Trait In Watermelon Research Articles

Assessment of Morpho-biochemical Traits in Watermelon (Citrullus lanatus) Cultivars Across Staggered Sowing Intervals Under the Agro-climatic Conditions of Assam, India

An experiment was conducted in the Experimental Farm, Department of Horticulture, Assam Agricultural University, Jorhat to study the effect of time of sowing on growth, yield and quality of the fruit and standardize the optimum time of sowing in watermelon. The experiment was laid out in Factorial Randomised Block Design with two varieties- Saraswati (V1) and Kiran (V2) and five different time of sowing- October(M1), November (M2), December (M3), January (M4) and February (M5). Observations on growth, yield and quality parameters were recorded at 60, 90 and 120 days after sowing. Results revealed that the variety Kiran sown in November recorded significantly the highest female flowers per plant (11.33), fruit set percentage (27.98 %) and fruit retention percentage (44.04 %). In addition this treatment combination was also able to register the maximum number of fruits per plant (2.67), fruit weight (4.32 kilogram), yield per plant (9.77 kilogram), yield per ha (44.58 tonnes), Total Soluble Solids (9.97 0 Brix), total sugar (9.12 %) and ascorbic acid (7.03 milligram per 100 gram). Thus, it may be inferred that watermelon variety Kiran sown in the month of November was the best treatment combination in terms of yield and yield attributing parameters and quality parameters as well.

Molecular Markers and Marker-Assisted Selection Provide Genetic Insights for Identifying Key Quantitative Trait Locus for Watermelon Rind Thickness.

Rind thickness (RT) is an important agronomic trait in watermelon [Citrullus lanatus (Thunb.) Mansf.] and affects watermelon storability. However, genetic studies on this trait, as well as gene regulation studies, are scarce and of limited production significance. We constructed a temporary F2 generation using the highly differentiated thick-rind watermelon 'XiaoXiGua-4' and the thin-rind watermelon 'DuanMan' as parents and localized the Cla97C02G044120 gene, which controls the thickness of watermelon rind, to the intervals of chromosome 2, CL2-32303995 and CL2-32316840, through 2 years of genetic analysis. No exonic mutations were found in this gene, but two promoter mutations resulted in changes in the promoter progenitor. Fluorescence quantitative PCR analysis revealed highly significant differences in expression at 1 d and 28 d, and the expression was significantly lower in thick-skinned watermelon varieties. Marker-assisted selection (MAS) for this trait was performed using the Caps marker CL2-32303995 and the InDel marker CL2-32316840, which not only verified the stability of the localization interval but also distinguished thick rind from thin rind. These results can be used for germplasm resource screening and have strong breeding significance.

Assessing seed health and resistance traits in watermelon against gummy stem blight

Assessing seed health and resistance traits in watermelon against gummy stem blight

Clpf encodes pentatricopeptide repeat protein (PPR5) and regulates pink flesh color in watermelon (Citrullus lanatus L.).

The gene controlling pink flesh in watermelon was finely mapped to a 55.26-kb region on chromosome 6. The prime candidate gene, Cla97C06G122120 (ClPPR5), was identified through forward genetics. Carotenoids offer numerous health benefits; while, they cannot be synthesized by the human body. Watermelon stands out as one of the richest sources of carotenoids. In this study, genetic generations derived from parental lines W15-059 (red flesh) and JQ13-3 (pink flesh) revealed the presence of the recessive gene Clpf responsible for the pink flesh (pf) trait in watermelon. Comparative analysis of pigment components and microstructure indicated that the disparity in flesh color between the parental lines primarily stemmed from variations in lycopene content, as well as differences in chromoplast number and size. Subsequent bulk segregant analysis (BSA-seq) and genetic mapping successfully narrowed down the Clpf locus to a 55.26-kb region on chromosome 6, harboring two candidate genes. Through sequence comparison and gene expression analysis, Cla97C06G122120 (annotated as a pentatricopeptide repeat, PPR) was predicted as the prime candidate gene related to pink flesh trait. To further investigate the role of the PPR gene, its homologous gene in tomato was silenced using a virus-induced system. The resulting silenced fruit lines displayed diminished carotenoid accumulation compared with the wild-type, indicating the potential regulatory function of the PPR gene in pigment accumulation. This study significantly contributes to our understanding of the forward genetics underlying watermelon flesh traits, particularly in relation to carotenoid accumulation. The findings lay essential groundwork for elucidating mechanisms governing pigment synthesis and deposition in watermelon flesh, thereby providing valuable insights for future breeding strategies aimed at enhancing fruit quality and nutritional value.

Quantitative trait loci identification reveals zinc finger protein CONSTANS-LIKE 4 as the key candidate gene of stigma color in watermelon (Citrullus lanatus)

Stigma color is a critical agronomic trait in watermelon that plays an important role in pollination. However, there are few reports on the regulation of stigma color in watermelon. In this study, a genetic analysis of the F2 population derived from ZXG1553 (P1, with orange stigma) and W1-17 (P2, with yellow stigma) indicated that stigma color is a quantitative trait and the orange stigma is recessive compared with the yellow stigma. Bulk segregant analysis sequencing (BSA-seq) revealed a 3.75 Mb segment on chromosome 6 that is related to stigma color. Also, a major stable effective QTL Clqsc6.1 (QTL stigma color) was detected in two years between cleaved amplified polymorphic sequencing (CAPS) markers Chr06_8338913 and Chr06_9344593 spanning a ~1.01 Mb interval that harbors 51 annotated genes. Cla97C06G117020 (annotated as zinc finger protein CONSTANS-LIKE 4) was identified as the best candidate gene for the stigma color trait through RNA-seq, quantitative real-time PCR (qRT-PCR), and gene structure alignment analysis among the natural watermelon panel. The expression level of Cla97C06G117020 in the orange stigma accession was lower than in the yellow stigma accessions with a significant difference. A nonsynonymous SNP site of the Cla97C06G117020 coding region that causes amino acid variation was related to the stigma color variation among nine watermelon accessions according to their re-sequencing data. Stigma color formation is often related to carotenoids, and we also found that the expression trend of ClCHYB (annotated as β-carotene hydroxylase) in the carotenoid metabolic pathway was consistent with Cla97C06G117020, and it was expressed in low amounts in the orange stigma accession. These data indicated that Cla97C06G117020 and ClCHYB may interact to form the stigma color. This study provides a theoretical basis for gene fine mapping and mechanisms for the regulation of stigma color in watermelon.

Genetic study of fruit quality traits in watermelon (<i>Citrullus lanatus</i>) prebred line derived from <i>Citrullus lanatus</i> var. <i>citroid</i>

Fruit quality is most important for commercially cultivated watermelon [Citrullus lanatus (Thunb.) Matsum and Nakai] cultivars and introgression of resistance gene from wild or related species is a major challenge and imperative to study the inheritance of internal and external fruit quality traits for utilizing in resistance breeding programme. Present study was carried out at the research farm of ICAR-Indian Agricultural Research Institute, New Delhi during summer 2020 to 2022 involving 4 seasons for identifying source of resistance, developing F1 and other subsequent generations (F2, BC1P1 and BC1P2) and evaluation of parental lines along with breeding population in watermelon. The resistant line DWM-45 was used as a female parent and crossed with commercially popular sweet watermelon variety Arka Manik to produce F1 and other generation to study the inheritance of internal and external fruit quality traits. Based on the segregation pattern of progeny it is concluded that fruit shape, rind pattern, seed coat colour and colour of flesh at margin near rind and at carpellar region followed monogenic inheritance. Furthermore, our findings revealed a complex genetic control with epistatic interactions for other fruit quality traits such as fruit length, fruit width, fruit weight and total soluble solids. This study provides valuable insights into the genetic basis of various fruit quality traits in watermelon which can have practical applications in breeding programmes, facilitating the development of improved watermelon varieties with desirable fruit characteristics.

Fine mapping and discovery of candidate genes for rind trait in watermelon

Abstract Fine mapping and discovery of watermelon rind trait candidate genes are of great significance for modern watermelon breeding and development. In this study, we used the high-resolution genetic mapping and genome-wide genetic variation detection technology, combined with genome survey and sequencing technology, to locate and discover the candidate genes for rind traits of star watermelon varieties ‘Su XuanBai’ and ‘SHLX21’. Firstly, we identified a total of eight quantitative trait loci (QTLs) related to watermelon rind traits on chromosome 6. Secondly, a total of 208,240 single nucleotide polymorphisms and 75,345 small Indels (insertions/deletions) were detected in the two parents by high-coverage re-sequencing, respectively. Based on the genetic variation of the two parents and combined with Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis using the planta database, the QTL region was reduced to 0.02 Mb. Finally, we identified the six potential regulatory factors for watermelon rind traits using real-time quantitative PCR. In conclusion, our results revealed the fine localization of candidate genes for watermelon rind traits and the successful discovery of candidate genes for regulating watermelon rind traits, which is of importance for watermelon rind traits and breeding-improved watermelon varieties.

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.

Integrated analysis of biparental and natural populations reveals CRIB domain-containing protein underlying seed coat crack trait in watermelon.

The scc locus of the watermelon seed coat crack trait was fine mapped on chromosome 3. Cla97C03G056110 (annotated as CRIB domain-containing protein) was regarded as the most likely candidate gene Seed coat crack (scc) is a special characteristic of watermelon compared with other cucurbit crops. However, information regarding the genetic basis of this trait is limited. We conducted a genetic analysis of six generations derived from PI 192938 (scc) and Cream of Saskatchewan (COS) (non-scc) parental lines and found that the scc trait was regulated by a single recessive gene through two years. Bulk segregant analysis sequencing (BSA-seq) and initial mapping placed the scc locus into an 808.8kb region on chromosome 3. Evaluation of another 1152 F2 plants narrowed the scc locus to a 277.11kb region containing 37 candidate genes. Due to the lack of molecular markers in the fine-mapping interval, we extracted the genome sequence variations in this 277.11kb region with in silico BSA among seventeen re-sequenced lines (6 scc and 11 non-scc) and finally delimited the scc locus to an 8.34kb region with only one candidate gene Cla97C03G056110 (CRIB domain-containing protein). Three single nucleotide polymorphism loci in the promoter region of Cla97C03G056110 altered cis-acting elements that were highly correlated with the nature watermelon panel. The expression of Cla97C03G056110 in seed coat tissue was higher in non-scc than in scc lines and was specifically expressed in seed coat compared with fruit flesh.

Genetic mapping of a single nuclear locus determines the white flesh color in watermelon (Citrullus lanatus L.).

Flesh color is an important trait in watermelon (Citrullus lanatus L.). Several flesh color genes have been identified in watermelon; however, the inheritance of and the molecular basis underlying the white flesh trait remain largely unknown. In this study, segregation populations were constructed by crossing the canary yellow flesh line HSH-F with the white flesh line Sanbai to fine-map the white flesh gene in watermelon. Genetic analysis indicated that the white flesh trait is controlled by a single recessive locus, termed Clwf2. Map-based cloning delimited the Clwf2 locus to a 132.3-kb region on chromosome 6. The candidate region contains 13 putative genes, and four of them-Cla97C06G121860, Cla97C06G121880, Cla97C06G121890, and Cla97C06G121900-were significantly downregulated in the white flesh compared to the canary yellow flesh watermelon fruits. The Cla97C06G121890 gene, which encodes a tetratricopeptide repeat protein, showed almost no expression in the white flesh fruit before maturity, whereas it had a very high expression in the canary yellow flesh fruit at 18 days after pollination. Transmission electron microscopy revealed rounded and regularly shaped chromoplasts in both the canary yellow and white flesh fruits. Further quantitative real-time PCR analysis showed that the expression levels of several key plastid division genes and almost the entire carotenoid biosynthesis pathway genes were downregulated in the white flesh compared to the canary yellow flesh fruits. This study suggests that the proliferation inhibition of chromoplasts and downregulation of the CBP genes block the accumulation of carotenoids in watermelon and lead to white flesh. These findings advance and extend the understanding of the molecular mechanisms underlying white flesh trait formation and carotenoid biosynthesis in watermelon.

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.

Molecular mapping of candidate gene regulating fruit stripe trait in watermelon

Molecular mapping of candidate gene regulating fruit stripe trait in watermelon

Genetic mapping and meta-analysis identifies several candidate genes for watermelon (Citrullus lanatus) fruit quality traits

Citron (Citrullus amarus), a wild relative of watermelon possesses white flesh with coarse texture and bland/bitter taste; this may cause undesirable effect on quality in watermelon breeding. It is therefore important to understand the genomic regions/genes governing fruit quality, while using this species in introgressive breeding to avoid linkage drag. Hence, in the current experiment an attempt has been made to understand genes/QTLs governing important fruit quality traits in an inbred line derived from C. amarus. BIL-53 (P1) characterized by creamish white flesh, low TSS, red colored seeds and flat fruit shape; and ice box type inbred line, IIHR-140–152 (P2) characterized by dark red colored flesh, high TSS, black colored seeds and oblong fruit shape were used as parents for this QTLs study. Among 693 markers screened, 202 (29.14%) markers were found to be polymorphic and were used for linkage map construction and QTL mapping. QTL mapping identified eleven major QTLs for fruit shape on chromosome 3, 4 and 11. Candidate gene analysis in these regions validated Cla011257 gene on chromosome 3 and predicted Cla016683 gene in a novel QTL region on chromosome 11 as a putative candidate for fruit shape. Similarly, one novel QTL was identified for total soluble solids on chromosome 11, candidate gene analysis in this region predicted Cla016890 and Cla016891 genes as putative candidates. For flesh color, this is the first attempt to map the genes/QTLs governing flesh color at the different regions of fruit through visual and colorimetric analysis. Results revealed fifteen major QTLs on chromosome 2, 4, 5, 6, 7 and 10 for flesh color at different regions. Candidate gene analysis predicted Cla020214 and Cla020121 on chromosome 2; Cla005011 on chromosome 4; Cla018767, Cla018768, Cla018769, Cla018770, Cla018771 on chromosome 6; Cla017416 and Cla017593 on chromosome 10 as a probable candidates genes governing flesh color at different regions. The results presented here provide valuable information for future studies on functional validation of putative candidate genes and breeding of important fruit quality traits in watermelon.

Development of Whole Genome SNP-CAPS Markers and Preliminary QTL Mapping of Fruit Pedicel Traits in Watermelon

Fruit pedicel (FP) is an important determinant of premium fruit quality that directly affects commercial market value. However, in-depth molecular and genetic basis of pedicel-related traits has not been identified in watermelon. Herein, a quantitative trait locus (QTL) mapping strategy was used to identify the potential genetic regions controlling FP traits based on newly derived whole-genome single nucleotide polymorphism based cleaved amplified polymorphism sequence (SNP-CAPS) markers. Next-generation sequencing based whole-genome re-sequencing of two watermelon parent lines revealed 98.30 and 98.40% of average coverage, 4,989,869 SNP variants, and 182,949 CAPS loci pairs across the reference genome, respectively. A total of 221 sets of codominant markers exhibited 46.42% polymorphism rate and were effectively genotyped within 100-F2:3 derived mapping population. The developed linkage map covered a total of 2,630.49 cM genetic length with averaged 11.90 cM, and depicted a valid marker-trait association. In total, 6 QTLs (qFPL4.1, qFPW4.1, qFPD2.1, qFPD2.2, qFPD8.1, qFPD10.1) were mapped with five major effects and one minor effect between the whole genome adjacent markers positioned over distinct chromosomes (02, 04, 08, 10), based on the ICIM-ADD mapping approach. These significant QTLs were similarly mapped in delimited flanking regions of 675.10, 751.38, 859.24, 948.39, and 947.51 kb, which collectively explained 8.64–13.60% PVE, respectively. A highly significant and positive correlation was found among the observed variables. To our knowledge, we first time reported the mapped QTLs/genes affecting FP traits of watermelon, and our illustrated outcomes will deliver the potential insights for fine genetic mapping as well as functional gene analysis through MAS-based breeding approaches.

BSA‐seq and quantitative trait locus mapping reveals a major effective QTL for carpel number in watermelon (Citrullus lanatus)

AbstractThe carpel number (CN) is related to fruit shape variation in watermelon and represents one of the most important agronomic traits. In this study, ZXG01553 (5‐CN type) and W1‐17 (3‐CN type) lines were used as parental material to construct F1, F2 and backcross populations for genetic inheritance analysis and QTL (quantitative trait locus) mapping. The F1 generation displayed the 3‐CN type and the frequency distribution of F2 individuals showed partial separation suggesting that the 3‐CN was dominant to 5‐CN trait and controlled by a major gene. Bulked‐segregant analysis (BSA‐seq) identified a chromosome segment related to the CN trait spanning 2.44 Mb on chromosome 7. Genetic linkage analysis using QTL mapping software narrowed this region to 244 Kb, and a major effective QTL was detected between markers Chr07‐30681552 and Chr07‐30923898. Twenty‐four genes were identified in the QTL region, in which Cla97C07G143260 annotated as Receptor‐like protein kinase 2 was the most likely candidate gene for the CN trait in watermelon. Our research provides new insights into the forward genetics of CN variation in cucurbit crops.

QTL mapping identifies novel loci and putative candidate genes for rind traits in watermelon.

The online version contains supplementary material available at 10.1007/s13205-022-03112-7.

Molecular Mapping of Candidate Gene Regulating the Fruit Stripe Trait in Watermelon

Molecular Mapping of Candidate Gene Regulating the Fruit Stripe Trait in Watermelon

A 2.09 Mb fragment translocation on chromosome 6 causes abnormalities during meiosis and leads to less seed watermelon

Seedlessness is a valuable agronomic trait in watermelon (Citrullus lanatus) breeding. Conventional less seed watermelons are mainly triploid, which has many disadvantages due to unbalanced genome content. Less seed watermelon can be achieved at the diploid level when certain reproductive genes are mutated or by chromosome translocation, which leads to defects during meiosis. However, the formation mechanism of diploid less seed watermelons remains largely unknown. Here, we identified a spontaneous mutant line, watermelon line “148”, which can set seeds normally when self-pollinated. A total of 148 × JM F1 hybrid plants exhibited seed number reductions to 50.3% and 47.3% of those of the two parental lines, respectively, which are considered to be less seed. Examination of pollen viability and hybridization experiments revealed that F1 hybrids produce semisterile pollen and ovules. Further cytological observations indicated that semisterility was a result of a reciprocal translocation of chromosomes, which exhibited one quadrivalent ring of four chromosomes at prometaphase I during meiosis. RT-qPCR analysis indirectly confirmed that the semisterile phenotype is caused by chromosome translocation rather than disruption of specific meiotic gene expression. F2 population genetic analysis indicated that the “148” watermelon line is a homozygous translocation and that the less seed phenotype of the F1 hybrid is prompted by one chromosome fragment translocation. The translocated fragment was further fine mapped to a 2.09 Mb region on chromosome 6 by whole-genome resequencing and genetic map cloning procedures. Our work revealed that a 2.09 Mb chromosome fragment translocation on chromosome 6, causing meiotic defects at metaphase I during meiosis, leads to diploid less seed watermelon. Our findings provide a new promising method for less seed watermelon breeding at the diploid level, as well as a fragment size reference for breeding less seed watermelon through artificially induced chromosome translocation.

Nucleotide variation in the phytoene synthase (ClPsy1) gene contributes to golden flesh in watermelon (Citrullus lanatus L.).

A gene controlling golden flesh trait in watermelon was discovered and fine mapped to a 39.08 Kb region on chromosome 1 through a forward genetic strategy, and Cla97C01G008760 (annotated as phytoene synthase protein, ClPsy1 ) was recognized as the most likely candidate gene. Vitamin A deficiency is a worldwide public nutrition problem, and β-carotene is the precursor for vitamin A synthesis. Watermelon with golden flesh (gf, which occurs due to an accumulated abundance of β-carotene) is an important germplasm resource. In this study, a genetic analysis of segregated gf gene populations indicated that gf was controlled by a single recessive gene. BSA-seq (Bulked segregation analysis) and an initial linkage analysis placed the gf locus in a 290-Kb region on watermelon chromosome 1. Further fine mapping in a large population including over 1000 F2 plants narrowed this region to 39.08Kb harboring two genes, Cla97C01G008760 and Cla97C01G008770, which encode phytoene synthase (ClPsy1) and GATA zinc finger domain-containing protein, respectively. Gene sequence alignment and expression analysis between parental lines revealed Cla97C01G008760 as the best possible candidate gene for the gf trait. Nonsynonymous SNP mutations in the first exon of ClPsy1 between parental lines co-segregated with the gf trait only among individuals in the genetic population and were not related to flesh color in natural watermelon panels. Promoter sequence analysis of 26 watermelon accessions revealed two SNPs in the cis-acting element sequences corresponding to MYB and MYC2 transcription factors. RNA-seq data and qRT-PCR verification showed that two MYBs exhibited expression trends similar to that of ClPsy1 in the parental lines and may regulate the ClPsy1 expression. Further research findings indicate that the gf trait is determined not only by ClPsy1 but also by ClLCYB, ClCRTISO and ClNCED7, which play important roles in watermelon β-carotene accumulation.

Fine mapping a ClGS gene controlling dark-green stripe rind in watermelon

The stripe pattern is an important agronomic trait in watermelon, which determines the fruit rind pattern and consumer choice. However, the genes controlling these traits are still largely unknown. In the present study, a dark-green stripe inbred line WT2 and a netted stripe inbred line WM204 were used for genetic analysis, which revealed that the dark-green stripe is controlled by a single dominant gene ClGS. By bulked-segregant analysis (BSA), the ClGS was primarily mapped on watermelon chromosome 6 by using F2 plants developed from a cross between WT2 and WM204. Next-generation sequencing-aided marker discovery and a large mapping population consisting of 1206 F2 plants was used for fine mapping of the ClGS gene, and it was further mapped into a 107 kb candidate region. There were 11 genes predicated in this candidate region and 10 of them were differentially expressed in the 1-DAP fruit rind between two parental lines. Furthermore, 64 SNPs and 3 Indels were detected in the CDS region of these candidate genes. To further confirm the candidate gene of ClGS, we investigated the sequence variations among 74 re-sequenced natural watermelon accessions by in silico bulk segregant analysis. A 3-bp insertion was identified in all the non-dark green stripe watermelon accession group, which was located on the 8th exon of Cla019205. A Indel marker developed harboring the insertion showed co-segregation with the phenotype in the F2 mapping population, and it was also in completely agreement with another 25 watermelon accessions by electrophoretic analysis. These evidences suggested Cla019205 is probably the candidate gene controlling dark-green stripe in watermelon. The results of this study will be helpful for better understanding of the stripe formation and marker-assisted selection in watermelon.