Investigating the influence of biotic and abiotic factors on the phytochemical variation of lingonberries (Vaccinium Vitis-idaea L.) in Norway

Lingonberry is an evergreen dwarf shrub abundant in the area of Nordic countries and a food traditionally regarded as a staple of Nordic diets. There is however limited commercial harvest of these readily available berries. The objective of this doctoral thesis is to investigate how the composition Norwegian lingonberries vary and is affected by abiotic and biotic growth conditions. The thesis consists of four papers of which three studies were conducted in controlled conditions investigating the effects of ripening, light conditions, and temperature during ripening on the composition of the targeted compounds in lingonberries. The fourth paper of the thesis investigates the variation in composition of wild Norwegian lingonberries and how different environmental factors influence this composition. In lingonberries, in total 29 phenolic compounds, sucrose, glucose and fructose as well as 4 organic acids and 77 volatile organic compounds were detected.. In the controlled studies time of harvest significantly influenced the quality of the lingonberries. Spectral light composition with supplemental blue wavelengths increased the content of anthocyanins, and slightly influenced the ratio of sugars to organic acids. There was only a limited effect of light intensity on the content of anthocyanins in lingonberries. Berries grown at lower temperatures had a higher content of anthocyanins and organic acids, whereas the other phenolic compounds were not significantly influenced. Latitude and temperature had the most significant effect on the content of anthocyanins in lingonberries. While light conditions only slightly influence berry quality, factors such as amount of precipitation during ripening, the density of deciduous trees, and altitude also significantly influenced berry quality. Precipitation influenced the content of organic acids in the field study. The result from this study further strengthens the evidence that lingonberries are a rich source for dietary polyphenols, and that berry quality increases with later harvest times. High quality lingonberries can be found across the country with large variation within local areas. The combination of field experiments and controlled experiments showed that weather conditions during ripening, latitude and density of deciduous trees all influence berry quality.