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.

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.

Cloning and Sequence Analysis of Lipoxygenase Gene cDNA from Cucumber Fruit (Cucumis sativus L.)

Lipoxygenases are nonheme-iron-containing dioxygenases that catalyze the hydroperoxidation of unsatrated fatty acids containing a cis, cis-1,4-pentadiene structure producing hydroperoxy acids with conjugated dienes.

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.

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%.

Ameliorating Effect of <i>Cucumis sativus</i>(Cucumbers) against Arsenic Induced Toxicity in Mice

In the entire world, about 200 million populations are exposed to arsenic poisoning in groundwater. Arsenic is a very poisonous metalloid and has three allotropic forms. The toxic inorganic arsenic is converted and utilized metabolically into organic form. It is primarily eliminated out from the human body through metabolic wastes like urine and is also deposited in the hair, nails and skin of the affected ones. Arsenic is known to be a carcinogen as Carcinogen category 1 in the forms of arsenic trioxide, arsenic pentoxide, arsenous acids, arsenic acid and their salts. The arsenic also affects the epidermal system, the nervous system and the vascular system of humans. In the present investigation for toxicological evaluation of arsenic Liver Function Tests & Kidney Function Tests have been considered. It is presumed that medicinal plants have significance in the present day in view of the lethal diseases like AIDS, cancer, hepatitis, nephritis sterility too for which no effective drugs are found till today in modern system of medicine. Medicinal plant based drugs generally have no side effects or the least side effect. Thus to evaluate an ameliorating effect, if any, to mitigate the arsenic toxicity in mice, for which Cucumis sativus (cucumbers) has been taken as curative measure. Sodium arsenite at the dose of 3 mg/kg body weight was administered for 4 weeks followed by the administration of Cucumis sativus (cucumbers) for 4 and 6 weeks at dose of 500 mg/kg body weight. Their biochemical levels like liver and kidney function tests were assayed and were found with elevated levels. But, after administration of aqueous extract of Cucumis sativus (cucumbers), there was significant amelioration in the biochemical levels. The protective effect of Cucumis sativus (cucumbers) was shown in the form of normalization of enzymatic and non-enzymatic activities represented by normalization of liver and kidney functions.

外源NO对NaCl胁迫下黄瓜(Cucumis sativus L.)幼苗生长和谷胱甘肽抗氧化酶系统的影响

采用营养液水培,研究了外源一氧化氮(NO)对黄瓜(Cucumis sativusL.)幼苗生长和叶片谷胱甘肽抗氧化酶系统的影响。结果表明,正常生长条件下添加NO能促进黄瓜幼苗生长,而添加NO信号传递途径关键酶鸟苷酸环化酶(cGC)抑制剂亚甲基蓝(MB-1)显著抑制了黄瓜幼苗的生长;添加NO显著缓解了盐胁迫对黄瓜幼苗生长的抑制,提高了叶片谷胱甘肽还原酶(GR)活性、脱氢抗坏血酸还原酶(DHAR)活性、抗坏血酸过氧化物酶(APX)及还原型谷胱甘肽(GSH)、抗坏血酸(ASA)含量,降低了氧化型谷胱甘肽(GSSG)含量,提高了GSH/GSSG,对单脱氢抗坏血酸还原酶(MDAR)活性无显著影响;NaCl胁迫下添加NO的同时添加MB-1抑制了GR活性的提高,GSH和ASA含量、GSH/GSSG均降低,GSSG含量提高,但对MDAR、APX和DHAR活性无显著影响,表明NaCl胁迫下NO对GR活性、GSH和ASA含量、GSH/GSSG的调节可能是通过cGC介导的,对MDAR无明显的调节作用,对DHAR、APX的调节还存在其它途径。

外源BR诱导黄瓜(Cucumis sativus L.)幼苗的抗盐性

【目的】明确外源油菜素甾醇(Brassinosteroid,BR)对黄瓜(CucumissativusL.)幼苗抗盐性的诱导作用。【方法】采用根际注射结合叶面喷施外源BR(0、0.005、0.01、0.05、0.1、0.2mg·L-1)的方法,比较分析了盐胁迫下幼苗植株盐害指数、抗氧化酶活性、渗透调节物质含量等生理指标。【结果】外源BR能够明显改善盐胁迫下黄瓜幼苗植株的生长发育状况,降低盐害指数,最高幅度达40.2个百分点(P﹤0.01),极显著地提高叶片细胞游离脯氨酸(Pro)和可溶性糖的含量、超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)等抗氧化酶活性(P﹤0.01),进而保护细胞膜的稳定性。【结论】外源BR可以有效诱导黄瓜幼苗的抗盐性,并且最佳浓度范围是0.01～0.05mg·L-1。

两个黄瓜(Cucumis sativus L.)叶色突变体的比较分析研究

通过对黄瓜黄绿叶突变体9110Gt和NCG-042植株表型观测、遗传分析和分子标记验证,证明9110Gt是区别于NCG-042的新叶色突变体。这两个黄绿叶突变体在表型上存在一定的区别:9110Gt在苗期表现叶色黄化,而NCG-042的心叶在整个生育期都表现黄化。遗传分析证明,两个突变体的叶色突变性状分别由两个不同的等位基因控制,且两基因间存在互补作用。分子标记的检测结果也进一步证实了这一结论。

外源亚精胺对盐胁迫下黄瓜(Cucumis sativus L.)叶绿体活性氧清除系统和结合态多胺含量的影响

采用营养液水培,研究了外源亚精胺(Spd)对NaCl胁迫下抗盐能力不同的两个黄瓜品种幼苗生长、叶绿体中活性氧清除系统、转谷酰胺酶(TGase)活性、结合态多胺含量及植株光合速率的影响。结果表明,外源Spd能提高NaCl胁迫下叶绿体中TGase活性、叶绿体结合态腐胺(Put)、Spd、精胺(Spm)及总多胺含量;提高超氧化物歧化酶(SOD)、抗坏血酸过氧化物酶(APX)和谷胱甘肽还原酶(GR)活性,提高抗坏血酸(AsA)、类胡萝卜素(Car)、还原型谷胱甘肽(GSH)含量及还原型谷胱甘肽/氧化型谷胱甘肽(GSH/GSSG)比值,降低脱氢抗坏血酸/抗坏血酸(DAsA/AsA)比值;同时显著降低叶绿体过氧化氢(H2O2)和丙二醛(MDA)含量,提高植株净光合速率,缓解NaCl胁迫对幼苗生长的抑制。表明Spd对黄瓜盐害的缓解作用之一可能是通过提高叶绿体结合态多胺含量和叶绿体活性氧清除能力,从而缓解盐胁迫对叶绿体膜的伤害。

侧面补光对温室黄瓜(Cucumis sativus L.cv.Shenchun)果实生长和品质的影响

为研究侧面补光对温室黄瓜果实生长和品质的影响,以黄瓜品种深春为材料,采用不同光质(8红1蓝、6红2绿1蓝、6红3蓝)LED灯开花结果期侧面补光,光源光通量密度为15μmol·m-2·s-1。每天补光8.0h(06:00-11:00;16:30-19:30),测定分析了侧面补光下黄瓜果实生长和品质等的变化。结果表明:3个不同补光处理的黄瓜果实瓜长、径粗及瓜重均高于对照处理,3个不同补光处理均明显提高黄瓜果实维生素C含量和氨基酸总含量,其中,维生素C含量以6红3蓝(6R3B)补光处理最高,8种人体必需氨基酸以及其他氨基酸含量和比例均以8红1蓝(8R1B)补光处理最高;而可溶性蛋白、可溶性糖、蔗糖、果糖、淀粉和还原糖含量,仅8红1蓝(8R1B)补光处理比自然光有显著提高。因此,开花结果期不同光质LED灯侧面补光能促进黄瓜果实生长和营养品质的增加,红光比例较高的8红1蓝(8R1B)补光处理效果最好。

黄瓜(Cucumis sativus L.)种子含油量性状的QTL定位与分析

应用SRAP和SSR技术,对黄瓜种子高含油量品系Ma7与低含油量品系M6杂交组合的F2群体进行检测,获得102个分子标记,构建了7个连锁群组成的分子标记遗传图谱;图谱总长764cM,标记间平均长度7.49cM。应用Windows QTL Cartographer2.5对种子含油量性状进行QTL扫描,在2009年秋季获得4个QTL位点,分别位于LG1、LG2和LG5连锁群,联合贡献率为32.7%。在2010年春季季获得5个QTL位点,分别位于LG1、LG2、LG5和LG6连锁群,联合贡献率为35.4%。通过对比春秋两季不同环境下的QTL位点发现,SOC_SP02和SOC_FA01分别位于LG1的74.7cM和72.2cM处,两位点相距2.5cM。此外,SOC_SP03和SOC_FA03两个微效QTL也存在部分的重叠,重叠区域为1.67cM,重叠的区间位于分子标记ME7OD17a和ME3EM8之间。另外,还估算了单个QTL的加性效应和显性效应,9个QTL的遗传效应均以加性效应为主。结果表明,对于种子油含量性状的等位基因增效作用既来自母本,又源自父本。

黄瓜（Cucumis sativus L．）组织培养与诱导四倍体再生植株

应用杨行黄瓜、长春密刺、农大秋光和杂种群丰、津研四号、津杂四号等黄瓜的子叶、真叶、茎段为外植体，离体培养诱导再生植株。比较了细胞分裂素（ＫＴ）与不同浓度的２，４－Ｄ和ＮＡＡ配比对诱导黄瓜愈伤组织的影响，及其所产生的愈伤组织分化培养的成苗率。所得结果表明：黄瓜在组织培养再生植株时，对生长激素极为敏感，只需极低浓度的２，４－Ｄ或ＮＡＡ即能诱导大量愈伤组织。激素浓度增高，出愈率提高，愈伤组织增殖加快，但分化能力下降。ＮＡＡ诱导成的愈伤组织比２，４－Ｄ诱导的易于分化。在诱导愈伤组织及胚性细胞发生时加入５００ｍｇ·Ｌ－１的秋水仙素经振荡液体培养４８，７２，９６ｈ再进行分化培养，出苗率分别为２５．６％、１８．５％、０．９％，对照为４６．８％。再生植株中３．５％～４．５％为四倍体，秋水仙素在分化培养中有抑制作用，处理９６ｈ的则很少分化再生植株。

连作土灭菌对黄瓜(Cucumis sativus)生长和土壤微生物区系的影响

采用盆栽试验的方法,对黄瓜的生长状况、抗病相关酶及土壤微生物区系特征进行了测定。结果表明:连作土灭菌能在较大程度上改善黄瓜的生长,灭菌土上生长的黄瓜的叶绿素含量、株高、叶面积和鲜重均大于连作土,但随氨基酸肥料(AAF)施用量的增加,灭菌土与连作土之间的差异变小。黄瓜叶片的SOD和POD活性在不施用AAF条件下灭菌土显著高于连作土,然而随着AAF施用量的增加,活性则相反。CAT活性及可溶性蛋白含量灭菌土所有处理均极显著高于相对应的连作土,MDA含量则显著低于相对应的连作土。灭菌土的细菌、真菌数量分别比连作土增加1.89～3.03倍和6.96～2.43倍,放线菌的增加幅度相对较小,真菌/细菌比值也显著提高。随AAF施用量的增加,连作土中的黄瓜枯萎病的致病菌(尖孢镰刀菌)减少,而灭菌土的所有处理均未分离到。土壤细菌的PCR-DGGE图谱分析表明,灭菌土DGGE图谱带明显比连作土增加,土壤间带谱的相似性降低,土壤微生物多样性指数增加。灭菌土上的黄瓜未见枯萎病发生,而连作土的黄瓜发病率达31.25%～68.75%。

Cytological Analyses on Development of Male and Female Gametophytes in an Interspecific Hybrid F1 from Cucumis hystrix Chakr. x Cucumis sativus L.

An interspecific hybrid F1 of Cucumis hystrix Chakr. x Cucumis sativus L. （NC4406） was used to establish the developmental sequence and to characterize the male and female gametophytes at cytological level for further understanding of the phylogenic relationship and the mechanism of fertility or sterility in the interspecific hybrid F1 The development of male and female gametophytes was studied through meiotic analysis and paraffin section observation technique, respectively. Meanwhile, the fertility level was assessed through hybrid F1 backcrossing to cultivated cucumber 4406. Variable chromosome configurations were observed in the pollen mother cells （PMCs） of hybrid F1 at metaphase Ⅰ , e.g., univalents, bivalents, trivalents, quadravalents, etc. At anaphase Ⅰ and Ⅱ, chromosome lagging and bridges were frequently observed as well, which led to the formation of polyads and only a partial number of microspores could develop into fertile pollen grains （about 23.3%）. Observations of the paraffin sections showed numerous degenerated and abnormal embryo sacs during the development of female gametophytes, and only 40% of the female gametophytes could develop into normal eight-nuclear megaspore. On an average, 22.8 and 6.3 seeds per fruit could be obtained from the reciprocal backcross. The interspecific hybrid F1 of C. hystrix x NC4406 was partially fertile; however, the meiotic behaviors of hybrid F1 showed a high level of intergenomic recombination between C. hystrix and C. sativus chromosomes, which indicated that it plays an important role for introgression of useful traits from C. hystrix into C. sativus.

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.

Comparative Assessment of the Proximate and Mineral Composition of <i>Cucumis sativus</i>L. and <i>Solanum aethiopicum</i>L. Fruit Samples Grown in South Eastern and North Central Regions of Nigeria Respectively

Studies were carried out to comparatively assess the proximate and mineral composition of Solanum aethiopicum L. and Cucumis sativus L. fruit samples grown in the South Eastern and North Central regions of Nigeria respectively, following standard analytical procedures and instrumentation. The mineral elements (Na, K, Zn and Ca) were determined using atomic absorption spectrophotometer after wet digestion of the samples while the proximate parameters (ash content, moisture content, crude fibre content, crude protein content, crude fat content and carbohydrate content) were determined in accordance with standard analytical procedures. The mean range of the moisture, crude fibre, crude protein, crude fat, ash and carbohydrate contents in the S. aethiopicum L. fruit samples grown in the North Central and South Eastern regions of Nigeria were 72.49 - 88.23, 2.15 - 3.67, 1.31 - 1.85, 0.43 - 0.76, 0.51 - 0.84 and 3.18% - 5.72% respectively. Additionally, the moisture, crude fibre, crude protein, crude fat, ash and carbohydrate contents in the Cucumis sativus L. fruit samples grown in the South Eastern and North Central regions of Nigeria, had mean range of values of 93.60 - 98.76, 0.53 - 0.77, 2.14 - 2.84, 0.29 - 0.46, 0.90 - 1.14 and 3.88% - 4.66% respectively. The range of mean values of Na, K, Zn and Ca in the S. aethiopicum L. fruit samples from the South Eastern and North Central regions of Nigeria were 0.36 - 0.57, 1.92 - 2.80, 0.84 - 1.01 and 0.43 - 0.61 μg/g respectively. Also, Na, K, Zn and Ca had mean range of values of 1.36 - 4.08, 10.16 - 13.09, 0.45 - 0.66 and 5.85 - 9.3 μg/g respectively in the C. sativus L. fruit samples grown in the South Eastern and North Central regions in Nigeria. The levels of the determined proximate of parameters and mineral elements in the studied fruit samples from the investigated regions of Nigeria were statistically significant. This therefore indicates that the geographical locations where these fruit samples grew could have significantly impacted on their nutrient content levels. The levels of the determined proximate parameters from the selected regions of Nigeria shows that consumption of the fruit samples (S aethiopicum L. and C. sativus L.) especially regularly, would help supply the essential nutrients and minerals required for a healthy living.

Comparative Assessment of the Phytochemical and Selected Heavy Metal Levels in <i>Cucumis sativus</i>L. and <i>Solanum aethiopicum</i>L. Fruit Sample Grown in South Eastern and North Central Regions of Nigeria Respectively

Studies were carried out to comparatively assess the phytochemical and heavy metal levels in Solanum aethiopicum L. and Cucumis sativus L. fruit samples grown in the South Eastern and North Central regions of Nigeria respectively using standard analytical procedures and instrumentation. The fruit samples were assayed for selected heavy metals (Pb, Cd and Cu) using atomic absorption spectrophotometer after wet digestion of the samples. The five detected phytochemicals (flavonoids, alkaloids, terpenoids, saponins and glycosides) were present at varying amounts in the investigated fruit samples from the South Eastern and North Central regions of Nigeria. The range of mean values of flavonoids, terpenoids, saponins and glycosides in the S. aethiopicum L. fruit samples from the two studied regions were 0.50 - 0.57, 0.53 - 1.26, 0.44 - 0.78, 1.12 - 1.93 and 0.40 - 0.50 mg/g respectively. The range of mean values of flavonoids, alkaloids, terpenoids, saponins and glycosides in the C. sativus L. fruit samples from the two studied regions of Nigeria were 1.27 - 1.69, 0.53 - 0.55, 0.96 - 1.51, 0.41 - 0.83 and 0.90 - 1.74 mg/g respectively. The range of mean vales of Pb, Cd, and Cu in the S. aethiopicum L. fruit samples from the two studied regions were 0.15 - 0.24, 0 - 0.01, 0.78 - 1.12 μg/g respectively. 0.31 - 0.40, 0.02 - 0.05 and 0.62 - 0.96 μg/g were the range of mean values of Pb, Cd and Cu respectively in the C. sativus L. fruit samples from the two studied regions of Nigeria. Of the three investigated heavy metals, only Cd was at toxic levels in the C. sativus L. fruit samples from the South Eastern and North Central regions of Nigeria. This is therefore a health concern to the fruit consumers that includes these fruits in their habitual daily fruit diets. Although the therapeutic and pharmaceutical benefits that would be derived from consuming, the investigated fruit samples has been shown in this study, there is therefore a possible risk of undue exposure to environmental pollutants such as heavy metal, especially through growing these fruits in polluted soils resulting from unwholesome anthropogenic practices. For fruit consumers to derive maximum health benefits from consuming these fruits, pollutants like heavy metals must be at non-toxic levels and this can only be achieved by ensuring that these fruits samples are grown and harvested in environments with less anthropogenic activities.

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.

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.