Search Results (31)

In this study, the insert length, location within the coat protein-encoding gene, and sequence orientation of the target fragment were optimized to construct an efficient virus-induced gene silencing (VIGS) system in melon using a Begomovirus solanumdelhiense vector. Existing systems are mostly RNA viruses, requiring in vitro synthesis of viral strands that are prone to degradation, although they exhibit high infectivity and stability in cucurbit hosts and ease of manipulation. This vector was selected for its more stable genome structure and these advantages. The melon phytoene desaturase (CmPDS), a key gene of carotenoid biosynthesis, was selected as a reporter gene to evaluate the effects of the VIGS system. Our results revealed that the melon leaves in all the VIGS treatments exhibited a typical photobleaching phenotype at 21 days post-inoculation. Moreover, reverse transcription quantitative real-time PCR revealed a significant reduction in the mRNA levels of PDS in melon. The highest silencing efficiency (lowest PDS mRNA levels) was achieved by the VIGS vector harboring a 165 bp CmPDS fragment at the 3′ end of the AV1. These findings not only establish a more efficient VIGS protocol for melon but also provide a foundation for developing novel virus-based silencing tools applicable to functional genomics and cucurbit crop improvement, particularly for traits requiring precise gene expression modulation such as disease resistance and fruit quality. Full article

Deep learning-based plant disease classification models often suffer from performance degradation when training data are limited. Hence, generative models offer a promising solution for model performance in plant disease classification. In this work, images representing powdery mildew, downy mildew, and healthy plant leaves were generated using traditional augmentation methods as well as both DCGAN and a modified DCGAN featuring residual connection blocks with varied activation functions. Evaluation metrics IS and FID revealed that the modified DCGAN consistently produced generative images with strong class-distinctive features and greater overall diversity compared to basic GAN methods, with an IS increment of 7.9% to 11.54% and FID decrement of 6.6% to 7.8%. After selecting the best augmentation method, we input the generated images into the training sets for the classification models, AlexNet, VGG16, and Goog-LeNet, to measure improvements in disease recognition. All classifiers benefited from the augmented datasets, with the modified DCGAN-based augmentation yielding the highest precision, recall, and accuracy. GoogLeNet outperformed all classification models, with an overall precision, recall, and F1-Score value of 98%. Notably, this generative approach minimized errors between visually similar categories, such as powdery mildew and healthy samples, by capturing subtle morphological differences. The results confirm that class-aware generative augmentation can both expand the number of training images and preserve the critical features necessary for discrimination, significantly boosting model effectiveness. These advances show the practical potential of generative models not only to enrich datasets but also to improve the accuracy and robustness of plant disease detection for real-world agricultural scenarios. Full article

Continuous planting results in a higher occurrence rate of oriental melon Fusarium wilt caused by Fusarium oxysporum f. sp. melonis (FOM), and treatment with Trichoderma can considerably alleviate the incidence of disease. However, the tripartite interaction mechanisms among T. harzianum–melon–rhizosphere microorganisms remain poorly understood in current research. Pot experiments elucidate the growth-promoting, antagonistic, and rhizosphere-regulating effects of T. harzianum on oriental melon. The experiment consisted of two treatments: (1) water control (CK), and (2) T. harzianum inoculation (MM) with three repetitions per treatment. Illumina high-throughput sequencing was employed to analyze the microbial community and associated metabolic pathways. Additionally, a comprehensive correlation analysis clarified how T. harzianum-modulated physiological factors regulate soil microbial communities to enhance melon resistance to FOM. T. harzianum inoculation significantly promoted plant growth, decreased the incidence rate of Fusarium wilt by 41.85%, and increased rhizosphere nitrate-N, pH, EC, and soil enzyme activity (e.g., sucrose and alkaline phosphatase). Notably, T. harzianum inoculation altered the rhizosphere microbial community’s relative abundance and structure, with the most striking changes in the fungal community. Principal coordinate analysis showed this fungal restructuring accounted for 44.9% of total community variation (37% from PCo1, 7.9% from PCo2). Soil-borne pathogens (e.g., Fusarium, Verticillium, Phytophthora) decreased in relative abundance with the inoculation of T. harzianum. Meanwhile, the microbial community shifted from a “fungal-dominated” to “bacterial-dominated” state: fungal proportion decreased by 9.47% (from 23.95% in CK to 14.48% in MM), while bacterial proportion increased by 9.47% (from 76.05% in CK to 85.52% in MM). Microbial abundance shifts primarily impacted amino acid and cofactor biosynthesis metabolic pathways. The application of T. harzianum modified the soil environment, restructuring microbial communities through these changes, which in turn regulated microbial metabolic pathways, creating a soil environment conducive to melon growth and thereby enhancing oriental melon resistance to FOM, while mitigating the obstacles of continuous cropping. Full article

Plant hormones are critical regulators of graft union healing, yet the specific role of exogenous naphthylacetic acid (NAA) in graft union healing efficiency and grafted seedling growth remains unexplored. In this study, we investigated the effects of exogenous NAA treatment (40 mg·L⁻¹) on graft union healing and grafted seedling quality in oriental melon scion grafted onto squash rootstock. Our results demonstrated that exogenous NAA application significantly accelerated vascular bundle reconnection, a key indicator of successful graft union formation. The exogenous NAA treatment enhanced indole-3-acetic acid (IAA) biosynthesis by upregulating key enzymes (TDC, PDC, FMO, NIT, and TAA) and gene expression (CmYUCCA10, CmCYP450, CmoCYP450, and CmoTAA1). The exogenous NAA treatment also upregulated critical graft healing-related genes (CmoWIND1, CmoWOX4, CmoCDKB1;2, CmTMO6, CmoTMO6, CmVND7, and CmoVND7). The exogenous NAA-treated seedlings exhibited better growth. These findings reveal the potential molecular and physiological mechanisms by which exogenous NAA promotes graft union healing of melon grafted onto squash. While the results highlight the potential of exogenous NAA as a grafting enhancer under controlled conditions, further field studies are also needed to validate its practical applicability in commercial production. Full article

Dehydrins (DHNs; late embryogenesis-abundant D11 family) are a class of hydrophilic proteins involved in plant abiotic stress response. However, there is less information regarding DHN gene function in cucurbit crops. Herein, 34 DHN gene family members were identified and characterized in Cucumis sativus, Cucumis melo, Citrullus lanatus, Benincasa hispida, Lagenaria siceraria, and Cucurbita maxima. The DHN genes in the six cucurbit crops exhibited greater collinearity within subfamilies than between different subfamilies. Responses to stress (including low-temperature, salt, cadmium, and aluminum stress) varied among the DHN members, with a significant alteration in the expression of the acidic SnKn-type DHN gene CmDHN3 in response to aluminum stress. Subcellular localization analysis confirmed that CmDHN3 is expressed in the nucleus and cytoplasm. Virus-induced gene silencing (VIGS) revealed a remarkable decrease in CmDHN3 expression, which markedly increased malondialdehyde content, relative conductivity, and proline content in the roots and leaves of plants under aluminum stress. Transcriptome analysis showed that the decreased CmDHN3 expression reduced the expression of water channel protein-encoding genes. Interactions between CmDHN3 and CmAQP1 (MELO3C007188) and between CmDHN3 and CmAQP2 (MELO3C020774) were confirmed using yeast two-hybrid assays. These results clarify the pathway by which dehydrin genes are involved in the transcriptional-level response of melon to aluminum stress and provide a theoretical basis to comprehensively analyze the functions of this gene family in cucurbit crops. Full article

N6-methyladenosine (m⁶A) methylation functions as a vital post-transcriptional and epigenetic modification in higher plants regulated by α-ketoglutarate-dependent dioxygenases (ALKBH). However, the role of ALKBH genes in oriental melon (Cucumis melo L.) fruit ripening has not been explored. Therefore, we treated oriental melon with an exogenous m⁶A demethylase inhibitor (mechlorfenamic acid) then analyzed endogenous ethylene production and ripening-related indicators to explore the effects of m⁶A methylation on ripening. Bioinformatics and real-time quantitative PCR analyses were used to determine the impact of ALKBH genes on key ethylene synthesis gene expression. Treatment effectively inhibited endogenous ethylene production, firmness changes, and soluble solid contents, thereby extending fruit ripening. Eight ALKBH gene family members belonging to five major groups were identified in the melon genome. All members were expressed in ripening fruits, with different expression patterns during ripening. CmALKBH6, CmALKBH7, and CmALKBH8 expression was inhibited by an ethylene inhibitor (1-methylcyclopropene). The transient overexpression (OE) of CmALKBH8 in oriental melon led to the increased expression of the ethylene synthesis genes CmACS1, CmACS2, and CmACO1. In summary, the ethylene-regulated gene CmALKBH8 may participate in oriental melon fruit ripening regulation by modulating the methylation levels of ethylene synthesis-related genes. These findings help us better understand how m⁶A methylation regulates melon ripening. Full article

We investigated the host status of harvest-ready green lemons, Citrus × limon (L.) Burm. F. cv. Lisbon (Rutaceae), to Oriental fruit fly (Bactrocera dorsalis), Mediterranean fruit fly (Ceratitis capitata), and melon fly (Zeugodacus cucurbitae) (Diptera: Tephritidae) in Hawaii using laboratory and field studies. In forced-infestation small-cage exposures (using 25 × 25 × 25 cm screened cages with 50 gravid females), punctured lemons were infested by Oriental fruit fly, Mediterranean fruit fly, and melon fly, whereas undamaged lemons were not infested. Field collection, packing, and incubation of approximately 58,420 mixed-grade fruit (commercial export quality and off grades) found no natural infestations and resulted in no fruit fly emergence. Field studies enclosing fruit on trees in sleeve cages that were stocked with 50 gravid females per cage resulted in no infestations. Commercial export-grade green Lisbon lemon fruit should, therefore, be considered a non-host for Oriental fruit fly, Mediterranean fruit fly, and melon fly. Full article

Korean melons (Cucumis melo var. makuwa), which have a short shelf life and are prone to browning, face challenges when exported over long-distance via maritime shipping. However, the high firmness and low suture browning rate of the ‘Eliteggul’ cultivar suggest its potential suitability for long-distance export. This study aimed to evaluate the export suitability of ‘Eliteggul’ by comparing it to the widely grown cultivar ‘Alchankkul’. Consumer preferences were assessed based on fragrance, sweetness, overall preference, appearance, and firmness. Both cultivars were grown and harvested in a commercial greenhouse in Seongju-gun, South Korea. After being treated with modified atmosphere film, the fruits were stored at 6 °C for 1 day, transported to Singapore in a shipping container at 7.4 °C for 13 days, and distributed at 22 °C for 3 days. After 14 days of storage, analysis in Singapore showed that ‘Eliteggul’ maintained a significantly higher firmness at 12.9 ± 0.3 kg·cm² compared to ‘Alchankkul’, which showed firmness at 8.1 ± 0.4 kg·cm². Additionally, ‘Eliteggul’ exhibited less browning on the white sutures at 1.3 ± 0.1, indicating better preservation of its quality than ‘Alchankkul’, at 2.0 ± 0.3. Even at 14 + 3 days, ‘Eliteggul’ maintained a firmness of 12.8 ± 0.2 kg·cm², which was significantly higher than that of ‘Alchankkul’, which showed a firmness of 7.7 ± 0.5 kg·cm². Consumer preference surveys (n = 78) conducted in the local market revealed that customers favored the fragrance and sweetness of ‘Alchankkul’. Correspondingly, an analysis of volatile organic compounds (VOCs) from melon juice using a Twister stir bar method showed that ‘Alchankkul’ had significantly higher levels of ethyl(methylthio)acetate, ethyl propanoate, and benzyl alcohol, known to contribute to a sweet flavor. Furthermore, a thermal desorption tube VOCs test indicated that hexyl acetate and 2-methylbutyl 2-methylbutyrate were also significantly higher in ‘Alchankkul’. Despite this result, there was no significant difference in the overall preference scores between the two cultivars. This study indicates that ‘Eliteggul’, with a superior firmness, reduced browning, and high consumer acceptance, is ideal for long-distance export, offering foundational data to bridge the research gap in export-oriented melons and support the broader distribution of Korean cultivars. Full article

Nitrogen is the primary nutrient for plants. Low nitrogen generally affects plant growth and fruit quality. Melon, as an economic crop, is highly dependent on nitrogen. However, the response mechanism of its self-rooted and grafted seedlings to low-nitrogen stress has not been reported previously. Therefore, in this study, we analyzed the transcriptional differences between self-rooted and grafted seedlings under low-nitrogen stress using fluorescence characterization and RNA-Seq analysis. It was shown that low-nitrogen stress significantly inhibited the fluorescence characteristics of melon self-rooted seedlings. Analysis of differentially expressed genes showed that the synthesis of genes related to hormone signaling, such as auxin and brassinolide, was delayed under low-nitrogen stress. Oxidative stress response, involved in carbon and nitrogen metabolism, and secondary metabolite-related differentially expressed genes (DEGs) were significantly down-regulated. It can be seen that low-nitrogen stress causes changes in many hormonal signals in plants, and grafting can alleviate the damage caused by low-nitrogen stress on plants, ameliorate the adverse effects of nitrogen stress on plants, and help them better cope with environmental stresses. Full article

Graft healing is a complex process affected by environmental factors, with temperature being one of the most important influencing factors. Here, oriental melon grafted onto pumpkin was used to study changes in graft union formation and sugar contents at the graft interface under night temperatures of 18 °C and 28 °C. Histological analysis suggested that callus formation occurred 3 days after grafting with a night temperature of 28 °C, which was one day earlier than with a night temperature of 18 °C. Vascular reconnection with a night temperature of 28 °C was established 2 days earlier than with a night temperature of 18 °C. Additionally, nine sugars were significantly enriched in the graft union, with the contents of sucrose, trehalose, raffinose, D–glucose, D–fructose, D–galactose, and inositol initially increasing but then decreasing. Furthermore, we also found that exogenous glucose and fructose application promotes vascular reconnection. However, exogenous sucrose application did not promote vascular reconnection. Taken together, our results reveal that elevated temperatures improve the process of graft union formation through increasing the contents of sugars. This study provides information to develop strategies for improving grafting efficiency under low temperatures. Full article

Melatonin (MT) is a vital hormone factor in plant growth and development, yet its potential to influence the graft union healing process has not been reported. In this study, we examined the effects of MT on the healing of oriental melon scion grafted onto squash rootstock. The studies indicate that the exogenous MT treatment promotes the lignin content of oriental melon and squash stems by increasing the enzyme activities of hydroxycinnamoyl CoA ligase (HCT), hydroxy cinnamaldehyde dehydrogenase (HCALDH), caffeic acid/5-hydroxy-conifer aldehyde O-methyltransferase (COMT), caffeoyl-CoA O-methyltransferase (CCoAOMT), phenylalanine ammonia-lyase (PAL), 4-hydroxycinnamate CoA ligase (4CL), and cinnamyl alcohol dehydrogenase (CAD). Using the oriental melon and squash treated with the exogenous MT to graft, the connection of oriental melon scion and squash rootstock was more efficient and faster due to higher expression of wound-induced dedifferentiation 1 (WIND1), cyclin-dependent kinase (CDKB1;2), target of monopteros 6 (TMO6), and vascular-related NAC-domain 7 (VND7). Further research found that the exogenous MT increased the lignin content of the oriental melon scion stem by regulating CmCAD1 expression, and then accelerated the graft healing process. In addition, the root growth of grafted seedlings treated with the exogenous MT was more vigorous. Full article

Melon (Cucumis melo L.) is an economically important Cucurbitaceae crop grown around the globe. The sweetness of melon is a significant factor in fruit quality and consumer appeal, and the soluble solids content (SSC) is a key index of melon sweetness. In this study, 146 recombinant inbred lines (RILs) derived from two oriental melon materials with different levels of sweetness containing 1427 bin markers, and 213 melon accessions containing 1,681,775 single nucleotide polymorphism (SNP) markers were used to identify genomic regions influencing SSC. Linkage mapping detected 10 quantitative trait loci (QTLs) distributed on six chromosomes, seven of which were overlapped with the reported QTLs. A total of 211 significant SNPs were identified by genome-wide association study (GWAS), 138 of which overlapped with the reported QTLs. Two new stable, co-localized regions on chromosome 3 were identified by QTL mapping and GWAS across multiple environments, which explained large phenotypic variance. Five candidate genes related to SSC were identified by QTL mapping, GWAS, and qRT-PCR, two of which were involved in hydrolysis of raffinose and sucrose located in the new stable loci. The other three candidate genes were involved in raffinose synthesis, sugar transport, and production of substrate for sugar synthesis. The genomic regions and candidate genes will be helpful for molecular breeding programs and elucidating the mechanisms of sugar accumulation. Full article

Forchlorfenuron is a widely used plant growth regulator to support the pollination and fruit set of oriental melons. It is critical to investigate the spatial distribution and migration characteristics of forchlorfenuron among fruit tissues to understand its metabolism and toxic effects on plants. However, the application of imaging mass spectrometry in pesticides remains challenging due to the usually extremely low residual concentration and the strong interference from plant tissues. In this study, a matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) method was developed for the first time to obtain the dynamic images of forchlorfenuron in oriental melon. A quantitative assessment has also been performed for MALDI-MSI to characterize the time-dependent permeation and degradation sites of forchlorfenuron in oriental melon. The majority of forchlorfenuron was detected in the exocarp and mesocarp regions of oriental melon and decreased within two days after application. The degradation rate obtained by MALDI-MSI in this study was comparable to that obtained by HPLC-MS/MS, indicating that the methodology and quantification approach based on the MALDI-MSI was reliable and practicable for pesticide degradation study. These results provide an important scientific basis for the assessment of the potential risks and effects of forchlorfenuron on oriental melons. Full article

Tephritid fruit flies are among the most destructive agricultural pests of fruits and vegetables worldwide and can impose trade barriers against the movement of fresh tropical commodities. Primary pre-harvest control methods for these flies rely on the spraying of conventional chemical insecticides or bait sprays. However, resistance to these control methods has been reported in fruit flies. Erythritol is a non-nutritive sugar alternative for human consumption, which has been tested and confirmed for its insecticidal properties against various insect pest species. In this study, using laboratory bioassays, we evaluated the insecticidal effect of erythritol alone or various erythritol formulations containing sucrose and/or protein on four tropical fruit fly species established in Hawaii (e.g., melon fly, Mediterranean fruit fly, oriental fruit fly, and Malaysian fruit fly). In addition, the effects of other non-nutritive hexose and pentose sugar alcohols, such as sorbitol, mannitol, and xylitol, were tested. Among the different standalone and combinatory treatments tested, 1M erythritol and a combinatory formulation of 2M erythritol + 0.5M sucrose appeared to be the most detrimental to the survival of all four species of tested flies, suggesting the potential of using erythritol as a non-toxic management tool for the control of tropical tephritid fruit flies. Full article

Since CO₂ is the fundamental substrate for photosynthesis, fluctuating concentrations have a direct effect on plant growth and metabolism. Accordingly, CO₂ enrichment within a certain range was found to improve photosynthesis, yields and the quality of plants. In order to further understand the underlying impact of CO₂ enrichment, this study employed an open-top chamber growth box model with the following two treatments: control treatment (CO₂ concentration: 380 ± 30 μL/L) and CO₂ enrichment (1200 ± 50 μL/L). The effects on leaf carbon assimilation, fruit yield and quality were subsequently determined. The net photosynthetic rate, intercellular CO₂ concentration, dry matter accumulation and soluble sugar content in the oriental melon leaves increased significantly on day 5 of CO₂ enrichment. Moreover, a significant increase in the activity of carbon assimilation-related enzymes Rubisco, RCA, FBPase and CA was also observed, with the upregulation of CmRubisco, CmRCA, CmFBPase and CmCA gene expression from day 15 of CO₂ enrichment. Thus, the yield per plant and content of soluble sugars and soluble solids in the fruit also increased significantly. These findings suggest that CO₂ enrichment has positive effects on oriental melon growth, increasing photosynthesis and the activity of photosynthetic carbon-assimilation-related enzymes and associated gene expression, thereby improving fruit yields and quality. These results provide a foundation for the CO₂ enrichment of oriental melon cultivated in solar greenhouses in autumn/winter and winter/spring. Full article