Current status of genetic transformation technology developed in cucumber(Cucumis sativus L.)

Genetic transformation is an important technique for functional genomics study and genetic improvement of plants. Until now, Agrobacterium-mediated transformation methods using cotyledon as explants has been the major approach for cucumber, and its frequency has been up to 23%. For example, significantly enhancement of the transformation efficiency of this plant species was achieved from the cotyledon explants of the cultivar Poinsett 76 infected by Agrobacterium strains EHA105 with efficient positive selection system in lots of experiments. This review is to summarize some key factors influencing cucumber regeneration and genetic transformation, including target genes, selection systems and the ways of transgene introduction, and then to put forward some strategies for the increasing of cucumber transformation efficiency. In the future, it is high possible for cucumber to be potential bioreactor to produce vaccine and biomaterials for human beings.

Inheritance of Powdery Mildew Resistance in Cucumber (Cucumis sativus L.) and Development of an AFLP Marker for Resistance Detection

Cucumber powdery mildew is one of the most destructive diseases of cucumber throughout the world. In the present study, inheritance of powdery mildew resistance in three crosses, and linkage of resistance with amplified fragment length polymorphism （AFLP） markers are studied to formulate efficient strategies for breeding cultivars resistant to powdery mildew. The joint analysis of multiple generations and AFLP technique has been applied in this study. The best model is the one with two major genes, additive, dominant, and epistatic effects, plus polygenes with additive, dominant, and epistatic effects （E-l-0 model）. The heritabilities of the major genes varied from 64.26% to 97.82%, and susceptibility was incompletely dominant for the two major genes in the three crosses studied. The additive effects of the two major genes and the dominant effect of the second major gene were high, and the epistatic effect of the additive-dominant between the two major genes was the highest in cross I . In cross II, the absolute value of the additive effect, dominant effect, and potential ratio of the first major gene were far higher than those of the second major gene, and the epistatic effect of the additive-additive was the highest. The genetic parameters of the two major genes in cross III were similar to those in cross II. Correlation and regression analyses showed that marker E25/M63-103 was linked to a susceptible gene controlling powdery mildew resistance. The marker could account for 19.98% of the phenotypic variation. When the marker was tested on a diverse set of 29 cucumber lines, the correlation between phenotype and genotype was not significant, which suggested cultivar specialty of gene expression or different methods of resistance to powdery mildew. The target DNA fragment was 103 bp in length, and only a small part was found to be homologous to DNA in the other species evaluated, which indicated that it was unique to the cucumber genome.

Effect of Low Concentration of Yttrium on Physiological Characteristics of Cucumber (Cucumis Sativus L.)

There is no doubt that rare earth elements stand an important position among the essential elements of plant growth and it is long time since they are first used as plant growth promoters. Given their effects on microstructure, most reports are focused on the toxicology rather than promotion. Using cucumis sativus L. (Jin Chun No.5) as experiment material, we try to find out the nutritional effects of low Y3+ concentrations on cucumber seedlings′ leaves. The present paper suggests that the rare earth elements act as micronutrients at low concentrations while they give rise to toxicity at high concentration. Benefits defeat toxicity with concentration ranging from 5 to 25 μmol·L-1. Through careful study, at the Y(NO3)3 concentration of 10 μmol·L-1 the content of chlorophyll as well as the activities of SOD, Cu-Zn SOD and the POD are the highest. It indicates 10 μmol·L-1 is the optimum concentration of yttrium for promoting the cucumber growth.

Nodulin 26-like intrinsic protein Cs NIP2;2 is a silicon influx transporter in Cucumis sativus L.

Nodulin 26-like intrinsic proteins(NIPs) are a family of channel-forming transmembrane proteins that function in the transport of water and other small molecules.Some NIPs can mediate silicon transport across plasma membranes and lead to silicon accumulation in plants,which is beneficial for the growth and development of plants.Cucumber is one of the most widely consumed vegetables;however,the functions of NIPs in this crop are still largely unknown.Here,we report the functional characteristics of Cs NIP2;2.It was found that Cs NIP2;2 is a tandem repeat of Cs NIP2;1,which had been demonstrated to be a silicon influx transporter gene.Cs NIP2;2 has a selectivity filter composed of cysteine,serine,glycine and arginine(CSGR),which is different from all previously characterized silicon influx transporters in higher plants at the second helix position.Xenopus laevis oocytes injected with Cs NIP2;2 c RNA demonstrated a higher uptake of silicon than the control,and the uptake remained unchanged under low temperature.Cs NIP2;2 was found to be expressed in the root,stem,lamina and petiole,and exogenous silicon treatment decreased its expression in the stem but not in other tissues.Transient expression of Cs NIP2;2-e GFP fusion sequence in onion epidermal cells showed that Cs NIP2;2 was localized to the cell nucleus,plasma membrane and an unknown structure inside the cell.The results suggest that Cs NIP2;2 is a silicon influx transporter in cucumber,and its subcellular localization and the selectivity filter are different from those of the previously characterized silicon influx transporters in other plants.These findings may be helpful for understanding the functions of NIPs in cucumber plants.

Fine Genetic Mapping of Dwarf Trait in Cucumber(Cucumis sativus L.)Using a RIL Population

Plant height in cucumber is not only an important trait for breeding,but also one of the model traits suitable for the study of developmental biology.Amplified fragment length polymorphism(AFLP)and simple sequence repeat(SSR)markers techniques were applied for the construction of genetic linkage maps in cucumber.To understand the dwarf trait genetic basis in cucumber,the quantitative trait loci(QTL)were identified using F_6 recombinant inbred line populations(RILs)comprising 336 lines from the cross between the two cultivars D0462(the dwarf)and DN129(the vine).In total,six SSR markers and 15 AFLP markers were detected on the five linkage groups covering 152.8 cM with a mean marker interval of 7.28 cM.Only one QTL was found to be linked with plant height and the dwarf trait locus remained in the fourth linkage group.The contributory percentage of the single QTL to plant height was 11.39%.

Genome-wide association study reveals candidate genes for gummy stem blight resistance in cucumber

Gummy stem blight(GSB),caused by Didymella bryoniae,is a serious fungal disease that leads to decline in cucumber yield and quality.The molecular mechanism of GSB resistance in cucumber remains unclear.Here,we investigated the GSB resistance of cucumber core germplasms from four geographic groups at the seedling and adult stages.A total of 9 SNPs related to GSB resistance at the seedling stage and 26 SNPs at the adult stage were identified,of which some are co-localized to previously mapped Quantitative trait loci(QTLs)for GSB resistance(gsb3.2/gsb3.3,gsb5.1,and gsb-s6.2).Based on haplotype analysis and expression levels after inoculation,four candidate genes were identified within the region identified by both Genome-wide association study(GWAS)and previous identified QTL mapping,including Csa3G129470 for gsb3.2/gsb3.3,Csa5G606820 and Csa5G606850 for gsb5.1,and Csa6G079730 for gsb-s6.2.The novel GSB resistant accessions,significant SNPs,and candidate genes facilitate the breeding of GSB resistant cucumber cultivars and provide a novel idea for understanding GSB resistance mechanism in cucumber.

Planting Adaptability of Four Kinds of Common Vegetabless in Shanghai

[Objectives]To explore the planting adaptability of vegetables in Shanghai.[Methods]In this paper,cowpea(Vigna unguiculate(L.)Walp.),cucumber(Cucumis sativus L.),eggplant(Solanum melongena L.)and potato(Solanum tuberosum L.)were selected as experimental materials and planted in the open air.The growth status,the occurrence of diseases and insect pests,and the taste evaluation of these four kinds of common vegetables were mainly studied.[Results]The results showed that the four kinds of common vegetables in Shanghai had strong growth,strong adaptability,less pests and diseases,and good taste.[Conclusions]The cowpea,cucumber,eggplant,and potato are suitable for planting in Shanghai.

Low Root Zone Temperature Limits Nutrient Effects on Cucumber Seedling Growth and Induces Adversity Physiological Response

Effects of root-zone temperatures （RZT） （12℃-RZT and 20℃-RZT） and different N, P, and K nutrient regimes on the growth, reactive oxygen species （ROS）, and antioxidant enzyme in cucumber seedlings were investigated in hydroponics. Strong interactions were observed between RZT and nutrient on the dry weight （P=0.001）, root length （P=0.001） and leaf area （P=0.05）. Plant dry weights were suppressed at low RZT of 12℃, while higher biomass and growth of cucumber seedlings were produced at elevated RZT of 20℃ under each nutrient treatment. Growth indexes （plant height, internode length, root length, and leaf area） at 12℃-RZT had less difference among nutrient treatments, but greater response was obtained for different nutrients at high RZT. RZT had larger effects （P=0.001） on cucumber seedling growth than nutrients. In addition, N was more effective nutrients to plant growth than P and K under low root temperature to plant growth. Higher hydrogen peroxide （H202）, malondialdehyde （MDA）, soluble sugar （SS） contents in leaves were observed at 12℃-RZT in all nutrient treatments than those at 20℃-RZT, indicating the chilling adversity damaged to plant growth. In general, antioxidant enzyme had larger response under low root-zone temperature. Superoxide dismutase （SOD） activities were higher in both leaves and roots while peroxidase （POD） and catalase （CAT） showed large different action in leaves and roots at both the two root-zone temperature.

Effects of 24-Epibrassinolide on Antioxidant System in Cucumber Seedling Roots Under Hypoxia Stress

This article aims to study the effects of exogenous 24-epibrassinolide （EBR） on the changes in ROS, activities of antioxidative enzymes and antioxidants in cucumber （Cucumis sativus L.） seedling roots under hypoxia stress. Seedlings of a hypoxiaresistant cultivar, Lühachun 4, and a hypoxia-sensitive cultivar, Zhongnong 8, were hydroponically grown for 8 d in normoxic or hypoxic nutrient solutions that were added or not added with 10^-3 mg L^-1 EBR. Under hypoxia stress, the ROS levels and the lipid peroxidation were significantly increased in the roots upon exposure to hypoxia stress, which were inhibited by EBR application. The EBR treatment significantly increased the seedlings growth and SOD, APX, GR activities, and contents of AsA and GSH under hypoxia stress. From the results obtained in this study, it can be concluded that oxidative damage on seedling roots by hypoxia stress can be considerably alleviated and the tolerance of plants was elevated.

Identification and Characterization of Tonoplast Sugar Transporter (TST) Gene Family in Cucumber

Tonoplast sugar transporters(TSTs)play essential roles in regulating plant growth,development,and response to various biotic and abiotic stresses.In this study,a total of three TST genes were identified by a genome-wide analysis in cucumber.Phylogenetic analysis showed that TST proteins from cucumber and other plant species can be classified into five groups,and nearly all TST members in the same groups displayed similarmotif distributions,transmembrane(TM)domains,and gene structures.All of the three CsTST genes possess a number of development-,stress-,and hormone-related cis-elements in the promoter sequences.Meanwhile,qRT-PCR assays revealed that the CsTST1 was expressed in fruits,flowers,leaves,and other tissues,and its expression varied significantly under various abiotic stresses such as cold,salt,drought(PEG),and abscisic acid(ABA).Finally,functional analysis of CsTST1 in yeast revealed that it was able to complement the deficiency in galactose,mannose and sucrose transport.These results revealed that CsTST1 can act as a functional sugar transporter to play important roles in cucumber growth and response to abiotic stress probably through affecting carbohydrate distribution.

Resistance of LaCl_3 to Oxidative Stress Induced by 2, 4-Dichlorophenoxy

Cucumber seedlings were sprayed with different concentrations of LaCl_3 for 3 d continuously. After 7 d of this treatment, the plants were treated with 1200 mg·L^(-1) 2,4-dichlorophennoxy(2,4-D) for 24 h. The leaves were harvested and rinsed with 5 mmol·L^(-1) EDTA. The concentrations of photosynthetic pigments, soluble protein and metabolites related to oxidative stress and the activities of antioxidant enzymes in leaves were assayed. The results show that the treatment with appropriate concentration of LaCl_3 has resistant effect on oxidative stress induced by 2, 4-D. Proper concentration of LaCl_3 promotes the activity of antioxidant system in plants and alleviates the damage caused by 2, 4-D.

Allelopathic Potential of Cucumber Tissues Aqueous Extracts

[Objective]The aim of this study was to explore allelopathic effects of the water-extracted crude of cucumber plant parts on seed germination and seedling growth of lettuce(Lactuca sativa L.),cabbage(Brassica pekinensis L.),radish(Raphanus sativus L.) and scallion(Allium fistulosum L.).[Method]The allelopathic effects of different cucumber tissues aqueous extracts were investigated on lettuce,cabbage,radish and scallion using the water-soluble allelopathic principle by seedling bioassay tests.[Result]The trends of inhibitory effects of different cucumber parts increased with increasing extract concentrations.The inhibition effects and the inhibition rate of three aqueous extracts were more significant on root growth than shoot length.Leaf aqueous extracts represented the most exhibited and root aqueous extracts representing the least inhibitory on seed germination,shoot length and root length of lettuce,cabbage,radish and scallion.[Conclusion]This study had provided basis for allelopathic character of different cucumber plant parts.

Rapid Amplification of Flanking Sequences of a Known DNA Region by Partial Restriction Digestion and Hot Start PCR

A simple and efficient method for cloning the flanking genomic sequences of a known DNA region is reported in this study. This method combined partial restriction endonuclease digestion, adaptor ligation, and a single round polymerase chain reaction. Total genomic DNA was partially digested with the frequent-cutting restriction enzyme Mse I. The partially digested products were ligated to an unphosphorylated adaptor. A hot start PCR amplification with Taq polymerase and dNTP was performed with a DNA-specific primer and the adaptor primer complementary to the adaptor and the Mse I recognition site. The amplified products were fractionated, cloned and sequenced. By this method, we cloned the downstream region of a gynoecious marker TG/CAC234 from cucumber （Cucumis sativus L.）.

Effects of Exogenous NO on Active Oxygen Metabolism in Cucumber Seedlings under NaCl Stress

Employing nutrient solution hydroponic method,the effects of exogenous nitric oxide（NO）on the growth and active oxygen metabolism in cucumber（Cucumis sativus L.）seedlings under NaCl stress were investigated.The results indicated that NaCl treatment significantly inhibited the growth of cucumber seedlings,while exogenous NO could significantly alleviate the inhibitory effects of NaCl stress on seedling growth.Especially,0.1 mmol/L SNP treatment exhibited better effects than 0.5 mmol/L SNP treatment on alleviating NaCl stress.Under 0.1 mmol/L NaCl stress,adding 0.1 mmol/L exogenous NO could significantly decrease the generation rate of O·-2and MDA content,significantly improve soluble protein content and enhance the activities of SOD,POD and CAT,thus reducing the damage of salt stress to cucumber seedlings.

Analysis of 50 Cucumber Accessions by RAPD Markers

Genetic diversity of 50 cucumber (Cucumis sativus L.) accessions from American, Holland, Japan and China was detected and evaluated using RAPD markers. 25 selected primers produced 215 scorable polymorphic RAPD bands and the ratio of polymorphism is 86.98%. Four main groups of cucumber accessions could be distinguished from UPGMA analysis: Occidental cucumber, South-China cucumber, North-China cucumber and Xishuangbanna cucumber. Our result confirmed that cucumber is a narrow-based germplasm, nevertheless RAPD analysis was stili useful in cucumber genotypic differentiation. More significantly, Xishuangbanna cucumber (Cucumis sativus L. Var Xishuangbannanesis Qi et Yuan), a mutation of cucumber, was clustered together to a special group in the study, which implied its special status in cucumber germplasm.

Quantitative trait locus analysis of lateral branch-related traits in cucumber(Cucumis sativus L.)using recombinant inbred lines

A group of 224 recombinant inbred lines (RILs) was derived from a narrow cross between 2 cucumber (Cucumis sativus L.) lines, namely, S94 (Northern China type with weak lateral branch growth potential and early lateral branch sprouting time) and S06 (Northern European type with strong lateral branch growth potential and late lateral branch sprouting time). These lines were then used for investigating lateral branch-related traits. A total of 36 quantitative trait loci (QTLs) were detected for the following 4 lateral branch-related traits: lateral branch average length (LBAL), lateral branch total length (LBTL), lateral branch number (LBN), and first lateral branch node (FLBN). Further, each QTL explained 3.1% (lbtl2.1, spring) to 32.3% (lbn2.3, spring) of the observed phenotypic variance. Eleven QTLs (lbal1.1, lbtl1.1, lbn1.2, flbn1.2, etc.) for different traits were found to be clustered on the e23m18d-ME23EM6c section (7.4 cM) of linkage group (LG) 1; further, 15 QTLs (lbal2.1, lbtl2.1, lbn2.1, flbn2.1, etc.) were found to be clustered on the S94A1-ME4SA4a section (13.9 cM) of LG2. Twenty-one QTLs explained more than 10% of the phenotypic variance. Moreover, lbtl1.3 (autumn, 26.2%, logarithm of odds (LOD) = 17.4; spring, 26.9%, LOD = 17.9) had stable position and contribution in both seasons. Several se-quence-anchor markers (CMBR40, F, CS30, S94A1, CSWTA11B, etc.) were closely linked with some QTLs for LBAL, LBTL, LBN, and FLBN, which can be used for the marker-assisted selection to improve the plant architecture in cucumber breeding.

黄瓜连作对根际土壤微生物群落结构的影响

采用变性梯度凝胶电泳(PCR-DGGE)技术研究黄瓜连作对根际土壤结构的影响,探索黄瓜(Cucumis sativus L.)连作1、3、5、7、9茬土壤中芽孢杆菌、假单胞菌菌群结构变化。研究发现,连作导致这两种菌的菌群结构发生改变。芽孢杆菌多样性指数在种植后30、40、50 d,从3茬开始先升高后降低,其中,种植后40 d,芽孢杆菌的多样性指数在5茬达到最高,总体呈先升后降趋势。种植后30、40、50 d,假单胞菌条带数及多样性指数分别在5、7茬较高。两种菌主成分分析表明菌群结构主要是在5、7茬表现出与其他茬次不同。

Immunolocalization of Arabinogalactan Proteins and Pectins in Floral Buds of Cucumber （Cucumis sativus L.） During Sex Determination

Abstract: Arabinogalactan proteins (AGPs) and pectins were detected in the floral buds of cucumber (Cucumis sativus L.) during its sex determination using the following monoclonal antibodies: MAC 207 (recognizes AGP epitopes); JIM 8 (recognizes a subset of AGP epitopes); and JIM 5 and JIM 7 (epitopes of pectins esterified to various degrees). In the stem apex meristem (SAM) of the cucumber, epitopes of MAC 207, JIM 7, and JIM 5 were localized in the cells from second to third peripheral layers when the sex organ primodium began to differentiate; epitopes of MAC 207 and JIM 5 were also detected in the ragged edge cells. A very dense labeling signal with MAC 207 was observed in the carpel and pistil primodium. The AGP epitopes recognized by JIM 8 were localized in the anther of the male flower and the anther-like portion of the stagnant stamen of the female flower. This suggests that the AGPs and pectins in the SAM of the cucumber are closely associated with the differentiation of the SAM, from meristematic cells to floral primodium. The subset of AGPs recognized by JIM 8 may play an important role in stamen formation.

弱光胁迫下黄瓜苗期下胚轴性状的遗传分析

【目的】阐明弱光胁迫下黄瓜下胚轴性状的遗传特点。【方法】以耐弱光黄瓜品系M22与不耐弱光黄瓜品系M14及其F1、F2、回交世代(B1、B2)为试验材料,应用F2群体分离分析方法与主基因+多基因模型分析法,于2007和2008年对弱光(日平均光强为100μmol/(m2.s))条件下黄瓜的下胚轴长与下胚轴粗进行遗传分析。【结果】群体分离分析结果表明,黄瓜F2代群体中下胚轴粗和下胚轴长性状遗传变异幅度均较小,其中下胚轴粗在2007和2008年的变异幅度分别为0.258和0.226cm,下胚轴长分别为8.5和4.5cm;广义遗传力较低,其中下胚轴粗在2007和2008年的广义遗传力分别为0.54和0.62,下胚轴长为0.60和0.69,表明不宜在F2代进行性状选择。主基因-多基因遗传分析表明,黄瓜下胚轴粗的遗传受1对加性主基因-加性-显性多基因模型(D_2)控制,B1、B2、F2世代主基因遗传率分别为27.03%,56.25%和60.38%。下胚轴长遗传受加性-显性-上位性多基因(C_0)控制,B1、B2、F2代多基因遗传率分别为74.38%,63.29%和83.37%。【结论】下胚轴粗遗传以主基因遗传为主;下胚轴长性状主要由微效多基因控制,受环境影响很大,不宜进行早代选择。

三种水溶性螯合肥在黄瓜上的比较试验

以黄瓜(Cucumis sativus L.)为试验材料,研究“阔拉”“阿卡顿蔬菜专用”“阿卡顿通用”3种水溶性螯合肥料对黄瓜株高、株幅、发病率及产量等方面的影响。结果表明,“阔拉”肥料黄瓜增产效果作用明显,且对黄瓜生长协调性方面都有明显促进作用,在黄瓜抗病性方面表现良好。