Optimising blueberry fruit nutritional quality using controlled spectra and mild stress treatment via polytunnel innnovation

Abstract

The blueberry fruit, renowned as an antioxidant superfood, belongs to the genus Vaccinium (family Ericaceae). It is rich in vitamins, minerals, and antioxidants, particularly flavonoids and phenolic acids. Polyphenolic compounds such as phenolics, flavonoids and anthocyanins are bioactive substances that contribute significantly to the fruit’s health benefits through their anti-inflammatory properties. Recently, changes in the cultivation of blueberries have led to increased use of polytunnels. Although these commercial translucent polymer covers protect the crop from the effects of adverse environmental conditions and bird damage, they also significantly reduce photosynthetically active radiation (PAR) and filter out ultraviolet (UV) radiation, impacting the bioactive composition of the fruits. Consequently, blueberries grown under these covers have a reduced antioxidant capacity compared to those grown in open fields. To address this, growers can use photo-selective covers and light-emitting diodes (LEDs) strategically to optimize the light spectrum available to plants. Additionally, applying abiotic stresses, such as salinity and nutrient solution deficits, can help increase antioxidant accumulation in blueberries. This thesis aimed to investigate the impact of abiotic stresses on blueberries cultivated under covered conditions and to develop agronomic practices that enhance the antioxidant capacity of the fruits, thereby improving the nutritional quality of the fruit. The study examined the effects of experimental photo-selective covers and blue LED light exposure on blueberry plants. The photo-selective covers included one shifting the green spectrum (500-600nm) into the red spectrum (600-700nm) (LLEAF®620) and another shifting the green spectrum into the far-red spectrum (700-800nm) (LLEAF®660). Additionally, the study evaluated the impacts on fruit of applied nutrient stress (suband supra-optimal concentrations) compared to ambient conditions. These interventions were evaluated in terms of fruit nutritional quality, measured in terms of bioactive compounds i.e., total phenolic content, total flavonoid content, total anthocyanin content and total antioxidant content.

Date of Thesis submission	2025
Original language	English
Awarding Institution	Western Sydney University
Supervisor	Richard Thomas (Supervisor), Sophie E. Parks (Supervisor) & Nijat Imin (Supervisor)