Pericarp browning is the key factor for the extension of shelf life and the maintenance of the commercial value of harvested litchi fruit. Water loss is considered a leading factor of pericarp browning in litchi fruit. In this study, based on the distinct structure of litchi fruit, which is a special type of dry fruit with the aril as the edible part, the effects of water supply via pedicel (WSP) treatment on pericarp browning and the fruit quality of litchi were investigated. Compared with the packaging of the control fruit at 25 °C or 4 °C, the WSP treatment was found to significantly reduce pericarp browning and the decay of litchi fruit. The WSP-treated fruit had a higher L* value, total anthocyanin content, and pericarp water content, and the pericarp was thicker. The WSP treatment significantly suppressed the increase in the electrolyte leakage of the pericarp and maintained higher ascorbic acid (AA) contents in the aril. In addition, the WSP treatment was effective in reducing the activity and gene expression of browning-related genes Laccase (ADE/LAC) and Peroxidase (POD) during the storage period. In conclusion, the WSP treatment could be an effective method to delay pericarp browning and maintain the quality of harvested litchi fruit, and this further supports that litchi fruit has dry fruit characteristics.

Litchi and longan are tropic/subtropic fruits harboring recalcitrant seeds that are covered with sugar-rich arils as the edible part. A rapid sugar content decline, called sugar receding, in the arils after the fruit maturation largely reduces the fruit quality, however, the mechanism is unclear. Litchi and longan fruits grow and mature in a hot and rainy season with dry spells between rainfalls. Here, we found that the seed maturation was around 2 weeks earlier than the fruit maturation, after which the sugar contents of the arils significantly decreased, while the fruits could stay on the tree for 1–2 months with high seed vigor. A continuously low-level fruit drop after the seed maturation resulted in continuous seed germination and seedling establishment in around 2–3 months. Blocking assimilate supply by storage of detached fruits or on-tree girdling-plus-defoliation for 7 days, the aril sugar contents of the treated fruits significantly decreased, while the sugar levels and vigor of the seeds increased, implying that the arils are sugar sources to maintain or even enhance the seed vigor and suggesting that sugar receding in arils benefits the recalcitrant seeds of litchi and longan to cope with dry spells after maturation.

Allele-specific expression (ASE) is a phenomenon in which the expression level of an allele from both parents is inconsistent, which is considered to play a key role in the differences between hybrids. As a typical climacteric fruit, banana undergoes a ripening process that affects the quality of the fruit. BaXi (Musa, AAA group) and Fen Jiao (Musa, ABB group) banana fruits show different traits during postharvest ripening, and their high-quality reference genomic sequences have been published. In this work, we analyzed differentially expressed genes (DEGs) in these two banana cultivars based on the transcriptomes during the postharvest stages. Additionally, the imbalance expression of alleles of DEGs in Fen Jiao banana fruit was analyzed, revealing that 27.2% (3 d) and 22.2% (6 d) of the 15,415 DEGs showed ASE. Then, the ASE profiles related to the post-ripening of banana fruit were built, focusing on ripening-related pathways, such as ethylene biosynthesis (62.5–83.3%), starch degradation (0–75%) and cell wall material degradation (34.6–90.9%). The ASE genes involved in ripening were more frequent than those associated with general gene expression. In addition, the candidate key genes of ASE alleles involved in ethylene synthesis and starch degradation were identified, including the alleles of MaACS7/MbACS7, MaACO2/MbACO6, MaACO3/MbACO7, MaACO8/MbACO13 and MaACO6/MbACO17 involved in ethylene biosynthesis, and those of MaAMY1/MbAMY3, MaBMY1/MbBMY2, MaBMY7/MbBMY8 and MaDPE2/MbDPE2 involved in starch degradation. The expression of the B genes of these key enzyme genes (ACS/ACO/AMY) is more active than that of the A genes in Fen Jiao bananas.

Litchi (Litchi chinensis Sonn.), an important fruit in south China, rapidly loses commercial value within 3–4 days at ambient temperatures due to poor storability. Previous studies have shown that 5 mg L⁻¹ CPPU (N-(2-chloro-4-pyridyl)-N′-phenylurea) application can improve postharvest storage of litchi fruit. In this study, we investigated the improved storability of litchi fruit by CPPU application from the perspectives of fruit maturity and seed vigor. Litchi fruit on the tree were treated with CPPU 2 weeks before commercial maturation. Fourteen days after CPPU application, the treated fruit exhibited 61% higher pericarp chlorophyll, 22% thicker pericarp and 76% lower anthocyanin concentrations than untreated controls, which indicates delayed on-tree fruit maturation. CPPU also remodeled the endogenous hormone profiles in the pericarp and seeds, elevating pericarp IAA and DHZR by 47% and 90%, representing active auxin and cytokinin forms, respectively. During the 12 days of ambient storage of the treated preharvest fruit, CPPU-treated fruit showed reduced pericarp browning, disease incidence, and electrolyte leakage, while maintaining a 72% marketable fruit rate against the control’s 25% and higher antioxidant enzyme (APX) activity, indicating an increase in fruit storability when compared to the control. Moreover, CPPU suppressed the upregulation of eight senescence-related genes, including LcLOX1.5-1, LcLOX1.5-2, and LcRNase3. Notably, seed vigor of the litchi fruit decreased with the progress of storage, while the CPPU treatment maintained higher seed vigor compared to the control. These results suggest that the enhanced litchi fruit storability by preharvest CPPU application may be linked to recalcitrant seed vigor maintenance, hormone profile modulation, and pericarp senescence delay.