Mango (Mangifera indica), a nutritionally rich tropical fruit, is significantly impacted by UV-B radiation, which induces oxidative stress and disrupts physiological processes. This study aimed to investigate mango pulp’s molecular and biochemical responses to UV-B stress (96 kJ/mol) from the unripe to mature stages over three consecutive years, with samples collected at 10-day intervals. UV-B stress affected both non-enzymatic parameters, such as maturity index, reactive oxygen species (ROS) levels, membrane permeability, and key enzymatic components of the ascorbate-glutathione (AsA-GSH) cycle. These enzymes included glutathione reductase (GR), gamma-glutamyl transferase (GGT), glutathione S-transferases (GST), glutathione peroxidase (GPX), glucose-6-phosphate dehydrogenase (G6PDH), galactono-1,4-lactone dehydrogenase (GalLDH), ascorbate peroxidase (APX), ascorbate oxidase (AAO), and monodehydroascorbate reductase (MDHAR). Transcriptomic analysis revealed 18 differentially expressed genes (DEGs) related to the AsA-GSH cycle, including MiGR, MiGGT1, MiGGT2, MiGPX1, MiGPX2, MiGST1, MiGST2, MiGST3, MiG6PDH1, MiG6PDH2, MiGalLDH, MiAPX1, MiAPX2, MiAAO1, MiAAO2, MiAAO3, MiAAO4, and MiMDHAR, validated through qRT-PCR. The findings suggest that UV-B stress activates a complex regulatory network in mango pulp to optimize ROS detoxification and conserve antioxidants, offering insights for enhancing the resilience of tropical fruit trees to environmental stressors.

Mango (Mangifera indica) is a highly valuable horticultural crop known for its quality and productivity. This study investigates the dynamic changes in physicochemical properties and glutathione and ascorbic acid metabolic pathways in mango pulp across various growth and development stages over two consecutive years (2021–2022 and 2022–2023) by transcriptomic analysis. Overall, the results demonstrate that during different ripening periods, the pulp shows increased levels of total soluble solids, relative conductivity, glutathione, and enzymes, while titratable acidity, malondialdehyde, reactive oxygen species, and ascorbic acid contents decreased. Moreover, transcriptomic analysis identified key differentially expressed genes from the glutathione and ascorbic acid metabolic pathways and validated them with qRT-PCR. In different comparisons, a total of 1776, 2513, and 828 DEGs were identified in 30 vs. 60, 30 vs. 90, and 60 vs. 90 days after flowering, respectively. Among them, seven DEGs were primarily enriched in relevant pathways, which included ascorbate peroxidase, ascorbate oxidase, glutathione peroxidase, gamma-glutamyl transferase, glutathione transferases, and glucose-6-phosphate dehydrogenase. The upregulation of these genes indicates that glutathione and AsA respond well to scavenging reactive oxygen species and maintain normal functioning in plants. This research sheds light on the molecular mechanisms of glutathione and ascorbic acid dynamic changes in mango pulp, providing valuable insights into the regulation of antioxidant and metabolic pathways during fruit growth and development.

In this study, an artificially simulated enhanced UV-B radiation treatment of 96 kJ/m²·d⁻¹ was applied with natural sunlight as the control. By observing changes in biological tissue damage, peroxidase (POD) enzyme activity, and hormone content, combined with transcriptome analysis and quantitative fluorescence PCR validation, this study preliminarily elucidated the physiological mechanisms of plant-specific peroxidase (POD) in responding to enhanced UV-B radiation stress. Enhanced UV-B treatment significantly inhibited biological tissue growth, particularly during the rapid growth stage. At this stage, the treatment exhibited higher malondialdehyde (MDA) content, indicating increased oxidative stress due to the accumulation of reactive oxygen species (ROS). Despite the inhibition in growth, the treatment showed improvements in the accumulation of organic nutrients as well as the contents of abscisic acid (ABA), salicylic acid (SA), and methyl jasmonate (MeJA). Additionally, an increase in POD activity and lignin content was observed in the treatment, especially during the middle period of the rapid growth period. Transcriptome analysis revealed that two POD multigene family members, LOC123198833 and LOC123225298, were significantly upregulated under enhanced UV-B radiation, which was further validated through qPCR. In general, enhanced UV-B radiation triggered a defence response in biological tissue by upregulating POD genes, which can effectively help to scavenge excess ROS.

Previous studies have shown that foliar spraying with a 0.3% CaCl₂ + 0.3% MgCl₂ solution can mitigate the “sugar receding” phenomenon in fruit pulp, partly by regulating sugar conversion in the pulp of ‘Feizixiao’ litchi (Litchi chinensis Sonn.). Given that calcium-dependent protein kinases (CDPKs) in plants regulate sugar metabolism by modulating the activity of key sugar conversion enzymes, this study investigated the expression response of CDPK genes in ‘Feizixiao’ litchi pulp to foliar calcium–magnesium nutrient treatment and their regulatory characteristics on sugar conversion. After the fruit set, ‘Feizixiao’ litchi trees were subjected to three consecutive foliar spray applications of 0.3% CaCl₂ + 0.3% MgCl₂, with water spraying as the control. The dynamic changes in peel h values and soluble sugar and monosaccharides, water-soluble calcium (Ca²⁺) and magnesium (Mg²⁺), plant hormones, and the concentration of CDPKs in the pulp were compared throughout fruit development. Key differentially expressed members of the CDPK gene family were screened through real-time quantitative PCR analysis. The results showed that the peel color transition occurred earlier in the control (CK) than in the treatment (T), but the coloration process accelerated in the treated fruit, leading to no significant difference in peel h values between the groups at 76 days after anthesis (DAA), when both reached the lowest levels. The total of soluble sugar in the pulp peaked at 70 DAA in both groups, but while the CK exhibited a significant decline thereafter, T maintained stable sugar levels, thereby mitigating the “sugar receding” phenomenon. Water-soluble calcium and water magnesium levels were significantly higher in the T at 42 and 63 DAA, with water calcium remaining significantly higher at 70 DAA. Furthermore, sucrose, glucose, fructose, abscisic acid (ABA) contents, and CDPK concentration were significantly higher in the T at 70 and 76 DAA. The CDPK gene family members LcCDPK1, LcCDPK2, LcCDPK3, LcCDPK4, LcCDPK5, LcCDPK9, LcCDPK15, and LcCDPK17 were upregulated in response to T. Among them, LcCDPK1, LcCDPK4, LcCDPK5, LcCDPK9, and LcCDPK17 were identified as key structural genes due to their significant correlation with soluble sugar content and CDPK concentration, as well as their differential expression between T and CK. In conclusion, foliar calcium–magnesium nutrient treatment upregulates the expression of these five CDPK gene family members by increasing the ABA levels in the pulp, leading to more CDPK accumulation. This accumulation inhibits sugar conversion and promotes sucrose and fructose accumulation, thereby mitigating the “sugar receding” phenomenon in ‘Feizixiao’ litchi pulp.

Inflorescence cutting is a critical cultural practice that enhances yield and fruit quality in mango cultivation. This study evaluated four treatments with the “Tainongyihao” mango: no cutting (CK), 1/3, 1/2, and 2/3 cutting of the central inflorescence axis, classified as light (L), medium (M), and heavy (H) cutting, respectively. Inflorescences were categorized by length, and field experiments were conducted during the growth periods of autumn–winter and winter–spring fruit in under-regulated and conventional harvest systems. The measured indicators include yield efficiency per unit trunk circumference, average fruit weight, reduced sugar content, total soluble solids (TSS), total titratable acids (TA), vitamin C content (Vc), and the TSS/TA ratio. Results indicated that light cutting was optimal for yield efficiency of autumn–winter fruit, while medium and heavy cutting were most effective for winter–spring fruit. Comprehensive fruit quality improved most under heavy cutting across all inflorescences. Long inflorescences benefited from heavy or medium cutting, medium inflorescences benefited from heavy cutting, and short inflorescences benefited from medium cutting. Interactive effects were observed between inflorescence-cutting treatments and inflorescence length, with fruit quality consistently improving under inflorescence-cutting treatments. Heavy cutting is recommended for manual operations, and all the results of this paper provide a foundation for developing artificial intelligence (AI)-based inflorescence-cutting technologies that enable precise and efficient mango cultivation practices.