Watermelon and melon are important members of the Cucurbitaceae family, offering high economic benefit and nutritional value. With the release and ongoing refinement of the watermelon and melon genomes, many target genes (or loci) for further biology regulation exploration and molecular breeding, have been identified. Herein, we describe recent progress in genetic mapping and molecular regulation mechanisms for fruit quality, fruit development, plant morphogenesis, and plant disease resistance. We further outline future research priorities and breeding frameworks for watermelon and melon. This review delineates molecular regulators of fruit and plant development, offering a framework to explore homologous mechanisms in other Cucurbitaceae members.

In this study, a stably inherited short-vine mutant, G42cs, was identified and obtained from an EMS-mutagenized watermelon mutant library. Phenotypic characterization, genetic analysis, preliminary mapping of the short-vine gene, and research on its application in breeding were subsequently conducted on this mutant. Investigation of field agronomic traits revealed that the mutant exhibited significant differences from the wild type in traits such as plant height, tendrils, petioles, fruit pedicel length, and fruit size, while other traits showed no notable differences. Cellular staining observation of mutant tissues revealed that, compared to the wild type, the apical tissues of the mutant possessed more bud primordia or leaf primordia. The stem cells of the mutant were smaller than those of the wild-type watermelon, exhibiting a more compact and crowded arrangement, along with a higher number of cells per unit area. Measurements of plant height of the F2 population revealed that the short-vine trait is controlled by a single pair of recessive genes. Subsequently, BSA-Seq was performed using the two parents and the F2 population, which preliminarily mapped the short-vine gene to a 4.5 Mb region on chromosome 1. A dCAPS marker was developed to assist in screening for short-vine materials. Breeding backbone lines were developed using this short-vine mutant and applied in seed production. Assessments of seed yield per unit area and labor inputs showed that utilizing this short-vine trait in seed production can effectively reduce overall costs, demonstrating certain practical value. This model offers a new approach for watermelon seed production.

Lipoxygenase (LOX) is ubiquitous in plants and functions as a key enzyme responsible for jasmonic acid (JA) biosynthesis, participating extensively in diverse plant physiological processes. Nevertheless, systematic characterization and functional investigation of LOX genes have rarely been reported in watermelon. In the present study, a total of 21 watermelon LOX genes were identified and collected. Subsequent phylogenetic classification and promoter cis-element analysis were performed, alongside expression profiling across different tissues and expression fluctuation assays following powdery mildew inoculation. We further cloned ClLOX6A and verified its biological function via transgenic overexpression. Compared with wild-type controls, susceptible watermelon lines overexpressing ClLOX6A exhibited markedly smaller lesion areas, reduced dead cell accumulation, restricted pathogen hyphal expansion and fewer conidia on leaf surfaces upon powdery mildew infection. Consistently, endogenous contents of JA, methyl jasmonate (MeJA) and OPDA were significantly elevated in ClLOX6A-overexpressing plants. Moreover, an uncharacterized protein ClDUF640 was newly identified to interact with ClLOX6A, which expands the molecular components of the JA-dependent regulatory cascade governing powdery mildew resistance. In addition, a KASP molecular marker designated pm-9564 was developed in this work to facilitate marker-assisted breeding for disease resistance in watermelon.

Abstract Watermelon (Citrullus lanatus) has undergone severe loss of genetic diversity due to domestication, necessitating the exploitation of wild relatives for trait improvement. While structural variations (SVs) represent a major source of genetic diversity, high-throughput SV genotyping remains technically challenging, and existing SNP arrays fail to capture presence/absence variations (PAVs) that differentiate wild from cultivated germplasm. Here, we developed the ‘Watermelon 40K SNP-SV Chip,’ the first liquid-phase genotyping chip enriched with SV markers, leveraging a telomere-to-telomere super-pangenome of seven Citrullus species. The chip comprises 7087 SV markers (enriched for PAVs) and 11 383 SNP/InDel markers. Technical validation in 12 accessions and large-scale genotyping of 228 diverse accessions demonstrated high reproducibility (≥98.5% concordance) and robust call rates (>97%), though performance declined in deeply divergent wild species. Genome-wide association studies revealed SV-specific signals for flesh color and rind pattern that co-localized with known QTL, including a strong candidate regulatory PAV upstream of LCYB. The predominance of rare variants (74.3% SVs with MAF < 0.05) limits statistical power for detecting QTL underlying polygenic domestication traits such as yield, but confers exceptional utility for tracking wild introgressions in early-generation breeding populations. The 40 K SNP-SV chip bridges the gap between fundamental SV research and practical breeding, enabling SV-assisted genomic selection for watermelon improvement.

Pollen tube growth represents a critical process in plant sexual reproduction, governed by the highly coordinated activities of ion channels that regulate polarized cell expansion. Among them, the slow anion channel (SLAC/SLAH) family plays a central role in mediating transmembrane anion fluxes, particularly nitrate (NO₃⁻). However, the identity and function of SLAH family members involved in pear pollen tube development remain largely unexplored. In this study, we identified and characterized PbrSLAH3b as a candidate nitrate-permeable anion channel highly expressed in pear pollen tubes. Expression profiling revealed that PbrSLAH3b is markedly induced by NO₃⁻ and peaks at the middle stage of pollen tube elongation. Subcellular localization analysis confirmed that PbrSLAH3b is targeted to the plasma membrane. Electrophysiological assays using a two-electrode voltage-clamp system demonstrated that PbrSLAH3b functions as an anion channel with high permeability to NO₃⁻ relative to other anions including Cl⁻ and SO₄²⁻. Notably, PbrSLAH3b mediated substantial nitrate-dependent currents in Xenopus laevis oocytes without the requirement for exogenous kinase co-expression. Moreover, antisense oligodeoxynucleotide (AS-ODN)-mediated knockdown of PbrSLAH3b significantly suppressed its transcript abundance and inhibited pollen tube elongation. Taken together, these results demonstrate that PbrSLAH3b is a NO₃⁻-permeable and NO₃⁻-activated anion channel that mediates NO₃⁻ transport to support pollen tube growth.

Drought stress is a major constraint on watermelon production worldwide. Conventional phenotyping methods for drought tolerance are often low-throughput and fail to capture dynamic physiological responses. This study validated the high-throughput phenotyping platform (Plantarray 3.0) against conventional methods by dynamically evaluating drought tolerance across 30 genetically diverse watermelon accessions. The Plantarray system quantified key dynamic traits, including transpiration rate (TR), transpiration maintenance ratio (TMR), and transpiration recovery ratios (TRRs), revealing distinct drought-response strategies. Principal component analysis (PCA) of these dynamic traits explained 96.4% of the total variance (PC1: 75.5%, PC2: 20.9%), clearly differentiating genotypes. A highly significant correlation (R = 0.941, p < 0.001) was found between the comprehensive drought tolerance rankings derived from Plantarray and conventional phenotyping. We identified five genotypes as highly tolerant and four as highly sensitive. The elite drought-tolerant germplasm, notably the wild species PI 537300 (Citrullus colocynthis) and the cultivated variety G42 (Citrullus lanatus), exhibited superior physiological performance and recovery capacity. The results demonstrate that the Plantarray system not only efficiently screens for drought tolerance but also provides deep insights into dynamic resistance mechanisms, offering a powerful tool and valuable genetic resources for breeding climate-resilient watermelon cultivars.

The KT/HAK/KUP is the largest K+ transporter family in plants, playing crucial roles in K+ absorption, transport, and defense against environmental stress. Sweet watermelon is an economically significant horticultural crop belonging to the genus Citrullus, with a high demand for K+ during its growth process. However, a comprehensive analysis of the KT/HAK/KUP gene family in watermelon has not been reported. 14 KT/HAK/KUP genes were identified in the genomes of each of seven Citrullus species. These KT/HAK/KUPs in watermelon were unevenly distributed across seven chromosomes. Segmental duplication is the primary driving force behind the expansion of the KT/HAK/KUP family, subjected to purifying selection during domestication (Ka/Ks < 1), and all KT/HAK/KUPs exhibit conserved motifs and could be phylogenetically classified into four groups. The promoters of KT/HAK/KUPs contain numerous cis-regulatory elements related to plant growth and development, phytohormone response, and stress response. Under K+ deficiency, the growth of watermelon seedlings was significantly inhibited, with cultivated watermelon experiencing greater impacts (canopy width, redox enzyme activity) compared to the wild type. All KT/HAK/KUPs in C. lanatus and C. amarus exhibit specific expression responses to K+-deficiency and drought stress by qRT-PCR. Notably, ClG42_07g0120700/CaPI482276_07g014010 were predominantly expressed in roots and were further induced by K+-deficiency and drought stress. Additionally, the K+ transport capacity of ClG42_07g0120700 under low K+ stress was confirmed by yeast functional complementation assay. KT/HAK/KUP genes in watermelon were systematically identified and analyzed at the pangenome level and provide a foundation for understanding the classification and functions of the KT/HAK/KUPs in watermelon plants.

The genetic regulatory basis of qualitative and quantitative phenotypes of watermelon is being investigated in different types of molecular and genetic breeding studies around the world. In this study, biparental F2 mapping populations were developed over two experimental years, and the collected datasets of fruit and seed traits exhibited highly significant correlations. Whole-genome resequencing of comparative parental lines was performed and detected single nucleotide polymorphism (SNP) loci were converted into cleaved amplified polymorphic sequence (CAPS) markers. The screened polymorphic markers were genotyped in segregating populations and two genetic linkage maps were constructed, which covered a total of 2834.28 and 2721.45 centimorgan (cM) genetic lengths, respectively. A total of 22 quantitative trait loci (QTLs) for seven phenotypic traits were mapped; among them, five stable and major-effect QTLs (PC-8-1, SL-9-1, SWi-9-1, SSi-9-1, and SW-6-1) and four minor-effect QTLs (PC-2-1 and PC-2-2; PT-2-1 and PT-2-2; SL-6-1 and SSi-6-2; and SWi-6-1 and SWi-6-2) were observed with 3.77–38.98% PVE. The adjacent QTL markers showed a good fit marker-trait association, and a significant allele-specific contribution was also noticed for genetic inheritance of traits. Further, a total of four candidate genes (Cla97C09G179150, Cla97C09G179350, Cla97C09G180040, and Cla97C09G180100) were spotted in the stable colocalized QTLs of seed size linked traits (SL-9-1 and SWi-9-1) that showed non-synonymous type mutations. The gene expression trends indicated that the seed morphology had been formed in the early developmental stage and showed the genetic regulation of seed shape formation. Hence, we think that our identified QTLs and genes would provide powerful genetic insights for marker-assisted breeding aimed at improving the quality traits of watermelon.

钾元素是植物生长发育过程中必需的主要矿质营养元素之一,对作物的产量和品质有决定性影响,细胞内K+含量水平在很大程度上受K+转运蛋白控制.通过生物信息学方法从全基因组水平鉴定出萝卜K+转运蛋白HAK/KUP/KT基因家族成员,并对其基因结构、蛋白质特性、保守基序、染色体定位、启动子顺式作用元件、系统进化及表达特性等进行分析.结果表明,鉴定出的17个萝卜HAK/KUP/KT基因不均等地分布在萝卜6条染色体及Scaffold00840上,根据与拟南芥的同源关系将其命名为RsHAK1～RsHAK17;RsHAKs基因结构、保守基序、蛋白质理化特性等均具有高度保守性,启动子区域存在大量与环境因素、植物激素、逆境胁迫应答等有关的顺式作用元件;系统进化分析结果显示,17个RsHAKs基因聚为4个亚家族,全基因组复制事件是RsHAKs基因扩张的主要驱动力.转录组和qRT-PCR表达分析结果表明,除RsHAK5仅在萝卜根部表达外,其他RsHAKs在萝卜各器官及发育过程中均有特异性表达,且在高钾渗透胁迫下在叶片中相对表达量显著上调,RsHAK3、RsHAK9、RsHAK11和RsHAK12在根部呈现明显的缺钾诱导表达模式.研究结果为进一步全面解析HAK/KUP/KT基因在萝卜中的生物学功能以及提高萝卜栽培品质提供了一定理论依据.

甜瓜霜霉病是威胁我国乃至世界甜瓜产业发展的主要病害之一.近几年,我国甜瓜的栽培面积呈不断扩大趋势,甜瓜霜霉病的发生也逐年增多.该病害传播速度快且防治难度大,对我国甜瓜的产量和品质造成了严重影响,同时也引起巨大的经济损失,严重制约了甜瓜产业的可持续发展,因此对于甜瓜霜霉病的深入研究尤为重要.为了防控该病害,从 19 世纪60 年代起,各国的科研工作者就陆续展开了关于甜瓜霜霉病的相关研究.本文以前人的研究为基础,围绕甜瓜霜霉病进行了系统全面的综述,主要包括甜瓜霜霉病的危害与症状识别、引起该病害的病原菌及其生理小种分化情况、侵染循环与发生规律、抗性相关研究、防治方法等五大方面.其中,对甜瓜霜霉病的抗性研究展开了详细阐述,具体分为抗性鉴定、抗性材料、抗性遗传分析、抗性资源分子标记及基因/QTL定位共4 个方面.另外,本文也对甜瓜霜霉病研究中存在的问题及解决办法进行了分析与讨论,以期为该病害的深入研究及科学防控提供参考.

Leaf color mutants are important materials for studying chloroplast and photomorphogenesis, and can function as basic germplasms for genetic breeding. In an ethylmethanesulfonate mutagenesis population of watermelon cultivar “703”, a chlorophyll-deficient mutant with yellow leaf (Yl2) color was identified. The contents of chlorophyll a, chlorophyll b, and carotenoids in Yl2 leaves were lower than those in wild-type (WT) leaves. The chloroplast ultrastructure in the leaves revealed that the chloroplasts in Yl2 were degraded. The numbers of chloroplasts and thylakoids in the Yl2 mutant were lower, resulting in lower photosynthetic parameters. Transcriptomic analysis identified 1292 differentially expressed genes, including1002 upregulated and 290 downregulated genes. The genes involved in chlorophyll biosynthesis (HEMA, HEMD, CHL1, CHLM, and CAO) were significantly downregulated in the Yl2 mutant, which may explain why chlorophyll pigment content was lower than that in the WT. Chlorophyll metabolism genes such as PDS, ZDS and VDE, were upregulated, which form the xanthophyll cycle and may protect the yellow‒leaves plants from photodamage. Taken together, our findings provide insight into the molecular mechanisms of leading to leaf color formation and chloroplast development in watermelon.

As agricultural drought becomes more frequent worldwide, it is essential to improve crop productivity whilst reducing the water consumption to achieve a sustainable production. Plant transpiration and water use efficiency (WUE) collectively determine 21 the yield performance, yet it is challenging to balance the two in breeding programs due 22 to still insufficient mechanistic understanding of the traits. Here we developed a method 23 of quantifying the genotype-specific traits reflecting sensitivity of transpiration to 24 radiation (Rad) and vapor pressure deficit (VPD) under evolving developmental stage 25 and water availability (S Tr-Rad and S Tr-VPD ). Our method takes advantages of the state- 26 of-the-art functional physiological phenotyping (FPP) and the principle of inversely 27 using simulation models. We revealed the genotypic difference of S Tr-Rad and S Tr-VPD in 28 three watermelon accessions, the dramatic change in each of them across the treatment 29 phases, and the quantitative impacts of them on dynamic WUE patterns. Based on our 30 findings, a general principle for transpiration ideotype design is proposed, which 31 highlights the benefits of lowering S Tr-VPD to increase WUE and increasing S Tr-Rad to 32 offset the decline of Tr. FPP-enabled phenomic selection will help screen for elite crops 33 lines with desired transpiration sensitivities.

CONSTANS-like (COL) genes play important regulatory roles in multiple growth and development processes of plants but have rarely been studied in Capsicum annuum. This study explored the evolutionary relationship and expression patterns of COL genes from C. annuum. A total of 10 COL genes were identified in the genome of the cultivated pepper Zunla-1 and were named CaCOL01-10. These genes were unequally distributed among five chromosomes and could be divided into three groups based on differences in gene structure characteristics. During evolutionary history, duplications and retentions were divergent among different groups of COL genes. Tandem duplication caused amplification of group I genes. Genetic distance among COL genes was the largest in group III, suggesting that group III genes undergo more relaxed selection pressure compared with the other groups. Expression patterns of CaCOLs in tissues were significantly different, with CaCOL08 exhibiting the highest expression in stem and leaf. Some COL orthologous genes showed markedly different expression patterns in pepper compared with tomato, such as COL_1 orthologs, which may be involved in fruit development in pepper. In addition, CaCOLs participated in the regulation of abiotic stresses to varying degrees. Five CaCOL genes were induced by cold, and CaCOL02 and CaCOL03 were specifically upregulated by cold and downregulated by heat. This study provides a theoretical basis for the in-depth understanding of the functions of COL genes in pepper and their molecular mechanisms involved in growth and development and responses to abiotic stresses.

为研究杏鲍菇渣基质化应用的适宜发酵条件,通过添加木薯渣、牛粪、双孢菇渣和设置不添加,添加0.05％、0.10％发酵菌剂3个试验组合,测定不同发酵阶段发酵产物发酵温度、积温、孔隙度、容重、可溶性盐浓度(EC)值及pH值等,并通过育苗试验对不同处理发酵产物基质化利用结果进行评价.结果表明,不同处理之间的有效积温存在差异,其中添加0.10％发酵菌剂的杏鲍菇渣处理有效积温最高;添加双孢菇渣处理的EC值均显著高于其他处理,添加牛粪处理的EC值始终最低;不同处理的pH值变化趋势不规律.发酵结束各处理的总孔隙度在43.04％～54.10％之间,通气孔隙在9.45％～30.44％之间,持水孔隙在20.72％～39.39％之间,容重在0.18～0.33 g/cm3之间.杏鲍菇渣和木薯渣混合发酵产物配制的育苗基质综合表现最好.综上,本试验条件下杏鲍菇渣发酵腐熟的最佳方法为每500 L杏鲍菇渣与500 L木薯渣混合.

在慈溪市现代农业园区引进21个小果型西瓜品种进行比较试验,通过盐碱土环境下植株长势、 抗性、 品质等指标的比较,筛选优质耐盐碱小果型西瓜品种.结果表明,早春红玉和兰芯耐盐碱性良好,综合品质佳,适宜作为盐碱地开发的优质西瓜品种在本地盐碱土示范推广种植.

With the application of SNP markers in breeding, KASP technology is of great value in crop fingerprint construction and seed purity detection due to its low cost, high throughput and high accuracy. SSR markers are commonly used for molecular identification and fingerprint of watermelon varieties, but the test process is complicated and inefficient. Fifty-four watermelon inbred lines including wild type, East Asian type and American type, and 25 watermelon hybrids with distinct agronomic traits were genotyped using KASP technology and 32 pairs of core SNP markers. The genetic distance and genetic background between the inbred lines were revealed, which provided a direction for watermelon breeding, and the fingerprints of Sumeng and Suchuang brand watermelon varieties were constructed. Two pairs of primers screened from 32 pairs of primers could be used for seed purity detection of Sumeng No.5,Sumeng No.6, Sumeng No.7, Sumeng No.9, Suchunag No.3, Suchuang No.4 and Suchuang No.5, a simple, fast and efficient method for variety identification and seed purity testing of watermelon.

以苏梦6号为代表的苏梦系列西瓜果实具有较好的耐裂性,为研究其果皮特性,测定西瓜果皮硬度,采集西瓜常规数量性状,观察果皮组织显微结构,测定果皮内含物含量,分析不同西瓜品种间果皮硬度相关性状差异.结果表明,不同西瓜品种间果皮硬度存在明显差异,果皮硬度越大,果皮石细胞群越丰富且排列越紧密、中果皮层细胞越大.相关性分析发现,西瓜果皮硬度与半纤维素含量呈极显著正相关,与果皮厚度、石细胞占周比、果实中心可溶性固形物含量呈显著正相关,与中果皮层细胞纵径呈显著负相关.通径分析发现,正向作用因子对西瓜果皮硬度直接通径系数较大的为:果皮厚度、果形指数、中果皮层细胞纵径、果皮半纤维素含量、边部可溶性固形物含量;负向作用因子直接通径系数较大的为:外绿果皮层厚度、果皮含水量、表皮层厚度、中心可溶性固形物含量、果皮纤维素含量;其中,果皮半纤维素含量、中心可溶性固形物含量、石细胞群占周比、果皮厚度、中果皮层细胞纵径对果皮硬度总作用系数绝对值均大于0.7,且仅中果皮层细胞纵径总作用系数为负.14个西瓜果皮硬度相关性状经主成分分析可归于4个主成分,累计贡献率为87.43％.西瓜果皮硬度受常规数量性状、果皮显微结构、内含物含量等综合影响.

以江苏淮安地方青萝卜品种紫芽青为材料,在萝卜"破肚"后喷施氨基多糖水溶肥,研究不同浓度的氨基多糖水溶肥处理对青萝卜生长、品质及抗氧化酶活性的影响.结果表明,适宜浓度的氨基多糖水溶肥处理可以增加青萝卜肉质根茎粗、地上部鲜质量和肉质根鲜质量,提高萝卜的根冠比;增强萝卜叶片的抗氧化酶活性,降低MDA的含量,提高植株对逆境的抗性;提高萝卜肉质根中可溶性总糖、干物质、可溶性蛋白、维生素C的含量,降低有机酸含量.不同浓度处理均以100 mg/mL效果最好,200 mg/mL处理反而对肉质根鲜质量及根冠比的增加有一定的抑制作用.由此可见,适宜浓度的氨基多糖水溶肥处理可以促进青萝卜肉质根生长,提高根冠比,增强植株对逆境的抗性,改善萝卜品质性状,在水果萝卜高效栽培中具有一定的应用价值.