In vitro antioxidant activity of callus culture of carrot （Daucus carom）

Carrot （Daucus carom） is a valuable source of health promoting ingredients such as anthocyanin, carotenes, phenolic compounds etc. These substances are important to man as a source of pharmaceuticals, fragrance, agrochemicals as well as food additives and used for prevention of many chronic diseases. Since these activities may be correlated with the presence of antioxidant compounds, extract of carrot and carrot callus were evaluated for their anthocyanin, flavonoids and total phenolic content as well as total antioxidant activity. Anthocyanin content was measured by spectrophotometric method. Total phenols and flavonoids were analyzed according to the Folin-Ciocalteu method and total antioxidant activity was assessed by ferric reducing/antioxidant power （FRAP） assay. Anthocyanin, flavonoids and total phenolic content were estimated to be 9.36 mg%, 46.96 mg% and 57.01 mg% for callus and 6.82 mg%, 32.96 mg% and 42.69 mg% for carrot, respectively, on fresh weight basis. The total antioxidant activity for the callus and carrot was found to be 51.13 mg, 118.77 mg, 91.08 mg and 140.08 mg equivalent and 79.40 mg, 184.44 mg, 141.43 mg and 217.52 mg equivalent to gallic acid, vitamin C, butylated hydroxyanisole （BHA） and trolox, respectively, when expressed per 100 g on fresh weight basis. The antioxidant activity of fresh carrot was found to be higher compared to its callus.     

胡萝卜遗传转化体系的建立

以新黑田五寸胡萝卜下胚轴为外植体,研究对胡萝卜抗性植株的影响因素及目的基因的整合情况,建立了较为完善的转化体系。实验结果表明:以胡萝卜下胚轴为材料,用苗龄7d,共培养2d,浸染15min的体系,Kan抗性芽的分化频率可达52%。获得抗性愈伤培养基:B5+0.1mg/L2,4-D+0.2mg/LKT+75mg/LKan+500mg/LCef,抗性芽诱导培养基:B5+100mg/LKan+500mg/LCef;抗性植株生根培养基:B5+0.1mg/LIBA+75mg/LKan+300mg/L:Cef;对转基因植株进行了PCR分子学检测,初步证明外源基因已整合到胡萝卜基因组中。     

胡萝卜抗冻蛋白的快速大量突变及原核表达

胡萝卜抗冻(DcAFP)具有典型的LRR特征,由约24个氨基酸残基组成重复单元,其中的保守基序是:P×××××L××L××L×LS×N×L×G×I,其中的保守天冬酰胺在与冰晶表面结合中起着关键的作用．为了探明该关键氨基酸对DcAFP重要性,需要对其进行一系列突变,以检测这些突变体的热滞可能发生的变化,而这需要构建大量的突变体．基于此,采用定点突变技术对该基序中保守的天冬酰胺进行了一系列的疏水性缬氨酸突变和亲水性的谷氨酰胺突变,并将这一系列突变体克隆至原核表达载体pET-11a中,在大肠杆菌BL21(DE3)中进行了高效表达与初步纯化,为后续测定其热滞活性的变化和验证天冬酰胺的重要性打下了基础．     

Nucleotide polymorphism in the carrot late embryogenesis abundant gene DC8/ECP63

Carrot (Daucus carota) somatic embryogenesis has been extensively used as an experimental system for studying embryogenesis. In several plant species, late embryogenesis abundant (LEA) genes are reported as the embryogenesis-related genes that are specifically expressed in embryonic tissues. Several LEA genes have been isolated for carrot somatic embryogenesis. The carrot LEA genes DC8 and ECP63 have very similar nucleotide sequences, and the gene pair is likely to be a nucleotide polymorphism. In several carrot cultivars, plants in which only DC8 was detected (DD genotype), only ECP63 was detected (EE genotype), and both DC8 and ECP63 were detected (DE genotype) have been observed via genomic PCR. Furthermore, distinct frequencies of the genotypes were observed in some carrot cultivars. These results suggested that detection of the nucleotide polymorphism might be useful in defining carrot cultivars. In addition, DC8 and ECP63, which include 14 amino acid insertions/deletions and 21 amino acid substitutions, may have similar effects on somatic embryogenesis, as all genotypes (DD, DE, and EE) were detected in some embryogenic cell lines. Therefore, the nucleotide polymorphism may be a useful candidate polymorphic marker that is easily detectable by PCR.     

胡萝卜愈伤组织诱导培养的研究

以胡萝卜"七寸人参"为试材,探讨了不同外植体、激素、培养基、光照对胡萝卜愈伤组织诱导的影响。结果表明:胡萝卜愈伤组织的诱导以下胚轴为外植体为宜;在添加2,4-D1.0mg/L和KT 0.5mg/L的MS培养基上愈伤组织的诱导频率为100%,且愈伤组织生长良好,增殖快速;光照对愈伤组织的诱导没有影响,但却进一步阻碍了愈伤组织的增殖生长。     

胡萝卜主要产量性状杂种优势及配合力分析

以３个不育系为母本，４个自交系为父本，按不完全双列杂交法配制１２个组合，进行杂种优势和配合力分析。结果表明，小区产量、单根重、根长和根粗均表现了明显的正向杂种优势，以小区产量和单根重的杂种优势较高；亲本一般配合力效应比组合特殊配合力效应更为重要，其中父本的作用大于不育系的作用；３０株系（Ｂ_３）小区产量、单根重、根长和根粗的一般配合力具有较大的正向效应值，丹富士分离株系（Ａ_２）心柱比例具有较大的负向效应值。从根形、根色及整齐度来看以丹富士分离株系（Ａ_１、Ａ_２）作母本，Ｂ_３为父本更为理想。     

春小麦、胡萝卜复种栽培技术研究

春小麦下茬复种胡萝卜栽培模式可提高单位面积土地利用率,促进农民增产增收。从品种选择、栽培过程、田间管理和收获几方面介绍春小麦、胡萝卜复种栽培技术的操作要点,以期为该栽培模式的大面积推广应用提供技术支持。     

鲜切胡萝卜的真空预冷研究

研究了不同切片厚度与预冷终温对鲜切胡萝卜真空预冷效果的影响,分析了经过真空预冷和未经真空预冷的鲜切胡萝卜在贮藏期内的呼吸强度、失重率、色差和硬度的变化。结果表明,鲜切胡萝卜可比完整胡萝卜节省2/3的预冷时间;在切片厚度6 mm和预冷终温6℃时,鲜切胡萝卜的真空预冷效果最佳,失重率为1.3%、芯部温度1.5℃、预冷时间7.3 min。采用真空预冷处理方法可有效抑制鲜切胡萝卜贮藏期内的呼吸强度,降低失重率,保持其较好的感官品质。     

The Identification and Exploitation of Resistance in Carrots and Wild Umbelliferae to the Carrot Fly, Psila rosae (F.)

Partial plant resistance to the carrot fly, Psila rosae, has been identified in several Nantes varieties of carrot, Daucus carota, which reduces larval damage to the roots and the number of pupae remaining in the soil after cropping by 50%. The resistance of the Nantes variety 'Sytan' was found to be consistent at 12 sites in 5 European countries over two seasons. The resistance has been shown to be based on antibiosis and correlated with concentrations of chlorogenic acid in the roots. The resistance complements cultural and chemical methods for controlling P. rosae. Thus, in field experiments over two seasons it was shown that carrots could be left in the ground for a longer period providing a greater sowing/harvesting interval with a resistant variety than a susceptible one because of the reduction in damage and the delayed development of insects on the resistant variety. In two seasons at two sites a partially-resistant variety required only one-third of the dose of insecticide to provide a marketable crop compared with a susceptible carrot variety. In a breeding programme involving the variety 'Sytan', male sterile lines, inbreds and selections with improved levels of resistance were developed. Much higher levels of resistance were identified in certain wild Daucus species and 15 years of crossing and selection produced lines with significantly higher levels of resistance than exists in the variety 'Sytan'. A range of resistant carrot material bred at Horticulture Research International has been released to seed companies for use in the production of improved carrot varieties. The partially-resistant variety 'Flyaway' was made available to amateur gardeners in 1993 and to commercial growers in 1995 as a result of this research.     

Occurrence of Pythium Ultimum Var. Ultimum in a Greenhouse on Spitsbergen Island, Svalbard

Pythium ultimum var. ultimum was isolated from carrot seedlings with damping off and from soil used for growing the plant in a greenhouse on Spitsbergen Island, Svalbard. The fungus caused severe damping off of carrot, cucumber and tomato seedlings after artificial inoculation. The rDNA internal transcribed spacer sequences of the Svalbard isolate were identical to those of Canadian and Japanese isolates of P. ultimum var. ultimum. The results suggest that the pathogen in the greenhouse on Svalbard was probably introduced from temperate regions through contaminated plants and/or soil imported to the island. This is the first record of P. ultimum var. ultimum within the Arctic zone.