Watermelon Genotypes Research Articles

Molecular, morphological and phytochemical characterization of some watermelon (Citrullus lanatus L.) genotypes

Molecular, morphological and phytochemical characterization of some watermelon (Citrullus lanatus L.) genotypes

Assessment of Different Cucurbit Genotypes for Resistance to Zucchini Yellow Mosaic Virus (ZYMV)

Members of the Cucurbitaceae family, which includes species with quite different characteristics, have been used for food, medicine, and ornamental purposes for a long time. However, most plant diseases and pests cause yield and quality losses in cucurbits, and one of the most important of these diseases is zucchini yellow mosaic virus (ZYMV), which one of the most common potyviruses worldwide and causes serious yield losses in cucurbit production worldwide. Zucchini Yellow Mosaic Virus shows symptoms such as yellowing, mottling, curling, deformation, mosaic, shortening and thickening of the internodes, and may also cause loss of yield and quality. As widely known, there is no effective chemical control of viral diseases, and the use of resistant or tolerant varieties is the most effective solution. In this study, 92 watermelon genotypes, 14 zucchinis (pumpkin seeds) and 29 ornamental pumpkins collected from different parts of Türkiye were tested against ZYMV. Symptoms of ZYMV in different watermelon genotypes and pumpkins were observed for 21 days. Genotypes showing systemic infection after inoculation were evaluated on a scale of 0-5. Also, RT-PCR studies were carried out on selecting nine symptomless control plants, seven ZYMV-sensitive genotypes showing 5-scale value, one genotype with 1-scale value considered tolerant, and one genotype belongs to C. lanatus var. citroides. According to the results, it was determined that some watermelon and ornamental pumpkin genotypes could be considered as tolerant. Watermelon, which was having accession number PI560016, was found resistant to Turkish local strain of ZYMV. Although different susceptibility levels were detected between watermelon genotypes, all pumpkin genotypes were discovered to be susceptible to the Turkish local strain of ZYMV.

Morphological characterization of some local watermelon (Citrullus lanatus L.) genotypes of Turkey

The scope of this study, some of the local Turkish watermelon genotypes were evaluated morphologically. A total of 20 local genotypes and three commercial varieties were assessed regarding their cotyledon, leaf, fruit, and seed phenotypes. An extensive morphological analysis was performed on a diverse set of genotypes. Traits such as cotyledon shape and color intensity, leaf size and lobing, and fruit size, shape, and color were measured and compared. Hierarchical clustering analysis, correlation matrices, and principal component analysis were employed to interpret the data. The study revealed significant morphological variability among the watermelon genotypes. Cotyledons ranged from narrow to broad, with a predominance of large sizes and dark green coloration. Leaf characteristics varied widely, with a notable distribution across different sizes and degrees of lobing. Fruit analysis showed a broad spectrum of shapes, sizes, and colors, indicating a rich genetic diversity. Two main genotype clusters were identified, suggesting a clear distinction based on morphological traits.

Determination of genetic diversity of edible-seeded watermelon genotypes using SRAP markers

The watermelon (Citrullus lanatus L.) is one of the most commonly grown and consumed vegetables in the world. Some genotypes of watermelon, which have significant variations, have a snack potential due to their seed characteristics. In this study, SRAP (Sequence Related Amplified Polymorphism) marker technique was used to determine the genetic relationship between some edible-seeded watermelon genotypes. A total of 166 bands were obtained in 24 genotypes and the polymorphism rate was calculated as 97.4%. Four main clusters were observed in the cluster analysis. It was determined that genotypes 2 and 7 clustered separately from the others. Structure analysis revealed that the genotypes consisted of two subpopulations. It was concluded that the edible-seeded watermelon genotypes can be genetically differentiated by the SRAP techniques. The results of this study can be used in breeding strategies for the improvement of the edible-seeded watermelon cultivars.

Morphological, Physiological, and Molecular Stomatal Responses in Local Watermelon Landraces as Drought Tolerance Mechanisms

Drought-tolerant plants have become a convenient model to study the mechanisms underlying drought tolerance in order to improve susceptible domesticated relatives. Various studies have shown that local landraces possess superior qualities that help them survive in harsh environmental conditions. One of the key mechanisms that helps with tolerance in crops is timely stomatal regulation. In this study, the physiological, morphological, and molecular stomatal responses in three drought-tolerant landraces (Clm-01–03) and hybrid (Clm-04) watermelons were evaluated under drought stress. The watermelon plants were grown under a water deficit (complete withholding of water) and non-stress conditions. The highest SPAD values were recorded for the Clm-03 and Clm-02 (50 ± 3) watermelon genotypes, and the lowest for Clm-04 (27 ± 0.37), showing this genotype’s tolerance and ability to maintain its systems during drought stress. Fluorescence parameters also gave important clues to the tolerant genotypes of Clm-02 and Clm-03 under drought stress, while the domesticated genotype showed a slow response to fluorescence parameters, which could lead to damage to the photosynthesis apparatus. During the drought period, the wild watermelon was found to have a limited stomatal opening as the drought progressed, and on day 9, it had the smallest opening of 23.1 ± 1.2 µm compared to any other genotype; most importantly, upon re-watering, it showed more rapid recovery than any other genotype. This was also expressed by mRNA quantification of stomatal aperture TFs, with an eight-fold increase in Cla004380 TFs recorded for wild watermelon. All of these mechanisms have been attributed to the tolerance mechanisms of the drought-tolerant watermelon genotype. This study provides important insight into the stomatal responses of probable tolerant watermelon accessions and suggests that improving the stomatal aperture of susceptible domesticated species would also improve their tolerance.

Some seed properties and molecular analysis with inter-primary binding site (iPBS) retrotranposons markers of edible-seeded watermelon genotypes

Some seed properties and molecular analysis with inter-primary binding site (iPBS) retrotranposons markers of edible-seeded watermelon genotypes

Comparative transcriptome analysis of resistant and susceptible watermelon genotypes reveals the role of RNAi, callose, proteinase, and cell wall in squash vein yellowing virus resistance.

Watermelon (Citrullus lanatus) is the third largest fruit crop in the world in term of production. However, it is susceptible to several viruses. Watermelon vine decline (WVD), caused by whitefly-transmitted squash vein yellowing virus (SqVYV), is a disease that has caused over $60 million in losses in the US and continues to occur regularly in southeastern states. Understanding the molecular mechanisms underlying resistance to SqVYV is important for effective disease management. A time-course transcriptomic analysis was conducted on resistant (392291-VDR) and susceptible (Crimson Sweet) watermelon genotypes inoculated with SqVYV. Significantly higher levels of SqVYV were observed over time in the susceptible compared to the resistant genotype. The plasmodesmata callose binding protein (PDCB) gene, which is responsible for increased callose deposition in the plasmodesmata, was more highly expressed in the resistant genotype than in the susceptible genotype before and after inoculation, suggesting the inhibition of cell-to-cell movement of SqVYV. The potential role of the RNA interference (RNAi) pathway was observed in the resistant genotype based on differential expression of eukaryotic initiation factor (eIF), translin, DICER, ribosome inactivating proteins, RNA-dependent RNA polymerase (RDR), and Argonaute (AGO) genes after inoculation. The significant differential expression of hormone-related genes, including those involved in the ethylene, jasmonic acid, auxin, cytokinin, gibberellin, and salicylic acid signaling pathways, was observed, emphasizing their regulatory roles in the defense response. Genes regulating pectin metabolism, cellulose synthesis, cell growth and development, xenobiotic metabolism, and lignin biosynthesis were overexpressed in the susceptible genotype, suggesting that alterations in cell wall integrity and growth processes result in disease symptom development. These findings will be helpful for further functional studies and the development of SqVYV-resistant watermelon cultivars.

Integrated Bulk Segregant Analysis, Fine Mapping, and Transcriptome Revealed QTLs and Candidate Genes Associated with Drought Adaptation in Wild Watermelon.

Drought stress has detrimental effects on crop productivity worldwide. A strong root system is crucial for maintaining water and nutrients uptake under drought stress. Wild watermelons possess resilient roots with excellent drought adaptability. However, the genetic factors controlling this trait remain uninvestigated. In this study, we conducted a bulk segregant analysis (BSA) on an F2 population consisting of two watermelon genotypes, wild and domesticated, which differ in their lateral root development under drought conditions. We identified two quantitative trait loci (qNLR_Dr. Chr01 and qNLR_Dr. Chr02) associated with the lateral root response to drought. Furthermore, we determined that a small region (0.93 Mb in qNLR_Dr. Chr01) is closely linked to drought adaptation through quantitative trait loci (QTL) validation and fine mapping. Transcriptome analysis of the parent roots under drought stress revealed unique effects on numerous genes in the sensitive genotype but not in the tolerant genotype. By integrating BSA, fine mapping, and the transcriptome, we identified six genes, namely L-Ascorbate Oxidase (AO), Cellulose Synthase-Interactive Protein 1 (CSI1), Late Embryogenesis Abundant Protein (LEA), Zinc-Finger Homeodomain Protein 2 (ZHD2), Pericycle Factor Type-A 5 (PFA5), and bZIP transcription factor 53-like (bZIP53-like), that might be involved in the drought adaptation. Our findings provide valuable QTLs and genes for marker-assisted selection in improving water-use efficiency and drought tolerance in watermelon. They also lay the groundwork for the genetic manipulation of drought-adapting genes in watermelon and other Cucurbitacea species.

Functional Quality and Radical Scavenging Activity of Selected Watermelon (Citrullus lanatus (Thunb.) Mansfeld) Genotypes as Affected by Early and Full Cropping Seasons.

Growing conditions and seasonal fluctuations are critical factors affecting fruit and vegetable nutritional quality. The effects of two partially overlapping cropping seasons, early (ECS; January-May) and full (FCS; March-July), on the main carpometric traits and bioactive components of different watermelon fruits were investigated in the open field. Four watermelon genotypes, comprising of three commercial cultivars 'Crimson Sweet', 'Dumara', 'Giza', and the novel hybrid 'P503 F1', were compared. The carpometric traits varied significantly between genotypes. Soluble solids and yield were higher under FCS than ECS. The variation affecting colour indexes between the two growing seasons exhibited a genotype-dependent trend. The antioxidant components and radical scavenging activity of watermelon fruits were also significantly affected by differences in received solar energy and temperature fluctuations during the trial period. The average citrulline, total phenolics and flavonoid contents were 93%, 71% and 40% higher in FCS than in ECS. A genotype-dependent variation trend was also observed for lycopene and total vitamin C between cropping seasons. The hydrophilic and lipophilic radical scavenging activities of the pulp of ripe watermelon fruits of the different genotypes investigated varied between 243.16 and 425.31 µmol Trolox Equivalent (TE) of 100 g-1 of fresh weight (fw) and from 232.71 to 341.67 µmol TE of 100 g-1 fw in FCS and ECS, respectively. Our results, although preliminary, show that the functional quality of watermelon fruits is drastically altered depending on the environmental conditions that characterize the ECS and LCS.

Creation of a watermelon haploid inducer line via ClDMP3-mediated single fertilization of the central cell.

The use of doubled haploids is one of the most efficient breeding methods in modern agriculture. Irradiation of pollen grains has been shown to induce haploids in cucurbit crops, possibly because it causes preferential fertilization of the central cell over the egg cell. Disruption of the DMP gene is known to induce single fertilization of the central cell, which can lead to the formation of haploids. In the present study, a detailed method of creating a watermelon haploid inducer line via ClDMP3 mutation is described. The cldmp3 mutant induced haploids in multiple watermelon genotypes at rates of up to 1.12%. These haploids were confirmed via fluorescent markers, flow cytometry, molecular markers, and immuno-staining. The haploid inducer created by this method has the potential to greatly advance watermelon breeding in the future.

Identification of the egusi seed trait locus (eg) and its suppressor gene associated with the thin seed coat trait in watermelon.

Egusi watermelon has a unique egusi seed type, which could be useful for breeding both edible seeds and edible flesh in watermelon. However, the genetic basis of the unique egusi seed type is not clear. In the present study, we first reported that at least two genes with inhibitory epistasis were responsible for the thin seed coat (unique egusi seed type) in watermelon. Inheritance analysis of five populations, including F2, BC, and BCF2, suggested that the thin seed coat trait was controlled by a suppressor gene together with the egusi seed locus (eg) in egusi watermelon. Based on high-throughput sequencing technology, two quantitative trait loci located on chromosome 1 and chromosome 6 were identified for the thin seed coat trait in watermelon. One of the loci, the eg locus on chromosome 6, was finely mapped to a genomic region of 15.7 kb, which contained only one candidate gene. Comparative transcriptome analysis highlighted differentially expressed genes involved in cellulose and lignin synthesis between watermelon genotypes varying in the thickness of the seed coat and provided several potential candidate genes for the thin seed coat trait. Taken together, our data suggest that at least two genes are complementarily involved in the thin seed coat trait and will be useful for cloning novel genes. The results presented here provide a new reference for uncovering egusi seed genetic mechanisms and valuable information for marker-assisted selection in seed coat breeding.

Evaluation of rootstocks resistant to gummy stem blight and their effect on the fruit yield and quality traits of grafted watermelon (Citrullus lanatus (Thunb.) Matsum. & Nakai)

ABSTRACT Three gummy stem blight (GSB) resistant watermelon (Citrullus lanatus var. citroides) genotypes (IIHR-82, IIHR-617 and BIL-53), two resistant bottle gourd (Lagenaria siceraria) genotypes (BG-95, BG-77-6-1) and three hybrid combinations based on watermelon genotypes (IIHR-617 × Arka Manik, IIHR-82 × Arka Manik and IIHR-82 × IIHR-617) were evaluated as rootstocks for yield, quality and GSB incidence in a sick plot during spring 2019, spring 2020 and spring 2021 at Indian Institute of Horticultural Research, Bangalore. The commercial watermelon hybrid NS-295 was used as a scion for grafting onto these rootstocks. Significant differences were observed among the grafted entries and checks in terms of disease incidence (PDI). Among agronomic traits, grafting significantly affected plant growth, earliness and yield in a desirable direction. The grafted scion onto the hybrid rootstocks and BG-95 could maintain its oblong fruit shape compared to those onto IIHR-82 and BIL-53, whereas BG-77-6-1 produced spherical fruits. Quality traits showed an improvement in terms of total soluble solids (TSS), flesh colour, total carotenoids and lycopene content among the grafted entries as compared to non-grafted controls. Overall, the use of hybrid rootstocks i.e. IIHR-82 × IIHR-617 and IIHR-82 × Arka Manik was found to be advantageous in managing GSB apart from imparting desirable agronomic and fruit quality traits.

Evaluation of Watermelon (Citrullus lanatus) Genotypes for Growth, Yield and Quality

Evaluation of Watermelon (Citrullus lanatus) Genotypes for Growth, Yield and Quality

Performance study of some cooking type watermelon genotypes

Performance study of some cooking type watermelon genotypes

Osmotic adjustment, production, and post-harvest quality of mini watermelon genotypes differing in salt tolerance

The mini watermelon is a crop with high yield potential in the Brazilian semiarid region; however, some problems, such as the salinity of irrigation water, can cause physiological and biochemical changes in the species, compromising production and post-harvest quality of the fruits. In the present study, two genotypes of mini watermelon (Citrullus lanatus L.) cultivated in a hydroponic system were evaluated for the effects of nutrient solution salinity on yield, fruit quality, and solutes content. The experimental design used was completely randomized, in a factorial scheme (5 × 2), with four replicates, each consisting of three plants. The mini watermelon genotypes ‘Champagne’ (CP) and ‘Fancy’ (FY) were cultivated in nutrient solutions with different electrical conductivity levels - ECsol (2.5 - control, 3.5, 4.5, 5.5, and 6.5 dS m−1). Production components, post-harvest variables of fruit quality and the contents of organic and inorganic solutes were evaluated. The increase in ECsol reduced the production variables, with the emphasis on the CP genotype, which stood out for comparatively mall production losses (45% - fruit mass); being considered tolerant to salt stress when compared to FY (57% - fruit mass). Fruit production showed a linear decrease, with a salinity threshold at 2.5 dS m−1 in both genotypes. The salinity increased the contents of total soluble solids (TSS) in both genotypes: for 9.5 to 10.6 °Brix (11.6%) in the CP genotype and from 9.7 to 12.1° Brix (24.7%) in the FY. Contents of organic and inorganic solutes, except proline, can act as indicator for the selection of salinity-tolerant mini watermelon genotypes. Despite the changes induced by salt stress in the physicochemical characteristics, the fruits remained within acceptable commercial standards for both genotypes. The FY genotype, though salt-sensitive is more suitable for hydroponic cultivation up to ECsol of 4.5 dS m−1, and both the genotypes can be used in systems up to with ECsol 6.5 dS m−1.

Phenotypic Variability of Root System Architecture Traits for Drought Tolerance among Accessions of Citron Watermelon (Citrullus lanatus var. citroides (L.H. Bailey).

Citron watermelon (Citrullus lanatus var. citroides) is a drought-tolerant cucurbit crop widely grown in sub-Saharan Africa in arid and semi-arid environments. The species is a C3 xerophyte used for multiple purposes, including intercropping with maize, and has a deep taproot system. The deep taproot system plays a key role in the species’ adaptation to dry conditions. Understanding the root system development of this crop could be useful to identify traits for breeding water-use efficient and drought-tolerant varieties. This study compared the root system architecture of citron watermelon accessions under water-stress conditions. Nine selected and drought-tolerant citron watermelon accessions were grown under non-stress (NS) and water stress (WS) conditions using the root rhizotron procedure in a glasshouse. The following root system architecture (RSA) traits were measured: root system width (RSW), root system depth (RSD), convex hull area (CHA), total root length (TRL), root branch count (RBC), total root volume (TRV), leaf area (LA), leaf number (LN), first seminal root length (FSRL), seminal root angle (SRA), root dry mass (RDM), shoot dry mass (SDM), root–shoot mass ratio (RSM), root mass ratio (RMR), shoot mass ratio (SMR) and root tissue density (RTD). The data collected on RSA traits were subjected to an analysis of variance (ANOVA), correlation and principal component analyses. ANOVA revealed a significant (p < 0.05) accession × water stress interaction effect for studied RSA traits. Under WS, RDM exhibited significant and positive correlations with RSM (r = 0.65), RMR (r = 0.66), RSD (r = 0.66), TRL (r = 0.60), RBC (r = 0.72), FSRL (r = 0.73) and LN (r = 0.70). The principal component analysis revealed high loading scores for the following RSA traits: RSW (0.89), RSD (0.97), TRL (0.99), TRV (0.90), TRL (0.99), RMR (0.96) and RDM (0.76). In conclusion, the study has shown that the identified RSA traits could be useful in crop improvement programmes for citron watermelon genotypes with enhanced drought adaptation for improved yield performance under drought-prone environments.

Effect of The Storage Period on the Antioxidant Properties of Different Watermelon Cultivars Grown in Tunisia

Postharvest storage conditions frequently affect nutritional quality of fruits and vegetables. Temperature and storage duration are the most important factors to extend shelf life and maintain quality of fresh watermelon. This study was conducted to determine the changes in the antioxidant properties of watermelon during storage. Fruits of the watermelon cultivars were harvested and stored at 5ºC for a period of 15 days. During storage antioxidant contents (lycopene and total phenolics) and total antioxidant activity were evaluated. The objective of this work was to determine the content of the antioxidant properties in different watermelon genotypes at four different postharvest storage periods (0, 5, 10 and 15 days). Furthermore, the nutritional quality is strongly influenced by the storage period. The cv Mahdia was the most suitable for extended storage periods.

Genetic Diversity Analysis by D2 Clustering for Mineral Nutrient Composition of Watermelon Genotypes (Citrullus sp.)

Background: Watermelon is an important cucurbit with rich genetic diversity. A great proportion of this diversity remains largely unexploited in terms of mineral nutrient composition. Methods: The contents of eight different mineral nutrients were determined in eighty diverse genotypes. D2 statistics and principal component analysis were used to cluster genotypes and understand the underlying variations in mineral nutrient compositions of watermelon genotypes. Result: Large variations in the content of many mineral contents such as Na, K and Zn were recorded. D2 analysis placed the eighty watermelon genotypes into 8 distinct clusters. Cluster I comprised of maximum number of genotypes (68) followed by Cluster II (6). All other 6 clusters consisted of 1 genotype each. Among 8 clusters, cluster II showed highest intra cluster distance (342.14) followed by cluster I (279.07), whereas minimum intra cluster distance recorded in cluster III, cluster IV, cluster V, cluster VI, cluster VII and cluster VIII (0.00). Based on inter-cluster distance the maximum diversity was observed between clusters VIII and VI (3234.85). D2 statistics showed that potassium content contributed highest (25%) to divergence followed by magnesium content (22.7%) and manganese content (11%). Principal component analysis revealed that the first two principal components (PCs) together controlled 52.92% of total variability. Based on higher genetic distance among clusters and higher mean value of genotypes for nutritional traits, DWM 164, DWM 129, DWM 165, DWM 115, DWM 142, DWM 117, DWM 45, DWM 196 and DWM 12 could be exploited in breeding programme as potential donors for developing nutrient- rich watermelon varieties/hybrids.

Genetic analysis of yield related traits in landrace × commercial watermelon hybrids

Watermelon [Citrullus lanatus var lanatus L.] is a major xerophytic crop originating in Africa especially grown in subtropical and tropical parts of the world. However, few adapted varieties are available to promote greater yield and make watermelon a viable commercial crop of choice. Path analysis and combining ability was carried out for yield related traits among three popular local landraces; Landrace1, Landrace 2 and Landrace 3 collected in Zimbabwe and three commercial watermelon varieties ‘Congo’, ‘Charleston Grey’ and ‘Crimson Sweet’ in plots arranged in an RCBD replicated 3 times. A complete diallel mating design was used to generate 36 F1 genotypes which together with the parents were evaluated for several quantitate traits. Data on correlations, path analysis, GCA and SCA between fruit yield and other traits were computed using Microsoft Excel and GenStat 17. Individual fruit weight (FIW) and the number of fruits per plant (NF) were found to be significantly linked with final fruit yield. Significant positive correlations were also observed on NF and number of female flowers (NFF), number of vines (NV), and FIW and these traits could be recommended as reliable selection indicators for creating high yielding watermelon genotypes. Path analysis showed that FIW and NF were the most important contributors to watermelon yield. GCA and SCA effects were significant and positive for yield which indicates that the traits are controlled by both additive and non-additive genes. ‘Crimson Sweet’ and ‘Landrace 1’ were the best pollen sources whereas ‘Landrace 1’ and ‘Landrace 2’ were the highest yielders when used as female parents. Overall, results from this study identified usable yield related proxies and need to incorporate local landraces germplasm in watermelon improvement.

Microsatellite analysis in some watermelon (Citrullus lanatus) genotypes

Conservation of genetic resources is essential for the continuation of future crop production. Watermelon (Citrul-lus lanatus), a member of Cucurbitaceae, is widely distributed in tropical and subtropical regions. The aim of this study was to reveal the genetic relationships with the help of microsatellite markers in a watermelon collection free of unnecessary repetitions, and to determine the success of SSR (Simple Sequence Repeats) primers developed in cucurbits. In this study, 96 watermelon genotypes with good agronomic characteristics were used among the geno types collected from different regions of Turkey and purified up to the S4-S6 (self-pollination) stage. In the study, 33 SSR primer pairs were used to determine the genetic relationship between watermelon genotypes. In the study, a total of 67 bands were obtained with SSR primers. As a result of UPGMA (Unweighted Pair Group Method Using Arithmetic Averages) analysis, genotypes showed similarity at the level of 0.84-1.00. The number of alleles detected per primer varied between 1 and 6. In terms of the total number of alleles obtained, CMCT44 (5 units) and Cgb4767 (6 units) loci produced the most alleles. Primers with high polymorphism rate and allele excess were determined, and the possibilities for use in genetic stability analyses, variety differentiation and other genetic analyses were determined.