Molecular Markers for Marker-Assisted Breeding for Biotic and Abiotic Stress in Melon (Cucumis melo L.): A Review.

Melon (Cucumis melo L.) is a globally grown crop renowned for its juice and flavor. Despite growth in production, the melon industry faces several challenges owing to a wide range of biotic and abiotic stresses throughout the growth and development of melon. The aim of the review article is to consolidate current knowledge on the genetic mechanism of both biotic and abiotic stress in melon, facilitating the development of robust, disease-resistant melon varieties. A comprehensive literature review was performed, focusing on recent genetic and molecular advancements related to biotic and abiotic stress responses in melons. The review emphasizes the identification and analysis of quantitative trait loci (QTLs), functional genes, and molecular markers in two sections. The initial section provides a comprehensive summary of the QTLs and major and minor functional genes, and the establishment of molecular markers associated with biotic (viral, bacterial, and fungal pathogens, and nematodes) and abiotic stress (cold/chilling, drought, salt, and toxic compounds). The latter section briefly outlines the molecular markers employed to facilitate marker-assisted backcrossing (MABC) and identify cultivars resistant to biotic and abiotic stressors, emphasizing their relevance in strategic marker-assisted melon breeding. These insights could guide the incorporation of specific traits, culminating in developing novel varieties, equipped to withstand diseases and environmental stresses by targeted breeding, that meet both consumer preferences and the needs of melon breeders.

Nontarget site-based resistance to nicosulfuron and identification of candidate genes in Cucumis melo L. var. agrestis Naud. via RNA-Seq transcriptome analysis.

Herbicide resistance is a worldwide concern for weed control. Cucumis melo L. var. agrestis Naud. (C. melo) is an annual trailing vine weed that is commonly controlled by nicosulfuron, acetolactate synthase (ALS)-inhibiting herbicides. However, long-term use of this herbicide has led to the emergence of resistance and several nicosulfuron resistant populations of C. melo have been found. Here we identified a resistant (R) C. melo population exhibiting 7.31-fold resistance to nicosulfuron compared with a reference sensitive (S) population. ALS gene sequencing of the target site revealed no amino acid substitution in R plants, and no difference in enzyme activity, as shown by ALS activity assays in vitro. ALS gene expression was not significantly different before and after the application of nicosulfuron. Pretreatment with the cytochrome P450 monooxygenase (P450) inhibitor malathion reduced nicosulfuron resistance in the R population. RNA-Seq transcriptome analysis was used to identify candidate genes that may confer metabolic resistance to nicosulfuron. We selected genes with annotations related to detoxification functions. A total of 20 candidate genes (7 P450 genes, 1 glutathione S-transferase (GST) gene, 2 ATP-binding cassette (ABC) transporters, and 10 glycosyltransferase (GT)) were identified; 12 of them (7 P450s, 1 GST, 2 ABC transporters, and 2 GTs) were demonstrated significantly differential expression between R and S by quantitative real-time RT-PCR (qRT-PCR). Our findings revealed that the resistance mechanism in C. melo was nontarget-site based. Our results also provide a valuable resource for studying the molecular mechanisms of weed resistance.

Evidence Supporting a Role of Alternative Splicing Participates in Melon (Cucumis melo L.) Fruit Ripening.

One key post-transcriptional modification mechanism that dynamically controls a number of physiological processes in plants is alternative splicing (AS). However, the functional impacts of AS on fruit ripening remain unclear. In this research, we used RNA-seq data from climacteric (VED, Harukei 3) and non-climacteric (PI, PS) melon cultivars to explore alternative splicing (AS) in immature and mature fruit. The results revealed dramatic changes in differential AS genes (DAG) between the young and mature fruit stages, particularly in genes involved in fruit development/ripening, carotenoid and capsaicinoid biosynthesis, and starch and sucrose metabolism. Serine/arginine-rich (SR) family proteins are known as important splicing factors in AS events. From the melon genome, a total of 17 SR members were discovered in this study. These genes could be classified into eight distinct subfamilies based on gene structure and conserved motifs. Promoter analysis detected various cis-acting regulatory elements involved in hormone pathways and fruit development. Interestingly, these SR genes exhibited specific expression patterns in reproductive organs such as flowers and ovaries. Additionally, concurrent with the increase in AS levels in ripening fruit, the transcripts of these SR genes were activated during fruit maturation in both climacteric and non-climacteric melon varieties. We also found that most SR genes were under selection during domestication. These results represent a novel finding of increased AS levels and SR gene expression during fruit ripening, indicating that alternative splicing may play a role in fruit maturation.

Genome-wide characterization and functional analysis of the melon TGA gene family in disease resistance through ectopic overexpression in Arabidopsis thaliana.

TGA-binding (TGA) transcription factors, characterized by the basic region/leucine zipper motif (bZIP), have been recognized as pivotal regulators in plant growth, development, and stress responses through their binding to the as-1 element. In this study, the TGA gene families in melon, watermelon, cucumber, pumpkin, and zucchini were comprehensively characterized, encompassing analyses of gene/protein structures, phylogenetic relationships, gene duplication events, and cis-acting elements in gene promoters. Upon transient expression in Nicotiana benthamiana, the melon CmTGAs, with typical bZIP and DOG1 domains, were observed to localize within the nucleus. Biochemical investigation revealed specific interactions between CmTGA2/3/5/8/9 and CmNPR3 or CmNPR4. The CmTGA genes exhibited differential expression patterns in melon plants in response to different hormones like salicylic acid, methyl jasmonate, and ethylene, as well as a fungal pathogen, Stagonosporopsis cucurbitacearum that causes gummy stem blight in melon. The overexpression of CmTGA3, CmTGA8, and CmTGA9 in Arabidopsis plants resulted in the upregulation of AtPR1 and AtPR5 expression, thereby imparting enhanced resistance to Pseudomonas syringae pv. Tomato DC3000. In contrast, the overexpression of CmTGA7 or CmTGA9 resulted in a compromised resistance to Botrytis cinerea, coinciding with a concomitant reduction in the expression levels of AtPDF1.2 and AtMYC2 following infection with B. cinerea. These findings shed light on the important roles of specific CmTGA genes in plant immunity, suggesting that genetic manipulation of these genes could be a promising avenue for enhancing plant immune responses.

Deciphering the Enhancing Impact of Exogenous Brassinolide on Physiological Indices of Melon Plants under Downy Mildew-Induced Stress.

Melon (Cucumis melo L.) is a valuable horticultural crop of the Cucurbitaceae family. Downy mildew (DM), caused by Pseudoperonospora cubensis, is a significant inhibitor of the production and quality of melon. Brassinolide (BR) is a new type of phytohormone widely used in cultivation for its broad spectrum of resistance- and defense-mechanism-improving activity. In this study, we applied various exogenous treatments (0.5, 1.0, and 2.0 mg·L-1) of BR at four distinct time periods (6 h, 12 h, 24 h, and 48 h) and explored the impact of BR on physiological indices and the genetic regulation of melon seedling leaves infected by downy-mildew-induced stress. It was mainly observed that a 2.0 mg·L-1 BR concentration effectively promoted the enhanced photosynthetic activity of seedling leaves, and quantitative real-time polymerase chain reaction (qRT-PCR) analysis similarly exhibited an upregulated expression of the predicted regulatory genes of photosystem II (PSII) CmHCF136 (MELO3C023596.2) and CmPsbY (MELO3C010708.2), thus indicating the stability of the PSII reaction center. Furthermore, 2.0 mg·L-1 BR resulted in more photosynthetic pigments (nearly three times more than the chlorophyll contents (264.52%)) as compared to the control and other treatment groups and similarly upregulated the expression trend of the predicted key enzyme genes CmLHCP (MELO3C004214.2) and CmCHLP (MELO3C017176.2) involved in chlorophyll biosynthesis. Meanwhile, the maximum contents of soluble sugars and starch (186.95% and 164.28%) were also maintained, which were similarly triggered by the upregulated expression of the predicted genes CmGlgC (MELO3C006552.2), CmSPS (MELO3C020357.2), and CmPEPC (MELO3C018724.2), thereby maintaining osmotic adjustment and efficiency in eliminating reactive oxygen species. Overall, the exogenous 2.0 mg·L-1 BR exhibited maintained antioxidant activities, plastid membranal stability, and malondialdehyde (MDA) content. The chlorophyll fluorescence parameter values of F0 (42.23%) and Fv/Fm (36.67%) were also noticed to be higher; however, nearly three times higher levels of NPQ (375.86%) and Y (NPQ) (287.10%) were observed at 48 h of treatment as compared to all other group treatments. Increased Rubisco activity was also observed (62.89%), which suggested a significant role for elevated carbon fixation and assimilation and the upregulated expression of regulatory genes linked with Rubisco activity and the PSII reaction process. In short, we deduced that the 2.0 mg·L-1 BR application has an enhancing effect on the genetic modulation of physiological indices of melon plants against downy mildew disease stress.

Deciphering the Genomic Characterization of the GGP Gene Family and Expression Verification of CmGGP1 Modulating Ascorbic Acid Biosynthesis in Melon Plants.

Ascorbic acid (AsA), also known as vitamin C, is a well-known antioxidant found in living entities that plays an essential role in growth and development, as well as in defensive mechanisms. GDP-L-galactose phosphorylase (GGP) is a candidate gene regulating AsA biosynthesis at the translational and transcriptional levels in plants. In the current study, we conducted genome-wide bioinformatic analysis and pinpointed a single AsA synthesis rate-limiting enzyme gene in melon (CmGGP1). The protein prediction analysis depicted that the CmGGP1 protein does not have a signaling peptide or transmembrane structure and mainly functions in the chloroplast or nucleus. The constructed phylogenetic tree analysis in multispecies showed that the CmGGP1 protein has a highly conserved motif in cucurbit crops. The structural variation analysis of the CmGGP1 gene in different domesticated melon germplasms showed a single non-synonymous type-base mutation and indicated that this gene was selected by domestication during evolution. Wild-type (WT) and landrace (LDR) germplasms of melon depicted close relationships to each other, and improved-type (IMP) varieties showed modern domestication selection. The endogenous quantification of AsA content in both the young and old leaves of nine melon varieties exhibited the major differentiations for AsA synthesis and metabolism. The real-time quantitative polymerase chain reaction (qRT-PCR) analysis of gene co-expression showed that AsA biosynthesis in leaves was greater than AsA metabolic consumption, and four putative interactive genes (MELO3C025552.2, MELO3C007440.2, MELO3C023324.2, and MELO3C018576.2) associated with the CmGGP1 gene were revealed. Meanwhile, the CmGGP1 gene expression pattern was noticed to be up-regulated to varying degrees in different acclimated melons. We believe that the obtained results would provide useful insights for an in-depth genetic understanding of the AsA biosynthesis mechanism, aimed at the development of improving crop plants for melon.

Sustainable cultivation of melon landraces: Effects of grafting on the accumulation of flavor-related compounds.

Melon landraces are highly appreciated by consumers who pay price premiums to compensate for lower yields, enabling on-farm conservation. However, they are highly susceptible to soilborne diseases. This study analyses the impact of Cucurbita and Cucumis rootstocks on the accumulation of flavor-related metabolites in Spanish landraces of the Ibericus melon group, as a strategy to promote their sustainable cultivation. Scion genotype was the main factor conditioning the accumulation of sugars and acids both under standard and saline organic farming conditions. The effects of grafting on organic acid accumulation were negligible, while the effects on sugar content were significant. The latter effects were dependent on specific scion-rootstock combinations, though wild Cucumis (e.g. Fian) rootstocks represent an alternative that should be further studied. The effect on the accumulation of volatiles was limited, and again depended on specific scion-rootstock combinations. The rootstock effect even differed between populations of the same landrace.

The effects of different rootstocks on aroma components, activities and genes expression of aroma-related enzymes in oriental melon fruit.

Grafting is widely applied in the cultivation of melon. In this study, 'Qinmi No.1' (Cucumis melo L.(QG)) and 'Ribenxuesong' (Cucurbita maxima Duch. (RG)) were used as rootstocks for 'Qingxin Yangjiaocui' (Cucumis melo L.). The results showed that grafting with muskmelon rootstocks had no significant effect on fruit aroma, but grafting with pumpkin rootstocks significantly reduced the odor intensity and odor preference scores of melon fruits. Compared with the fruits from self-grafted plants (SG), four new aromatic volatiles with a sweet smell were detected, the alcohol dehydrogenase (ADH) activity was significantly decreased at 30 DAP, but unaffected at 42 DAP in QG fruits. There was no difference for alcohol acetyltransferase (AAT) activity between QG and SG fruits. The expression level of CmADH2 was significantly higher at 30 DAP and 42 DAP, but CmAAT2 was significantly lower at 42 DAP in QG fruits compared with SG fruits. In RG fruits, the main aroma compounds including butanoic acid ethyl ester, 2-methyl-2-butene-1-al, and 2-methylheptan-1-al were absent, while the volatile compounds with unpleasant odor characteristics including trans, cis-2,6-nonadien-1-ol, (E,E)-2,4-heptadienal, octanoic acid, and styrene were detected. Compared with SG fruits, 1-nonanol and 1-heptanol with green odor characteristics were significantly increased, but eucalyptol and farnesene with fruity aroma characteristics were significantly decreased in RG fruits. The ADH activity of RG fruits was significantly lower than that of SG fruits at 30 DAP and the AAT activity was significantly lower than that of SG fruits at 42 DAP. In addition, the expression levels of CmADH and CmAAT homologs in RG fruits were significantly lower than those in SG or QG fruits. These results show that grafting with pumpkin rootstocks affected the main aroma components, reduced ADH and AAT activities, and down-regulated the expression levels of CmADHs and CmAATs in the melon fruits. This study reveals the mechanism of different rootstocks on melon fruit aroma quality, and lays a theoretical foundation for the selection of rootstocks in melon production. Future studies using overexpression or CRISPR/CAS system to obtain stable transgenic lines of genes encoding key aromatic volatiles, would be promising to effectively improve the flavor quality of melon.

First Report of Leaf Spot on Cucumis melo L. Caused by Arcopilus aureus in China.

Cucumis melo L. is an important fruit with widespread consumption and commercial value. However, an undescribed disease affecting Hami melon (Cucumis melo L. var. Luhoutian) plants has consistently emerged in the Qihe region of Dezhou, Shandong Province of China since 2021. The disease can occur in both seedling and mature stages of Hami melon plants, and in severely diseased areas, the incidence rate was seen as 40 to 80%. During the seedling stage, the initial symptom is the appearance of water-soaked spots on the leaves. As the disease progresses, the leaves develop necrotic spots, and severely affected plants may exhibit stem rot and decay. In the mature stage, the disease primarily affects the leaves, causing necrotic spots and chlorosis. Under conditions of high humidity, black mold can be observed in the affected areas. Small pieces of symptomatic leaves from six different infected plants were collected and surface-sterilized with 5% NaClO for 3 min and 75% alcohol for 30 s for pathogen isolation (Wang et al., 2020). After rinsing with sterile water and blotted on sterile filter paper, the tissues were established on potato dextrose agar (PDA) media and incubated at 28℃ for 3-4 days. Pure isolates showed up at PDA were obtained through single-spore isolation. Colonies of all 16 isolates obtained by single-spore isolation had similar morphological characteristics on the PDA medium, the mycelium of the isolate appears dense and yellowish-brown on the PDA medium, and also secretes a brownish-red pigment on PDA. Under the opticalmicroscope, the perithecia from PDA media are subglobose spherical in shape, 80-100 µm in diameter, brownish by reflected light, wholly and densely hairy. Terminal hairs are very dense, greyish by reflected light, olive brown to reddish brown by transmitted light, thick-walled, arcuate, circinate, or spirally coiled at the apex. The ascospores within the perithecia are elliptical or droplet-shaped, initially colorless hyaline but later becoming subhyaline slightly gray, with dimensions of 7-9 µm × 4-5 µm. The morphological characteristics of the isolates were consistent with the description of Arcopilus aureus (Wang et.al. 2016). The internal transcribed spacer (ITS) region and ß-tubulin genes of three randomly selected isolates were PCR amplified and sequenced using primers ITS4/ITS5 and Bt2a/Bt2b. The sequences of ITS and ß-tubulin genes were submitted to NCBI with GenBank Accession No. OR539527 and OR640972, respectively. Based on morphological features and phylogenetic analysis, we concluded that the isolates belonged to A. aureus. Pathogenicity tests were conducted by placing agar plugs-containing fungal mycelia and agar blocks (control) on leaves of Hami melon seedlings (n=12) grown at 28°C with 60% humidity in a greenhouse, the assay was repeated three times. Symptoms appeared on the pathogen-inoculated leaves seven days after inoculation, whereas the control treatment remained symptomless. The pathogens were reisolated from diseased leaves and identified as A. aureus based on morphological, and molecular phylogenetic analysis, while Koch'sostulate was used to confirm its life mode. To the best of our knowledge, this is the first report of leaf spot caused by A. aureus on Cucumis melo L. in China.

Developmental stages and episode-specific regulatory genes in andromonoecious melon flower development.

BACKGROUND AND AIMS: Given the lack of specific studies on floral development in melon (Cucumis melo L.), we carried out an extensive study involving morphological and transcriptomic analyses to characterize floral development in this species. METHODS: Using an andromonoecious line, we analysed the development of floral buds in male and hermaphrodite flowers with both light microscopy and scanning electron microscopy. Based on flower lengths, we established a correlation between the developmental stages and four main episodes of floral development and conducted an extensive RNA sequencing analysis of these episodes. KEY RESULTS: We identified 12 stages of floral development, from the appearance of the floral meristems to anthesis. The main structural differences between male and hermaphrodite flowers appeared between stages 6 and 7; later stages of development leading to the formation of organs and structures in both types of flowers were also described. We analysed the gene expression patterns of the four episodes in flower development to find the genes that were specific to each given episode. Among others, we identified genes that defined the passage from one episode to the next according to the ABCDE model of floral development. CONCLUSIONS: This work combines a detailed morphological analysis and a comprehensive transcriptomic study to enable characterization of the structural and molecular mechanisms that determine the floral development of an andromonoecious genotype in melon. Taken together, our results provide a first insight into gene regulation networks in melon floral development that are crucial for flowering and pollen formation, highlighting potential targets for genetic manipulation to improve crop yield of melon in the future.

Pre-germination treatments of melon seeds for the production of seedlings irrigated with biosaline water

Abstract Melon production in the Brazilian semi-arid region is subject to the use of marginal waters with high salinity. However, the use of regulators and bioactivators in seed treatment can mitigate the harmful effects of salts in irrigation water. In this context, the objective was to evaluate the effect of pre-germination treatments with plant regulators and bioactivator in melon seeds for the production of seedlings irrigated with biosaline water from fish farming effluent. For this, two trials with the Goldex and Grand Prix hybrids were carried out separately. A completely randomized design was used in a 4 × 3 factorial scheme (pre-germination treatments × water dilutions). In addition to the control, the seeds were treated with salicylic and gibberellic acids and thiamethoxam. The waters used for irrigation were local-supply water, fish farming effluent (biosaline water) and these diluted to 50%. Physiological and biochemical analyses were performed for fourteen days. Biosaline water (5.0 dS m-1) did not affect the emergence of Goldex melon seedlings, but compromised the establishment of the Grand Prix cultivar. Seed pre-treatments with salicylic and gibberellic acids attenuate the effects of water salinity and promote growth modulations, resulting in more vigorous melon seedlings.

Resumo A produção de meloeiro no semiárido brasileiro está sujeita a utilização de águas marginais com salinidade elevada. Entretanto, a utilização de reguladores e bioativadores no tratamento de sementes podem mitigar os efeitos nocivos dos sais na água de irrigação. Nesse sentido, objetivou-se avaliar o efeito de tratamentos pré-germinativos com fitorreguladores e bioativador em sementes de melão para a produção de mudas irrigadas com água biossalina de efluente de piscicultura. Para isso, dois ensaios com os híbridos Goldex e Grand Prix foram realizados separadamente. Utilizou-se delineamento inteiramente casualizado em esquema fatorial 4 × 3 (tratamentos pré-germinativos × diluições de água). Além do controle, as sementes foram tratadas com os ácidos salicílico e giberélico, e tiametoxam. As águas utilizadas para irrigação foram a de abastecimento local, efluente de piscicultura (água biossalina) e estas diluídas a 50%. Durante quatorze dias foram realizadas as análises fisiológicas e bioquímicas. A água biossalina (5,0 dS m-1) não afetou a emergência de plântulas de meloeiro Goldex, mas prejudicou o estabelecimento da cultivar Grand Prix. Os pré-tratamentos de sementes com os ácidos salicílico e giberélico atenuam os efeitos da salinidade da água e promovem modulações no crescimento, proporcionando mudas de meloeiro mais vigorosas.

Pre-germination treatments of melon seeds for the production of seedlings irrigated with biosaline water / Tratamentos pré-germinativos de sementes de melão para a produção de mudas irrigadas com água biossalina

Abstract Melon production in the Brazilian semi-arid region is subject to the use of marginal waters with high salinity. However, the use of regulators and bioactivators in seed treatment can mitigate the harmful effects of salts in irrigation water. In this context, the objective was to evaluate the effect of pre-germination treatments with plant regulators and bioactivator in melon seeds for the production of seedlings irrigated with biosaline water from fish farming effluent. For this, two trials with the Goldex and Grand Prix hybrids were carried out separately. A completely randomized design was used in a 4 × 3 factorial scheme (pre-germination treatments × water dilutions). In addition to the control, the seeds were treated with salicylic and gibberellic acids and thiamethoxam. The waters used for irrigation were local-supply water, fish farming effluent (biosaline water) and these diluted to 50%. Physiological and biochemical analyses were performed for fourteen days. Biosaline water (5.0 dS m-1) did not affect the emergence of Goldex melon seedlings, but compromised the establishment of the Grand Prix cultivar. Seed pre-treatments with salicylic and gibberellic acids attenuate the effects of water salinity and promote growth modulations, resulting in more vigorous melon seedlings.

Resumo A produção de meloeiro no semiárido brasileiro está sujeita a utilização de águas marginais com salinidade elevada. Entretanto, a utilização de reguladores e bioativadores no tratamento de sementes podem mitigar os efeitos nocivos dos sais na água de irrigação. Nesse sentido, objetivou-se avaliar o efeito de tratamentos pré-germinativos com fitorreguladores e bioativador em sementes de melão para a produção de mudas irrigadas com água biossalina de efluente de piscicultura. Para isso, dois ensaios com os híbridos Goldex e Grand Prix foram realizados separadamente. Utilizou-se delineamento inteiramente casualizado em esquema fatorial 4 × 3 (tratamentos pré-germinativos × diluições de água). Além do controle, as sementes foram tratadas com os ácidos salicílico e giberélico, e tiametoxam. As águas utilizadas para irrigação foram a de abastecimento local, efluente de piscicultura (água biossalina) e estas diluídas a 50%. Durante quatorze dias foram realizadas as análises fisiológicas e bioquímicas. A água biossalina (5,0 dS m-1) não afetou a emergência de plântulas de meloeiro Goldex, mas prejudicou o estabelecimento da cultivar Grand Prix. Os pré-tratamentos de sementes com os ácidos salicílico e giberélico atenuam os efeitos da salinidade da água e promovem modulações no crescimento, proporcionando mudas de meloeiro mais vigorosas.

Molecular Marker-Assisted Mapping, Candidate Gene Identification, and Breeding in Melon (Cucumis melo L.): A Review.

Melon (Cucumis melo L.) is an important crop that is cultivated worldwide for its fleshy fruit. Understanding the genetic basis of a plant's qualitative and quantitative traits is essential for developing consumer-favored varieties. This review presents genetic and molecular advances related to qualitative and quantitative phenotypic traits and biochemical compounds in melons. This information guides trait incorporation and the production of novel varieties with desirable horticultural and economic characteristics and yield performance. This review summarizes the quantitative trait loci, candidate genes, and development of molecular markers related to plant architecture, branching patterns, floral attributes (sex expression and male sterility), fruit attributes (shape, rind and flesh color, yield, biochemical compounds, sugar content, and netting), and seed attributes (seed coat color and size). The findings discussed in this review will enhance demand-driven breeding to produce cultivars that benefit consumers and melon breeders.

Efficacy of Carotenoid-Loaded Gelatin Nanoparticles in Reducing Plasma Cytokines and Adipocyte Hypertrophy in Wistar Rats.

The present study investigated the effect of gelatin-based nanoparticles (EPG) loaded with a carotenoid-rich crude extract (CE) on systemic and adipose tissue inflammatory response in a model with inflammation induced by a high glycemic index and high glycemic load diet (HGLI). Nanoparticles synthesized were characterized by different physical and chemical methods. The in vivo investigation evaluated Wistar rats (n = 20, 11 days, adult male with 21 weeks) subdivided into untreated (HGLI diet), conventional treatment (nutritionally adequate diet), treatment 1 (HGLI + crude extract (12.5 mg/kg)), and treatment 2 (HGLI + EPG (50 mg/kg)) groups. Dietary intake, caloric intake and efficiency, weight, inflammatory cytokines tissue concentration, visceral adipose tissue (VAT) weight, histopathological analysis, and antioxidant activity in plasma and VAT were investigated. EPG showed the same physical and chemical characteristics as previous batches (95.2 nm, smooth surface, and chemical interactions between materials). The EPG-treated group was the only group promoting negative ∆dietary intake, ∆caloric efficiency, and ∆weight. In addition, it presented a significant reduction (p < 0.05) in IL-6 and leptin levels and a greater presence of multilocular adipocytes. The results suggest that EPG can act as a nutraceutical in adjuvant therapy for treating inflammatory diseases associated with adipose tissue accumulation.

Hybridization Between the Canary Melon and a Vietnamese Non-sweet Melon Cultivar Aiming to Improve the Growth Performance and Fruit Quality in Melon (Cucumis melo L.).

Canary melon has been widely consumed as a dessert fruit due to its fragrance, sweetness, and flavorful taste. However, the cultivation of this cultivar has been challenged in Vietnam because of its weak growth performance and high susceptibility to local pathogens. In this study, we aim to generate the hybrid melon lines between the Canary melon and a local non-sweet melon that are expected to produce good quality fruits as well as to show better growth performance in the local cultivation conditions. Two crossing pairs including (1) MS hybrid (♂ non-sweet melon × â™€ Canary melon) and (2) MN-S hybrid (♂ Canary melon × â™€ non-sweet melon) were carried out and two hybrid lines were subsequently obtained. Next, different phenotypic and physiological parameters such as stem length, stem diameter, 10th leaf diameter, fruit size, fruit weight, and fruit sweetness (pH, °Brix, and soluble sugar contents) were examined and compared between the parental lines (Canary melon and non-sweet melon) and the hybrid lines (MS and MN-S). The results showed that the stem length and fruit size and weight of MS and MN-S hybrids were higher than those of Canary melon. Basically, the content of sugars (sucrose, glucose, and fructose) is a primary and important factor in determining the sweetness of the melon. The pH, °Brix, sucrose and glucose contents of MS hybrid and Canary melon fruits were higher in comparison to MN-S and non-sweet melon fruits. Accordingly, the transcript levels of different sugar metabolism-related genes including SUCROSE SYNTHASE 1 (SUS1), SUS2, UDPGLC EPIMERASE 3 (UGE3), and SUCROSE-P SYNTHASE 2 (SPS2) were examined in all studied lines. In the fruits, the expression levels of these genes were found to be highest in the Canary melon, average in the MS hybrid, and relatively low in the MN-S hybrid and non-sweet melons. Taken together, the heterosis in terms of plant and fruit size was obviously observed in this crossing approach. The relatively high fruit sweetness in the MS hybrid (the mother is Canary melon) also implies that the choice of the mother for crossing is very important since it can determine the fruit quality of the offspring.

Fusarium pernambucanum Causing Leaf Yellow Spot on Melon (Cucumis melo L.), a New Disease in China.

Melon (Cucumis melo L.) is a member of the Cucurbitaceae family, and is an important economic and horticultural crop. In March 2022, melon plants in greenhouses exhibited severe leaf yellow spot symptoms in Changjiang County (109°13'N, 19°28'E), Hainan Province. The incidence of the disease was about 30-50%. Lesions initially appeared as yellow dots on leaves and expanded irregularly. Gradually, brown spots appeared, and finally the whole leaves turned yellow and resulted in blighting and death of foliage (Figure 1.). A total of four symptomatic plants were sampled from about 0.2 ha of an area. Symptomatic leaves were excised, surface disinfected with 2% (w/v) NaOCl, rinsed three times with sterile distilled water, and placed on potato dextrose agar (PDA) followed by incubation at 25°C in the dark for 5 days. The pure cultures were obtained by the hyphal-tip method. A total of eight fungal isolates with similar colony characteristics were recovered from the four symptomatic plants. Three DNA fragments (ITS, TEF1, and RPB2) of the eight isolates showed 100% sequence identity based on the molecular identification methods described below. Therefore, one of the isolates, M2JP-3, was chosen for identification and test of the pathogenicity. The colony of M2JP-3 on PDA at 25°C for 5 days was white with yellow-brown pigmentation in the center (Figure 2A-B). From 10-day-old cultures grown on CLA (Fisher et al. 1982), macroconidia (n = 50) were falcate, slender, curved dorsiventrally, tapering towards both ends, 3 to 7 septate, and measured 24.5 to 52.1 x 3.7 to 4.7 µm. The microconidia (n = 50) were straight or slightly curved, septate 0 to 2, and measured 9.9 to 16.3 x 2.5 to 3.7 µm (Figure 2C-E). For molecular identification, genomic DNA was extracted using the method previously described (Khan et al. 2021),the internal transcribed spacer (ITS), translation elongation factor 1α (TEF1) and DNA-dependent RNA polymerase subunit II (RPB2) were amplified, respectively, using primers ITS1/ITS4 (White et al. 1990), EF1/ EF2 (O'Donnell et al. 1998), and 5F2/7cR (Reeb et al. 2004). The 529 bp (ITS), 723 bp (TEF1), and 965bp (RPB2) sequences were deposited in GenBank with acce. nos. OP303211, OP312675 and OP312674, respectively. A phylogenetic tree was constructed using the concatenated three gene sequences of M2JP-3 and that of the Fusarium incarnatum-equiseti species complex (FIESC) (Xia et al. 2019) based on Maximum Likelihood (Figure 3). M2JP-3 was grouped together with the F. pernambucanum strain NRRL 32864 (accession no. GQ505702 for ITS, GQ505613 for TEF1and GQ505791 for RPB2), and shared 100% concatenated sequence identity. For pathogenicity tests of M2JP-3, seeds of melon cultivar Jinmeiren were surface disinfected and sowed in soil in three replicated pots in a greenhouse at 26 °C under natural light. Healthy leaves of the melon plants were wounded with needles and inoculated with mycelial plugs of M2JP-3 or PDA plugs as control. . Symptoms similar to the original greenhouse symptoms were observed at 7 days after inoculation (Figure 4). The control leaves were asymptomatic. The same fungus was reisolated from the inoculated leaves, as identified based on morphology and molecular evidence, which confirmed the Kochs' postulates. To our knowledge, this is the first time Fusarium pernambucanum has been recorded causing leaf yellow spot disease on melon. Further, findings of the present study will help to develop effective disease management strategies against Fusarium pernambucanum Leaf Yellow Spot on melon in China.

Genome-wide identification, evolution, and expression analysis of MLO gene family in melon (Cucumis melo L.).

Powdery mildew (PM) is one of the main fungal diseases that appear during the cultivation of the melon fruit crop. Mildew Resistance Locus "O" (MLO) is known as a gene family and has seven conserved transmembrane domains. An induced functional loss of a specific MLO gene could mainly confer PM resistance to melons. However, the genomic structure of MLO genes and its main role in PM resistance still remain unclear in melon. In this study, bioinformatic analysis identified a total of 14 MLO gene family members in the melon genome sequence, and these genes were distributed in an uneven manner on eight chromosomes. The phylogenetic analysis divided the CmMLO genes into five different clades, and gene structural analysis showed that genes in the same clade had similar intron and exon distribution patterns. In addition, by cloning the CmMLO gene sequence in four melon lines, analyzing the CmMLO gene expression pattern after infection, and making microscopic observations of the infection pattern of PM, we concluded that the CmMLO5 (MELO3C012438) gene plays a negative role in regulating PM-resistance in the susceptible melon line (Topmark), and the critical time point for gene function was noticed at 24 and 72 hours after PM infection. The mutational analysis exhibited a single base mutation at 572 bp, which further results in loss of protein function, thus conferring PM resistance in melon. In summary, our research evidence provides a thorough understanding of the CmMLO gene family and demonstrates their potential role in disease resistance, as well as a theoretical foundation for melon disease resistance breeding.

Sodium silicate treatment accelerates biosynthesis and polymerization of suberin polyaliphatics monomers at wounds of muskmelon.

Suberin polyaliphatics (SPA) is an important component of healing closing layer at fruit wounds. However, few study is available on the effect of sodium silicon treatment on SPA monomers biosynthesis and polymerization at muskmelon wounds. In this study, sodium silicate enhanced PLA2 (Phospholipase A2, PLA2) expression and enzyme activity, increased oleic acid, linoleic acid, and linolenic acid contents, and degree of fatty acids unsaturation at wounds. Sodium silicate upregulated the expressions of LACS4 (Long chain acyl CoA synthetase, LACS), KCS10 (ß-ketoacyl CoA synthase, KCS), CYP86B1 (Cytochrome P450 oxygenase, CYP), FAR3 (Fatty acyl CoA reductase, FAR), GPAT1 (Glycerol-3-phosphate acyltransferase, GPAT) and ABCG6 (ATP-binding cassette transporter), as well as their enzymes activities and ABC content. It is suggested that sodium silicate accelerates the deposition of SPA at muskmelon wounds by increasing the degree of fatty acids unsaturation, and promoting SPA monomers biosynthesis.

Thorough Characterization of ETHQB3.5, a QTL Involved in Melon Fruit Climacteric Behavior and Aroma Volatile Composition.

The effect of the QTL involved in climacteric ripening ETHQB3.5 on the fruit VOC composition was studied using a set of Near-Isogenic Lines (NILs) containing overlapping introgressions from the Korean accession PI 16375 on the chromosome 3 in the climacteric 'Piel de Sapo' (PS) genetic background. ETHQB3.5 was mapped in an interval of 1.24 Mb that contained a NAC transcription factor. NIL fruits also showed differences in VOC composition belonging to acetate esters, non-acetate esters, and sulfur-derived families. Cosegregation of VOC composition (23 out of 48 total QTLs were mapped) and climacteric ripening was observed, suggesting a pleiotropic effect of ETHQB3.5. On the other hand, other VOCs (mainly alkanes, aldehydes, and ketones) showed a pattern of variation independent of ETHQB3.5 effects, indicating the presence of other genes controlling non-climacteric ripening VOCs. Network correlation analysis and hierarchical clustering found groups of highly correlated compounds and confirmed the involvement of the climacteric differences in compound classes and VOC differences. The modification of melon VOCs may be achieved with or without interfering with its physiological behavior, but it is likely that high relative concentrations of some type of ethylene-dependent esters could be achieved in climacteric cultivars.

Beta-galactosidase gene family genome-wide identification and expression analysis of members related to fruit softening in melon (Cucumis melo L.).

BACKGROUND: Texture quality is impotent for melon (Cucumis melo L.) fruit. ß-galactosidase (ß-Gal, EC 3.2.1.23) is an important cell wall glycosyl hydrolase involved in fruit softening, However, the ß-Gal gene (BGALs) family hasn't been identified genome-wide in melon. Thus, it's necessary to conduct an in-depth bioinformatic analysis on melon BGALs family and to seek out the key members who participated in melon fruit softening. RESULTS: A total of 21 BGALs members designated as CmBGAL1-CmBGAL21 were identified genome-wide in melon, clustered into A-G seven clades. Among them, three duplications CmBGAL1:CmBGAL3, CmBGAL19:CmBGAL21, and CmBGAL20:CmBGAL21 happened. For conserved domains, besides the Glyco_hydro_35 domain (PF01301), all the members also contained the GHD domain (PF17834) except for CmBGAL12, and the Gal_Lectin (PF02140) domain existed in most CmBGALs at the C-termini. Motifs, protein secondary and tertiary structure analysis showed that the CmBGAL12 is a unique member. Moreover, protein-protein association network analysis showed that the CmBGAL12 is the only node protein. Furthermore, spatiotemporal expression pattern analysis by quantitative real-time PCR (qRT-PCR) suggested that most of CmBGALs expressed in tissues with vigorous cell wall remodeling/disassembly. In addition, cis-acting regulatory elements analysis in promoters inferred that CmBGALs might participate in diverse responsiveness to phytohormone, biotic and abiotic signaling. CONCLUSIONS: A novel clade of CmBGAL members (Clade F) related to melon fruit softening was discovered, since their expression showed a specific surge in the mature fruit of 'HPM' with mealy texture (softening sharply), but not in 'HDB' with crisp texture (softening bluntly). The homologous CmBGAL7-11 in Clade F exhibited identical spatiotemporal expression patterns may multiple genes leading to melon fruit softening.