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Organic acids are key components that determine the taste and flavor of fruits and play a vital role in maintaining fruit quality and nutritive value. In this study, the fruits of two cultivars of passion fruit Yellow (Passiflora edulis f. flavicarpa) and purple (Passiflora edulis f. edulis) were harvested at five different developmental stages (i.e., fruitlet, green, veraison, near-mature and mature stage) from an orchard located in subtropical region of Fujian Province, China. The contents of six organic acids were quantified using ultra-performance liquid chromatography (UPLC), activities of citric acid related enzymes were determined, and expression levels of genes involved in citric acid metabolism were measured by quantitative real-time PCR (qRT-PCR). The results revealed that citric acid was the predominant organic acid in both cultivars during fruit development. The highest citric acid contents were observed in both cultivars at green stage, which were reduced with fruit maturity. Correlation analysis showed that citrate synthase (CS), cytosolic aconitase (Cyt-ACO) and cytosolic isocitrate dehydrogenase (Cyt-IDH) may be involved in regulating citric acid biosynthesis. Meanwhile, the PeCS2, PeACO4, PeACO5 and PeIDH1 genes may play an important role in regulating the accumulation of citric acid. This study provides new insights for future elucidation of key mechanisms regulating organic acid biosynthesis in passion fruit. [ABSTRACT FROM AUTHOR]

This study was conducted to analyze the effect of molybdenum (Mo) on the level of macronutrients (Mg, K, Ca), micronutrients (Na, Zn, B, Mo, Mn, Fe, Co, Ni, Cu) and toxic elements (Cd, Sn, As, Cr, Hg, Pb) in leaves and fruit tissues (peel, pulp & seed) of loquat using inductively coupled plasma-mass spectrometry (ICP-MS). Fruits were obtained from a loquat orchard located in Fujian (Yun Xiao/Zhangzhou). Loquat leaves showed 3.99, 23.90, 57.68 and 9.79-fold increase in the concentrations of Mg, K, Ca and B as affected by exogenously applied Mo, while a significant (p ≤ 0.05) reduction was observed in Na, Mo, Mn, Co, Ni, Cu, Sn, As, Cr, Hg, and Pb contents. In fruit peel, Mo induced 1.05, 1.56, 2.26, 1.15, 1.39, 1.30 and 1.89-fold increase in Mg, K, Na, Zn, B, Co and Ni, respectively, and Mo, Mn, Fe, Cu, Cr, and Pb contents were reduced. Fruit pulp showed elevated contents of Na, B, Co, Ni, and Sn by 25.65, 26.57, 70.09, 12.33 and 0.99%, respectively, and decreased concentrations of Mg, K, Ca, Zn, Mo, Mn, Fe, Cu, Cd, and Cr. Similarly, in loquat seeds, under the influence of Mo application, levels of K, Na, Zn, Fe, and Cr were uplifted by 14.75, 41.54, 12.71, 536.47 and 656.27%, respectively, while Mg, Ca, Mn, Co, Cu, Sn, and Hg were reduced significantly (p ≤ 0.05). Overall, mineral concentrations detected in the leaves and fruit tissues of loquat were greatly influenced by the application of Mo. Although the concentration of Sn in fruit pulp was increased by the foliar application of Mo, the fruits were under safe limits for human consumption. [ABSTRACT FROM AUTHOR]