Stages Of Fruit Development Research Articles

Foliar Spraying of Potassium Sulfate during Fruit Development Comprehensively Improves the Quality of Citrus Fruits

Sugar accumulation is influenced by various fertilizer treatments, of which potassium spraying is the most effective. However, the effect of different potassium sources as a foliar application at different fruit development stages on citrus fruits is still unclear. In this study, three different potassium fertilizers and one water (F1: 0.65% KNO3, F2: 0.88% KH2PO4, F3: 0.56% K2SO4, and F4: water) were sprayed on Citrus reticulata cv. Nanfeng at cell division, cell expansion, fruit ripening, and throughout fruit developmental stages, respectively. Results showed that the six-time K2SO4 application had the best function in enhancing fruit physiological attributes such as fruit weight and the total carotenoids; also, this treatment significantly decreased TA (titratable acid), increased fruit TSS (total soluble solids), soluble sugar content, and TSS:TA ratio. Furthermore, K2SO4 spraying obviously increased the expression of CsCWINV-2/6 in the segment membrane, and CsSUT-1/2 and CsVPP-1/2 in fruit juices. Taken together, six-time application of K2SO4 throughout fruit developmental stages produced better fruit quality, at least through enhancing sink strength and promoting sugar transportation in citrus fruits. This study might effectively contribute to maximizing fruit quality and its marketability.

Dynamic Transformations in Fruit Color, Bioactive Compounds, and Textural Characteristics of Purple-Fleshed Dragon Fruit (Hylocereus costaricensis) Across Fruit Developmental Stages Under Humid Tropical Climate

Purple-fleshed dragon fruit is gaining popularity worldwide due to its distinctive characteristics and health benefits. This climbing cactus, introduced to humid tropical climates, presents challenges in assessing fruit quality. The dynamic transformations in fruit color, bioactive compounds, and textural attributes across 11 developmental stages from 10 to 32 days after flowering under humid tropical conditions were studied. Color analysis revealed significant intensification of red-violet hues, with L* values decreasing by 14.74% and a* values increasing from −8.14 to 32.96. The color transformation is initiated in the pulp at 25 days and the peel at 27 days after flowering. Betalain synthesis commenced after 20 days with rapid accumulation between 25 and 32 days, correlating with color development. Antioxidant activity increased from 79.38% at 10 days to 86.76% at 20 days, followed by a steady decline. Phenolic content peaked at 121.40 mg gallic acid equivalent per 100 g at 25 days before declining, while the flavonoid content decreased with the advancement of fruit development. Concurrent reduction in peel thickness and fruit firmness was also observed. These findings show that purple-fleshed dragon fruit can adapt well to humid tropical conditions, with a 32-day developmental cycle, offering vital insights into quality and maturation phases.

The R2R3 MYB700 activates the expression of biosynthetic genes involved in the accumulation of (+)-catechin but not (-)-epicatechin in Chinese plum fruits (Prunus salicina Lindl.)

Chinese plum fruits are rich in phenolic compounds from the flavan-3-ol family, including (+)-catechin and (-)-epicatechin, widely associated with sensory attributes such as bitterness and astringency, beneficial for human health, and involved in enzymatic browning. Leucoanthocyanidin reductase (LAR) and anthocyanidin reductase (ANR) enzymes catalyze (+)-catechin and (-)-epicatechin biosynthesis, respectively. It has been described that genes encoding for LAR and ANR are transcriptionally regulated by transcription factors belonging to MYB, bHLH, and bZIP families. In this study, we examined two Chinese plum cultivars (‘98–99’ and ‘Angeleno’) with different flavan-3-ol profiles to characterize MYB transcription factors involved in malus the accumulation of (+)-catechin and (-)-epicatechin in fruits. We observed that fruits of ‘98–99’ accumulate a higher content of (+)-catechin than (-)-epicatechin, while ‘Angeleno’ displays an opposite profile. We identified PsaMYBPA1, PsaMYB7, and a MYB transcription factor not previously described in the literature, which we named PsaMYB700. The expression of PsaMYB700 was up to 10-fold higher in ‘98–99’ than ‘Angeleno’ at the earliest fruit developmental stage. Promoter activation assays indicated that PsaMYBPA1 activates the flavan-3-ol-related genes LAR, anthocyanidin synthase (ANS), and ANR, while PsaMYB7 and PsaMYB700 activate LAR and ANS. In contrast to PsaMYBPA1 and PsaMYB7, PsaMYB700 displays high activation levels without the presence of a bHLH co-regulator. Further, the expression levels of PsaMY700 positively correlate with the higher (+)-catechin accumulation in fruits of ‘98–99,’ compared with ‘Angeleno.’ Finally, we detected a PsabZIP5 with similar expression levels between cultivars, which activates the promoters of PsaMYBPA1, PsaMYB7, and PsaMYB700. This study elucidates the roles of PsaMYBPA1, PsaMYB7, PsaMYB700 and PsabZIP5 in flavan-3-ol biosynthesis, highlighting a hierarchy of transcriptional regulation of these compounds.

Genome-wide survey and expression analysis of JAZ genes in watermelon (Citrullus lanatus).

BACKGROUND JAZ: (Jasmonate ZIM-domain) genes play important roles in plant growth and JA signaling pathway which is correlated with fruit ripening process. However, there have been few reports on the genome-wide identification of JAZ genes in watermelon and its relationship with fruit ripening. METHODS AND RESULTS: In this study, bioinformatics approaches were employed to identify ClaJAZ genes of watermelon at the genome-wide levels. Further exploration delved into the phylogenetic relationships, chromosomal mappings, promoter dynamics, expression, and architectural features of the JAZ genes. The results showed that a total of 9 ClaJAZ genes unevenly distributed across six chromosomes were identified in the watermelon genome, and they all have conserved Jas and TIFY domains. These JAZ genes were divided into four distinct groups with five genes involved in inter-chromosomal tandem duplication events, and members of the same subgroup exhibited a high degree of similarity in their gene structure and protein motif patterns. Analysis of the promoter regions of the ClaJAZ genes indicated the presence of cis-acting elements associated with hormonal responses, stress, and developmental processes. Gene expression analysis through real-time quantitative PCR (qRT-PCR) showed that there were spatiotemporal differences in the expression of ClaJAZ genes at various stages of fruit development. Among them, ClaJAZ7 has the highest level of transcriptional expression and showed strong promoter activity. CONCLUSIONS: This study conducted a comprehensive analysis of the ClaJAZ genes and provided insights into the role of ClaJAZ in the development and ripening of watermelon fruit.

Genome-wide identification, structural characterization and expression profiling of AP2/ERF gene family in bayberry (Myrica rubra)

BackgroundBayberry is the most economically significant fruit within the Myricaceae family, having high nutritional and medicinal value. The AP2/ERF family is a class of transcription factors found mainly in plants. However, the bayberry AP2/ERF gene family has not previously been studied.ResultsIn this study, 113 members of the bayberry AP2/ERF gene family were identified. According to the phylogenetic tree, the members of this group are divided into three subfamilies, namely AP2, ERF, and DREB. The gene structure and conserved motifs were analyzed. Chromosome localization showed that 95 genes were unevenly distributed on 8 chromosomes and 18 genes were located on the skeleton. Gene collinearity analysis of the bayberry AP2/ERF gene family showed 12 segmental duplication events, involving 21 AP2/ERFs. In addition, we further investigated the evolutionary relationship of the AP2/ERF gene family between bayberry and six other species. It was found that bayberry was most closely related to Populus trichocarpa and Malus pumila, with 153 and 141 homologous gene pairs, respectively. Cis-acting elements indicated that AP2/ERFs were related to phytohormone responses, light response, abiotic and biotic stress tolerance. Transcriptomic data showed that the expression pattern of AP2/ERF gene was different in bayberry space electric field treatment and at different stages of fruit development. The results of GO annotation revealed the biological processes, cellular component and molecular function that the AP2/ERF genes were involved. And KEGG enrichment analysis indicated that these genes were mainly clustered in genetic information processing and metabolism pathways.ConclusionsThe AP2/ERF gene was identified in the genome of bayberry, and its structure, conserved motif, and phylogenetic relationship were analyzed. These findings of this study serve as a reference for the genome-wide identification of the AP2/ERF gene family in other species and groundwork for future research on the function of AP2/ERF genes in bayberry.

Impact of crown architecture on light availability, gas exchange, flowering and fruiting in jamun (Syzygium cumini [L.] Skeels)

Experiments were conducted to assess the impact of crown architecture on light availability beneath the trees, flowering, fruiting, yield and quality of jamun (Syzygium cumini [L.] Skeels). Trees were maintained as control, palmette and open centre crown. Impact was evaluated for three consecutive years, i.e. 2017–2019. Diffuse light beneath the trees ranged from 69.7 ± 2.22 to 45.9 ± 1.45%, whereas direct light varied from 30.4 ± 0.97 to 54.1 ± 1.78%. At flowering and fruit development stage (June), photosynthesis rate (A) in control trees was 12.5 ± 0.43 μmol CO2/m2/s; however, at fruit maturity and dormancy (August), it was only 9.5 ± 0.35 μmol CO2/m2/s. Similarly, in palmette and open centre trees, photosynthesis rate at flowering and fruit development stage was 13.5 ± 0.46 and 15.7 ± 0.54 μmol CO2/m2/s, respectively; whereas at fruit maturity and dormancy, photosynthesis rate dropped to 10.5 ± 0.39 and 11.7 ± 0.43 μmol CO2/m2/s, respectively. Substantial variation in stomatal conductance (gs), vapour pressure deficit (VPD) and transpiration rate (E) was also found. Days to start flowering ranged from 92 ± 0.33 to 98 ± 0.33. Similarly, days to end flowering varied from 99 ± 0.07 to 107 ± 0.36, days to fruit set 132 ± 0.33 to 139 ± 0.33 and days to fruit maturity 176 ± 0.48 to 184 ± 0.63. Significant variation in fruit length, fruit width and fruit weight was also found. Total soluble solids in fruit pulp varied from 9.0 ± 0.15 to 12.2 ± 0.149°Brix and fruit yield 62.3 ± 1.5 to 86.7 ± 1.33 kg per tree. Noteworthy variation in fruit quality traits was also recorded. This study illustrates that crown architecture has considerable impact on gas exchange parameters, flowering, fruiting, yield and quality of jamun.

PpMYB10.1 regulates peach fruit starch degradation by activating PpBAM2.

Starch degradation, a crucial source for soluble sugar, significantly influences fruit flavor development during ripening. Key enzymes in this process include α-amylases (AMYs) and β-amylases (BAMs). In this study, we identified 5 PpAMYs and 9 PpBAMs in peach and categorized them into three and four groups, respectively, based on the gene structures and the phylogenetic analysis. Subsequent expression analysis revealed thatelevated levels of PpAMY1, PpAMY5, and PpBAM2 were detected in the middle and late stages of fruit development, suggesting their positive involvement in starch degradation during peach fruit ripening. Transient overexpression experiments conducted in peach fruits and callus further demonstrated that overexpression of PpBAM2 significantly reduced starch content, indicating its important role in starch degradation during peach fruit ripening. Furthermore, we identified a R2R3-MYB transcription factor, PpMYB10.1, which activated the expression of PpBAM2 through the direct interacting with its promoter. In addition, transient overexpression of PpMYB10.1 could significantly reduce starch content in peach callus. Consequently, our findings highlight the positive role of PpBAM2 in peach starch degradation, with PpMYB10.1 serving as an activator during this process.

Unveiling the unique aroma of Morus macroura through integrated volatile metabolome and transcriptome analysis

Mulberries, especially the ‘BaiChang’ (Morus macroura) variety known for its creamy flavour, are highly valued by consumers and the market for their high nutritional value and unique aroma. However, the formation mechanism of its unique aroma compounds remains unclear. This study employed a combination of volatile metabolomics and transcriptomics analyses to examine volatile organic compounds (VOCs) and transcriptional changes at different developmental stages of ‘BaiChang’ mulberries. A total of 663 VOCs were identified, with 342 of annotated with different odours. Differential analysis revealed that the three comparison groups shared 56 differential metabolites, and each group contained 35, 56 and 17 unique differential metabolites. Among them, the 69 differential metabolites related to sweet, waxy, coconut and oil were screened. The content of 2(3H)-furanone, 5-hexyldihydro drastically increased during the S3 stage, and its aroma characteristics are consistent with the sensory phenotype. Among these, γ-decalactone is inferred to be the key VOC in ‘BaiChang’ mulberries. By integrating transcriptome data, 13 key structural genes were identified as potentially related to the synthesis of γ-decalactone, including CYPs, FAE, FAH, ACXs and EHLs. Most of these genes are highly expressed during the later stages of fruit development. Additionally, a preliminary dynamic relationship between lactones and esters was inferred during the development of ‘BaiChang’ mulberries. Furthermore, by combining weighted gene coexpression and K-means analyses, it was found that the biosynthesis of lactones and esters may be regulated by ethylene induction and transcription factors such as MYB, NAC, MDDS and bZIP. This study lays the foundation for understanding of the regulatory mechanisms underlying the formation of the unique aroma of ‘BaiChang’ mulberries and provides new insights for the further exploration of superior mulberry varieties.

Accumulation of mineral nutrients in fruit peel and pulp of loquat (Eriobotrya japonica) cultivars during fruit developmental stages

The experiment was conducted during 2023 at Punjab Agricultural University, Ludhiana, Punjab to assess the changes of mineral nutrients in peel and pulp of loquat cultivars at four developmental stages to explore its nutraceutical potential. During the development of loquat fruits, K and Zn content both in peel and pulp showed increasing trend from 60–92 DAFS. Similarly, Ca content in loquat peel, Fe and Mn content in pulp also exhibited increasing trend. While P, Cu and Mg content showed a decreasing trend in both peel and pulp. Likewise, Ca content in loquat pulp, Fe and Mn content in peel decreased from 60–92 DAFS. This study provides an insight regarding the accumulation of mineral nutrients in fruit peel and pulp in loquat cultivars during four fruit developmental stages which could be helpful for exploring its nutraceutical potential.

Absorption and translocation to fruit for cesium applied on apple tree leaf surface.

We investigated the behavior of stable Cs+ ions contained in droplets applied directly on the leaf surfaces of plumleaf crab apple trees (2-3years old Malus domestica 'Alps Otome') at three different fruit growing stages: before bearing fruit, early fruit development and late fruit development stages. Most of the Cs was rapidly transferred from the leaf surfaces into the applied leaves after application, and then gradually transferred to the fruit through the branches. The mean proportion of Cs transferred to fruit by harvest time ranged from 11 to 30% not directly depending on the fruit growing stages. Cs absorption from leaf surfaces was faster at early and late fruit development stages than before bearing fruit stage, and Cs transfer from leaf surfaces to the fruit was faster as the fruit growing stage progressed. To describe the transfer of Cs, we constructed a compartment model using the datasets of obtained for each fruit growing stage. However, it did not well reproduce the measured values, showing that further studies are necessary.

Transcriptome and genome-wide analysis of the mango glycosyltransferase family involved in mangiferin biosynthesis

Mangiferin, a C-glucosyl xanthone, is a biologically active glycoside naturally synthesized in mango. Glycosyltransferase can catalyze the biosynthesis of mangiferin. In this study, we identified 221 members of the UGT glycosyltransferase family in mango. The 221 MiUGT genes were grouped into 13 subfamilies through phylogenetic tree analysis with Arabidopsis, Chinese bayberry, and mango. All UGT family members in mango were unevenly distributed on 17 chromosomes and found that tandem duplication dominated the expansion of UGT family members in mango. Purification selection primarily influenced the evolution of the mango UGT family members. In addition, cis-element analysis of the mango UGT gene family revealed the presence of MYB binding sites, which are involved in flavonoid biosynthesis; which further supports the role of UGT family members in the synthesis of flavonoids. To verify these results, we analyzed the expression of UGT family members in mango leaves, stems, and different developmental stages of fruit peel. The RNA-seq and qRT-PCR results showed significant differences in the expression patterns of MiUGT genes in various tissues and developmental stages of mango. We identified MiUGT gene-specific expression at different stages of fruit development. These results lay a theoretical foundation for research on the relationship between members of the mango UGT family and the synthesis of flavonoids, mangiferin.

Investigation on torsional forces and angles at the nut and pedicel junction (NPJ) revealed varying cashew apple (hypocarp) and nut separation efficiency at different developmental stages in cashew

Cashew is a highly valued tree nut crop that is widely grown for nourishment and industrial applications. The study of fruit and nut separation forces is a necessary for efficiently detaching the nuts from the swollen pedicel or hypocarp referred to as cashew apple (pseudo fruit). In this study, the torsional/twisting forces (TF) required for separating the nuts from the cashew apples (CA) were analyzed at the nut pedicel junction (NPJ) in different cultivars at different fruit developmental stages [BBCH (BiologischeBundesanstalt, Bundessortenamt und ChemischeIndustrie) stage code: 711, 713, 715, 717, 719, 811, 813, 815, 817, 819] and days after fall to devise strategies for efficient separation of nuts and CAs. The TF and torsional/twisting angle (TA) were measured using a novel strain gauge-based reaction type torque transducer and a customized fixture. The CA firmness (CAF), and CA cavity depth, length, and width at the NPJ were also measured. Significant variations were observed in the TF and the TA at different fruit developmental stages and days after fall (DAF) in the studied cultivars. The TFs increased from 711 to 813 stages and subsequently declined from 813 to 819 stages and with increasing DAF. Further, the TA increased significantly with the development of fruits from 711 to 819 stages and days after fall. The analysis of the relationship between TF and the physical properties of CA showed that CA firmness and CA cavity depth at the NPJ had significant positive correlations. Further, the analysis of the relationship between the TA and the CA properties showed that CA firmness has significantly negative correlations. The findings of this study are valuable for the development of new cashew cultivars with low TF and TA suitable for mechanical separation and the designing of machinery with versatile end-effectors and twisting mechanisms for efficient separation of nuts from CAs.

Biocontrol Agents Inhibit Banana Fusarium Wilt and Alter the Rooted Soil Bacterial Community in the Field.

Banana is an important fruit and food crop in tropical and subtropical regions worldwide. Banana production is seriously threatened by Fusarium wilt of banana (FWB), a disease caused by Fusarium oxysporum f. sp. cubense, and biological control is an important means of curbing this soil-borne disease. To reveal the effects of biocontrol agents on inhibiting FWB and altering the soil bacterial community under natural ecosystems, we conducted experiments at a banana plantation. The control efficiency of a compound microbial agent (CM), Paenibacillus polymyxa (PP), Trichoderma harzianum (TH), and carbendazim (CA) on this disease were compared in the field. Meanwhile, the alterations in structure and function of the rooted soil bacterial community in different treatments during the vigorous growth and fruit development stages of banana were analyzed by microbiomics method. The results confirmed that the different biocontrol agents could effectively control FWB. In particular, CM significantly reduced the incidence of the disease and showed a field control efficiency of 60.53%. In terms of bacterial community, there were no significant differences in the richness and diversity of banana rooted soil bacteria among the different treatments at either growth stage, but their relative abundances differed substantially. CM treatment significantly increased the ratios of Bacillus, Bryobacter, Pseudomonas, Jatrophihabitans, Hathewaya, and Chujaibacter in the vigorous growth stage and Jatrophihabitans, Occallatibacter, Cupriavidus, and 1921-3 in the fruit development stage. Furthermore, bacterial community function in the banana rooted soil was affected differently by the various biocontrol agents. CM application increased the relative abundance of multiple soil bacterial functions, including carbohydrate metabolism, xenobiotic biodegradation and metabolism, terpenoid and polyketide metabolism, lipid metabolism, and metabolism of other amino acids. In summary, our results suggest that the tested biocontrol agents can effectively inhibit the occurrence of banana Fusarium wilt and alter the soil bacterial community in the field. They mainly modified the relative abundance of bacterial taxa and the metabolic functions rather than the richness and diversity. These findings provide a scientific basis for the use of biocontrol agents to control banana Fusarium wilt under field conditions, which serves as a reference for the study of the soil microbiological mechanisms of other biocontrol agents.

NAC family gene CmNAC34 positively regulates fruit ripening through interacting with CmNAC-NOR in Cucumis melo

Melon (Cucumis melo) is an important economic horticulture crop cultivated worldwide. NAC (NAM, ATAC, and CUC) transcription factors play crucial roles in the transcriptional regulation of various developmental stages in plant growth and fruit development, but little about their gene function is known in melon. Here, we identified 78 CmNAC family genes containing integrated and conserved NAM (no apical meristem) domain in the melon genome by performing genome-wide identification and bioinformatics analysis. Transcriptome data analysis and qRT-PCR results showed that most CmNACs are specifically enriched in the vegetative organ or the reproductive organ in melon. Through genetic transformation, we found that overexpression of CmNAC34 in melons led to the early ripening fruits, suggesting its positive role in promoting fruit maturation. Through performing yeast two-hybrid and bimolecular fluorescence complementation assays, we verified the direct protein interaction between CmNAC34 and CmNAC-NOR. The expression pattern of CmNAC34 and CmNAC-NOR were similar in melon tissues, and subcellular localization also revealed their nuclear protein characteristic. We transformed CmNAC-NOR in melon and found that its overexpression resulted in the early ripening fruits. Then, the yeast one-hybrid and dual luciferase reporter gene assay explored that CmNAC34 protein can bind to the promoters of two Glyoxalase (GLY) genes, which were involved in the abscisic acid signal pathway and associated with the fruit regulation. These findings revealed the molecular characteristics, expression profile, and functional pattern of the NAC family transcription factors genes and provided an insight into the molecular mechanism of CmNAC34 in regulating climacteric fruit ripening.

Dynamic Changes in Pectin Composition, Flesh Firmness and Oxidoreductase Enzymes Across Different Stages of Fruit Development in Loquat Cultivars

Dynamic Changes in Pectin Composition, Flesh Firmness and Oxidoreductase Enzymes Across Different Stages of Fruit Development in Loquat Cultivars

The H2S-responsive transcription factor ERF.D3 regulates tomato abscisic acid metabolism, leaf senescence, and fruit ripening.

Hydrogen sulfide (H2S) is a signaling molecule that regulates plant senescence. In this study, we found that H2S delays dark-induced senescence in tomato (Solanum lycopersicum) leaves. Transcriptome and RT-qPCR analyses revealed an Ethylene Response Factor ERF.D3 is quickly induced by H2S. H2S also persulfidated ERF.D3 at amino acid residues C115 and C118. CRISPR/Cas9-mediated gene editing and gene overexpression analyses showed that ERF.D3 negatively regulates leaf senescence and fruit ripening. Abscisic acid (ABA) levels were reduced by ERF.D3 overexpression, suggesting ERF.D3 might regulate ABA metabolism. Additionally, the abscisic acid 8'-hydroxylase-encoding gene CYP707A2, which is required for ABA degradation, was identified as an ERF.D3 target gene through transcriptome data, RT-qPCR, dual-luciferase reporter assays and electrophoretic mobility shift assays. ERF.D3 persulfidation enhanced its transcriptional activity towards CYP707A2. Moreover, the E3 ligase RNF217 ubiquitinated ERF.D3, which may accelerate fruit ripening during the late stage of fruit development. Overall, our study provides valuable insights into the roles of a H2S-responsive ERF.D3 and its persulfidation state in delaying leaf senescence and fruit ripening and provides a link between H2S and ABA degradation.

Transcriptomic Analysis During Olive Fruit Development and Expression Profiling of Fatty Acid Desaturase Genes.

The olive fruit is a drupe whose development and ripening takes several months from flowering to full maturation. During this period, several biochemical and physiological changes occur that affect the skin color, texture, composition, and size of the mesocarp. The final result is a fruit rich in fatty acids, phenolic compounds, tocopherols, pigments, sterols, terpenoids, and other compounds of nutritional interest. In this work, a transcriptomic analysis was performed using flowers (T0) and mesocarp tissue at seven different stages during olive fruit development and ripening (T1-T7) of the 'Picual' cultivar. A total of 1755 genes overexpressed at any time with respect to the flowering stage were further analyzed. These genes were grouped into eight clusters based on their expression profile. The gene enrichment analysis revealed the most relevant biological process of every cluster. Highlighting the important role of hormones at very early stages of fruit development (T1, Cluster 1), whereas genes involved in fatty acid biosynthesis were relevant throughout the fruit developmental process. Hence, genes coding for different fatty acid desaturase (SAD, FAD2, FAD3, FAD4, FAD5, FAD6, and FAD7) enzymes received special attention. In particular, 26 genes coding for different fatty acid desaturase enzymes were identified in the 'Picual' genome, contributing to the improvement of the genome annotation. The expression pattern of these genes during fruit development corroborated their role in determining fatty acid composition.

Determination of nutritional sufficiency ranges for pomelo (Citrus grandis Osbeck) grown on alluvial soils using DRIS.

Pomelo is an important tropical fruit with a high nutrient content and economic value in the Vietnamese Mekong Delta (VMD). The Diagnosis and Recommendation Integrated System (DRIS) helps determine the leaf nutrient status of various plants worldwide. However, the DRIS-based nutritional balance in pomelo leaves remains to be established. Therefore, in this study, we aimed to (i) construct the DRIS norms and indices for nutrients, including macronutrients (N, P, K, Ca, and Mg) and trace elements (Cu, Fe, Zn, and Mn) in pomelo leaves, and (ii) establish nutrient sufficiency value ranges for sustainable pomelo cultivation in the VMD. We collected 270 leaf samples at three stages of pomelo growth, i.e., flowering, fruit development, and postharvest, and calculated DRIS indices for various nutrients. The DRIS indices established for various nutrients in pomelo leaves were accurate and reliable, as indicated by the high coefficient of determination (R2 = 0.43-0.93, p < 0.05) between nutrient concentrations and their DRIS indices. We observed that pomelo leaves were deficient in N (IN = -6.82), P (IP = -24.0), and Fe (IFe = -0.40) at the flowering stage and most deficient in P (IP = -15.6), K (IK = -11.7), Fe (IFe = -0.50), and Mn (IMn = -2.31) at the fruit development stage. However, only N (IN = -2.64) and P (IP = -13.4) shortages were observed at the postharvest stage. Thus, in this study, we evaluated nutrient value ranges (deficient, balanced, and excess) in pomelo leaves at their different growth stages and established DRIS indices for various nutrients. The results contribute to our understanding of the nutritional status of pomelo leaves, which can help growers improve plant health for sustainable pomelo production.

Reduced Fertilization and Magnesium Supplementation: Modulating Fruit Quality in Honey Pomelo (Citrus maxima (Burm.) Merr.)

The excessive use of chemical fertilizers in the Guanxi honey pomelo production area has led to severe soil acidification and magnesium (Mg) deficiency, adversely affecting pomelo fruit quality. To address this issue, an integrated nutrient optimization model crucial for ensuring the sustainable and environmentally friendly development of the Guanxi honey pomelo industry has been explored. In a three-year experiment, two fertilizer treatments were implemented: a farmer fertilizer practice (FP) and an NPK reduction plus foliar Mg fertilizer (OPT + fMg). We investigated the impact of this integrated optimized fertilization measure on pomelo fruit quality from three aspects: flavor (sugars and organic acids), nutrition (vitamin C and mineral elements), and antioxidant properties (phenolics, flavonoids, and phytic acid). The results revealed that the OPT + fMg treatment improved fruit flavor by reducing acidity (titratable acid, citric acid, and quinine), while having a minimal impact on sugar components (sucrose, fructose, and glucose). Additionally, the OPT + fMg treatment increased the total phenolics, total flavonoids, and phytic acid in the fruit peel, enhancing its potential antioxidant quality. However, the OPT + fMg treatment reduced the mineral nutrient quality (excluding calcium) in the fruit. As for the fruit developmental period, the OPT + fMg treatment significantly increased the total flavonoid concentration in the peel from the mid-expansion fruit stage, followed by notable increases in phytic acid in the peel during the mid-to-late expansion fruit stage. The total phenolic concentration in the peel significantly rose only during the late fruit development stage. The most pronounced effect was observed on phytic acid in both peel and pulp. The influence of the OPT + fMg treatment on the mineral nutrients (excluding calcium) primarily occurred during the mid-to-late expansion fruit stage. Overall, the OPT + fMg treatment significantly improved the comprehensive nutritional quality of pomelo fruit, providing valuable insights for scientifically reducing fertilizer application while enhancing fruit quality.

An in-depth study of anthocyanin synthesis in the exocarp of virescens and nigrescens oil palm: metabolomic and transcriptomic analysis.

Oil palm (Elaeis guineensis Jacq.) is a very important tropical woody oil plant with high commercial and ornamental value. The exocarp of the oil palm fruit is rich in anthocyanosides and proanthocyanidins, which not only give it a bright colour, but also mark the maturity of the fruit. The study of the dynamic change pattern of anthocyanoside content and important anthocyanoside metabolism-related regulatory genes during oil palm ripening is conducive to the improvement of the ornamental value of oil palm and the determination of the optimal harvesting period of the fruits. We analyzed the virescens oil palm (AS) and nigrescens oil palm (AT) at 95 days (AS1, AT1), 125 days (AS2, AT2) and 185 days (AS3, AT3) after pollination were used as experimental materials for determining the changes in the total amount of anthocyanins as well as their metabolomics and transcriptomics studies by using the LC-MS/MS technique and RNA-Seq technique. The results showed that the total anthocyanin content decreased significantly from AS1 (119µg/g) to AS3 (23µg/g), and from AT1 (1302µg/g) to AT3 (170µg/g), indicating a clear decreasing trend during fruit development. Among them, the higher flavonoids in AS and AT included anthocyanins such as peonidin-3-O-rutinoside (H35), pelargonidin-3-O-rutinoside (H21), and cyanidin-3-O-glucoside (H7), as well as condensed tannins such as procyanidin B2 (H47), procyanidin C1 (H49), and procyanidin B3 (H48). Notably, nine genes involved in the anthocyanin biosynthetic pathway exhibited up-regulated expression during the pre-development stage of oil palm fruits, particularly during the AS1 and AT1 periods. These genes include: Chalcone synthase (CHS; LOC105036364); Flavanone 3-hydroxylase (F3H; LOC105054663); Dihydroflavonol 4-reductase (DFR; LOC105040724, LOC105048473); Anthocyanidin synthase (ANS; LOC105035842), UDP-glucose: flavonoid 3-O-glucosyltransferase (UFGT; LOC105039612); Flavonoid 3',5'-hydroxylase (F3'5'H; LOC105036086, LOC105044124, LOC105045493). In contrast, five genes demonstrated up-regulated expression as the fruits developed, specifically during the AS3 and AT3 periods. These genes include: Chalcone synthase (CHS; LOC105036921, LOC105035716); Chalcone isomerase (CHI; LOC105045978); UDP-glucose: flavonoid 3-O-glucosyltransferase (UFGT; LOC105046326); Flavonoid 3'-hydroxylase (F3'H; LOC105036086). Most of differentially expressed genes exhibited up-regulation during the early stages of fruit development, which may contribute to the elevated anthocyanin content observed in oil palm fruits of both types during the pre-developmental period. Furthermore, the expression levels of most genes were found to be higher in the AT fruit type compared to the AS fruit type, suggesting that the differential expression of these genes may be a key factor underlying the differences in anthocyanoside production in the exocarp of oil palm fruits from these two fruit types. The findings of this study provide a theoretical foundation for the identification and characterization of genes involved in anthocyanin synthesis in oil palm fruits, as well as the development of novel variations using molecular biology approaches.