Parthenocarpy is an important agricultural trait that not only produces seedless fruits, but also increases the rate of the fruit set under adverse environmental conditions. The study of parthenocarpy in Cucurbitaceae crops has considerable implications for cultivar improvement. This article provides a comprehensive review of relevant studies on the parthenocarpic traits of several major Cucurbitaceae crops and offers a perspective on future developments and research directions.

Cytokinins (CKs) are thought to play important roles in fruit development, especially cell division. However, the mechanisms and regulation of CK activity have not been well investigated. This study analysed CK concentrations and expression of genes involved in CK metabolism in developing tomato (Solanum lycopersicum) ovaries. The concentrations of CK ribosides and isopentenyladenine and the transcript levels of the CK biosynthetic genes SlIPT3, SlIPT4, SlLOG6, and SlLOG8 were high at anthesis and decreased immediately afterward. In contrast, trans-zeatin concentration and the transcript levels of the CK biosynthetic genes SlIPT1, SlIPT2, SlCYP735A1, SlCYP735A2, and SlLOG2 increased after anthesis. The expression of type-A response regulator genes was high in tomato ovaries from pre-anthesis to early post-anthesis stages. These results suggest that the CK signal transduction pathway is active in the cell division phase of fruit development. This study also investigated the effect of CK application on fruit set and development. Application of a synthetic CK, N-(2-chloro-pyridin-4-yl)-N'-phenylurea (CPPU), to unpollinated tomato ovaries induced parthenocarpic fruit development. The CPPU-induced parthenocarpic fruits were smaller than pollinated fruits, because of reduction of pericarp cell size rather than reduced cell number. Thus, CPPU-induced parthenocarpy was attributable to the promotion of cell division, not cell expansion. Overall, the results provide evidence that CKs are involved in cell division during development of tomato fruit.

The molecular signals for the development of the ovary into fruit following ovule fertilization are not clear. However, in many species, including tomato (Lycopersicon esculentum Mill.), auxins and auxin transport inhibitors can substitute for fertilization as activators of fruit set, suggesting that this plant hormone plays a key role in this process. In agreement, transgenes for auxin biosynthesis expressed under ovary- or ovule-specific promoters were shown earlier to enable parthenocarpic (i.e. seedless) fruit development. In the present study, we tested an alternative approach for the induction of parthenocarpy that is based on ovary-specific expression of the Agrobacterium rhizogenes-derived gene rolB. This gene was chosen because rolB transgenic plants manifest several syndromes characteristic of auxin treatment. Tomato plants transformed with a chimeric construct containing the rolB gene fused to the ovary- and young-fruit-specific promoter TPRP-F1 developed parthenocarpic fruits. Fruit size and morphology, including jelly fill in the locules of the seedless fruits, were comparable to those of seeded fruits of the parental line. Although it is not known whether ROLB signals for the same cassette of genes involved in fertilization-dependent fruit development, it clearly activates a battery of genes that enable successful completion of seedless fruit development in tomato.

Brassinosteroids (BRs) are essential for many biological processes in plants, however, little is known about their roles in early fruit development. To address this, BR levels were manipulated through the application of exogenous BRs (24-epibrassinolide, EBR) or a BR biosynthesis inhibitor (brassinazole, Brz) and their effects on early fruit development, cell division, and expression of cyclin and cyclin-dependent kinases (CDKs) genes were examined in two cucumber cultivars that differ in parthenocarpic capacity. The application of EBR induced parthenocarpic growth accompanied by active cell division in Jinchun No. 4, a cultivar without parthenocarpic capacity, whereas Brz treatment inhibited fruit set and, subsequently, fruit growth in Jinchun No. 2, a cultivar with natural parthenocarpic capacity, and this inhibitory effect could be rescued by the application of EBR. RT-PCR analysis showed both pollination and EBR induced expression of cell cycle-related genes (CycA, CycB, CycD3;1, CycD3;2, and CDKB) after anthesis. cDNA sequences for CsCycD3;1 and CsCycD3;2 were isolated through PCR amplification. Both CsCycD3;1 and CsCycD3;2 transcripts were up-regulated by EBR treatment and pollination but strongly repressed by Brz treatment. Meanwhile, BR6ox1 and SMT transcripts, two genes involved in BR synthesis, exhibited feedback regulation. These results strongly suggest that BRs play an important role during early fruit development in cucumber.

Parthenocarpy is an important agronomic trait in cucumber (Cucumis sativus L.) production. However, the systematic identification of parthenocarpic germplasms from national gene banks for cucumber improvement remains an international challenge. In this study, 201 cucumber lines were investigated, including different ecotypes. The percentages of parthenocarpic fruit set (PFS) and parthenocarpic fruit expansion (PFE) were evaluated in three experiments. In natural populations, the PFS rates fit a normal distribution, while PFE rates showed a skewed distribution, suggesting that both PFS and PFE rates are typical quantitative traits. Genetic analysis showed that parthenocarpy in different ecotypes was inherited in a similar incompletely dominant manner. A total of 5324 single nucleotide polymorphisms (SNPs) associated with parthenocarpy were detected in a Genome-wide association study (GWAS) of parthenocarpy in the 31 cucumber lines, from which six parthenocarpic loci, including two novel loci (Pfs1.1 and Pfs4.1), were identified. Consequently, fifteen of the elite lines that were screened presented relatively stronger parthenocarpy ability (PFS > 90%, PFE > 50%), among which six cucumber lines (18007s, 18008s, 18022s, 18076s, 18099s, and 18127s) exhibited weak first-fruit inhibition. Three lines (18011s, 18018s, and 18019s) were screened for super ovary parthenocarpy, which showed more attractive performance. Four low-temperature-enhanced parthenocarpy lines (18018s, 18022s, 18029s, and 18012s) were identified, which were suited for breeding for counter-season production. Our approaches could help increase efficiency and lead to parthenocarpy improvements for modern cucumber cultivars.

Parthenocarpy was induced in cucumber Cucumis sativus L. by foliar application of morphactin. Morphactin (chlorfluorenol) was most effective in inducing parthenocarpy when applied in the flowering stage, and the response was enhanced by prior treatment with Ethrel (2-chloroethylphosphonic acid). Morphactin stimulated pistillate flower development in a monoecious cultivar but did not modify sex expression of a gynoecious line.

以黄瓜(Cucumis sativus L.) 单性结实品系EP26与非单性结实品系ZR22为试材, 研究外源亚精胺(Spd) 和多胺合成抑制剂MGBG处理对子房(幼果) 内源多胺含量和蛋白质组成的影响及其与黄瓜单性结实和幼果发育的关系。结果表明: 花前2 d对ZR22不授粉子房施用外源亚精胺能显著提高子房内源亚精胺、精胺与腐胺水平, 促进其单性结实和果实生长, 而花前2 d对EP26不授粉子房外源施用MGBG则显著降低其子房内源亚精胺和精胺水平, 提高了内源腐胺水平, 导致子房萎蔫。运用SDS-PAGE法研究了外源亚精胺和MGBG处理后子房中可溶性蛋白质组成的变化, 结果表明: ZR-2用外源Spd处理, 开花当天至花后3 d的子房中出现了分子量为55 kD与37 kD的两种特异蛋白质, 花后1 d至花后3 d又出现了88 kD与82 kD两种特异蛋白质; 单性结实品系EP26用MGBG处理子房, 开花当天至花后3 d出现了47 kD与25kD两种特异蛋白质, 引起85 kD、45 kD与10 kD蛋白质的消失。这些结果表明, 外源多胺和多胺合成抑制剂处理可能是通过改变内源多胺水平和蛋白质合成而影响单性结实和子房(幼果) 发育。

The effect was investigated of seasonal differences between winter and spring on the development of parthenocarpic and fertilized fruits in two squash cultivars, Zucchini Elite F1 and Bushy White. The former had stronger parthenocarpic characteristics than the latter. The effect of night temperature on growth of the parthenocarpic fruits was most pronounced, both rate of growth and final weight increasing with decreasing temperature. Whereas long days inhibited development of parthenocarpic fruits, the heaviest and longest fruits were obtained under normal day-length conditions.

The endogenous levels of auxin, gibberellin, and inhibitors were followed in monoecious and gynoecious cucumber (Cucumis sativus L.) plants, and in plants treated with the ethylene-releasing compound Ethephon (2-chloroethyl phosphonic acid). Higher auxin inhibitor and lower gibberellin levels were associated with female tendency. The endogenous level of gibberellin and auxin decreased in Ethephon-treated plants. Application of Ethephon induced a rise in abscisic acid. Root application of abscisic acid promoted female tendency of gynoecious cucumbers grown under conditions which increase maleness. High CO(2) levels, which are known to antagonize ethylene, increased maleness of gynoecious cucumbers. The possibility of interrelationship between gibberellin, auxin, ethylene, and abscisic acid on sex expression are discussed.

Background: Parthenocarpy is an important trait for yield and quality in many plants. But due to its complex interactions with genetic and physiological factors, it has not been adequately understood and applied to breeding and production. Finding novel and effective quantitative trait loci (QTLs) is a critical step towards understanding its genetic mechanism. Cucumber (Cucumis sativus L.) is a typical parthenocarpic plant but the QTLs controlling parthenocarpy in cucumber were not mapped on chromosomes, and the linked markers were neither user-friendly nor confirmed by previous studies. Hence, we conducted a two-season QTL study of parthenocarpy based on the cucumber genome with 145 F-2:3 families derived from a cross between EC1 (a parthenocarpic inbred line) and 8419 s-1 (a non-parthenocarpic inbred line) in order to map novel QTLs. Whole genome re-sequencing was also performed both to develop effective linked markers and to predict candidate genes. Results: A genetic linkage map, employing 133 Simple Sequence Repeats (SSR) markers and nine Insertion/Deletion (InDel) markers spanning 808.1 cM on seven chromosomes, was constructed from an F-2 population. Seven novel QTLs were identified on chromosomes 1, 2, 3, 5 and 7. Parthenocarpy 2.1 (Parth2.1), a QTL on chromosome 2, was a major-effect QTL with a logarithm of odds (LOD) score of 9.0 and phenotypic variance explained (PVE) of 17.0 % in the spring season and with a LOD score of 6.2 and PVE of 10.2 % in the fall season. We confirmed this QTL using a residual heterozygous line97-5 (RHL97-5). Effectiveness of linked markers of the Parth2.1 was validated in F-3:4 population and in 21 inbred lines. Within this region, there were 57 genes with nonsynonymous SNPs/InDels in the coding sequence. Based on further combined analysis with transcriptome data between two parents, CsARF19, CsWD40, CsEIN1, CsPPR, CsHEXO3, CsMDL, CsDJC77 and CsSMAX1 were predicted as potential candidate genes controlling parthenocarpy. Conclusions: A major-effect QTL Parth2.1 and six minor-effect QTLs mainly contribute to the genetic architecture of parthenocarpy in cucumber. SSR16226 and Indel-T-39 can be used in marker-assisted selection (MAS) of cucumber breeding. Whole genome re-sequencing enhances the efficiency of polymorphic marker development and prediction of candidate genes.

Through a novel phenotyping method, four QTLs were consistently associated with increased parthenocarpic fruit set in North American processing cucumber that accounted for over 75 % of observed phenotypic variation. Parthenocarpy is a desirable trait with potential for increasing yield and quality in processing cucumber production. Although many successful parthenocarpic fresh market cucumber varieties have been developed, the genetic and molecular mechanisms behind parthenocarpic expression in cucumber remain largely unknown. Since parthenocarpy is an important yield component, it is difficult to separate the true parthenocarpic character from other yield related traits. In the present study, we developed a novel phenotypic approach for parthenocarpic fruit set focusing on early fruit development. Two hundred and five F families derived from a cross between the highly parthenocarpic line 2A and low parthenocarpic line Gy8 were phenotypically evaluated in three greenhouse experiments. Seven QTLs associated with parthenocarpic fruit set were detected. Among them, one each on chromosomes 5 and 7 (parth5.1 and parth7.1) and two on chromosome 6 (parth6.1 and parth6.2) were consistently identified in all experiments, but their relative contribution to the total phenotypic variation was dependent on plant growth stages. While each of the four QTLs had almost equal contribution to the expression of the trait at commercial harvest stage, parth7.1 played an important role in early parthenocarpic fruit set. The results suggested that parthenocarpic fruit set can be accurately evaluated with as few as 20 nodes of growth. The QTLs identified in this study for parthenocarpic fruit set are a valuable resource for cucumber breeders interested in developing parthenocarpic cultivars and to researchers interested in the genetic and molecular mechanisms of parthenocarpic fruit set.

【目的】单性结实性是影响设施黄瓜产量和品质的重要性状。深入解析黄瓜单性结实性状遗传规律并对其进行QTL定位,有助于提高设施专用黄瓜品种育种效率。【方法】以强单性结实自交系‘6457’和弱单性结实自交系‘6426’构建的重组自交系F_2:8为材料,基于3年表型数据,采用黄瓜基因组测序SSR分子标记构建黄瓜遗传连锁图谱,结合QTL-Seq分析,对黄瓜单性结实性进行QTL定位。【结果】黄瓜单性结实性状符合数量遗传特征。利用SSR标记构建了1张包含11个连锁群的遗传图谱,覆盖基因组555.0 cM,平均图距为6.8 cM。2016—2018年春季在3号染色体上均检测到1个与黄瓜单性结实性相关的QTL位点,位于标记SSR19430和SSR15419之间（3.33—5.57 Mb）,遗传距离6.6 cM,贡献率分别为11%、12.5%和6.3%。进一步进行QTL-Seq分析,发现4个与黄瓜单性结实性相关的QTL,分别位于1号（4.38—11.00 Mb）、3号（2.24—10.66 Mb）、6号（15.67—17.93 Mb,26.33—27.49 Mb）染色体上。其中在3号染色体上检测到的QTL与Map QTL所得的QTL区间重叠。推测Csa3G047740、Csa3G073810、Csa3G043910和Csa6G362930为与黄瓜单性结实性状相关的候选基因。【结论】分别在1、3、6号染色体上检测到4个与黄瓜单性结实性相关的QTL位点,其中3号染色体上的QTL年度间稳定,贡献率较高。

Parthenocarpy is a pivotal trait that enhances the yield and quality of fruit crops by enabling the development of seedless fruits. Here we unveil a molecular framework for the regulation and domestication of parthenocarpy in cucumber (Cucumis sativus L.). We previously discovered a natural non-parthenocarpic mutant and demonstrated that the AP2-like transcription factor NON-PARTHENOCARPIC FRUIT 1 (NPF1) is a central regulator of parthenocarpy through activating YUC4 expression and promoting auxin biosynthesis in ovules. A Phe-to-Ser substitution at amino acid residue 7 results in a stable form of NPF1 that is localized in the nucleus. An A-to-G polymorphism (SNP-383) within an NPF1-binding site in the YUC4 promoter significantly enhances the activation of NPF1 towards YUC4, leading to an increased rate of parthenocarpy. Additionally, NPF1 influences bitterness by reducing cucurbitacin C biosynthesis through the suppression of Bt expression. Our results suggest a two-step evolutionary model for parthenocarpy and fruit bitterness during cucumber domestication.© 2025. The Author(s), under exclusive licence to Springer Nature Limited.

The role of gibberellins (GAs) in tomato (Solanum lycopersicum) fruit development was investigated. Two different inhibitors of GA biosynthesis (LAB 198999 and paclobutrazol) decreased fruit growth and fruit set, an effect reversed by GA(3) application. LAB 198999 reduced GA(1) and GA(8) content, but increased that of their precursors GA(53), GA(44), GA(19), and GA(20) in pollinated fruits. This supports the hypothesis that GA(1) is the active GA for tomato fruit growth. Unpollinated ovaries developed parthenocarpically in response to GA(3) > GA(1) = GA(4) > GA(20), but not to GA(19), suggesting that GA 20-oxidase activity was limiting in unpollinated ovaries. This was confirmed by analyzing the effect of pollination on transcript levels of SlCPS, SlGA20ox1, -2, and -3, and SlGA3ox1 and -2, encoding enzymes of GA biosynthesis. Pollination increased transcript content of SlGA20ox1, -2, and -3, and SlCPS, but not of SlGA3ox1 and -2. To investigate whether pollination also altered GA inactivation, full-length cDNA clones of genes encoding enzymes catalyzing GA 2-oxidases (SlGA2ox1, -2, -3, -4, and -5) were isolated and characterized. Transcript levels of these genes did not decrease early after pollination (5-d-old fruits), but transcript content reduction of all of them, mainly of SlGA2ox2, was found later (from 10 d after anthesis). We conclude that pollination mediates fruit set by activating GA biosynthesis mainly through up-regulation of GA20ox. Finally, the phylogenetic reconstruction of the GA2ox family clearly showed the existence of three gene subfamilies, and the phylogenetic position of SlGA2ox1, -2, -3, -4, and -5 was established.

We have characterized the tomato (Lycopersicon esculentum Mill.) MADS box gene TM29 that shared a high amino acid sequence homology to the ArabidopsisSEP1, 2, and 3(SEPALLATA1, 2, and 3) genes. TM29 showed similar expression profiles toSEP1, with accumulation of mRNA in the primordia of all four whorls of floral organs. In addition, TM29 mRNA was detected in inflorescence and vegetative meristems. To understandTM29 function, we produced transgenic tomato plants in which TM29 expression was down-regulated by either cosuppression or antisense techniques. These transgenic plants produced aberrant flowers with morphogenetic alterations in the organs of the inner three whorls. Petals and stamens were green rather than yellow, suggesting a partial conversion to a sepalloid identity. Stamens and ovaries were infertile, with the later developing into parthenocarpic fruit. Ectopic shoots with partially developed leaves and secondary flowers emerged from the fruit. These shoots resembled the primary transgenic flowers and continued to produce parthenocarpic fruit and additional ectopic shoots. Based on the temporal and spatial expression pattern and transgenic phenotypes, we propose that TM29functions in floral organ development, fruit development, and maintenance of floral meristem identity in tomato.