The root-knot nematode (Meloidogyne incognita) poses a major threat to global agriculture by impairing root function, reducing nutrient uptake, and ultimately limiting seed development and crop productivity. This study investigated the molecular and metabolic defense responses of Cucumis metuliferus (prickly pear) to M. incognita infection. Gene expression and metabolic pathway reprogramming in M. incognita-infected roots were examined using integrated transcriptomics and metabolomics approaches. The identified genes were involved in stress responses and defense activation. Furthermore, metabolite profiling revealed significant shifts in secondary metabolite production, with an upregulation of defense-related compounds like jasmonic acid, salicylic acid, and prostaglandins. KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway enrichment analysis highlighted critical pathways such as biotin metabolism and nucleotide metabolism, underscoring the adaptive metabolic responses of C. metuliferus plants. GO (Gene Ontology) analysis from the integrated transcriptomics and metabolomics data highlighted significant upregulation of enzymatic pathways, transporter activities, and reorganization of cellular structures. Furthermore, KEGG pathway analysis revealed activation of secondary metabolite biosynthesis, immune-related signaling pathways, and metabolic reprogramming including increased carbon metabolism and nucleotide biosynthesis. This study provides a valuable molecular framework for breeding of M. incognita-resistant cultivars, ultimately supporting more stable seed distribution and agricultural productivity in M. incognita-prone regions.

Watermelon fruit flesh displays various colors. Although genetic loci underlying these variations are identified, the molecular mechanism remains elusive. Here, we assembled a chromosome-scale reference genome of an elite watermelon and developed integrated genetic maps using single nucleotide polymorphism (SNP) and structural variation markers. Several key genetic varients for fruit shape and flesh color were identified. Two variants associated with flesh color were further studied, including one copy number variant (CNV, a triplicate of 1.2 kb DNA) in the promoter region of REDUCED CHLOROPLAST COVERAGE 2 (ClREC2) and one SNP in Lycopene β-Cyclase (ClLCYB) coding region. These two variants together explained 99.7% of the flesh color variations in 314 watermelon accessions. The SNP in ClLCYB was the same as previously reported, disrupting ClLCYB function. The CNV could strongly enhance ClREC2 expression, consequently increasing the expression of carotenoid biosynthesis genes, the number of plastoglobules within chromoplasts, and carotenoid level in mature fruit flesh. Finally, we proposed a "two-switch" genetic model by integrating two major causative loci, which can explain the formation of the four main flesh colors in different watermelon accessions. These results provide new insights into the regulation of carotenoid biosynthesis and color formation in plants.

China has a long history in melon cultivation and accumulated remarkable diversity in melon germplasm across its diverse agroecological regions. As the genetic foundation for crop improvement, melon germplasm collection serve as critical assets supporting molecular breeding programs, genomic studies, and commercial cultivar development in the horticultural sector. China has established a medium-to long-term conservation, distribution, and utilization strategic framework for melon germplasm. The National Mid-term Genebank for Watermelon and Melon (Zhengzhou) was established in 2001. It mainly conserve the seed of watermelon and melon germplasms. The primary responsibilities include collection, conservation, reproduction, identification, innovation and distribution for these germplasm resources, which ensures the mid-term conservation of melon germplasm resources. As of December 2024, the National Mid-term Genebank for Watermelon and Melon (Zhengzhou) has collected and conserved 2206 melon germplasm resources from 89 different countries in the world. These melon germplasm resources have catalyzed advancements in the breeding of new varieties, and fundamental research domains, such as genomic evolution and domestication origins, trait-specific marker development (such as quality and disease resistance, stress resistance, and so on). These measures have contributed to the cultivar structural optimization of and the promotion of sustainable development of the melon industry. This review presents an overview of the development history and progress of the melon germplasms conservation. And innovative utilization and intend s to offer the theoretical and practical references for enhancing the utilization efficiency of melon germplasm resources and upgrading of the industry in China.

Watermelon (Citrullus lanatus) is one of the top ten fruit-bearing species in the world and is mainly grown for its edible fruit. However, the understanding of watermelon fruit size is still incomplete, with relatively few studies on the genetic and molecular mechanisms of this trait. In the present study, three segregation populations from one novel germplasm with small fruit and different inbred lines with medium fruit, big fruit and giant fruit, respectively, were constructed to locate and fine map one new quantitative trait locus (QTL) on chromosome 8 for fruit size in watermelon. Inheritance analysis of these three populations suggested that small fruit was controlled by a single recessive gene in watermelon. We located a new QTL for fruit size on chromosome 8, and developed markers to conduct fine mapping of the genomic region and to identify candidate genes. Specifically, we constructed a high-density genetic linkage map using restriction-site associated DNA (RAD)-based high-throughput genotyping data from a second-filial generation (F2) mapping family derived from novel germplasms with small fruit and big fruit. The total genetic map length was 1315.53 cM with an average inter-locus distance of 0.18 cM, which contained 7,272 high-quality single nucleotide polymorphism (SNP) markers distributed on 11 linkage groups corresponding to the number of chromosome pairs in watermelon. Genome wide QTL mapping revealed one significant QTL (fs-chr8) on chromosome 8 associated with fruit size. One major QTL (fs-B171) on chromosome 8 was also identified in another BC1 population derived from giant watermelon and small watermelon, which overlapped with fs-chr8. Moreover, based on the markers obtained from next-generation sequencing of the parental lines, we conducted fine mapping of the interval to a 304 kb region (from 26.83 to 27.14 Mb) on chromosome 8 using 7 polymerase chain reaction (PCR) based markers. The PCR based markers confirmed the accuracy of our mapping results for watermelon fruit size. Finally, candidate genes underlying fruit size were identified from the reference genome 97103v2, including genes related to cytochrome P450 family enzymes, gibberellin-regulated proteins, transcription factor and basic leucine zipper (bZIP) transcription factor family proteins. Our study provides fine mapping results for watermelon fruit size and will lay the foundation for the identification of candidate genes to elucidate the molecular mechanism underlying fruit size in this species.

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.

火参果是我国近年发展较快的新型瓜类作物,针对我国火参果种质资源稀少的现状,笔者持续开展了火参果种质资源引进、收集和保存工作,对前期引进的42份火参果种质资源的主要果实性状进行了初步评价,筛选出部分优异种质;另以优异种质TY18与TY19-2为亲本,通过杂交转育方式创制出无刺、黄果类型种质,该种质拥有明显不同于常规种质的果实外形和较高可溶性固形物含量的优质性状,为一种新种质,暂命名为火星20,具有良好的栽培应用价值和育种利用前景.

Internode length (IL) is an important characteristic of plant architecture of watermelon (Citrullus lanatus L.). A dwarf type plant phenotype can support the greater planting density and land utilization for well growth of crop plants. In this study, two watermelon lines "W1-1 (standard vine) and ZXG01061 (dwarf vine)" were used as parental lines and F-1, F-2, BC1P1 and BC1P2 generations were developed for dwarf trait inheritance analysis and candidate gene identification. Genetic analysis of two year's collected phenotypic data indicated that watermelon dwarfism was regulated by a single recessive gene (cladw). Bulked segregant analysis sequencing (BSA-seq) total of 1.24-Mb genomic region harbouring the candidate dwarfism gene on chromosome 9. Fine genetic with 1,097 F-2 plants signified that the cladw locus was finally delimited to a 203-kb region containing 10 candidate genes (including five genes annotated as GID1L2 gibberellin (GA) receptors). Endogenous hormone quantification analysis also showed that the internode GA content of ZXG01061 was higher than that of W1-1. When ZXG01061 plants were treated with exogenous application of GA(3), then original plant height was not recovered, indicating that ZXG01061 is GA insensitive. Further, Cla010254 and Cla010256 (annotated as gibberellin receptor GID1L2) exhibted base deletions in ZXG01061 compared with W1-1. The expression of Cla010254 in W1-1 was significantly higher than that of ZXG01061. In conclusion, our results indicated that Cla010254 is a candidate gene for regulating the watermelon dwarfism trait.

Textural quality of watermelon fruit is mainly determined by rind hardness/firmness and its related traits. The determination of genetic regions harboring QTLs/gene(s) has a primary worth in genetic breeding studies. In this study, whole genome BSA-seq and QTL mapping through newly developed CAPS markers were successfully performed, respectively. Total 133-F2 mapping individuals were derived from crossing of P1 ‘1061’ and P2 ‘812’ and slefing of F1 offspring. Whole genome BSA-seq revealed major genetic region controlling rind hardness trait on chromosome 10. The genetic linkage map was assembled by genotyping of 133 pairs of codominant CAPS markers which spanned total 2606.38 cM length with averaged 19.60 cM distance among whole genome flanking markers. Moreover, CAPS markers based QTL analysis revealed total 5 putative QTLs [2 rind-hardness (RH), 1 rind toughness (RTO), 1 rind thickness (RTH) and 1 fruit weight (FW)] on three distinct chromosomes (2, 9, and 10), which mainly contributed 5.44–49.11% PVE. Interestingly, the combined molecular techniques expressed putative genetic region controlling rind hardness at chromosome 10. According to the BSA-seq result, major genetic region was detected between 1792001 and 4036000 bp on chromosome 10 with 2.24 Mb range, while from QTLs analysis, two co-localized focal QTLs “RH10 and RTO10” revealed 20 and 39 predicted genes at shortened genetic distances of 292.76 kbp and 405.31 kbp, respectively. A significant correlation and normal distribution frequencies for rind-phenotypes were also noticed. In crux, our combined techniques proved as an effective mapping strategies for identification of QTLs/gene(s) and provided a strong theoretical basis for future breeding studies in watermelon.

为了实现西瓜果实形状的分子精准鉴定,利用"国家西瓜甜瓜中期库"的资源和高通量测序平台,利用两个不同的杂交分离群体(F2和BC1P1)分别鉴定到1个159 bp插入缺失和1个非同义SNP导致的果形突变(由圆果形变为长果形),且SNP突变在159bp插入缺失的基因组区域内.利用这个SNP开发CAPS标记Markersun在两个群体和128份西瓜种质中进行分析,发现标记Markersun在两个群体中与果形表型共分离;在西瓜种质中可同时区分插入缺失和SNP的变异,且与果形表型共分离.同时这两个变异与果形的共分离在196份西瓜核心种质的基因型分型中也得到验证.此外,通过对不同类型西瓜种质的基因型分析发现,SNP变异导致的长果形出现的时间更早且独立遗传,而159bp插入缺失引起的长果形是栽培西瓜驯化过程中产生的.本研究中首次利用不同类型的西瓜核心种质实现了西瓜果形的分子精准鉴定,还挖掘到两个西瓜果形的功能变异并开发标记,为西瓜果形的分子精准鉴定提供技术支撑,同时为果形性状基因功能验证提供靶标,加速了西瓜果形性状基因的调控机理研究.

Seed size is an important agronomic trait in watermelon, but the candidate genes and underlying molecular mechanism are not fully known. In the present study, genetic analysis of the BC1 population derived from two parental lines revealed that watermelon seed size is controlled by a single locus and medium seeds are dominant to tomato seeds. In addition, we constructed a genetic linkage map. The total length of the linkage map was 1629.92 cM, with an average distance of .16 cM. QTL mapping and resequencing analysis identified a 13.96-kb chromosomal deletion on chromosome 2. There were only two genes (Cla97C02G045390 and Cla97C02G045400) present in the corresponding region. Transcriptome data of tomato seed and medium seed watermelons showed that the two genes were always highly expressed in medium seed plants but expressed at low or no levels in tomato seed plants. Moreover, two markers indicated that the genes were related to watermelon seed size. Our present study provides key genetic variation and potential candidate gene of watermelon seed size and lays the foundation for the molecular mechanism of seed size.

火参果是我国近年来引进和栽培的新型瓜类水果作物,具有坐果能力强、果实外观漂亮、风味独特、经济效益高和发展前景广阔等优点.就火参果遗传多样性及分类地位、种质资源评价与栽培、抗性及其利用、营养和药用功能成分方面回顾了国内外研究进展,并对火参果栽培技术要点进行总结.此外,由于目前的火参果鲜食品质难以满足大众化的消费需求,市场空间较为有限,制约了火参果产业的进一步发展,提出了解决这个问题相关的建议,旨在为促进我国火参果产业发展提供借鉴.

为了探究甜瓜种子萌发期耐盐性鉴定评价和筛选的最佳NaCl浓度,使用了20个不同的甜瓜种质在不同质量浓度NaCl处理下进行萌发试验.结果显示,NaCl质量浓度为8 g·L-1时,只有少数甜瓜发芽率显著降低;NaCl质量浓度为12 g·L-1时,不同种质甜瓜的发芽率差异明显;NaCl质量浓度为16 g·L-1时,所有甜瓜的发芽率均大幅降低;NaCl质量浓度为20 g·L-1时,90％的种质发芽率为0.发芽指数及根长数据显示,所有甜瓜在不同质量浓度的NaCl处理下的种子活力和根系生长均受到抑制,质量浓度越高抑制作用越强.综合以上结果,甜瓜萌发期耐盐性鉴定的最佳NaCl质量浓度为12 g·L-1,耐盐性筛选的最佳NaCl质量浓度为16 g·L-1,最佳数据统计时间为萌发第4天.20份甜瓜种质资源中,S02('且末泰热')的耐盐性较强,S14('金巴齿')对盐处理最为敏感,耐盐性最差.

从国家西瓜甜瓜种质中期库(郑州)和美国农业部国家种质资源中心选取厚皮、薄皮和野生甜瓜种质共191份,利用在甜瓜染色体上均匀分布的43个SSR标记鉴定其基因型,评价其遗传多样性,并利用4 ℃恒温条件下种质幼苗的冷害指数和低温处理前后的叶肉组织超微结构变化评价不同类型种质的耐冷性.结果 显示,SSR标记共检测到366个等位基因,平均8.512,平均观测杂合度和期望杂合度分别为0.074和0.704,平均多态性信息含量为0.668.UPGMA法将所有种质聚为4个类群,Ⅰ类群仅有2份印度野生种质,Ⅱ类群包含来自印度的34份野生和15份薄皮种质,Ⅲ类群含有地理分布广泛的51份厚皮和1份野生种质,Ⅳ类群由来自东亚的75份薄皮、7份厚皮和6份野生种质组成.Bayesian算法将所有种质分为3个亚群,主要对应厚皮、野生和薄皮3类种质.通过计算3类种质间的分化系数和雷氏距离,结果发现厚皮种质与薄皮种质间的分化最大,野生种质与薄皮或厚皮种质间的分化相对较小,不同类型种质多样性水平表现为:野生种质＞厚皮种质＞薄皮种质.3类种质幼苗的冷害指数趋向正态分布,薄皮种质的耐冷性要优于野生和厚皮种质.叶肉组织超微观察显示,薄皮种质蛤蟆酥5在低温处理前后的细胞超微结构变化不大,其耐冷性较强,而厚皮种质凤凰在低温处理后,叶绿体大量解体,细胞超微结构遭到破坏,其耐冷性较弱.

表型性状是遗传物质在特定环境下的具体表现,是进行种质/品种评价和遗传多样性研究的重要组成部分.笔者根据120份不同生态型的栽培西瓜种质在代表我国西北、华北和华南生态区的新疆昌吉、河南新乡和海南三亚进行2 a(年)的品质、形态特征和生物学特性等22个重要性状的表型精准鉴定,以及在枯萎病抗性鉴定、病毒病抗性鉴定、耐湿热鉴定的基础上,形成了规模化的西瓜种质资源表型精准鉴定方案,为西瓜种质资源分发利用、种质创新和基因挖掘提供参考,也可为西瓜新品种定向选育奠定基础.

甜瓜苦味物质严重影响其口感和品质.本研究利用不苦的薄皮甜瓜品系C69和苦的薄皮甜瓜品系C14构建了一个包含100个单株的F2群体.首先利用2b-RAD测序构建一个遗传连锁图谱.其次,结合群体的苦味性状进行全基因组的QTL定位和关联分析.然后,利用2b-RAD测序特有的技术优势进行群体的获得与缺失变异(PAV)的挖掘.最后,利用亲本的重测序信息确定控制苦味性状的关键基因.结果 发现,F1的果实表现出强烈的苦味,F2群体中苦与不苦的单株分别为81个和19个,符合3:1的分离比(x 2=1.92,P=0.1659),表型表明所用甜瓜材料的苦味主要是由一个显性的基因位点控制.利用477个SNP标记构建一张包含10个连锁群的连锁图谱,总长为337.79 cM,标记间平均间隔0.71 cM.全基因组QTL定位在8号连锁群(对应9号染色体),检测到一个解释表型变异为20％的甜瓜苦味QTL.全基因组关联分析检测到7个SNPs与苦味性状相关,全部位于9号染色体苦味QTL的基因组区域.通过PAV分型分析仅发现一个特有的大片段缺失(21707702～21743072 bp),位于QTL区域,且在所有的不苦株系中存在,而苦的株系中不存在.基于两个亲本材料的深度重测序信息,发现这个PAV的区域更大,约为62Kb,共涉及到9个连续的基因(MELO3C005601、MELO3C005602、MELO3C005603、MELO3C005604、MELO3C005605、MELO3C005606、MELO3C005607、MELO3C005608和MELO3C005609),其中5个是细胞色素P450基因.构建的系统发育树表明,这5个细胞色素P450基因与参与葫芦素C/B/E合成的细胞色素P450基因簇CYP81Q58、CYP81Q59和CYP712D8在一个进化枝,可能行使类似的功能,为潜在的类似于黄瓜葫芦素C合成的基因簇的一部分.前人通过比较基因组学研究获得的2个控制葫芦素B合成的bHLH转录因子CmBr(MELO3C005610和CmBt(MELO3C005611)同在9号染色体,与本研究检测到的PAV紧密换在一起.我们的研究结果为后续不苦甜瓜的育种提供了新的理论支撑和分子辅助育种目标.

Melon (Cucumis melo L., 2n=2x=24) is a eudicot diploid plant species belongs to the Cucurbitaceae family, which is famous for its specific biological properties and economic importance. Melon with high cucurbitacin contents taste unpleasant and are not preferred by consumers, but the underlying molecular mechanism for the bitterness related trait is not fully known. Therefore, the study of bitterness in melon has important practical value. Exploring the genetic rules of bitterness related traits and the key genes in the process of biosynthesis and metabolic regulation, as well as developing the molecular markers related to the bitterness of melon can provide guidance for the selection of non-bitter taste melon varieties and furnish reference for related studies of cucurbitacin. Here, we constructed a genetic linkage map using type IIB endonucleases restriction-site associated DNA (2b-RAD) based high throughput SNP genotyping data of a BC1 mapping family. The total length of the linkage map was 851.53 cM, with an average distance of 1.11 cM between adjacent markers. Genetic analysis of F-2 and BC1 populations derived from two parental lines (C68 with non-bitter taste and C69 with bitter taste) revealed that the melon bitterness related trait is controlled by dual locus, and bitterness is dominant to non-bitterness. QTL mapping identified 3 significant QTLs in 2 linkage groups (LGs). Then, based on the InDel markers obtained from deep re-sequencing of the two parents, we verified the accuracy of the mapping interval. Especially, the Polymerase Chain Reaction (PCR) based co-separation markers on chromosome 2 and chromosome 5 revealed that the genotypes perfectly matched with the phenotypes in F2 and XC6 population, which further proves the accuracy of our mapping results for melon bitterness. Our present study will provide fine mapping of melon bitterness related trait and facilitate marker-assisted selection for the development of non-bitterness cultivars.

The flesh color of watermelon (Citrullus lanatus) is an important fruit quality trait that helps to determine fruit attractiveness and is potentially beneficial to human health. Previous inheritance analyses determined that a single dominant gene, Yscr , produces the scarlet red flesh color rather than the coral red flesh color in watermelon. However, no genomic region or gene-based molecular markers for the locus Yscr have been reported thus far. In the present study, two high-density genetic maps and whole-genome variation detection aided by genome resequencing were first map the flesh color locus Yscr to a small region on chromosome 6 based on two independent populations derived from two scarlet red-fleshed lines and two coral red-fleshed lines. Two major quantitative trait loci located in the same genomic regions were identified in the F2 and BC1P2 populations and explained 90.36% and 75.1% of the phenotypic variation in flesh color, respectively. Based on the genetic variation in the two parental lines, newly developed PCR-based markers narrowed the Yscr region to 40 Kb. Of the five putative genes in this region, four encoded glycine-rich cell wall structural proteins, which implied that a new regulatory mechanism might occur between scarlet red- and coral red-fleshed in watermelon. Moreover, the genotypes of two newly developed InDel markers (InDel27_fc6 and InDel28_fc6) were completely consistent with the phenotypes in the F2 and BC1P2 populations and all 56 scarlet red-fleshed watermelon accessions. The results presented here provide valuable information for marker-assisted selection of flesh color breeding and the functional validation of candidate genes in watermelon.

本文对国家西瓜甜瓜中期库建立前后的不同历史阶段的种质资源工作进行回顾,将我国西瓜甜瓜种质资源工作划分为以栽培和育种利用为主的起步阶段、以资源繁种编目入长期库保存为主的推进阶段和西瓜甜瓜中期库筹建及运行阶段,并对国家西瓜甜瓜中期库的种质资源工作现状进行了总结,同时对未来的西瓜甜瓜种质资源工作进行了展望和建议.

【目的】研究西瓜属6个主要变种的染色体核型特征,为西瓜属作物品种亲缘关系鉴定及新品种培育等提供细胞学参考。【方法】以西瓜属6个主要变种饲用西瓜（PI296341）、普通西瓜（黑崩筋）、黑籽瓜（内蒙黑中片）、红籽瓜（江西信丰）、黏籽西瓜（PI254723）、药西瓜（PI386015）的根尖为试验材料,采用常规制片法制片,对其染色体数目、核型和进化趋势进行分析,并对6个变种的亲缘关系进行聚类分析。【结果】西瓜属6个主要变种的染色体类型均为二倍体（2n=2x=22）,含有不同数量的m和M染色体;根据相对长度系数可知各变种包括L、M 2 、M 1 和s等4种类型,其中L型染色体在饲用西瓜（PI296341）、普通西瓜（黑蹦筋）、黑籽瓜（内蒙黑中片）、红籽瓜（江西信丰）、药西瓜（PI386015）中均有出现,只有黏籽西瓜（PI254723）中未见;s型染色体在红籽瓜和黏籽西瓜中未出现,在其他4个变种中均有出现。西瓜属6个主要变种染色体的平均臂比值为1.09～1.36,核型类型属1A型和1B型,核型不对称系数为52.20%～57.42%。西瓜属6个主要变种的染色体核型进化程度由高到低依次为黑籽瓜（内蒙黑中片）、黏籽西瓜（PI254723）、饲用西瓜（PI296341）、药西瓜（PI386015）、普通西瓜（黑蹦筋）和红籽瓜（江西信丰）。【结论】西瓜属6个主要变种的核型特征具有一定程度的差异,核型进化趋势总体由对称向不对称发展;在核型特征上,饲用西瓜与药西瓜、药西瓜与普通西瓜亲缘关系较近,而红籽瓜（江西信丰）与其他5个变种亲缘关系较远。