Location effects across northeastern Europe on bioactive compounds in apple fruit
A multi-location trial was performed in apple orchards planted in 2005 under a uniform scheme in Poland, Lithuania, Latvia and Estonia. The aim of this study was to evaluate the impact of the geographical apple-tree growing location on the accumulation of dominant bioactive compounds in apple fruits: phenolics and triterpenes as the most valuable substances for human health. The study included two apple cultivars, ‘Auksis’ and ‘Ligol’, on B.396 rootstock and was carried out from 2016 to 2018. Geographical apple-tree growing location had a significant impact on the composition and total content of the tested bioactive compounds in apple fruits. Increased accumulation of phenolic and triterpene compounds was recorded in the south–north direction. This could be explained by the different climate conditions in the trial locations: the sum of active temperatures gradually decreased by 200–300 °C in the south–north direction, and the vegetation period becomes shorter. Apples grown in Estonia, depending on the tested cultivar, had 77–139% more total phenolic compounds. Significant differences were recorded for all groups of phenolic compounds. The differences between the trial sites in accumulation of triterpene compounds were lower, although apples in at farthest north location had 18–32% more total triterpene compounds than apples grown in south.