The blackberry (Rubus L.) is a berry fruit with high capacity for drought stress tolerance. In this study, the rooted clones of blackberry cv. ‘Kiowa’ growing in pots and produced by tissue culture were subjected to 14 days of drought stress for investigation of the physiological changes and leaf morphological characteristics. After the treatment, the leaf relative water content (RWC) on days 10 and 14 was significantly lower than that of the controls. Accordingly, the stress imposed an evident increase in the leaf electrolyte leakage. The superoxide dismutase activity under drought stress gradually decreased; meanwhile, the peroxidase activity displayed a higher level. At the elongation stage, both ascorbic acid (AsA) and glutathione (GSH) accumulation revealed a rising trend. Afterward, micromorphological observation revealed that with the increasing duration of stress, cellular morphology of the leaf epidermis endured a series of expansion changes. Moreover, the drought progression seemingly enhanced the stomatal length on day 7, and the stomatal width and opening on day 10, respectively. By day 14, the treated leaves demonstrated a striking increase in stomata density than before. Cell walls of the leaf epidermal and spongy tissue cells were thickened with prolonged drought. In particular, from day 10, the spongy tissue cells were clearly squeezed and filled with sclerenchyma. These results indicated that blackberry clones exhibited adaption to drought, which was reflected by the changes in leaf RWC, electrolyte leakage and antioxidative enzyme activities, the elevation of AsA and GSH concentrations and responses of leaf micromorphology.

With improving living standards, traditional blueberry planting modes cannot meet commercial demands, and blueberry cultivation with soilless substrate has become a popular solution in the blueberry industry. In this study, different soilless substrate treatments were found to markedly influence fruit appearance and intrinsic quality. The fruit in the 50:50 peat/pine bark (v/v) (FPB) treatment group had the maximum single fruit weight, largest vertical diameter, and brightest color, as well as the highest 1,1-diphenyl-2-picrylhydrazyl (DPPH) value, solid-acid ratio and anthocyanin content. The fruit in the 50:50 pine bark/rice husk (v/v) (FBR) treatment group had the highest total phenol and flavonoid levels, largest drip loss value, and lowest total pectin content and firmness value. Metabolomic analysis showed that flavonoid, carbohydrate, and carbohydrate conjugate, and amino acid, peptide, and analog levels were significantly different between groups. Fruit in the FPB group had the highest sucrose, D-fructose 1,6-bisphosphate, salidroside, tectorigenin, naringenin chalcone, trifolirhizin, and galangin contents. The increase in the relative expression of phenylalanine (Phe) promoted the synthesis of fruit polyphenols in the FBR group. Our results provide new insights into the effects of different substrates on the quality of blueberries and a reference for the soilless substrate cultivation of blueberries.

Blueberry is a high-quality fruit tree with significant nutritional and economic value, but the intricate mechanism of sugar accumulation in its fruit remains unclear. In this study, the ripe fruits of blueberry cultivars ‘Anna’ and ‘Misty’ were utilized as experimental materials, and physiological and multi-omics methodologies were applied to analyze the regulatory mechanisms of the difference in sugar content between them. The results demonstrated that the ‘Anna’ fruit was smaller and had less hardness than the ‘Misty’ fruit, as well as higher sugar content, antioxidant capability, and lower active substance content. A total of 7067 differentially expressed genes (DEGs) (3674 up-regulated and 3393 down-regulated) and 140 differentially abundant metabolites (DAMs) (82 up-regulated and 58 down-regulated) were identified between the fruits of the two cultivars. According to KEGG analysis, DEGs were primarily abundant in phenylpropanoid synthesis and hormone signal transduction pathways, whereas DAMs were primarily enriched in ascorbate and aldarate metabolism, phenylpropanoid biosynthesis, and the pentose phosphate pathway. A combined multi-omics study showed that 116 DEGs and 3 DAMs in starch and sucrose metabolism (48 DEGs and 1 DAM), glycolysis and gluconeogenesis (54 DEGs and 1 DAM), and the pentose phosphate pathway (14 DEGs and 1 DAM) were significantly enriched. These findings suggest that blueberries predominantly increase sugar accumulation by activating carbon metabolism network pathways. Moreover, we identified critical transcription factors linked to the sugar response. This study presents new understandings regarding the molecular mechanisms underlying blueberry sugar accumulation and will be helpful in improving blueberry fruit quality through breeding.

Ellagic acid (EA) is present at relatively high concentrations in many berries and has many beneficial health effects, including anticancer properties. To improve the development and utilization of blackberry fruit nutrients, we divided Hull blackberry fruits into five growth periods according to color and determined the EA content in the fruits in each period. The EA content in the green fruit stage was the highest at 5.67 mg/g FW. Single-factor tests and response surface methodology were used to optimize the extraction process, while macroporous resin adsorption and alkali dissolution, acid precipitation, and solvent recrystallization were used for purification. The highest purity of the final EA powder was 90%. The anticancer assessment results determined by MTT assay showed that EA inhibited HeLa cells with an IC₅₀ of 35 μg/mL, and the apoptosis rate of the cells increased in a dose-dependent manner, with the highest rate of about 67%. We evaluated the changes in the mRNA levels of genes related to the EA-mediated inhibition of cancer cell growth and initially verified the PI3K/PTEN/AKT/mTOR pathway as the pathway by which EA inhibits HeLa cell growth. We hope to provide a theoretical basis for the deep exploration and utilization of this functional food.

Blueberry is a nutrient-rich berry, and its taste and flavor directly determine the consumer preference. Until now, few studies have focused on the comparison of fresh food quality and the key metabolites in superior fresh-eating blueberry cultivars. Herein, fruit quality indicators of 10 highbush blueberry cultivars were evaluated using ‘Bluerain’ as the control. Appearance quality analysis of fruits showed that ‘Brigitta’ had a larger fruit size and ‘Anna’ was the smallest. ‘Anna’ fruits, followed by ‘O′Neal’, had the highest ratio of soluble solids to acidity because of their lowest titratable acidity content. Despite the high soluble sugar content, the antioxidants in ‘Anna’ fruits such as total flavonoids, anthocyanins and vitamin C were lowest among all cultivars, while ‘Duke’ seemed to have opposite patterns. Furthermore, a total of 553 and 557 metabolites were identified by non-targeted metabolomics liquid chromatography-tandem mass spectrometry (LC-MS/MS) in positive and negative ion mode, respectively. Particularly, the numbers of differentially accumulated metabolites (DAMs) were the most between the ‘O′Neal’ vs. ‘Bluerain’ group. The DAMs involved in the metabolic pathways, sesquiterpenoid and triterpenoid biosynthesis, monoterpenoid biosynthesis, galactose metabolism, starch and sucrose metabolism, may be mainly related to the synthesis of flavor and carbohydrate substances. Moreover, the expression patterns of genes involved in sugar metabolism were verified by quantitative real-time PCR (qRT-PCR) analysis in different cultivars. Therefore, the systematical comparison of the quality characteristics, metabolites and expression profiles of related genes in highbush blueberries with good flavor could provide some basis for further research on fresh fruit breeding of blueberries.

This study aimed to better understand the impacts of various nitrogen (N) forms on blueberry growth and development, as well as to increase blueberry (Vaccinium spp.) N utilization efficiency. We selected the blueberry cultivar ‘Anna’ as the experimental material, and four N treatments were applied throughout the key vegetative growth stage: N deficiency (CK), ammonium-N (T1), nitrate-N (T2), and amide-N (T3). The growth parameters, physiology indexes, and ultrastructure changes in blueberry seedlings were explored. At the same time, the Pearson correlation model was used to analyze the correlation among each physiology index. The results showed that blueberry plants grew better under T1 and T3 treatments, with increased biomass, N content, chlorophyll content, and photosynthetic efficiency. Under T1 treatment, the leaves had lower O₂^˙− generation rate and MDA concentration, but higher superoxide dismutase (SOD), glutamate synthetase (GOGAT), and glutamine synthetase (GS) activity. Compared to T1 treatment, T2 treatment dramatically enhanced peroxidase (POD) activity, glucose content, and free amino acid content, particularly Arg content. Furthermore, N deficit treatment inhibited plant growth while increasing free radicals, POD, catalase (CAT), and glutamate dehydrogenase (GDH) activities, as well as the content of antioxidant compounds. Correlation and principal component analysis showed that photosynthetic properties, chlorophyll content, antioxidant system, amino acid levels, and N metabolizing enzyme activity were significantly affected by different N forms. This study can serve as a scientific foundation for optimal N regulation and management in blueberries.