How does fertilizer management strategy in soilless blueberry cultivation change the phytochemical profile and phenoloxidases activity during fruit ripening?

Highbush blueberry fruits have attracted a lot of attention from consumers due to their exquisite taste and considerable quantities of bioactive compounds. This premium-class foodstuff also contains antioxidant enzymes (phenoloxidases) implicated in the degradation of polyphenols that lead to discoloration and loss of antioxidant activity during fruit ripening. Despite substantial progress in research focused on fruit quality, unanswered questions remain about the effect of fertilizer strategy in soilless blueberry cultivation on the phytochemical content and phenoloxidases activities. Therefore, this study aimed to compare the individual effect of mineral fertilizers (Min treatment) and combined application of organic and mineral fertilizers (Org-Min treatment) the content of targeted primary and secondary metabolites, as well as phenoloxidases activities of blueberry cultivar 'Bluecrop' grown in pots.

The sugar content and sweetness index were not affected by the fertilizer treatment, while the predominant organic acids content (citrate and malate) increased significantly by the Org-Min treatment in both years studied. The Org-Min treatment also stimulated the synthesis of phenolic acids, primarily chlorogenic and p-coumaric acid, while the Min treatment contributed to significant increase in polyphenol oxidase (PPO) activity in both years of the study.

The Org-Min treatment in annual amounts of 72 kg ha^-1 nitrogen, 48 kg ha^-1 phosphorus, and 68 kg ha^-1 potassium had the most pronounced positive effect on the content of phenolic bioactives, which indicates that a partial replacement of mineral by organic fertilizers can be recommended in soilless cultivation of blueberries. © 2024 Society of Chemical Industry.