Fruit quality is certainly influenced by biotic and abiotic factors, and a main quality attribute is the external appearance of the fruit. Various possible agronomical approaches are able to regulate the fruit microenvironment and, consequently, improve fruit quality and market value. Among these, fruit bagging has recently become an integral part of fruits’ domestic and export markets in countries such as Japan, China, Korea Australia and the USA because it is a safe and eco-friendly technique to protect fruits from multiple stresses, preserving or improving the overall quality. Despite increasing global importance, the development of suitable bagging materials and, above all, their use in the field is quite laborious, so that serious efforts are required to enhance and standardize bagging material according to the need of the crops/fruits. This review provides information about the effects of bagging technique on the fruit aspect and texture, which are the main determinants of consumer choice.

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.

Flavonoids play a key role as a secondary antioxidant defense system against different biotic and abiotic stresses, and also act as coloring compounds in various fruiting plants. In this study, fruit samples of purple (Passiflora edulis f. edulis) and yellow (Passiflora edulis f. flavicarpa) passion fruit were collected at five developmental stages (i.e., fruitlet, green, veraison, maturation, and ripening stage) from an orchard located at Nanping, Fujian, China. The contents of flavonoid, anthocyanin, proanthocyanin, and their metabolites were determined using ultra-performance liquid chromatography-mass spectrometry (UPLC-MS), activities of key enzymes involved in flavonoid metabolism were measured, and expression profiling of related genes was done using quantitative real-time PCR (qRT-PCR). The results revealed that total flavonoids, anthocyanins, and procyanidins were found to be increased in the fruit peel of both cultivars with fruit maturity. Total flavonoids, anthocyanins, procyanidins, flavonoid metabolites (i.e., rutin, luteolin, and quercetin), and anthocyanin metabolites (i.e., cyanidin-3-O-glucoside chloride, peonidin-3-O-glucoside, and pelargonidin-3-O-glucoside) were found abundant in the peel of purple passion fruit, as compared to yellow passion fruit. Principle component analysis showed that the enzymes, i.e., C4H, 4CL, UFGT, and GST were maybe involved in the regulation of flavonoids metabolism in the peel of passion fruit cultivars. Meanwhile, PePAL4, Pe4CL2,3, PeCHS2, and PeGST7 may play an important role in flavonoid metabolism in fruit peel of the passion fruit. This study provides new insights for future elucidation of key mechanisms regulating flavonoids biosynthesis in passion fruit.

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.

SWEETs (sugars will eventually be exported transporters) have various physiological and biochemical roles in plant growth, including pollen development, seed nourishment, nectar secretion, and longer-distance sugar transportation. The SWEET genes were identified in various plant species, but they have not yet been thoroughly characterized. Here, we discovered 21 putative SWEET genes from the Eriobotrya japonica Lindl. genome. For further elucidation, comprehensive bioinformatics analysis was utilized to determine the physicochemical properties, gene organization, conserved motifs, cis-regulatory elements, gene duplication, and phylogenetic relationships of EjSWEET genes. Most of the SWEET proteins were predicted to be located on the plasma membrane or vacuole. Gene organization and motif analysis showed that the numbers of exons and motifs in each gene ranged strikingly, between 5 and 6 and between 5 and 8, respectively. Synteny analysis showed that the tandem or segmental duplication played a dynamic role in the evolution of SWEET genes in loquat. Likewise, we analyzed the expression patterns of EjSWEET genes in the root, stem, leaf, flower, and fruit of loquat. Some genes exhibited varying expression in loquat tissues, indicating their potential roles in plant development. The relative expression levels of EjSWEET1, EjSWEET3, and EjSWEET16 were noticeably higher in ripened fruits, suggesting their possible role in the transportation and unloading of sugars in fruits. The present study provides initial genome-wide identification and characterization of the SWEET gene family in loquat and lays the foundation for their further functional analysis.