
fruit weight, volume, density, hardness, soluble solids, titratable acids and calcium content, and comprehensive quality
evaluation of apples was carried out based on these seven quality indicators. The results demonstrated that single fruit weight
and volume markedly increased with increasing tree age. When the trees entered the peak fruit period (16 years old), they
remained basically stable. Fruit density showed no significant difference with tree age. Fruit hardness slowly declined with
the increase of tree age. But the differences in the fruit hardness of apple trees of different ages did not reach the significance
level. Soluble solid contents in the fruits of trees of different ages showed fluctuation, and titratable acids first increased
and then decreased with increasing tree age. Changes in calcium content presented a V-shaped trend with the extension of
tree age. Comprehensive evaluation showed the fruit quality exhibited an ascending trend with tree age up to 16 years and
significantly declined when the tree was over 25 years old. According to the above analysis, the fruit quality of apple trees
from the best growing areas to the north of the Weihe River was unstable. The relatively stable fruiting period for the best
fruit quality was confined to trees ranging in age from 16 to 25 years old. The fruit quality was deteriorated significantly in
trees aged over 25 years old.

Key words: tree age, Fuji apple, quality analysis, comprehensive evaluation indicators, regions to the north of the Weihe River