Crimson Sweet Research Articles

Effect of mineral fertilizers on the yield and growth parameters of watermelon in Kazakhstan

Abstract The study aims to determine the optimal regimes of mineral fertilization for the yield of commercial watermelon fruits. The research goal is to analyze how fertilization regimes affect the growth parameters of this plant, such as weight per fruit and average fruit weight per plant. The research subjects are watermelon varieties, such as two Crimson Sweet varieties (including hybrid Producer Hollar) and Kholodok. The study involved a field survey on the territory of Zhana Tau, a farm located in the Aktobe area of the Republic of Kazakhstan. The experimental design encompassed the following fertilizer applications: Variant I – N30P40K60, Variant II – N60P60K120 and Variant III – N90P60K120. The study found that mineral fertilizers have a significant impact on the yield and growth parameters of watermelon fruits. After the application of N30P40K60, the weight per fruit was 8.13 kg for Crimson Sweet and 8.35 kg for Kholodok. The highest fruit weight indicator, 11.45 kg, was achieved when hybrid Producer Hollar was cultivated with N90P60K120. The highest yield (55.9 t/ha) was recorded when growing hybrid Producer Hollar with N90P60K120. The yield of the Crimson Sweet and Kholodok varieties, with the same level of fertilization, amounted to 49.6 t/ha and 51.2 t/ha, respectively. Correlation-regression analysis of the data on watermelon yield showed that this parameter tends to increase with the increase in the use of mineral fertilizers. Therefore, further research may focus on studying the influence of even higher levels of each macroelement and their combined effects on crop structure and fruit quality in watermelon cultivation.

Assessment of Lycopene Levels in Dried Watermelon Pomace: A Sustainable Approach to Waste Reduction and Nutrient Valorization

Watermelon suffers substantial post-harvest losses owing to strict quality standards, resulting in 20–30% of the crop being left unharvested. This study investigated the potential of valorizing dried watermelon pomace (DWP), a byproduct of watermelon juice extraction, focusing on its lycopene content—a potent antioxidant. This study assessed lycopene stability in DWP from four watermelon cultivars (Perla Nera®, Gavina®, Crimson Sweet, and Asahi Miyako) under different storage conditions (vial-sealed and vacuum-sealed). The lycopene content in freshly prepared DWP samples ranged from 0.734 to 1.572 mg/g db. The results indicated that vacuum-sealed samples exhibited significantly slower lycopene degradation than vial-sealed samples, highlighting the impact of air exposure on lycopene stability. After 90 days of storage, lycopene content in vacuum-sealed samples ranged from 0.214 to 1.234 mg/g db, while that in vial-sealed samples ranged from 0.013 to 0.731 mg/g db. Furthermore, this study assessed the effect of pretreatments with ascorbic acid (pretreatment A) and a mixture of ascorbic and citric acids (pretreatment B) on lycopene stability. Pretreatment B showed superior effectiveness, yielding higher lycopene levels than pretreatment A (p < 0.05). The stabilizing effects of ascorbic acid and citric acid were attributed to their antioxidant properties and their roles as pH regulators and chelators.

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.

Influence of the application of humic substances on the growth of watermelon and melon seedlings

Growing watermelon (Citrullus lanatus) and melon (Cucumis melo) is an important activity in the Brazilian Cerrado; however, many factors limit cultivation, including the difficulty of producing high-quality seedlings. In this study, the effect of humic substances (HS) on growth of ‘Crimson Sweet’ watermelon and ‘Yellow’ melon seedlings was evaluated. An experiment was carried out in a completely randomized design with five HS treatments applied to the soil: 0 (control), 5, 10, 15, and 20 g L-1. The growth of watermelon and melon seedlings was influenced by the application of humic substances. Use of HS increased plant height, stem diameter, root length, root volume, shoot dry biomass, root dry biomass, and Dickson’s quality index. HS boost plant growth, whose improved root system may have provided greater absorption and accumulation of mineral nutrients. Based on the quality of the seedlings (Dickson index), the application of 14 g L-1 of HS is recommended for watermelon seedling production and 15 g L-1 of HS for melon seedling production.

Estimation of Genetic Distance Using RAPD Markers for Five Varieties of Citrullus lanatus L.

This experiment was conducted at the department of Horticulture and Landscape department, Tikrit University. The aim was to analyze genetic variation in five varieties of Citrullus lanatus L. by using Random Amplified polymorphic DNA (RAPD) based on polymerase chain reaction (PCR) technique. DNA was isolated from plant leaves and 15 random primers were used. Variations between amplified pieces for each variety was detected by migrating samples on an agarose gel. The results showed a difference in the number of DNA replicated bundles and their molecular weights. The total number of bundles was 101, of which 83 were differentiated. The primer OP H-08 had the highest number of bands, while the lowest number was 1 bands for the primer OP D-18. There was also differences in the primers efficiencies. The primer OP H-08 showed the highest efficiency (12.871), and the primer OP D-18 showed the lowest (0.990). The primers OP F-05 and OP H-08 displayed the highest discriminating power(14.457), while the primers OP B-14, OP D-18 and OP E-03 recorded the lowest (0). The genetic distance had values ranged between 0.235 - 0.562. The largest genetic distance was between the varieties Charleston Gray and King Charleston. However, the varieties Charleston Gray and Crimson Sweet had the least distance.

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.

Paramyrothecium nigrum, causing leaf blight disease on watermelon in Iran

<i>Paramyrothecium nigrum</i>, causing leaf blight disease on watermelon in Iran

First Report of Lasiodiplodia brasiliensis Causing Root Rot on Watermelon in Brazil.

Watermelon (Citrullus lanatus (Thumb.) Matsum. & Nakai) is an important crop in Brazil both for export and domestic consumption. In October 2019, watermelon plants showing decline and root rot symptoms were surveyed in 16 commercial fields in Baraúna's municipality (Rio Grande do Norte, Brazil). The disease prevalence was 12.5%, and the average incidence was 5%. Affected root segments were cut into small pieces and surface-disinfected with 70% ethyl alcohol and 1.5 % NaOCl for 1 and 2 min, respectively. Tissues were plated onto potato dextrose agar (PDA) and incubated at 25°C for 7 days. Fungal colonies developed from the infected tissues were dark or greyish, and pure cultures were obtained by hyphal tip isolation technique. Six fungal isolates with the same morphology were obtained. Two of them were selected for morphological and molecular characterization (CFC-1123 and CFC-1124). Isolates grew rapidly in PDA, covering the entire surface of the Petri dishes within 3 days. The aerial mycelium was initially white, turning dark greenish-gray after 4 to 5 days of incubation at 25°C in the dark. Isolates produced pycnidia and conidia in water-agar medium with sterilized pine needles after 30 days of incubation at 25°C under near-UV light. The conidia were initially hyaline and brown with central transverse septum and longitudinal streaks when mature. Conidia were ellipsoid to oval (22.83 ± 3.1 µm long and 11.58 ± 1.5 µm wide). Based on morphological features, the isolates were initially identified as Lasiodiplodia sp. (Phillips et al. 2013). To confirm the identification, genomic DNA was extracted and the internal transcribed spacer (ITS) region as well as fragments of the translation elongation factor 1-α (TEF) and β-tubulin 2 (TUB) genes were amplified using the primer pairs ITS1/ITS4 (White et al. 1990), EF1-728F/EF1-986R (Carbone and Kohn 1999) and Bt2a/Bt2b (Glass and Donaldson 1995), respectively. The sequences were deposited in GenBank under accession numbers OL841380, OL865376 and OL890691 for CFC-1123, and OL841381, OL865377 and OL890692 for CFC-1124. Maximum likelihood phylogenetic analysis of the concatenated sequences of ITS, TEF and TUB gene regions of some reference sequences and ex-types of Lasiodiplodia spp. was performed. Phylogenetic analysis revealed that the isolates grouped in the L. brasiliensis clade (Netto et al. 2014) with 80/79% of bootstrap. The isolates were deposited in the Culture Collection of Phytopathogenic Fungi from Cariri (CFC) at the Universidade Federal do Cariri (Crato, Brazil). Pathogenicity of the two isolates was determined using colonized wheat grains as inoculum source. One watermelon seed (cv. Crimson Sweet) was placed in a sterile plastic pot (500-mL) filled with 6 cm layer of a substrate composed of soil and Tropstrato® (5:1 w/w). Three wheat grains (50 mg) colonized with each isolate were placed 10 mm above the seed and covered with the substrate. Control pots were inoculated only with sterile wheat grains. There were five replicates for each isolate. The pots with seedlings were maintained in a greenhouse at 28 ± 2°C under natural light conditions. The inoculated seedlings showed poor growth, withering and drying leaves 45 days after inoculation (DAI), and subsequently root rot symptoms and death at 60 DAI. Control seedlings remained asymptomatic. The pathogen was re-isolated from all inoculated seedlings and identified by conidia morphology to fulfill Koch's postulates. Lasiodiplodia brasiliensis has been reported to cause postharvest rot and gummosis of watermelon (Farr and Rossman 2022). However, to our knowledge, this is the first report of watermelon decline caused by this fungus in Brazil and worldwide. This finding must be considered for developing efficient control strategies for the disease.

Germinação e vigor de sementes de melancia tratadas com estimulante de crescimento

ABSTRACT Direct sowing is the most used watermelon propagation method in Brazil. Therefore, the use of treated seeds is an alternative for improving uniformity of plant stands at planting. Thus, the objective of this study was to assess the effects of seed treatments with biostimulant on the germination and vigor of watermelon [Citrullus lanatus (Thunb.) Matsum &amp; Nakai] seeds of the cultivar Crimson Sweet. A completely randomized experimental design with four replications was used. The seed treatments consisted of six biostimulant (Agressive Desperta®) rates (0, 1, 2, 3, 4, and 5 mL kg-1). Seed germination speed index, seedling length, seedling dry weight, seedling emergence in the field, and seedling emergence speed index were evaluated. The treatment of watermelon seeds with biostimulant resulted in increases in seed germination speed and seedling length and dry weight as the biostimulant rate was increased. Seedling percentage and emergence speed increased up to the rate of 3 mL kg-1 under field conditions; however, application of higher rates resulted in phytotoxicity.

VOCs Analysis of Three Different Cultivars of Watermelon (Citrullus lanatus L.) Whole Dietary Fiber.

In this study, the trend of VOCs of dietary fiber samples, coming from three different watermelon cultivars Citrullus lanatus L. (variety Gavina®®, Crimson Sweet, and Asahi Miyako) was investigated. This foodstuff, obtained as a by-product of residual agri-food production, has gained increasing attention because of its many bioactive components and high dietary fiber content. The result is a fibrous material for specific applications in food manufacturing, such as corrector for some functional and technological properties. In this study, a method based on headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS) was used to characterize the aromatic profiles of the dried raw materials. Therefore, the VOCs of the samples of the three cultivars were investigated. Experimental results have shown that watermelon fibers generate VOCs, which can be grouped into six common classes of analytes. The different distributions of the identified compounds made it possible to effectively differentiate the three cultivars studied based on their peculiar aroma profiles. In particular, Gavina®® fiber is distinguished by the high content of terpenes, Asahi Miyako by the presence of aldehydes generated as fatty acid metabolites, and Crimson Sweet by the higher content of acetyl esters.

The effect of some different watermelon varieties on Melon Weevil Acythopeus curvirostris persicus population in Sulaimani Governorate

This study was conducted during April–August 2020, in an open field at Qularasi Research Station, Sulaimani, Kurdistan Region-Iraq, to determine the effect of watermelon variety on population density of melon weevil Actopeus curvirostris persicus. Results showed that the melon weevil has distinct daily activities. Two activity peaks were observed in late-June and early-July. The general mean of population density on June 28 was (1.611) weevil /week, which was less than July 4 (2.583) weevils/week, the lowest number of weevils were observed at 7:00 am on the variety (Qamar F1) with (0.789) weevil/hour. Whereas, the highest number of weevil was observed at 7:00 am on Crimson Sweet variety with (1.525) weevil/hour. However, at 11:00 am, all varieties (Charleston Gray, Topgun F1, king Charles, Qamar F1, and Crimson Sweet) recorded the highest number of weevil (4.571, 4.238, 4.048, 4.048 and 1.524) weevil/hour, respectively. The population densities of melon weevil were high on all watermelon varieties in the last week of June and first week of July. Temperature, relative humidity, and wind speed correlations showed a great effect on melon weevil population density during the study period. The correlation was negative significant (-0.208) for temperature in the variety Crimson Sweet, while it was positive significant in the other varieties of Charleston Gray, Topgun F1, and King Charles with (0.165, 0.183 and 0.147), respectively. The correlation was positive significantly for relative humidity in the variety Crimson Sweet) with (0.165) however, it was negative significant for wind speed in the variety Topgun F1 with (0.137).

Raman Spectroscopy Detects Changes in Carotenoids on the Surface of Watermelon Fruits During Maturation.

A non-invasive and non-destructive technique, Raman spectroscopy, was explored to distinguish different maturity stages (20, 30, 40, and 50 days after anthesis) of watermelon (Citrullus lanatus) fruits from four cultivars: Fascination, Orange Crisp, Amarillo and Crimson Sweet. Spectral acquisition from the fruit surface was carried out at the wavelength range of 400–2,000 cm−1 using a handheld Raman spectrometer equipped with 830 nm laser excitation source. The spectra were normalized at 1,438 cm−1 which was assigned to CH2 and CH3 vibration. Detecting changes in the spectral features of carotenoids on the surface of watermelon fruits can be used as a marker to monitor the maturity of the fruit. The spectral analysis confirmed the presence of two major carotenoids, lutein and β-carotene, and their intensity decreased upon maturity on the fruit surface. Identification of these pigments was further confirmed by resonance Raman spectra and high-performance liquid chromatography analysis. Results of partial least square discriminant analysis of pre-processed spectra have demonstrated that the method can successfully predict the maturity of watermelon samples with more than 85% accuracy. Analysis of Variance of individual Raman bands has revealed a significant difference among the stages as the level of carotenoids was declined during the ripening of the fruits. Thus, Raman spectral signatures can be used as a versatile tool for the non-invasive determination of carotenoid changes on the watermelon fruits’ surface during ripening, thereby enabling effective monitoring of nutritional quality and maturity indices before harvesting the watermelon.

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.

Inheritance of resistance to damping-off (Rhizoctonia solani) in watermelon

This study aimed to find sources of resistance to damping-off and to determine the inheritance of resistance in watermelon. Firstly, 72 watermelon accessions were inoculated with CMM 1053 isolate of Rhizoctonia solani. Only two accessions (BGH 29 and BGH 76) were considered moderately resistant to the disease. The inoculated plants without symptoms from accession BGH-29 identified as resistant were self-fertilized and the inbred line S1 was used for the crosses. The reaction to R. solani after inoculation of the segregating populations of the cross and backcrosses between susceptible cultivar Crimson Sweet and the inbred line BGH-29 was evaluated. In other experiment eight S1 lines of watermelon were inoculated with six different isolates of R. solani and the reaction was evaluated by partial diallel analysis using the Griffing’s method IV to obtain estimates of general resistance ability (GRA), general aggressiveness ability (GAA), and specific interaction ability (SIA). According to ratings of the susceptible and resistant parents, generations F1, F2, BC1 (F1 × P1) and BC2 (F1 × P2), resistance to damping-off was conferred by at least nine genes with additive effect and low heritability which indicates polygenic inheritance. The results of the diallel analysis corroborate with the analysis of segregating population, indicating inheritance of resistance was horizontal, since 46.1% of the total sum of squares of the variation observed in the crosses was due to GRA, while the SIA corresponded to only 20.39% of variation. This is the first report about inheritance of resistance to damping-off caused by R. solani in watermelon.

Response of watermelon growth, yield, and quality to plant density and variety in Northwest Ethiopia

Abstract A field experiment was conducted with irrigation in 2018 and 2019 at three locations to identify the optimum plant density and adaptive variety for better watermelon yield and quality. It consisted of five densities (24,690, 13,888, 8,888, 6,172, and 4,535 plant ha−1) and two varieties (Crimson Sweet and Sugar Baby) with factorial combination in randomized complete block design with three replications. Plant density and variety were not affected by location and season. The response of watermelon in yield, quality, and growth was influenced by plant density and variety. The highest fruit yield of 32.1 t ha−1 was obtained from the highest plant density, which was statistically similar with the yield of 31.9 t ha−1 obtained with the second highest plant density. However, about 71% of the fruits produced with the highest plant density were mini-sized in the fruit size category, whereas only about 59% were mini-sized with the second highest plant density. Any addition of plant density beyond 13,888 ha−1 did not gain additional yield but reduced in quality attributes. Better fruit physical attributes and total soluble solid were recorded from the lowest plant density. Therefore, Crimson Sweet variety with 120 and 60 cm inter- and intra-row spacing, respectively, which accommodates the plant density of 13,888 ha−1, is optimum for watermelon production.

Productivity and quality of watermelon fruits as a function of doses potassium in the Western Amazon

Potassium is the nutrient most demanded by watermelon, performing various physiological and biochemical functions, and its availability in the soil influences the production and quality of fruits. However, there is no recommendation for specific fertilization for the state of Rondônia, which has limited the production and quality of the harvested fruits. The objective of this work was to evaluate the effects of potassium doses on the productivity and quality of watermelon fruits, cultivar Crimson Sweet, in southern Western Amazonia. The experiment was carried out at the Federal University of Rondônia, in the municipality of Rolim de Moura, in an experimental design in randomized blocks, with five treatments and four replications. The treatments were doses 0 (control), 50, 100, 150 and 200 kg ha-1 of K2O. The variables analyzed were fruit mass, longitudinal and transverse diameter of fruits, number of fruits per plant, soluble solids content, exocarp thickness and productivity. Potassium doses did not influence the mean mass and longitudinal and transverse diameter of the fruits. The number of fruits per plant increased linearly as a function of the potassium doses applied, and with 157 kg ha‑1 of K2O the highest values of °Brix were obtained. The dose of 147.2 kg ha-1 of K2O promotes yields 61.6% above the national average and 82% above the state average.

Morphological and Physio-Biochemical Responses of Watermelon Grafted onto Rootstocks of Wild Watermelon [Citrullus colocynthis (L.) Schrad] and Commercial Interspecific Cucurbita Hybrid to Drought Stress

This study aimed to assess the morphological and physio-biochemical responses of a commercial watermelon (Citrullus lanatus (Thunb.) Matsum. and Nakai) cv. ‘Crimson Sweet’ grafted onto a drought-tolerant rootstock of wild watermelon (bitter apple, Citrullus colocynthis (L.) Schrad, ‘Esfahan’) in comparison with an ungrafted ‘Crimson Sweet’ watermelon or one grafted onto a commercial interspecific Cucurbita hybrid (Cucurbita maxima Duch. × Cucurbita moschata Duch.) rootstock (‘Shintoza’) under water stress. The experiment was conducted in pots under a controlled environment in a greenhouse, and water stress was imposed by maintaining moisture level in pots at 100% (well water (WW)) or 50% (water deficit (WD)) of container capacity (CC). WD significantly decreased most of the morphological traits in ungrafted and grafted plants, while the decrease in growth traits was lower in grafted plants than ungrafted plants. The response of grafted plants onto wild watermelon rootstock (‘Esfahan’) for most of the affected parameters (shoot fresh and dry weight, vine length and internodal length) was, however, comparable to those grafted onto commercial Cucurbita hybrid rootstock (‘Shintoza’). Plants grafted onto bitter apple (wild watermelon) exhibited a relatively lower decrease in growth and biomass, besides showing higher antioxidant activity (e.g., guaiacol peroxidase) concomitant with the lower accumulation of malondialdehyde and electrolyte leakage in the leaf tissues in comparison with ungrafted plants. The overall growth performance, as well as those under water stress conditions in commercial rootstock-grafted watermelon, was related to its better plant water status (e.g., high relative water content) which was likely ascertained by its greater root efficiency. This suggests that watermelons grafted onto bitter apple rootstock and Cucurbita hybrid rootstock were constitutively more resistant to drought, with higher efficiency in mitigating oxidative stress than ungrafted treatment. The above findings demonstrated that bitter apple, a well-adapted desert species, can be used as an alternative rootstock to commercial rootstocks (e.g., ‘Shintoza’) for watermelon grafting under water stress conditions. In addition, bitter apple rootstock can be involved in rootstock breeding programs to improve drought tolerance in watermelon.

CHEMICAL FERTILIZATION THROUGH FERTIRRIGATION IN THE EVALUATION OF THE BIOCHEMICAL CHARACTERISTICS OF THE WATERMELON FRUITS

The objective of this work was to evaluate the effects of splitting in three different doses of phosphorus and potassium, combined with each other, and it was applied fertirrigation in watermelon crop, and to evaluate their effects on fruit quality. The statistical was in a complete randomized block design, and the treatments were arranged in a factorial scheme (3 x 3) in subdivided splits, resulting in 9 treatments with tree replications, totaling 27 plots in the experimental area. In the horizontal plots the three doses of phosphorus fertilization (100, 150 and 300 kg.ha-1 of P2O5) were randomly allocated, and in the subplots the three potassium doses (50, 100 and 200 kg.ha-1 of K2O), were applied in fertirrigation. The cultivar used was Crimson Sweet. Seventy-Six days after planting (DAP) the biochemical characteristics of watermelon fruits were evaluated: total soluble solids (TSS), total treatable acidity (TTA) and potential of hydrogen (pH). According to the results, it was verified that only the chemical value of the TSS fruits, presented significant statistical differences between the studied doses because of the different source of fertilization K and P increased the soluble solid contents, the content of reducing sugars, and decreased pH. It was observed the different doses of K and P did not influence in the fruit quality parameters when it was analyzed separated: TTA and pH but the TTA values are according to consumer market standards. The best doses in order to economy of fertilizer were (150 kg ha-1 de P2O5 e 50 kg ha-1 of K2O).

Yield response of watermelon (Citrullus lanatus Thunb.) cultivars to varied fertilizer rates in Rwanda

The choice of cultivar and adequate nutrition are vital for good watermelon (<i>Citrullus lanatus</i>) production. This study evaluated the yield performance of four watermelon cultivars: ‘Sugar Baby’, ‘Crimson Sweet’, ‘Sukari F1’ and ‘Julie F1’ under four different NPK fertilizer rates: 50, 75, 100 and 125 % of the recommended dose (RD) (90:60:60 kg ha^-1 of Nitrogen (N): Phosphorus (P): Potassium (K). The experiment was laid out in a split-plot design, with cultivars in the main plots, fertilizer in the subplots and three replications. The experiment was conducted in two seasons: 2017A and 2017B at two sites; Karama and Rubona. A higher number of fruits per plant (5.1-5.8) was obtained with ‘Julie F1’ + 75 or 100 % of RD at both sites and in both seasons, followed by ‘Sukari F1’ + 100 % of RD and the open-pollinated cultivar A higher fruit weight (4.4-5 kg) was obtained with ‘Julie F1’ and ‘Sukari F1’ under 125 % of the RD. Plots planted with ‘Julie F1’ and treated with 75 % or 100 % of RD recorded higher fruit yield per plant (20.9-27.5 kg) and higher fruit yield per ha (104.2-137.3 t). From these results, it can be concluded that the high yield performance of watermelon in the study area can be obtained with ‘Julie F1’ using 75 % (67.5: 45: 45 kg ha^-1) of the recommended dose of NPK fertilizer.

Yield response of watermelon (Citrullus lanatus Thunb.) cultivars to varied fertilizer rates in Rwanda

The choice of cultivar and adequate nutrition are vital for good watermelon (<i>Citrullus lanatus</i>) production. This study evaluated the yield performance of four watermelon cultivars: ‘Sugar Baby’, ‘Crimson Sweet’, ‘Sukari F1’ and ‘Julie F1’ under four different NPK fertilizer rates: 50, 75, 100 and 125 % of the recommended dose (RD) (90:60:60 kg ha^-1 of Nitrogen (N): Phosphorus (P): Potassium (K). The experiment was laid out in a split-plot design, with cultivars in the main plots, fertilizer in the subplots and three replications. The experiment was conducted in two seasons: 2017A and 2017B at two sites; Karama and Rubona. A higher number of fruits per plant (5.1-5.8) was obtained with ‘Julie F1’ + 75 or 100 % of RD at both sites and in both seasons, followed by ‘Sukari F1’ + 100 % of RD and the open-pollinated cultivar A higher fruit weight (4.4-5 kg) was obtained with ‘Julie F1’ and ‘Sukari F1’ under 125 % of the RD. Plots planted with ‘Julie F1’ and treated with 75 % or 100 % of RD recorded higher fruit yield per plant (20.9-27.5 kg) and higher fruit yield per ha (104.2-137.3 t). From these results, it can be concluded that the high yield performance of watermelon in the study area can be obtained with ‘Julie F1’ using 75 % (67.5: 45: 45 kg ha^-1) of the recommended dose of NPK fertilizer.