Cationic heavy metals are highly toxic and often coexist with large concentration gradients in wastewater, making their efficient removal particularly challenging. In this study, corn straw (CS) and steam-exploded corn straw (SCS) were employed as carrier materials to prepare MgO biochar composites (MgO/CS and MgO/SCS) via an impregnation-precipitation-pyrolysis method. After normalization based on MgO content, the adsorption capacity ratios of MgO/SCS to MgO/CS reached 1.95 for Pb2+, 1.37 for Cu2+ and 1.93 for Zn2+, clearly demonstrating the importance of carrier material. MgO/SCS exhibited excellent adsorption capacities for Pb2+ (1466 mg g- 1), Cu2+ (711 mg g- 1) and Zn2+ (635 mg g- 1), along with ultrafast adsorption kinetics (76.8% of the equilibrium adsorption capacity for Pb2+ can be achieved within 20 min) and strong tolerance toward acidic conditions and coexisting substances. Mechanistic analyses revealed that Pb2+ and Zn2+ adsorption was dominated by surface precipitation, whereas Cu2+ adsorption involved both precipitation and complexation. More importantly, 2 g L- 1 MgO/SCS can remove all cationic heavy metals from the electroplating, mining and smelting simulated wastewater, reducing residual heavy metal concentrations to levels far below the corresponding Chinese discharge standards. The superior performance and broad-spectrum adsorption capabilities of MgO/SCS, which are due to the localized alkaline microenvironments formed by ultrafine MgO nanoparticles, together with its cost-effectiveness, making it highly promising for industrial applications.

Perfluorooctanesulfonic acid (PFOS) poses a potential threat to human health owing to its exceptional environmental persistence and bioaccumulation. Biochar exhibits considerable potential for PFOS removal, and metal/heteroatom doping or co-doping has been shown to effectively enhance its efficiency. In this study, Fe-N co-doped biochar was fabricated from agricultural rice straw waste, using potassium ferrate and melamine as precursors for Fe and N, respectively. The PFOS removal performance of the as-prepared biochar in solution was systematically evaluated by investigating the effects of initial solution pH, contact time, initial PFOS concentration, and co-existing substances (i.e., anions and humic acid). Results demonstrated that the Fe-N co-doped biochar pyrolyzed at 800 °C (Fe/N-BC8) possessed a significantly higher specific surface area of 290.76 m2/g, larger than that of the pristine biochar (BC8) with 12.95 m2/g. Moreover, the modified surface chemistry of Fe/N-BC8 endowed it with superior adsorption capacity and broader pH adaptability for PFOS. The PFOS adsorption behavior on Fe/N-BC8 was well fitted by the liquid film diffusion and the Langmuir-Freundlich model. Fe/N-BC8 exhibited a considerable PFOS adsorption capacity with a maximum value of 2.06 mg/g. Surface characterizations of Fe/N-BC8 revealed that the incorporated Fe-N active sites play a critical role in PFOS removal, which was governed by a synergism of electrostatic attraction, surface complexation (i.e., ligand exchange), and hydrophobic interactions. This work provides a high-performance and cost-effective adsorbent for PFOS remediation, and offers a novel design strategy and theoretical basis for developing functionalized biochars of persistent organic pollutants.

Co-contamination of phosphate and arsenate is common in wastewater and aquatic environments due to their chemical similarity. However, it remains challenging to simultaneously remove and selectively separate them via adsorption. Here, quasi-amorphous La2O3 nanoparticles loaded steam-exploded straw biochar (La-BC) were synthesized via impregnation-precipitation-low temperature pyrolysis. La-BC exhibited exceptional adsorption capacities of 79.7 mg P g-1 and 205.4 mg As g-1. When phosphate and arsenate coexisted, La-BC reduced their concentrations from 1 mg L-1 to 0.002 and 0.009 mg L-1, respectively. Phosphate adsorption proceeds mainly via surface precipitation, whereas arsenate removal relies on surface precipitation combined with ligand exchange. La-BC exhibits extremely rapid adsorption rates for phosphate, particularly within the first 3 min. In contrast, the equilibrium time of arsenate is 10 h. This pronounced kinetic disparity enables La-BC to selectively separate phosphate from phosphate-arsenate binary solutions in a time-dependent manner, with a maximum separation factor of 397. Leaching and biochar aging tests demonstrate the high stability of La-BC-P and La-BC-As. This study proposes a sustainable and feasible strategy to fabricate adsorbents from biomass for simultaneous removal of phosphate and arsenate and selective recovery of phosphate.

Conventional drinking water treatment processes exhibit limited efficiency in removing humic acid (HA), making it difficult to effectively suppress the formation risk of disinfection by-products (DBPs). To address this issue, an electrochemical pretreatment system integrating synergistic oxidation, flocculation, and co-precipitation processes was developed. This system employs electro-activated ferrous (EAF) to enhance HA removal and thereby mitigate the formation of DBPs precursors at the source. Using a Ti/TiO2-Ta2O5-IrO2 anode and a graphite cathode, under the conditions of 30 mg L-1 Fe2+ dosage, 3 mA cm-2 current density, and 2 cm electrode spacing, the removal rate of natural organic matter reached 92.62% ± 1.99%. Analysis via three-dimensional excitation-emission matrix fluorescence spectroscopy (3D-EEM) and ultraviolet-visible absorption spectroscopy (UV-Vis) collectively confirmed that macromolecular HA underwent significant oxidative cleavage and adsorption removal in the reaction system. Hydroxyl radicals (·OH) attacking HA molecules were identified as the key mechanism driving oxidative degradation. Meanwhile, the continuous redox cycling of iron species (Fe2+/Fe3+) in the system facilitated this process, and the resulting Fe3+ effectively removed HA and their degradation products through flocculation. Furthermore, the coexistence of Fe, O, and C elements within the flocs, along with the identified coordination structures between HA and Fe(OH)3, directly confirms the binding of organic matter, such as HA, onto iron hydroxide flocs. Finally, the applicability of this technology was validated in real water samples, and its disinfection efficacy was evaluated through microbial diversity analysis.

Simple wet chemical method was used to prepare Cu(OH)2 nanowire-coated copper mesh (denoted as Cu(OH)2-CM). Following modification with phytic acid (PA) and polyethyleneimine (PEI), superhydrophilic/underwater superoleophobic copper mesh (denoted as Cu(OH)2/PA/PEI-CM) with excellent mechanical and chemical stability was obtained. The Cu(OH)2/PA/PEI-CM exhibited efficient separation for various oil/water mixtures. Importantly, Cu(OH)2/PA/PEI-CM shows superior anti-crude oil fouling properties. A 280-cycle test (with only four cleanings) using a 2 cm2 Cu(OH)2/PA/PEI demonstrates a large separation capacity, long-term stability and self-cleaning performance of the mesh during the treatment of a 11.2 L crude oil/water mixture. These distinct advantages give the Cu(OH)2/PA/PEI-CM great potential for practical application in separating oil pollutants from water.

Fusarium wilt, caused by the soil-borne Fusarium oxysporum f.sp. niveum (FON), is a devastating disease constraining global watermelon production. While three physiological races (0, 1 and 2) are established, resistance mechanisms to the foundational race remain largely unexplored. This study first evaluated seedling resistance to FON race 0 across 41 diverse watermelon accessions revealing that wild germplasm (Citrullus amarus) possessed superior resistance with 24.4% classified as highly resistant, whereas cultivated accessions were predominantly susceptible. The resistant accession WM216 and susceptible G42 were selected for in-depth analysis. Physiological assessment demonstrated that WM216 mounted a robust and systemic defence response, characterized by a significant post-inoculation induction of ROS-scavenging enzymes like catalase and peroxidase. Integrated transcriptome and BSA-seq analysis identified a major resistance QTL on chromosome 8 (15-22 Mb). Cross-referencing these datasets pinpointed a single key candidate gene, ClG42_08g0072500, encoding a two-component response regulator (ARR family) implicated in cytokinin signalling. Expression profiling suggested this gene may act as a negative regulator of resistance. Our findings underscore the invaluable resistance alleles present in wild watermelon germplasm, provide a foundational genetic map for FON-0 resistance and deliver critical molecular resources for marker-assisted breeding of durable Fusarium wilt-resistant cultivars.

As an emerging environmental pollutant, the presence and spread of antibiotic resistance genes (ARGs) in drinking water systems pose a severe challenge to global public health. This paper systematically reviews the sources, spatiotemporal distribution, transmission mechanisms, removal efficacy, and health risks of ARGs in drinking water systems. Research indicates that ARGs primarily originate from agricultural livestock farming, medical wastewater, and urban water circulation systems. Their distribution exhibits significant spatiotemporal heterogeneity, with enrichment during summer months and heightened contamination in estuaries and economically developed regions. Horizontal gene transfer (HGT) and vertical gene transfer (VGT) jointly drive the transmission of ARGs in drinking water systems. HGT primarily facilitates the rapid spread of ARGs and their transmission across different hosts, whereas VGT contributes to their long-term persistence and enrichment within stable ecological niches such as biofilms. Within drinking water treatment processes, units such as coagulation, sedimentation, and filtration demonstrate inconsistent efficacy in removing ARGs. While chlorination disinfection can inactivate some microorganisms, it may induce the release and transfer of ARGs, potentially promoting the enrichment of resistant bacteria. Biofilm formation within water distribution networks further creates a favorable environment for ARGs retention and transmission, increasing the risk to end users' water safety. Therefore, this review proposes an integrated control framework incorporating source control, treatment process optimization, distribution system management, and risk monitoring to effectively mitigate ARGs, ensure drinking water safety, and curb the spread of antibiotic resistance.

The uniformity and speed of seedling emergence are particularly important in vegetable industrial seedlings. A higher germination rate can shorten the seedling cycle and increase seedling uniformity in melon (Cucumis melo L.). However, the molecular mechanisms underlying the regulation of seed germination in melon remain largely unknown. Golden2-like (CmGLK) has been identified as a key transcription factor involved in chloroplast development, and we found that it also plays a role in regulating seed germination rate in melon. The near-isogenic line of Cmglk (Cmglk-NIL) and CmGLK knockout mutants in melon exhibited slower seed germination rates than those in wild-type lines, while the overexpression of CmGLK in tomato (Solanum lycopersicum L.) showed significantly increased germination rates. Comparative transcriptome analysis revealed that numerous abscisic acid (ABA)-related genes were involved in seed germination. Furthermore, the Cmglk-NIL and CmGLK knockout mutants exhibited increased sensitivity to exogenous ABA during seed germination, while the CmGLK overexpression lines in tomato showed reduced sensitivity to ABA. Bioinformatics analysis and experimental validation indicated that CmGLK could directly bind to the promoter of the H SUBUNIT OF MG-CHELATASE (CmCHLH) gene, thereby activating its expression. Functional validation via CmCHLH overexpression in tomato resulted in a significantly increased seed germination rate, demonstrating its positive regulatory role in germination. These findings identify a CmGLK-CmCHLH regulatory module that regulates seed germination rate through the ABA pathway in melon. They also enhance our understanding of the mechanisms underlying melon seed germination and provide a reference for seed germination regulation in other crops.

Biochar loaded with MgO is a promising adsorbent for the removal and recovery of phosphate from aqueous solutions. However, its phosphate adsorption capacity is unsatisfactory, especially at low phosphate concentrations. Loading nanoscale MgO onto biochar is an effective strategy. Here, ultrafine MgO nanoparticles and MgO nanosheets were loaded onto biochar from steam-exploded straw (UMB and SMB) via an impregnation- precipitation-pyrolysis method. The crystal sizes of ultrafine MgO nanoparticles and MgO nanosheets were about 6-8 nm and 10-16 nm, respectively. The phosphate adsorption capacity of UMB at C0 = 100 mg P L- 1 was 219.4 mg P g- 1 , which was higher than that of SMB (164.9 mg P g- 1 ). The results suggest that surface precipitation was the dominant adsorption mechanism and the hydration process and the smaller particle size of MgO may play a key role in the superior phosphate removal by UMB. Removal tests in real low-concentration phosphate water samples showed that 0.05 g L- 1 UMB could reduce the phosphate concentration from 0.17 mg P L- 1 to 0.01 mg P L- 1 . In addition, phosphate could be desorbed from UMB in varying environments, and therefore has the potential to be used in fertilizer production or directly as a slow-release fertilizer.

Genotyping by Target Sequencing (GBTS) technology, known for its flexibility, high efficiency, high throughput, and low cost, has been increasingly employed in molecular breeding. However, there is still limited study on the design and development of high-throughput genotyping tools in watermelon. In this study, we identified 112 000 high quality SNPs by analyzing the resequencing data of 43 cultivated watermelon accessions. 11 921 and 6094 SNPs were selected for developing two sets of watermelon liquid-phase chips with different marker densities, named Watermelon 10K and 5K, respectively. Furthermore, the SNPs and Indels of most mapped gene/QTLs for many agronomic important traits in watermelon were also integrated into the two chips for foreground selection. These chips have been tested using GBTS technology in various applications in watermelon. The genotyping of 76 accessions by Watermelon 5K liquid-phase chip showed an average detection rate of 99.28 % and 81.78 % for cultivated and wild watermelon accessions, respectively. This provided enough markers information for GWAS and two significant QTLs, ssc1.1 and ssc1.2, associated with soluble sugar content were detected. Furthermore, BSA-seq analysis for non-lobed leaf and dwarf traits were validated by liquid-phase chips, and the candidate region was consistent with our previous studies. Additionally, we precisely introduced the Cldw1 and Clbl genes into an elite inbred line WT2 using Watermelon 5K for assisted selection, resulting in the development of three new germplasm with good plant architecture. As a high-throughput genotyping liquid-phase SNP array, the Watermelon 10K and 5K chips will greatly facilitate functional studies and molecular breeding in watermelon.

Spines are an important trait of cucumber fruit that affects commercial quality, smoothness, transportation, storage, and pesticide residue retention. Spine Base Size1 (CsSBS1), a C2H2 zinc-finger transcription factor, has been identified as a determinant of cucumber fruit spine size, though its molecular mechanism remains unclear. Here, our study found that exogenous ethylene treatment partially restored the small spine base phenotype in the Cssbs1 near-isogenic line (NIL) S-SB and knockout lines, while the ethylene inhibitor aminoethoxyvinylglycine reduced spine base size in wild-type L-SB plants. Further investigation revealed that CsSBS1 directly bound to the promoter of the ethylene-biosynthesis gene 1-aminocyclopropane-1-carboxylate oxidase 2 (CsACO2) and activated its expression. Silencing CsACO2 through RNA interference inhibited fruit spine base expansion in wild-type plants, whereas enhanced CsACO2 expression resulted in larger spine bases in S-SB plants. Additionally, knockout of CsTTG1 led to smaller fruit spine bases and decreased ethylene release. Genetic and biochemical analyses indicated that CsTTG1 enhances CsSBS1-mediated transcriptional activation of CsACO2. Overall, our results reveal a CsSBS1-CsTTG1 regulatory module that regulates fruit spine base size via CsACO2-mediated ethylene biosynthesis in cucumber.

Photosynthesis serves as the primary source of nutrients synthesized in higher plants, and improving photosynthetic efficiency can significantly increase crop yield and fruit quality. Leaf color mutants represent ideal materials for studying chloroplast development and photosynthesis mechanisms and have been widely characterized in field crops. However, relevant research on watermelon leaf color mutants remains scarce. In this study, we isolated a yellow-green phenotype mutant, PKH352, from an EMS-mutagenized watermelon mutant library. The chlorophyll content and maximal photochemical efficiency in PKH352 were significantly decreased. Genetic analysis showed that the mutated trait was controlled by a single nuclear gene, which was named Clygp (Citrullus lanatus yellow-green plant). Through MutMap and linkage analysis in an F2 population of 440 plants, we identified a single nucleotide polymorphism (SNP) mutation within ClG42_04g0106300, which encoded a signal recognition particle 54 kDa protein, as the causal variant for the yellow-green phenotype. Further validation using a CRISPR/Cas9-mediated system confirmed that knockout of ClG42_04g0106300 results in the yellow-green phenotype in watermelon. In addition, comparative transcriptomic analysis revealed that mutations in ClG42_04g0106300 greatly affected the expression of key genes associated with chloroplast development and photosynthesis, providing strong evidence that this gene plays a critical role in these biological pathways. Taken together, these findings provide insights into the molecular mechanisms underlying chloroplast development and photosynthetic efficiency, offering a theoretical basis for breeding watermelon varieties with high photosynthetic efficiency.

The dwarf structure is an important agronomic trait in watermelon, which can increase plant density and is useful for lab-saving cultivation. Cldw-1 encodes an ABCB transporter protein controlling plant height in watermelon, making it useful in dwarf breeding. However, the regulatory mechanism of Cldw-1 in dwarf formation remains unclear. In this study, a donor parent WM102 carrying the Cldw-1 gene was crossed with a recurrent parent WT4, resulting in BC1F1, BC2F1, and BC2F2 populations. In each generation, the Cldw-1 co-segregating marker dCAPS3 was used for foreground selection and 108 polymorphic SSR markers were used for background selection to develop the near isogenic lines (NIL) of Cldw-1. We ultimately obtained a dw-NIL1 in BC2F2 with a proportion of recurrent parent genome (PRPG) of 98.50 % in WT4 background. Compared to WT4, the plant height, internode number, internode length and tendril length was significantly reduced in the dw-NIL1. Cytological observations indicated that the reduction in cell length lead to shorter stems, while an increase in cell number resulted in thicker stems in the dw-NIL1. Transcriptome analysis of the stems of WT4 and dw-NIL1 identified 518 differentially expressed genes (DEGs) with 392 up-regulated and 126 down-regulated. Among them, a number of DEGs were related to auxin signaling pathway, which are known to regulate plant height. Cell wall biosynthesis and modification, as well as protein modifications, were significantly enriched. These results not only provide important germplasms for dwarf breeding, but also will be helpful for better understanding the molecular mechanisms of plant height development in watermelon.

Cyromazine, a widely used insect growth regulator, accumulates in livestock manure and poses risks to beneficial insects such as black soldier fly larvae (BSFL) during waste bioconversion. This study isolated two bacterial strains capable of degrading cyromazine, Bacillus subtilis CYR1 (CYR1) and Bacillus velezensis CYR2 (CYR2), from contaminated chicken manure. Both strains demonstrated significant degradation efficiency via hydrolysis of cyromazine to cyanuric acid, a less toxic metabolite. However, in chicken manure systems, degradation efficiency reached a plateau at approximately 20 %, likely due to preferential utilization of alternative nitrogen sources and inherent metabolic constraints. These findings highlight the potential of microbial remediation to mitigate cyromazine contamination while underscoring the need for strain optimization and comprehensive ecotoxicological assessments.

Watermelon is an economically important horticultural crop cultivated worldwide. The ERF family is one of the largest transcription factor families in plants and plays an extensive role in regulating growth, development, hormone signaling, and stress responses. Although the ERF family has been characterized in various plant species, it remains unexplored in watermelon. In this study, we identified 118 ClERF family members in Citrullus lanatus and classified them into ten subgroups. We conducted comprehensive analyses of their physicochemical properties, evolutionary relationships, chromosomal locations, collinearity, gene structures, conserved motifs, and promoter cis-regulatory elements. Furthermore, we comprehensively analyzed the expression patterns of subgroup VIII genes and transcriptional responses to abiotic stresses (cold, salt), a biotic stress (Fusarium wilt), and hormone treatments (ABA, MeJA, SA, BR and ETH). Crucially, functional analysis demonstrated that overexpression of ClERF054 significantly enhanced plant susceptibility to cold and salt stresses. This research establishes a theoretical foundation for understanding the ClERF gene family in watermelon and provides important insights into the functional divergence of subgroup VIII members in hormone signaling and biotic/abiotic stress responses, while also facilitating investigations into the regulatory mechanisms of ClERF054 under cold and salt stresses.

Senescence is a complex biological process coordinately regulated by multiple genes at the molecular level. Deciphering its regulatory mechanisms holds significant potential for enhancing crop yield and stress resistance. However, the study on identification of senescence-related genes in watermelon has been limited by low genetic diversity. In this study, we identified an early-senescence watermelon inbred line, WM103, which displayed a pale green phenotype at the seedling stage that transitions to yellow at maturity. Genetic analysis indicated the early-senescence phenotype was controlled by a single recessive gene. Combined by BSA-seq and linkage analysis in a large F2 population, we identified Cla97C10G186360 as the candidate gene, which encoded a BALANCE OF CHLOROPHYLL METABOLISM (ClBCM) protein. Further functional validation through virus-induced gene silencing and CRISPR/Cas9-mediated knockout confirmed that the down-regulation and loss of function of ClBCM can accelerate senescence. RNA-seq analysis revealed that the ClBCM was involved in the chlorophyll metabolism pathway, and these chlorophyll degradation-related genes were significantly up-regulated in WM103. Molecular interaction assays revealed a direct physical interaction between ClBCM and ClSGR. Furthermore, we found WRKY family transcription factors were significantly enriched in differentially expressed genes. In vivo and in vitro experiments showed ClWRKY53 directly bound to the ClBCM promoter and suppressed its transcription, thereby promoting chlorophyll degradation and senescence. These findings provide novel insights into the molecular regulation of senescence in watermelon and establish a theoretical framework for genetic improvement of fruit yield and stress tolerance in cucurbit crops.

Biofilms have extensive applications and important roles in biological processes. This study aimed to investigate the effect and mechanism of low-concentration sulfamethoxazole (SMX) on biofilm development in biofilters. The effects of various SMX concentrations (0, 100 ng/L, 1000 ng/L) on microbial development were compared. Compared with the control group without SMX, the start-up period of R2 and R3 filters with SMX added was decreased by 9 % and 21 %, respectively. Under antibiotic stimulation, reactive oxygen species (ROS) and bis-(3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP) concentrations increased, aligning with changes in extracellular polymer content and biofilm formation. Microbial community results showed that the presence of SMX promoted the growth of some manganese-oxidizing bacteria (MnOB), such as Massilia, Pedomicrobium, Sphingopyxis, Pseudomonas, and Bacillus. Functional gene analysis further revealed higher expression levels of genes related to c-di-GMP transformation in the presence of SMX. These findings suggest that microbial communities can adapt to their environment by accelerating biofilm formation at lower antibiotic concentrations. The results of this study provide new insights into the impact of low-concentration antibiotics on biofilm development and offer a crucial reference for biofilter design and optimization.

The early flowering and less lateral branches in watermelon hold significant agricultural value. The synergistic effects of these traits provide an ideal template for watermelon plant architecture improvement. However, the molecular regulatory networks underlying the development of lateral organs (including branches and flowers) in watermelon remain unclear. In this study, we found ClTFL1 knockout lines significantly promote flowering time and inhibit lateral branching and tendril formation, while also leading to a mild apical flower phenotype. These findings indicate that the function of ClTFL1 in watermelon is more extensive than that of its homologous genes in Arabidopsis, rice, and tomato. Through yeast two-hybrid screening, we identified the interacting proteins of ClTFL1, including members of the 14-3-3 family ClGRF8, ClGRF9, and ClGRF12. Bimolecular fluorescence complementation (BiFC) assays further demonstrated ClTFL1 could directly interact with the ClGRF8, ClGRF9, and ClGRF12 protein. The knockout of ClGRF8 and ClGRF12 leads to reduced lateral branches and early flowering. These phenotypes are highly consistent with those of ClTFL1 knockout mutants. Our findings demonstrate the important role of the ClTFL1-ClGRFs module in regulating lateral organ development and flowering time in watermelon, offering important targets for watermelon plant architectural modification and molecular breeding.

Electrochemiluminescence (ECL) is highly recommended in chiral recognition. ECL-based chiral sensors highly desire a sensitive sensing interface for signal conversion and absolute chiral discrimination. The ECL emission based on a luminol-dissolved O2 system received much attention due to its nontoxicity and stability. However, the drawback of weak ECL emission hinders the fast signal conversion from chiral discrimination to ECL response. Herein, the amplification strategy of ECL emission is proposed based on the electrochemical reduction enhanced O2 reduction reaction (ORR). Cadmium sulfide decorated on carbon-nanotubes (CdS/CNTs) with easy synthesis, wide-pH operation, and suitable valence-conduction band position is employed. Upon cathodic scan, the electrons transfer from electrochemically reduced-CdS/CNTs to O2 and H2O2, thus accelerating the generation of reactive oxide species (ROS) and furthering ECL emission. Furthermore, the chiral ECL sensing interface is well-designed by combining the chiral recognition of D-amino acid oxidase (DAAO) with the signal transduction and amplification of CdS/CNTs-enhanced ECL emission. During DAAO-catalyzed enantioselective-oxidations of alanine, the O2 is converted to H2O2, which tunes the ROS generation. With synergetic regulations of ROS generation by nano-derived CdS/CNTs and bio-derived DAAO, alanine enantiomers are highly discriminated and the L-alanine is quantitatively detected with the most competitive detection limit so far (0.014 fM).

During the pre-anthesis stage, high chlorophyll levels in petals result in a green hue in many plants. Upon anthesis, chlorophyll degradation uncovers other pigments, thereby influencing pollinator attraction and reproductive success in insect-pollinated crops. In the watermelon accession WM109, a novel petal phenotype characterized by a yellow-green hue was observed, significantly different from the canonical yellow petal phenotype typically associated with this species. Genetic analysis using F2 populations revealed that this yellow-green petal trait is controlled by a single recessive gene. By screening SSR primer pairs with the constructed yellow and yellow-green DNA pools and genotyping F2 individuals, the responsible gene was mapped to a 139.7 kb interval on watermelon chromosome 11, containing two candidate genes. Through sequence analysis, expression profiling, and functional verification of these candidates, a gene encoding a MYB transcription factor with a base insertion was identified as the key determinant of this unusual phenotype, which is characterized by elevated chlorophyll levels and increased chloroplast density. Given the limited current knowledge regarding the relationship between MYB transcription factors and chlorophyll biosynthesis, these findings enhance our understanding of the molecular mechanisms underlying chlorophyll production.