Does Strain Affect Fruit Color Development, Anthocyanin Content and Fruit Quality in Gala Apples? A Comparative Study Over Three Seasons

Abstract

The effect of strain and season on fruit color development, anthocyanin content and fruit quality was evaluated over a 3 year period (2004-2006) in ‘Gala’ apples ( Malusx domesticaBorkh.) at Lleida (northeastern Spain). The assessment period ranged from 4 wk before, to one wk after, commercial harvest. Based on fruit color (hue angle values and averages for red color covering the fruit surface) and anthocyanin content, the most colored strains were ‘Buckeye Gala’, ‘Royal Beaut’ (barely semi-striped) and ‘Ruby Gala’ (blushed). ‘Brookfield’, ‘Schniga’ (both striped) and ‘Obrogala’ (semi-striped), provided similar values with an intermediate level of color, while ‘Galaxy’ and ‘Mondial Gala’ (both striped) were the least colored varieties. The most important increase in both fruit color and anthocyanin content was recorded from 2 wk before commercial harvest and continued to increase after commercial harvest. Highly colored strains developed a red color on both sides of the fruit with greater averages of fruit surface color area, while less colored strains exhibited differences in color intensity between opposite sides, more bicolored fruits, and lower fruit color area. Season had a differential effect on fruit color of medium and low colored strains. However, in highly colored strains, skin color, anthocyanin content and average fruit surface area tend to be similar from one season to another. The relationship between hue angle, L* or a*/b* ratio and anthocyanin content allowed a cheap, easy, non-destructive prediction of anthocyanin content.

Fruit size and yield were, in general, similar for all strains. Other fruit quality parameters, such as fruit firmness, soluble solids content (SSC), titratable acidity (TA), and starch index, did not significantly differ among strains for the different harvest dates. Fruit quality parameters were not significantly different with respect to seasonal differences nor strain. Differences among strains in fruit color and anthocyanin content were not related to differences in fruit quality parameters and starch degradation. Consequently, color is not a good harvest index for colorful strains. We suggest that starch index could be a better index for picking these strains.