Accumulation of sugars and associated gene expression in highbush blueberries differ by cultivar, ripening stage, and storage temperature

BACKGROUND: The sweetness of highbush blueberries is a sensory quality standard for consumers. Changes in metabolites and expression of associated genes induce variation in the sensory quality of blueberries. OBJECTIVE: This work investigated the ripening mechanism of blueberries by measuring changes in organic acids and sugar content as well as the gene expression levels associated with sugar accumulation, such as β amylase, invertase, sucrose phosphate synthase, and tonoplast monosaccharide transporter genes, before and after harvesting. METHODS: We used three different blueberry cultivars (Duke, Sierra, and Elizabeth) that we harvested at two ripening stages in a randomized complete block design and then kept at room temperature or 4°C for 7 days. The organic acids and sugar content were measured via HPLC, and gene expression levels were analyzed by qPCR. RESULTS: Cultivars, ripening stage, and storage conditions affected the synthesis of sugars and degradation of organic acids to determine the sweetness in blueberries and the expression of tagged genes and analyses of compounds involved in the metabolic mechanism. CONCLUSIONS: The results provide insights into the mechanism underlying the ripening and the postharvest quality. This study may support the selection of suitable blueberry cultivars that meet customer demand.