| Summary: | Abstract Berries have an outer layer of hydrophobic cuticular wax which plays a role in preventing non-stomatal water loss and protection against UV-B radiation. In this thesis, the chemical composition and morphology of cuticular wax in the fruit of Nordic wild berry species, namely bilberry (Vaccinium myrtillus L.), lingonberry (V. vitis-idaea L.), bog bilberry (V. uliginosum L.), and crowberry (Empetrum nigrum L.) were explored. In bilberry, glossy type (GT) mutant and wild-type (WT) fruits at different developmental stages were investigated for the chemical composition, morphology, and biosynthesis of cuticular wax. Further, the effect of temperature and precipitation on the chemical composition of cuticular wax of bilberry fruit was studied through a latitudinal gradient from Latvia to Finland and Norway. The effect of temperature on the cuticular wax of bilberries was investigated through phytotron experiments. Results showed that triterpenoids were the dominant compound class in the cuticular wax of bilberry and lingonberry, whereas fatty acids and alkanes dominated in bog bilberry and crowberry, respectively. During bilberry fruit development, a decrease in the proportion of triterpenoids was observed with an increase in total aliphatic compounds. A higher proportion of triterpenoids along with a lower proportion of fatty acids and ketones was found in GT fruit cuticular wax compared with WT. A lower density of crystalloid structures on GT fruit than on WT fruit could be attributed to a lower content of ketones and fatty acids. Wax biosynthetic genes CER26-like, FAR2, CER3-like, LTP, MIXTA, and BAS exhibited prevalent expression in bilberry fruit skin, indicating their role in cuticular wax biosynthesis and secretion. Generally, through the latitudinal gradient, a decrease in the proportion of triterpenoids was observed in cuticular wax of bilberry fruit in the studied seasons. In phytotron studies, an increase in temperature led to an increase in the proportion of triterpenoids, as well as decrease in ...
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