Photosynthesis in leaves and siliques of winter oilseed rape (Brassica napus L.)

The rate of photosynthesis and its relation to tissue nitrogen content was studied in leaves and siliques of winter oilseed rape (Brassica napus L.) growing under field conditions including three rates of nitrogen application (0, 100 or 200 kg N ha^-1) and two levels of irrigation (rainfed or irrigated at a deficit of 20 mm). The predominant effect of increasing N application under conditions without water deficiency was enhanced expansion of photosynthetically active leaf and silique surfaces, while the rate of photosynthesis per unit leaf or silique surface area was similar in the different N treatments. Thus, oilseed rape did not increase N investment in leaf area expansion before a decline in photosynthetic rate per unit leaf area due to N deficiency could be avoided. Much less photosynthetically active radiation penetrated into high-N canopies than into low-N canopies. The specific leaf area increased markedly in low light conditions, causing leaves in shade to be less dense than leaves exposed to ample light. In both leaves and siliques the photosynthetic rate per unit surface area responded linearly to increasing N content up to about 2 g m^-2, thus showing a constant rate of net CO₂ assimilation per unit increment in N (constant photosynthetic N use efficiency). At higher tissue N contents, photosynthetic rate responded less to changes in N status. Expressed per unit N, light saturated photosynthetic rate was three times higher in leaves than in silique valves, indicating a more efficient photosynthetic N utilization in leaves than in siliques. Nevertheless, from about two weeks after completion of flowering and onwards total net CO₂ fixation in silique valves exceeded that in leaves because siliques received much higher radiation intensities than leaves and because the leaf area declined rapidly during the reproductive phase of growth. Water deficiency in late vegetative and early reproductive growth stages reduced the photosynthetic rate in leaves and, in particular, siliques of medium- and high-N plants, but not of low-N plants.     

油菜烯醇酶基因的克隆与分析(英文)

烯醇酶(enolase)是糖酵解途径中的一个重要酶类,它能够催化磷酸甘油酸酯(2-PGA)生成磷酸烯醇丙酮酸酯(PEP)。我们通过RACE-PCR方法从油菜(Brassica napus L. )中克隆到了编码烯醇酶的全长基因。序列分析表明该基因全长cDNA为1624bp,拥有一个由444个氨基酸组成的开放读码框,所编码的蛋白质分子量为47.38kD,等电点为5.78。比较发现,油菜烯醇酶与已分离出的其他烯醇酶氨基酸序列有较高的同源性。Southern杂交结果显示烯醇酶以低拷贝形式在油菜基因组中存在。RT-PCR和Northern分析表明烯醇酶基因在100mmol/L盐浓度胁迫条件下表达量上升,而在低温诱导时表达量下降。该研究表明所克隆基因是植物烯醇酶基因家族的新成员。     

油菜烯醇酶基因的克隆与分析

烯醇酶(enolase)是糖酵解途径中的一个重要酶类,它能够催化磷酸甘油酸酯(2-PGA)生成磷酸烯醇丙酮酸酯(PEP).我们通过RACE-PCR方法从油菜(Brassica napus L.)中克隆到了编码烯醇酶的全长基因.序列分析表明该基因全长cDNA为1 624bp,拥有一个由444个氨基酸组成的开放读码框,所编码的蛋白质分子量为47.38 kD,等电点为5.78.比较发现,油菜烯醇酶与已分离出的其他烯醇酶氨基酸序列有较高的同源性.Southern杂交结果显示烯醇酶以低拷贝形式在油菜基因组中存在.RT-PCR和Northern分析表明烯醇酶基因在100 mmol/L盐浓度胁迫条件下表达量上升,而在低温诱导时表达量下降.该研究表明所克隆基因是植物烯醇酶基因家族的新成员.     

Boron efficiency in oilseed rape: I. Genotypic variation demonstrated in field and pot grown Brassica napus L. and Brassica juncea L.

Boron (B) efficiency of oilseed rape (Brassica napus) and mustard (B. juncea) genotypes was determined on a low B soil at Mt. Compass, South Australia. B efficiency was observed in oilseed rape genotypes, Zhongyou 821, Dunkeld and Zheyou 2, and in mustard genotypes Pusa Bold and CSIRO 6. Genotypes grown in the field were also grown under glass-house conditions, in pots filled with pre-washed sand extracted from the Mt. Compass field site. Two B treatments, one B adequate (0.25 mg B kg⁻¹ soil) and one B deficient (imposed by omission) were used to indicate whether vegetative response to B could predict final yield response and provide a more convenient selection criterion for identifying B-efficient germplasm. Vegetative response of 35 d old (D35) genotypes grown in pot culture closely reflected field response, indicating the expression of B efficiency traits in early growth, and its potential use in selection. This revised version was published online in June 2006 with corrections to the Cover Date.     

Pathways of infection of Brassica napus roots by Leptosphaeria maculans

Infection of Brassica napus cotyledons and leaves by germinating ascospores of Leptosphaeria maculans leads to production of leaf lesions followed by stem cankers (blackleg). Leptosphaeria maculans also causes root rot but the pathway of infection has not been described. An L. maculans isolate expressing green fluorescent protein (GFP) was applied to the petiole of B. napus plants. Hyphal growth was followed by fluorescence microscopy and by culturing of sections of plant tissue on growth media. Leptosphaeria maculans grew within stem and hypocotyl tissue during the vegetative stages of plant growth, and proliferated into the roots within xylem vessels at the onset of flowering. Hyphae grew in all tissues in the stem and hypocotyl, but were restricted mainly to xylem tissue in the root. Leptosphaeria maculans also infected intact roots when inoculum was applied directly to them and hyphae entered at sites of lateral root emergence. Hyphal entry may occur at other sites but the mechanism is uncertain as penetration structures were not observed. Infection of B. napus roots by L. maculans can occur via above- and below-ground sources of inoculum, but the relative importance of the infection pathways under field conditions is unknown.     

Complexity and expression of the glutamine synthetase multigene family in the amphidiploid crop Brassica napus

In the amphidiploid genome of oilseed rape (Brassica napus) the diploid ancestral genomes of B. campestris and B. oleracea have been merged. As a result of this crossing event, all gene loci, gene families, or multigene families of the A and C genome types encoding a certain protein are now combined in one plant genome.In the case of the multigene family for glutamine synthetase, the key enzyme of nitrogen assimilation, six different cDNA sequences were isolated from leaf and root specific libraries. One sequence pair (BnGSL1/BnGSL2) was characterized by the presence of amino- terminal transit peptides, a typical feature of all nuclear encoded chloroplast proteins. Two other cDNA pairs (BnGSR1-1/BnGSR1-2 and BnGSR2-1/BnGSR2-2) with very high homology between each other were found in a root specific cDNA library and represent protein subunits for cytosolic glutamine synthetase isoforms.Comparative PCR amplifications of genomic DNA isolated from B. napus, B. campestris and B. oleracea followed by sequence–specific restriction analyses of the PCR products permitted the assignment of the cDNA sequences to either the A genome type (BnGSL1/BnGSR1- 1/BnGSR2-1) or the C genome type (BnGSL2/BnGSR1-2/BnGSR2-2). Consequently, the ancestral GS genes of B. campestris and B. oleracea are expressed simultaneously in oilseed rape. This result was also confirmed by RFLP (restriction fragment length polymorphism) analysis of RT-PCR products.In addition, the different GS genes showed tissue specific expression patterns which are correlated with the state of development of the plant material. Especially for the GS genes encoding the cytosolic GS isoform BnGSR2, a marked increase of expression could be observed after the onset of leaf senescence.     

转基因油菜的基因流及生态风险

综合评述了转基因油菜的基因流及其生态风险.油菜作为最早的转基因作物之一目前已在加拿大和澳大利亚大面积商业化应用.(常)异花授粉作物油菜的天然异交率可达30%左右,也易与其它芸苔属作物杂交,因此转基因油菜的生态风险已引起各国科学家的高度重视.转基因油菜主要通过与其野生近缘种的花粉交换和与非转基因油菜的花粉交换两种方式进行花粉的输出.基因可能逃逸到相关野生近缘种,但在大田环境下能够得到杂种的可能性很小;由于基因的漂流在油菜田块间确实存在,因此在种植转基因油菜的过程中必须考虑其间隔距离.     

Differential response of oilseed rape (Brassica napus L.) cultivars to low boron supply

Three experiments were carried out on an alluvial sandy loam (Udifluvent) at Tonglu, Zhejiang Province, P.R. China from 1992 to 1995, to determine the genotypic range in boron (B) efficiency of 16 oilseed rape (Brassica napus L.) cultivars, to identify the B-efficient cultivars and to identify specific responses which can be utilised for selection in a breeding program. The 16 cultivars which included high-quality and conventional types differed significantly in survival, plant height, leaf area, shoot dry weight and seed yield; however, the ranking of the cultivars for their seed yield or other plant traits differed with B treatment. With severe B deficiency (CaCl2 extractable B < 0.26 mg/kg) and no boron applied, none of the cultivars exhibited significant B efficiency, with seed yield <300 kg/ha. With moderate B deficiency (CaCl2 extractable B 0.34 mg/kg or 0.17 kg B/ha applied), seed yield varied significantly among the cultivars from 397 to 1889 kg/ha in year 1 and from 616 to 1260 kg/ha in year 3. Zhongyou 821 and 92-13 were the most B-efficient and Wanyou 324, Huashuang 2 and Su 2051 were the most B-inefficient cultivars under moderate B deficiency. Significant differences were found among the cultivars in leaf B concentration; however, there was no close relationship between leaf B concentration and seed yield responses to B of oilseed cultivars. Of all the growth parameters measured, leaf area was the early indicator best correlated with subsequent seed yield and may be useful for evaluating the response of cultivars to low B supply. Contrary to current opinion, it was also found that high-quality oilseed rape cultivars were not all sensitive to low B supply nor were all conventional cultivars B-efficient.     

不同硼效率甘蓝型油菜品种细胞壁中硼的分配

应用不同硼效率甘蓝型油菜品种 ,研究硼在细胞壁中的分配。硼主要结合在细胞壁中 ,缺硼显著提高硼在细胞壁中的分配比例。根系细胞壁硼含量显著低于叶片 ,但根系细胞壁硼占根系总硼量之比例显著高于叶片。同一品种根系及其细胞壁、老叶细胞壁硼含量受生育期影响较小 ,新叶及其细胞壁、老叶硼含量受生育期影响较大。在正常供硼条件下 ,硼高效品种根系细胞壁和叶片细胞壁硼含量均低于低效品种 ;正常和缺硼条件下 ,硼高效品种细胞壁硼占器官总硼量之比例均低于低效品种。说明硼低效品种需较多的硼构建细胞壁。     

RFLP和AFLP分析白菜型油菜和甘蓝型油菜遗传多样性及其在油菜改良中的应用价值

采用RFLP和AFLP标记对来自中国和欧美的7份甘蓝型油菜和22份白菜型油菜进行了遗传多样性分析。在这29份材料中,166个酶-探针组合和2对AFLP引物共检测到1477个RFLP标记和183个AFLP标记。RFLP数据显示以拟南芥EST克隆作探针比用油菜基因组克隆做探针能检测到更多的多态性位点,且采用EcoR Ⅰ或BamH Ⅰ酶切比HindⅢ酶切多态性好,白菜型油菜和甘蓝型油菜中基因的拷贝数平均都为3个左右。UPGMA聚类分析表明中国白菜型油菜的遗传多样性比甘蓝型油菜和欧美白菜型油菜丰富,欧美甘蓝型油菜与欧美白菜型油菜聚为一类,而与中国甘蓝型油菜差异更大。中国白菜型油菜丰富的遗传多样性为中国甘蓝型油菜的改良提供了宝贵的资源,揭示了利用白菜型油菜A基因组和甘蓝型油菜A基因组间亚基因组杂种优势的可能性。     

Hormonal requirement and tissue competency for shoot organogenesis in two cultivars of Brassica napus

An investigation of the regeneration ability of explants taken from the floral stem of Brassica napus var. oleifera was performed in the winter cultivars Darmor and Bienvenu. Our purpose was to compare the regeneration ability of the two genotypes, to compare the competence of the different tissues of the stem and then to study histologically the regeneration of shoots. A strong genotypic effect was observed between the two cvs; Bienvenu had a poorer ability to produce shoots when cultured in the presence of benzyladenine: regeneration commenced later; the percentage of explants producing shoots and the number of shoots per regenerating explant were much lower. The comparison between the regeneration ability of different explants, i.e stem segments, internal stem segments, thin cell layer and peels, showed that the superficial tissues were able to regenerate roots but not shoots. Contrariwise, internal stem segments regenerated only shoots. The origin of shoots was investigated in stem segments of cv. Darmor. A kinetic histological analysis showed the basic role played by phloem and phloem-associated cells in shoot formation.     

膜下滴灌水氮调控对南疆棉花产量及水氮利用率的影响

为探明水氮调控对膜下滴灌棉花的生长特性、产量构成因素以及水氮利用效率的影响,设置了3个灌溉水量和5个氮素水平进行大田棉花膜下滴灌试验.结果表明: 随着灌溉水量的增加,棉花的株高、主茎叶数、果枝数和叶面积指数显著增加,棉花叶、茎干物质积累增加,但抑制了根系生长,与低(4950 mm·hm^-2)和高(6750 mm·hm^-2)灌水量处理相比,中灌水量(5850 mm·hm^-2)处理平均单株有效铃数和单铃质量分别增加0.96、0.4个和0.22、0.11 g.与其他施氮处理相比,施氮量为300 kg·hm^-2时棉花茎直径显著增加,促进了棉花蕾、铃和根系的发育,而且在灌水量为5850 mm·hm^-2条件下,棉花干物质由营养器官向生殖器官的分配比灌水量为4950和6750 mm·hm^-2处理分别增加5.1%和29.6%.灌溉水量对棉花产量有显著影响,对衣分率影响不显著,而施氮量对棉花产量和衣分率都有一定的影响,但灌溉水量过低会抑制氮肥增产效应的发挥.在本试验条件下,灌水量为5850 mm·hm^-2、施氮量为300 kg·hm^-2时,棉花生长健壮,株型结构优化,显著促进了干物质向生殖器官的运转,有效铃数、单铃质量和衣分增加,产量达到最高(6992 kg·hm^-2),水分利用效率和氮肥利用率分别达1.45 kg·m^-3和45.9%.     

Leaf senescence in Brassica napus: expression of genes encoding pathogenesis-related proteins

Genes that are expressed during leaf senescence in Brassica napus were identified by the isolation of representative cDNA clones. DNA sequence and deduced protein sequence from two senescence-related cDNAs, LSC94 and LSC222, representing genes that are expressed early in leaf senescence before any yellowing of the leaves is visible, showed similarities to genes for pathogenesis-related (PR) proteins: a PR-1a-like protein and a class IV chitinase, respectively. The LSC94 and LSC222 genes showed differential regulation with respect to each other; an increase in expression was detected at different times during development of healthy leaves. Expression of both genes was induced by salicylic acid treatment. These findings suggest that some PR genes, as well as being induced by pathogen infection, may have alternative functions during plant development, for example in the process of leaf senescence.     

油菜油分、蛋白质和硫苷含量相关性分析及QTL定位

为定位与油分、蛋白质和硫苷含量等品质性状相关的数量性状位点（QTL）,以2个含油量较高的甘蓝型油菜（Brassica napus）品系8908B和R1为研究材料,配置正反交组合。在正反交F2代群体中,含油量和蛋白质含量都存在极显著的负相关,相关系数分别为-0．68和-0．81,含油量和硫苷含量相关性不显著：蛋白质含量和硫苷含量在正交群体中相关性不显著,但在反交群体中存在显著负相关（相关系数r=-0．45）。利用正交F2代群体中的118个单株,构建了包含121个标记的遗传连锁图谱,图谱长1298．7cM,有21个连锁群（LGs）。采用复合区间作图法,在连锁图上定位了2个与含油量有关的QTL,分别位于LG8和LG10,其贡献率分别为4．8％和13．7％,增效基因都来源于R1;定位了2个与蛋白质含量有关的QTL：pr01和pr02,分别位于LG1和LG3,其贡献率分别为15．2％和14．1％,位点pr07由8908B提供增效基因,pro2则由R1提供增效基因：定位了4个与硫苷含量有关的QTL,其中LG20上有2个,LG4和LG8上各1个,它们的贡献率在1．9％-25．4％之间,除LG20上glu7的增效基因来自R1外,其余3个QTL位点均由8908B提供增效基因。     

Growth responses in oilseed rape (Brassica napus L.) to combined applications of the triazole chemicals triapenthenol and tebuconazole and interactions with gibberellin

Crop height in the oilseed rape cv. Ariana was reduced more by the triazole retardant triapenthenol at 490 g ai ha^–1, applied as a combined spray with the triazole fungicide tebuconazole at 250 g ai ha^–1, than when triapenthenol was applied alone. The growth responses following combined treatment appeared to be additive of the component effects.Initial inhibition of stem extension and leaf expansion by tebuconazole was followed by compensatory growth; the pattern of responses was similar to that with triapenthenol applied at approximately one tenth of the rate. However, different mechanisms of effects on growth were indicated by competitive interaction with gibberellic acid.     

The importance of sampling immature leaves for the diagnosis of boron deficiency in oilseed rape (Brassica napus cv. Eureka)

Plant analysis can diagnose boron (B) deficiency when the standards used have been properly developed by establishing that a close relationship exists between B concentration in a plant part and its physiological function. The purpose of the present study was to demonstrate the importance of choosing the growing immature leaves for B deficiency diagnosis and for establishing critical B concentrations for the diagnosis of B deficiency in oilseed rape (Brassica napus). In Experiment 1, the plants were subject to seven levels of B supply using programmed nutrient addition, for the estimation of critical B concentrations in plant parts for shoot growth. In Experiment 2, the plants were treated with two levels of B supply in solution: 10 (+B) and 0 (-B) M B, for the estimation of functional B requirements for leaf elongation. The results showed that critical B concentrations varied amongst the plant parts sampled and decreased with leaf age. As B taken up by roots is largely phloem-immobile, B concentrations in mature leaves are physiologically irrelevant to plant B status at the time of sampling, giving rise to a significant over- or underestimation of the B requirement for plant growth. By contrast, a growing, immature leaf, in this case the youngest open leaf (YOL), was the most reliable plant part for B deficiency diagnosis. Critical B concentrations developed from both methods were comparable-i.e. 10–14 mg B kg^–1 dry matter in the YOL at vegetative growth stages up to stem elongation.