Citron Watermelon Research Articles

Morphophysiological and biochemical investigation of the potential of citron watermelon (Citrullus lanatus var. citroides) rootstock under different irrigation regimes

Morphophysiological and biochemical investigation of the potential of citron watermelon (Citrullus lanatus var. citroides) rootstock under different irrigation regimes

Phenotypic Characterization of Citron Watermelon (Citrullus lanatus var. citroides) Genotypes for Bioenergy Production

Citron watermelon (Citrullus lanatus var. citroides) is an important climate smart crop, characterized by high oil content in the seeds and it is a popular fruit in southern Africa. To determine best performing genotypes eight phenotypic traits were assessed to identify cultivars with potential for biodiesel production. A field experiment was conducted at Sebele Agricultural Research Station, in Southern Botswana, during 2019 to 2020 cropping season. Four (4) melon genotypes were planted in a Randomized Complete Block Design replicated three times and eight (8) characters were assessed. Except seed oil content (26.6%) there was significant (P < 0.05) difference among all the traits, an indication of higher genetic diversity in the selected citron watermelon. SC1-Sesoswane, exhibited highest seed yield (1540 kg/ha) and oil yield (435.03 kg/ha) while MMB-280-Lerotse recorded lowest seed yield and oil yield of 548.1 kg/ha and 144 kg/ha respectively. There was a significant correlation of (0.9) between oil yield (kg/ha), number of fruits produced, and seed yield (kg/ha), an indication that increasing the seed yield will positively increase the amount of oil produced. This study revealed the potential bioenergy production of the four cultivars. However, SC1-Sesoswane appears a more promising alternative cultivar for feedstock for biodiesel production.

Mapping the genetic architecture of low-temperature stress tolerance in citron watermelon.

Sweet-fleshed watermelon (Citrullus lanatus) is an important vegetable crop of the tropical origin. It is widely grown and consumed around the world for its hydration and nutritional quality values. Low-temperature stress can affect early planting, seedling establishment, and expansion of crop production to new areas. A collection of 122 citron watermelon (Citrullus amarus) accessions were obtained from the USDA's National Plant Germplasm Repository System gene bank in Griffin, GA. The accessions were genotyped using whole genome resequencing to generate single nucleotide polymorphisms (SNPs) molecular markers and screened under cold-stressed and non-stressed control conditions. Four low-temperature stress tolerance related traits including shoot biomass, vine length, maximum quantum efficiency of photosystem II, and chlorophyll content were measured under cold-stressed and non-stressed control treatment conditions. Correlation analysis revealed the presence of positive relationships among traits. Broad-sense heritability for all traits ranged from 0.35 to 0.73, implying the presence of genetic contributions to the observed phenotypic variation. Genomic regions underlying these traits across several citron watermelon chromosomes were identified. Four low-temperature stress tolerance related putative candidate genes co-located with the peak SNPs from genome-wide association study. These genomic regions and marker information could potentially be used in molecular breeding to accelerate genetic improvements for low-temperature stress tolerance in watermelon.

Genetic control of flowering time and fruit yield in citron watermelon.

Flowering time and fruit yield are important traits in watermelon crop improvement. There is limited information on the inheritance and genomic loci underlying flowering time and yield performance, especially in citron watermelon. A total of 125 citron watermelon accessions were evaluated in field trials over two growing seasons for days to male and female flowers, fruit count, fruit weight, and fruit yield. The germplasm was genotyped with more than two million single-nucleotide polymorphism (SNP) markers generated via whole-genome resequencing. Trait mapping was conducted using a genome-wide association study (GWAS). Broad-sense heritability for all traits ranged from moderate to high, indicating that genetic improvement through breeding and selection is feasible. Significant marker-trait associations were uncovered for days to female flower (chromosomes Ca04, Ca05, Ca08, and Ca09), fruit count (on Ca02, Ca03, and Ca05), fruit weight (on Ca02, Ca06, Ca08, Ca10, and Ca11), and fruit yield on chromosomes Ca05, Ca07, and Ca09. The phenotypic variation explained by the significant SNPs ranged from 1.6 to 25.4, highlighting the complex genetic architecture of the evaluated traits. Candidate genes relevant to flowering time and fruit yield component traits were uncovered on chromosomes Ca02, Ca04, Ca05, Ca06, Ca09, and Ca11. These results lay a foundation for marker-assisted trait introgression of flowering time and fruit yield component traits in watermelons.

Genome-wide association study of soluble solids content, flesh color, and fruit shape in citron watermelon.

Fruit quality traits are crucial determinants of consumers' willingness to purchase watermelon produce, making them major goals for breeding programs. There is limited information on the genetic underpinnings of fruit quality traits in watermelon. A total of 125 citron watermelon (Citrullus amarus) accessions were genotyped using single nucleotide polymorphisms (SNPs) molecular markers generated via whole-genome resequencing. A total of 2,126,759 genome-wide SNP markers were used to uncover marker-trait associations using single and multi-locus GWAS models. High broad-sense heritability for fruit quality traits was detected. Correlation analysis among traits revealed positive relationships, with the exception of fruit diameter and fruit shape index (ratio of fruit length to fruit diameter), which was negative. A total of 37 significant SNP markers associated with soluble solids content, flesh color, fruit length, fruit diameter, and fruit shape index traits were uncovered. These peak SNPs accounted for 2.1%-23.4% of the phenotypic variation explained showing the quantitative inheritance nature of the evaluated traits. Candidate genes relevant to fruit quality traits were uncovered on chromosomes Ca01, Ca03, Ca06, and Ca07. These significant molecular markers and candidate genes will be useful in marker-assisted breeding of fruit quality traits in watermelon.

Determination of the Microspore Development Concerning Floral Morphology for Improving Drought Tolerant Citron Watermelon (Citrullus lanatus var. citroides) Rootstocks Via Androgenesis.

The negative effects of abiotic stress factors (especially drought and salinity) that arise due to global climate change are increasing in today’s agricultural production. To eliminate the negative effects of these stress factors, some cultural practices have been implemented such as the breeding of tolerant cultivars and rootstock, exogenous applications of PGPR, AMF, and chemical substances, etc. Contrary to exogenous applications, providing tolerance with breeding methods has an important role in efficient and sustainable agriculture. Androgenesis is a phenomenon for the induction and development of microspore-derived pure lines, as initial material for F1 cultivar breeding, in different vegetable crops. Success in microspore embryogenesis is considerably related to the culture of microspores at an appropriate developmental stage. There is no standard protocol for the anther culture in citron watermelon (Citrullus lanatus var. citroides). Thus, a relation between floral morphology (bud length and width, bud index, sepal position, petal color), and microspore development (microspore diameter, uninucleated and binucleated phases) was investigated in citron. The male flower buds were collected at different sizes and microspore development was observed in both light and fluorescence microscopy. A strong positive relationship was detected between flower bud morphology and the specific stages of microspore development. To the author’s knowledge, this is the first report to indicate that the microspore developmental stage can be estimated by flower bud morphology, and applied in the anther/microspore culture of citron watermelon.

Phytochemical analysis and antibacterial activity of Citrullus lanatus var. citroides (Citron watermelon) fruit and the effect of temperature on the biological activity of the rind

The use of indigenous plants for food, water and medicinal purposes dates back to decades of years. In southern Africa the fruit flesh and rind of Citrullus lanatus var. citroides are cooked as porridge with maize meal and served to sick people by traditional healers. The seeds are dried, roasted and eaten as nuts or ground into flour to make bread. The aim of this study was to determine the biological activities of the seed and flesh of Citrullus lanatus var. citroides fruit and evaluate the effect of temperature on rind bioactivity. The rind was exposed to various temperatures. Total phenolics, tannins, flavonoids, nutritional content and antioxidant activity were estimated using spectrometric methods. Antibacterial activity was determined using micro-broth dilution and bioautography. Total polyphenolic contents were greatest in the seeds, followed by the flesh and rind respectively. Potassium was the most abundant element present in the flesh, seeds and untreated rind control. The flesh had higher antioxidant activity than the rind and seeds. Pseudomonas aeruginosa was the most susceptible pathogen for both the seeds and flesh where minimum inhibitory concentrations between 0.02–0.31 mg/mL were determined. High temperatures led to a significant loss in rind bioactivity. Lower temperatures must be considered when preparing C. lanatus var. citroides products to preserve the potential therapeutic properties which supplement its nutritional content.

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.

Citrullus lanatus natural product library: A hoard of viable potential inhibitor candidates for diabetes mellitus type II therapeutic target enzymes

The ethnomedicinal function of several cucurbit species (cucumber, squash, melon, gourd, etc.) on diseases (i.e. diabetes, microbial infections, cancer, etc.), and as free radical scavengers have been reported. However, there remains infinitesimal record on citron watermelon broad use, which reflects the reason for wide oversight of underutilization, from lack of recognition for functional food crop development and commercialization. The objective of this study focus towards identifying the natural phytochemicals of C. lanatus on water melon molecules online database for insilico computational approach to screened for suitable antidiabetic lead, and construction of phylogenetic relatedness of target Type 2 Diabetes Mellitus proteins was conducted to predict reoccurrence of insilico analysis output with other homologous target proteins. The T2DM protein targets, phytochemical and standard inhibitory drugs are mined from different databases. Insilico docking analysis, and adme/toxicity profiling was virtually screened for the best fit. In additionally, phylogenetic relationship of the target proteins was aligned and construction with other homologous protein targets to predict the reoccurrence confidence of results on compounds. Seventeen phytochemicals out of the nineteen potential drug candidates substantially passed the profiling test. Also, homologous protein targets with &gt; 90% bootstrap confidence are likely to produce a reoccurring insilico result. Thus, these phytochemicals fulfil all the enlisted criteria and it is suggestively determined to be suitable for the development of potent antidiabetic drugs. It is evident that phytochemicals from Citrullus lanatus produced satisfactory insilico output, and this reflect it to be a probable reservoir containing other potential therapeutic drug candidates for antidiabetic drug discovery and development. Additionally, derivatives can be developed for further effective screening result.

Characterization of genetic diversity of citron watermelon landrace accessions of South Africa through simple sequence repeat markers

ABSTRACT Profiling the genetic diversity of germplasm collections is fundamental for selection programs and strategic conservation. Citron watermelon (Citrullus lanatus var. citroides [L.H. Bailey] Mansf. ex Greb.) is an under-researched cucurbit crop despite providing food and nutritional security in sub-Saharan Africa. There is limited information on genetic relationships of South African citron watermelon accessions for effective breeding. The objective of this study was to determine the extent of genetic diversity among 48 South African citron watermelon landrace accessions using selected simple sequence repeat (SSR) markers to identify genetically divergent accessions for trait integration and variety development. The SSR markers amplified a total of 24 alleles, with a mean expected heterozygosity value of 0.38, indicating moderate genetic diversity among the studied accessions. The mean polymorphic information content value of 0.21 indicated low discriminatory power of the SSR markers. Analysis of molecular variance attributed 8%, 75%, and 17% of the molecular variation between populations, among accessions and within accessions, respectively. Three distinctive genetic groups were identified based on cluster analysis, which aided the selection of genetically diverse citron watermelon accessions for breeding and cultivar development.

Drought tolerance assessment of citron watermelon (Citrullus lanatus var. citroides (L.H. Bailey) Mansf. ex Greb.) accessions based on morphological and physiological traits

Long-term cultivation of citron watermelon under water-constrained environments in sub-Saharan Africa resulted in the selection and domestication of highly tolerant genotypes. However, information on the magnitude of variation for drought tolerance in citron watermelon is limited for the effective selection of suitable genotypes for breeding. The objective of this study was to determine variation for drought tolerance among South African citron watermelon landrace accessions for selection and use as genetic stock for drought-tolerance breeding in this crop and closely-related cucurbit crops. Forty genetically differentiated citron watermelon accessions were grown under non-stress (NS) and drought-stress (DS) conditions under glasshouse environment. Data of physiological (i.e., leaf gas exchange and chlorophyll fluorescence parameters) and morphological traits (i.e., shoot and root system architecture traits, and fruit yield) were collected and subjected to various parametric statistical analyses. The accessions varied significantly for assessed traits under both NS and DS conditions which aided classification into five groups, namely; A (highly drought-tolerant), B (drought-tolerant), C (moderate drought-tolerant), D (drought-sensitive) and E (highly drought-sensitive). Drought-tolerant genotypes produced more fruit yield with less water compared with drought-sensitive genotypes. Several physiological and morphological parameters correlated with fruit yield under DS condition namely: instantaneous water-use efficiency (r = 0.97), leaf dry weight (r = 0.77), total root length (r = 0.46) and root dry weight (r = 0.48). The following accessions, namely: WWM-46, WWM-68, WWM-41(A), WWM-15, WWM-64, WWM-57, WWM-47, WWM-37(2), WWM-79, WWM-05 and WWM-50) were identified as highly drought-tolerant and recommended for drought-tolerance breeding in this crop or related cucurbit crops such as sweet dessert watermelon.

Nutrient composition and physical properties of citron watermelon (Citrullus lanatus var. citroides (L.H. Bailey) Mansf. ex Greb.) seeds are related to seed coat visual appearance

Roasted citron watermelon seeds are eaten as snacks based on maturity indices. Association between coat colour, nutrient composition and physical properties is unknown. Therefore, seed coat thickness (SCT), hardness and popping yield (PY) may influence roasting quality and chewability. Understanding seed nutrient composition, physical properties, and coat colour associations allows selection for desirable traits. Forty accessions were analysed for mineral elements using flame atomic emission spectrometry (FAES) for K and flame atomic absorption spectrometry (FAAS) for Mg, Cu, Mn, and Zn. Physical properties such as (seed thickness (ST), weight required to crack seed (WRCS), SCT, and PY were analysed. Data was subjected to correlation and Principal Component Analysis. Significant differences were observed for mineral elements and physical properties (P < 0.05). Dark and red seeds had high ST and SCT but low WRCS, Cu and Zn compared to brown seeds. Significantly lower PY and high Ca content were recorded for dark seeds. Dark seeds had high hemicellulose (19.58%), cellulose (39.17%) and lignin (30.08%). Popping yield was positively correlated with lightness (r = 0.72; P < 0.001) and negatively correlated with Ca (r = -0.77; P < 0.001). Seeds with lighter colours had higher popping yield and less Ca, implying that coat colour influences palatability, nutrient composition and physical properties. Study findings will guide breeding strategies to enhance the nutritive value of seeds.

Mathematical modeling and thermodynamic properties in the drying of citron watermelon seeds

ABSTRACT Citron watermelon is an agricultural product of excellent economic potential. Its seeds are widely used for oil extraction, serving as an energy source, showing nutritional characteristics that make them a suitable product to be studied. Thus, the objective was to characterize citron watermelon seeds regarding their physicochemical composition, in addition to determining drying kinetics, fitting mathematical models to the data, and determining the effective diffusivity coefficients and thermodynamic properties. The seeds were dried in a convective dryer, varying the drying temperature, with air velocity of 1.0 m s-1. With the increase in drying temperature, there were reductions in moisture content, water activity (aw), ash concentration, total titratable acidity, lipids and reducing sugar. Citron watermelon seeds are rich in lipids and ash, have low sugar concentration and low acidity; their drying kinetics was very well described by the Two Terms and Approximation of Diffusion models, followed by the models of Midilli and Page, which resulted in acceptable fits. Effective diffusivity accompanied the increase in drying temperature, and this behavior was well fitted by an Arrhenius-type equation. Enthalpy and entropy variations were reduced with drying temperature, with increments in Gibbs free energy.

Genetic resources of bottle gourd (Lagenaria siceraria (Molina) Standl.] and citron watermelon (Citrullus lanatus var. citroides (L.H. Bailey) Mansf. ex Greb.)- implications for genetic improvement, product development and commercialization: A review

Bottle gourd (Lagenaria siceraria (Molina) Standl.] and citron watermelon (Citrullus lanatus var. citroides (L.H. Bailey) Mansf. ex Greb.) are amongst the widely grown yet under-researched cucurbits genetic resources in sub-Saharan Africa (SSA). Fresh immature leaves, fruit and seed are used for food and medicinal purposes in the region. Furthermore, both species are used as rootstock and donors of novel genes for commercial production and breeding of sweet dessert watermelon cultivars. Despite their economic value and contribution to food and nutrition security in the region, bottle gourd and citron watermelon genetic resources remain under-utilized and largely un-explored for commercial product development. The objective of this review was to document the unique values of bottle gourd and citron watermelon for genetic improvement and development of value-added food and non-food products, and to highlight regional and global efforts on conservation, production, processing, commercialization and various enterprise development of these important indigenous species. The review discussed on the value of both crops as a rootstock to improve fruit yield and quality of cultivated watermelon. This is followed by important summaries on phenotypic and genetic variation of bottle gourd and citron watermelon genetic resources and implications for new cultivar design. Finally, the review highlighted value-added non-food and food-based products developed based on indigenous knowledge systems in SSA and availability and access to genetic resources of bottle gourd and citron watermelon for breeding, product design and deployment.

Estimates of the variance components, heritability and genetic gains of phenotypic traits in citron watermelon (Citrullus lanatus var. citroides)

AbstractThe present study estimated variance components, heritability and genetic advance of phenotypic traits in citron watermelon to guide selection of superior genotypes for direct production and breeding. Thirty‐six citron watermelon landrace accessions were evaluated across two seasons using a 6 × 6 alpha lattice design with three replications. High broad‐sense heritability and genetic advance as per cent of the mean were recorded for fruit length at 83.86% and 4730.45%, seed length (77.73% and 1731.27%), hundred seed weight (73.73% and 4027.36%), fruit diameter (70.44% and 2949.64%) and fruit weight (70.39% and 8490.05%), respectively. Step‐wise regression analysis revealed marketable fruit yield (Myld) and total number of fruits per plant (TNFr) explained 89% (R2 = .89) of total variation for total fruit yield per plant (TFYld), whereas number of seed per fruit (NSPFr) and hundred seed weight (HSW) explained 92% (R2 = .92) of total variation for seed yield per fruit (SYPFr). Citron watermelon landrace accessions WWM03, WWM14, WWM16, WWM39, WWM65, WWM67 and WWM79 with high TFYld and SYPFr were selected for production or breeding.

Variation in South African citron watermelon (Citrullus lanatus var. citroides [L.H. Bailey] Mansf. ex Greb.) landraces assessed through qualitative and quantitative phenotypic traits

Citron watermelon [Citrullus lanatus var. citroides (L.H. Bailey) Mansf. ex Greb.] is an important genetic resource serving for food, feed, and breeding dessert watermelon (C. lanatus var. lanatus) and other cross-compatible species. Wide phenotypic variation exists among South African citron watermelon landraces which are yet to be systematicaly assessed for diverse uses and cultivar design. The objective of this study was to assess phenotypic diversity of citron watermelon landrace accessions of South Africa and to select desirable genotypes with suitable agronomic and horticultual traits for direct production, breeding and conservation. Thirty six citron watermelon landrace accessions were evaluated under field conditions in two seasons using a 6 × 6 alpha lattice design with three replicates. Data on key qualitative and quantitative traits were collected and subjected to non-parametric and parametric statistical analyses. The accessions showed wide phenotypic variation and unique traits for genetic improvement. Positive and significant correlations (p < 0.001) were recorded between total fruit yield per plant with plant height (r = 0.64), number of harvestable fruits (r = 0.70), number of marketable fruits (r = 0.73) and marketable fruit yield (r = 0.96). Seed yield per plant positively and significantly (p < 0.001) correlated with number of male flowers (r = 0.68), plant height (r = 0.61) and total fruit yield (r = 0.79). Prinicipal component analysis identified nine components which accounted for 86.38% of total variation amongst accessions for assessed phenotypic traits. Citron watermelon accessions WWM16, WWM67 and WWM79 were high-yielding suitable for fruit production for food or livestock feed. Accessions namely WWM03, WWM09, WWM16, WWM39, WM64 and WWM76 produced high fruit number and marketable fruit yield per plant which are recommended as parental genotypes for breeding. Furthermore, accessions WWM04, WWM15, WWM24, WWM28, WWM46, WWM66, WWM68, WWM76 and WWM79 were selected with higher seed production for the food or feed industry. The study recommends citron watermelon accessions such as WWM14, WWM16, WWM39, WWM41, WWM67 and WWM79 for use as leafy vegetables owing to their profuse branching ability and longer vine production. Whereas accessions including WWM03, WWM17, WWM35, WWM40, WWM50, WWM67, WWM79 and WWM85 are selected with larger fruit size. Accessions WWM05 and WWM09 are sour-flesh types which are suitable genetic stocks for breeding sweet-and-sour dessert watermelons. Orange-fleshed accessions such as WWM03, WWM04, WWM46, WWM64, WWM66 and WWM67 are recommended for fresh consumption, cooking, processing or variety design. Accessions WWM02, WWM03, WWM08, WWM14, WWM16, WWM23, WWM38, WWM40, WWM41 and WWM67 have red and white seed coat colour which are superior selections to prepare roasted citron watermelon seed snack.

Citron Watermelon Potential to Improve Crop Diversification and Reduce Negative Impacts of Climate Change

Citron watermelon (Citrullus lanatus var. citroides (L.H. Bailey) Mansf. ex Greb.) is an underexploited and under-researched crop species with the potential to contribute to crop diversification in Sub-Saharan Africa. The species is cultivated in the drier parts of Southern Africa, mainly by smallholder farmers who maintain a wide range of landrace varieties. Understanding the molecular and morpho-physiological basis for drought adaptation in citron watermelon under these dry environments can aid in the identification of suitable traits for drought-tolerance breeding and improve food system resilience among smallholder farmers, thus adding to crop diversification. This paper reviews the literature on drought adaptation of Citrullus lanatus spp. (C3 xerophytes), using the systematic review approach. The review discusses the potential role of citron watermelon in adding to crop diversification, alternative food uses, and potential by-products that can be processed from the crop, and it analyzes the role of Sub-Saharan African farmers play as key actors in conserving citron watermelon germplasm and biodiversity. Finally, the review provides a summary of significant findings and identifies critical knowledge gaps for further research.

How do rootstocks of citron watermelon (Citrullus lanatus var. citroides) affect the yield and quality of watermelon under deficit irrigation?

Deficit irrigation practices and utilization of rootstocks that are tolerant to water stress are critical strategies for the protection of water resources and sustainable irrigation management, especially in arid and semi-arid areas. Therefore, this study was carried out to investigate the yield and quality of watermelon grafted onto different rootstocks under deficit irrigation conditions during 2017 and 2018 in the Konya Plain of Turkey, where the semi-arid climate is prevalent. In this study, five different plant materials, such as citroides1 (A1), citroides2 (A2), gourd (A3), hybrid TZ148 (A4) rootstocks grafted with the Crimson Tide variety, and non-grafted Crimson Tide as control (K1), were used as the main-plots. Five different irrigation levels, calculated by taking into account the amounts of cumulative water (Ep) that evaporated at 7-day intervals from Class A Pan (I100 = 1.00Ep; I75 = 0.75Ep; I50 = 0.50Ep; I35 = 0.35Ep, and I0 = rain-fed), were used as the sub-plots.When the average of experimental years was considered, the highest rate of evapotranspiration (ET) was found in the plot A4I100 (615 mm). The highest fruit yield was obtained from the A4I100 (93.4 t/ha), and an increase in yield of up to 35 % was achieved in the A4I100, compared to non-grafted plants applied I100 irrigation level (K1I100). The analysis of data by both separate evaluation and principal component analysis (PCA) revealed that the yield values obtained from plants grafted onto A4, A1, and A2 rootstocks applied I75 irrigation level were higher than non-grafted plants applied I100 irrigation level. The water productivity (WP) and irrigation water productivity (IWP) ranged between 7.1–17.4 kg/m3 and 11.7–25.0 kg/m3, respectively, and a significant increase in the values of WP and IWP was achieved by grafting. This two-year study revealed that the performances of citron watermelon rootstocks were found close to the TZ148 rootstock in terms of fruit yield, certain yield components, WP, and IWP. Thus, it has also been demonstrated that the citron watermelons could be used commercially as watermelon rootstocks, and citron watermelon rootstocks could be used as watermelon rootstocks in breeding programs, in order to save water, especially in arid and semi-arid regions.

Rootstock effects on seed yield and quality in watermelon

This research was conducted to investigate rootstock effects on seed yield and quality in watermelon. The work was conducted in the experimental fields and laboratories of the Department of Horticulture of the University of Cukurova in the 2016 and 2017 growing seasons. Watermelon cv. Crimson sweet (CS) scion was grafted onto three different rootstocks (Cucurbita ‘NUN-9075’, Lagenaria ‘Argentario’, and citron watermelon ‘PI296341’). Plants were assessed according to their main stem length, main stem diameter, number of nodes, biomass, pollen production and development, fruit yield and quality, and seed yield and quality. NUN-9075/CS and Argentario/CS graft combinations resulted in higher average stem length, plant biomass, fruit yield and quality, seed yield, seed emergence, and germination percentage. There was no significant difference observed between graft combinations in pollen viability, pollen germination, and normal pollen production. No significant difference was observed between graft combinations in accelerated ageing (AA), and the seed germination decreased after AA of 192 h. In the second year (2017), there was higher main stem length, main stem diameter, total fruit yield, seed yield, and number of seeds per fruit compared to the first year (2016). Based on the results of this study, NUN-9075 rootstock performed better than other rootstocks; hence, it is recommended as the best rootstock.

Genetic diversity and population structure of watermelon (Citrullus sp.) genotypes.

Genetic polymorphism amid plant species is a crucial factor for plant improvement and maintaining their biodiversity. Evaluation of genetic diversity amongst plant species is significant to deal with the environmental stress conditions and their effective involvement in the breeding programs. Hence, in present study, an attempt has been made towards the genetic assessment of individual and bulked populations of 25 watermelon genotypes, belonging to Citroides (citron watermelon) and Lanatus (dessert watermelon) group from Konya, Thrace, Turkmenistan, Saudi Arabia and Turkey. The employed Random Amplified Polymorphic DNA (RAPD) and Inter-Simple Sequence Polymorphism (ISSR) marker systems provided 69.4 and 95.4% polymorphisms, respectively. Different clustering methods showed clear grouping of the genotypes based on the geographical origin and species. Citron genotypes from Turkmenistan stood apart from all the Turkish Lanatus genotypes. However, Saudi Arab Lanatus genotype grouped with native Turkish varieties indicating the genetic linkage. Among all the Turkmenistan Citron genotypes, Turkmenistan-11 was the most distinct form. Moreover, sufficient genetic variation was found between the commercial and native Lanatus genotypes of Turkey as well as Citron genotypes of Turkmenistan. Hence, it will be beneficial to include these genotypes in the future breeding programs to transfer disease-resistant alleles from Citron to Lanatus genotypes.