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Yan, Yifan

University of British Columbia

Blueberry (Vaccinium spp.) is an important horticultural crop with high economic and nutritional values. Anthocyanins are the pigments determining fruit surface color, one of the most important quality traits affecting consumers’ choices; cuticular waxes are the major components of the cuticle affecting fruit water loss and determining fruit shelf-life. In this thesis, time-course changes of anthocyanins and cuticular waxes were characterized during blueberry ripening and storage; the effects of these changes on fruit surface color and water loss were determined; the candidate genes underlying cuticular wax deposition were identified in blueberries by transcriptome analysis. Different types of glycosylated anthocyanins were detected, and variations in their relative abundances determined distinct anthocyanin profiles among genotypes. Variations in anthocyanin concentrations and profiles did not correlate to variations in fruit surface color among genotypes. Cuticular waxes affected fruit surface color, and a higher content of beta-diketones – the second largest group of wax compounds in blueberries – determined a lighter fruit surface. The majority of blueberry water loss occurred through fruit cuticle; however, the contribution of cuticle versus stem scar varied among genotypes. The profile of triterpenoids – the most abundant group of wax compounds – played a critical role in determining fruit water loss, and a higher ratio of oleanolic acid to ursolic acid was associated with a lower water loss. The total wax content (micrograms cm–2) decreased during ripening, mainly due to fruit expansion. The total wax load (micrograms berry–1) increased during storage, suggesting de novo synthesis and deposition of cuticular waxes. Transcriptome analysis revealed putative genes related to biosynthesis of triterpenoids in blueberries. Five putative oxidosqualene cyclases (OSC-Like1–5) catalyze the production of various triterpene alcohols (e.g., alpha-amyrin, beta-amyrin, and lupeol), the rate limiting step in triterpenoid production. Three putative CYP716A subfamily monooxygenases (CYP716A-Like1–3) underlay the production of triterpene acids (e.g., oleanolic acid and ursolic acid). This study provides novel insights on the roles of anthocyanins and cuticular waxes in determining fruit surface color and water loss in blueberries during fruit ripening and postharvest storage. These insights will allow blueberry breeding programs to develop new varieties with improved color and shelf-life.

Text

2024-09-30

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/85884

Plant Science

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/