施氮和灌水对冬小麦叶片光合特性和籽粒产量的影响

大田条件下设置不同的施氮和灌水水平,研究施氮量和灌水量对冬小麦(Triticum aestivum L.)叶片光合作用生理及籽粒形成的影响。结果表明,施氮和灌水提高叶片Fv/Fm和Pn,并显著提高冬小麦籽粒产量、单位面积穗数和每穗粒数。施氮明显降低千粒重,而适量灌水明显提高千粒重。

水稻同源四倍体三系法杂种优势利用研究

水稻是重要的粮食作物，其产量的增加和品质的改良都是关系国计民生的大事。就我国现阶段的国情而言，水稻产量在现有水平上稳步提升仍是未来十几年甚至几十年农业生产最重要的目标之一。尽管根据“超级杂交水稻育种”的战略设想和水稻育种实践，通过不断地改进育种技术可望在更高的产量水平上进行水稻杂种优势利用，在稻属植物内还具有很大的产量潜力可以挖掘。然而，仅仅从现有的种质基础出发，要更大幅度提高水稻单产，实现“超级杂交稻”的目标也存在一些困难：现有的推广品种是二倍体，尽管种类众多，但是其基因组的来源相对单一；同时，水稻基因组DNA含量也是作物中最少的，基因组内寻求开发潜力有一定困难；水稻作为C3植物，光合利用效率不高也是制约水稻产量提高的因素之一。因此，寻求常规手段以外的技术突破或者方法创新，是实现“超级杂交稻”的目标的迫切需求。本研究利用秋水仙素能抑制细胞分裂中纺锤丝的收缩、使细胞染色体加倍的作用，对水稻幼穗诱导的愈伤组织细胞进行加倍，并分化出再生植株；创制出水稻同源四倍体新的种质材料，在此基础上选育水稻同源四倍体雄性不育三系材料，并实现水稻同源四倍体的三系配套，开展水稻同源四倍体杂种优势利用和四倍体杂交水稻选育研究，建立水稻同源四倍体杂种优势利用的新技术体系。这不仅有助于倍性水平杂种优势的开拓和利用，同时也将为我国新世纪“超级稻”育种研究开辟一条新的技术途径。 水稻幼穗诱导愈伤组织并分化成苗是一项成熟、简单的组织培养技术。本研究以普通二倍体水稻亲本为材料，用秋水仙素进行水稻的多倍体化诱导，创制同源四倍体水稻三系亲本材料并对其进行鉴定。多倍体化以秋水仙素诱导的愈伤组织培养为基础，研究不同秋水仙素浓度梯度和愈伤组织诱导培养基组合对诱导四倍体植株的影响。结果表明在MS+2,4 D 1.0mg/L+ KT0.2mg/L+ IAA0.2mg/L 和500mg/L的秋水仙素处理下，水稻愈伤组织染色体加倍（有最高的效率）效果较好，平均加倍频率可达25.26%，其中，材料CDR22和IR26诱导较易成功，加倍频率分别达到75%和26.5%；相对材料94109 1.3%加倍频率和冈46B 10.8%加倍频率，诱导率差异极显著。 对水稻四倍体材料进行了形态学鉴定结果表明，与二倍体水稻对照相比其株高、穗长、花粉育性等主要农艺性状，确定四倍体材料在穗长和千粒重两方面极显著提高，种子的长度和宽度也显著增长。对花粉育性鉴定，确认水稻四倍体不育系材料仍为不育，保持系材料自交和杂交可育，恢复系材料自交和杂交可育。对四倍体材料进行细胞形态、染色体数目等方面进行细胞学鉴定，经核型分析表明水稻四倍体材料具有48条染色体，是二倍体水稻的两倍。水稻四倍体材料根尖分生组织细胞与二倍体的根尖分生组织细胞相比，细胞体积、细胞核和核仁显著增大。四倍体三系材料在细胞有丝分裂中期均可规则排列在赤道板，并能均等地移向两极；后期观察中没有发现染色体分离滞后现象，分裂末期细胞能够形成大小相对均一的子细胞。水稻同源四倍体三系材料细胞分裂未见异常，植株生长发育正常。 从1996年至2006年，针对结实率、有效分蘖、着粒数和穗长等主要农艺性状，通过系谱选育的方法，对培育的同源四倍体水稻亲本材料进行了连续选择和改良，取得较好成效。表现为结实率的改良效果极佳，所有改良材料的平均结实率均呈上升趋势，如D237（29.70％→72.70％）、DTB（19.55％→53.21％）等。有效分蘖总体呈现上升趋势，但在不同的年份，如1998和2002存在较大的负向波动。部分材料改良效果明显，如D19B（5.87→13.50）、D什香 (7.00→12.00)等；同时一些材料如DTB和D明恢63虽然总体略有提高，但在不同的年份波动很大，因此存在较大改良阻力，原因还有待进一步研究。着粒数的改良上升趋势比较显著，除保持系的DTB之外，其余材料的平均着粒数有显著提高。穗长的改良阻力较大，虽然不同材料总体上有所提高，但效果并不显著，并且不同年份有较大负向波动（2001）。此外还对株高、剑叶长等性状也进行了选择，但效果不显著，原因有待进一步提高。同源四倍体材料产量相关性状遗传改良幅度不一致，保持系和恢复系间的遗传改良效果也存在差异。这为同源四倍体水稻的进一步利用打下了良好的基础。 籼稻和粳稻亚种间杂交及杂种优势利用的主要障碍就是其低的结实率。而同源四倍体杂交水稻的研究为提高杂交水稻的杂种优势利用创造了新的途径。本研究通过随机区组设计方案，挑选性状优良的二倍体水稻材料，包括雄性不育系，保持系和恢复系进行秋水仙素诱导加倍，从而获得同源四倍体水稻对应的三系材料。利用选育的优良水稻同源四倍体三系材料，配制7个杂交组合，杂交F1代与其恢复系亲本进行比较，用于计算超亲优势（HB）；而杂交F1代与生产上大面积推广的二倍体杂交品种汕优63进行比较，用于计算杂种优势。结果显示，同源四倍体杂交水稻的超亲优势表现为：每株有效穗变化幅度为1.4%至105.9%，总粒数为0.5%至74.3%，每穗实粒数为17.6%至255.7%，结实率为9.6%至130.4%。这些农艺性状的改良使得这7个杂种F1的理论产量的超亲优势高达64.8%至672.7%。小区试验中四倍体杂交水稻组合T461A/T4002和T461A/T4193分别比二倍体对照汕优63提高46.3%和38.3%以上，除一个品种以外所有品种产量均接近或高于汕优63的产量。同源四倍体水稻强大的杂种优势表明，亚种间杂交育性低的问题可通过四倍体化及强化选择来解决。此外，同源四倍体杂交水稻器官的巨大性也是其产量提高的有利因素，水稻同源四倍体三系杂种优势利用研究具有一定的理论价值和商业生产潜力。 Rice is one of the major food crops, the improvement of the production and quality of it is an important thing related to the people's livelihood. On China's current national conditions, steadily increase of the rice yield based on the current level is still one of the most important goals in the next decade or even decades of agricultural production. According to the "super hybrid rice breeding" the strategic and rice breeding practice, improvement of the use of hybrid rice heterosis through continuous improvements in breeding technology is expected to get a higher level of rice yield, there are also a great yield potential can be exploited. However, there are also some difficulties to increase rice yield obviously and implement the goal of "super hybrid rice" based on the existing germplasm: Rice varieties in promotion are diploid, although there are many varieties, but their genome are from a comparatively single source; Meanwhile, the rice genome DNA are the least among the crops, it is difficult to exploit the development potential within the genome; Rice as C3 plants, photosynthetic efficiency is not high, it is one of the factors constraint rice yield. Therefore, seeking technological breakthroughs or innovative methods different from conventional means is the urgent needs to reach the target of "super hybrid rice". Using colchicine inhibit spindle contraction during cell division, double the cell chromosome, we induced callus cells from rice panicle to be doubled, and differentiated regeneration; we created a new autotetraploid rice germplasm material, and on that basis we bred male sterility three line autotetraploid rice materials, and the achieved the three line rice autotetraploid matchmaking, researched in autotetraploid rice heterosis usage and tetraploid hybrid rice breeding, constituted a new technology system of autotetraploid hybrid rice heterosis utilization. This not only helps the tetraploid rice heterosis exploration and use, but also inaugurates a new technical means for China in the new century "super rice" breeding research. We chose ordinary diploid rice as materials, using colchicine to induce the polyploidization, created the autotetraploid rice three-line materials and identified them. The polyploidization was based on the colchicine-induced callus tissue culture, and we experimented different colchicine concentrations and culture mediums to induce tetraploid plants, confirmed that the optimal concentration for inducement was 500 mg/L, the average induce rate was 25.26 %. Among all the materials, CDR22 and IR26 had higher induced rate; in contrary, 94109 and GANG46B had lower induced rate, the difference was significant. Autotetraploid materials was identified of both morphological and cytological, compared plant height, length of pollen sterility, and other major agronomic traits with a diploid rice as the control plant, identified that the autotetraploid materials had very significant advantages in ear length and thousand-grain weight, as well as the size of the seeds. Cytology identification included observation of the cell morphology, the number of chromosomes, and karyotype analysis on the autotetraploid materials confirmed that their chromosome number was 48, twice of the diploid rice. Mitoses in the three lines were common: chromosomes arrayed normally in metaphase and separated balanced into the two poles, chromosome moved without lagging in anaphase and daughter cells normally formed in telophase except one. It has been proved that tetraploid rice has normal meiosis as their diploid relatives, which usually including series of sub-phases as interphase, prophase I (five sub-phases), prophase II, metaphase I, II, anaphase I, II and telophase I, II. However, abnormal phenomena, such as formation of tetravalent, trivalent and univalent, chromosome lagging and so on, which would finally block meiosis. Configurations of chromosome in metaphaseⅠwere versatile in structure and form accept the bivalent. That condition varied in different strain, suggesting more complex paring configurations and more versatile genetic characters in tetraploid rice. All these abnormalities in meiosis contributed to low fertility of gamete and might consequently resulted in low seed setting. Successive selection and improvement on seed set, productive tiller per plant, total grains per panicle, panicle length and so on had been carried out from 1996 to 2006. The raise of seed sets was significant in both restorers and maintainers. Seed sets of some strains were improved more significantly than others, for example D237（29.70％→72.70％）、DTB（19.55％→53.21％）and et al.. Productive tiller per plant was improved to some extant. The tendency of improvement was rising on the whole but changed in some years such as 1998 and 2002. Part of the stains increased greatly, such as D19B（5.87→13.50）、Dshixiang (7.00→12.00) and so on, but some strains including DTB and Dminghui63 only increased little and decreased in some years by unknown reason. Total grains per panicle increased significantly and all strains except DTB increased. Improvement of panicle length termed to be hard. Different strains showed different capacities for improvement and floating existed in different years for example 2001. It has been proved that other agronomical traits including plant length, flag leaf length and so on could be improved but not significantly by selection also. In a word, agronomical traits could be raised by successive selection that is prerequisite for further utility of autotetraploid rice. Poor fertility is the main barrier for utilizing heterosis between the two rice (Oryza stiva L.) sub-species, indica and japonica. Recently, the development of autotetraploid hybrids (2n=4x=48) has been suggested as a new method for increasing heterosis in hybrid rice. Using standard experimental protocols, the elite diploid rice male sterile, maintainer, and restorer lines were colchine-doubled and autotetraploid counterparts were obtained. Seven resulting hybrids were analyzed for heterobeltiosis (HB), where the F1 was compared to the male parent, and the degree of heterosis, where the F1 was compared to the diploid commercial hybrid, Shanyou 63. The HB among the autotetraploid hybrids ranged from 1.4 to 105.9% for the productive panicles per plant, 0.5 to 74.3% for total kernels per panicle, 17.6 to 255.7% for filled kernels per panicle, and 9.6 to 130.4% for seed set. Improvements in these yield components resulted in the HB for kernel yield ranging from 64.8 to 672.7% among the seven hybrids. Hybrids T461A/T4002 and T461A/T4193 yielded 46.3 and 38.3% more, respectively than Shanyou 63, and all other hybrids but one yielded the same or more than Shanyou 63. The high heterosis for yield suggests that hybrid sterility between two rice sub-species may be overcome by using tetraploid lines followed by intensive selection. Also, the gigantic features of the autotetraploid hybrids may establish a plant structure able to support the higher yield.

糯小麦杂交后代的基因型鉴定及Wx基因的效应研究

糯小麦在食品加工业、淀粉加工业及其它工业上有着重要用途，是近年来许多国家小麦研究的重要课题。国外糯小麦选育尚未突破高产与糯性相结合的难点，国内目前还没有培育出高蛋白强筋型的糯小麦品种，这在一定程度上与缺乏合适的育种方法和高效、实用的糯小麦分子标记辅助育种技术有关。国内外对Wx基因效应的研究主要利用缺体－四体系、重组自交系或近等基因系，还未见有利用遗传背景相同的BC5F2代回交改良群体的报道。 糯性位点近等基因系是小麦淀粉品质育种的重要材料，而我国目前还没有一套中国栽培小麦遗传背景的糯性位点近等基因系。为了选育部分糯小麦、全糯小麦和中国栽培小麦遗传背景的糯性位点近等基因系，我们利用Wx蛋白电泳和高效实用的分子标记技术体系来鉴定糯小麦杂交后代的基因型，结果证明该体系能有效地用于糯小麦的分子标记辅助育种。以中国春糯性位点全套近等基因系为研究材料，对小麦Wx基因的6个STS标记和1个CAPS标记进行了筛选，改良PCR扩增条件以及产物检测方式后，从这些标记中筛选出3个标记，包括鉴定Wx-A1、Wx-D1位点的2个共显性STS标记和Wx-B1位点的1个显性STS标记。利用上述3个分子标记从BC5F2 代回交改良群体中筛选出了8种Wx基因型，经卡方检验，其分离比符合3对基因的分离比例，其中基因型为aabbdd的植株有2株，直链淀粉含量分别为1.81%和0.82%，为全糯小麦；基因型为AAbbdd，aabbDD的部分糯性植株各有1株，直链淀粉含量分别为15.24%和17.57%。以上4株植株的农艺性状和品质性状接近回交亲本“川育12”，并明显优于全糯材料“98Y1441”，表明采用回交法与Wx基因分子标记辅助选择相结合，有助于培育高产、优质的全糯和部分糯小麦。同时，本研究中建立的分子标记技术体系，也为选育具有中国栽培小麦遗传背景的糯性位点近等基因系奠定了基础。 在基因型鉴定的基础上，利用糯小麦杂交后代BC5F2代回交改良群体研究了各基因缺失降低直链淀粉含量的效果和各基因合成直链淀粉的能力，以及直链淀粉含量与农艺性状、品质性状、淀粉糊化特性等的相关性。缺失不同Wx基因的8种基因型，直链淀粉含量差异显著。研究单缺失基因型发现，减少效应最大的是Wx-B1b基因，Wx-B1b和Wx-D1b基因没有显著差异，减少效应最小的是Wx-A1b基因。研究双缺失基因型发现，Wx基因合成直链淀粉的能力，Wx-B1a基因最高，Wx-A1a基因最低，而Wx-B1a和Wx-D1a基因差异很小；直链淀粉含量与株高、穗长、小穗数、穗粒数、千粒重等农艺性状相关不显著，表明淀粉品质育种可以与高产育种实现有机结合；直链淀粉含量与SDS-沉降值呈显著负相关(r=-0.726)，说明直链淀粉含量降低在一定程度上有利于提高小麦营养与加工品质，这一结果至今未见有文献报道；全糯类型的淀粉糊化特性与其他类型显著不同，具有最高的峰值粘度和稀懈值，最低的低谷粘度、最终粘度、反弹值、峰值时间、糊化温度、起始糊化温度，表明糯小麦淀粉在食品和工业上具有特殊用途；稀懈值与直链淀粉含量呈极显著负相关(r=-0.969)，其他粘度参数与直链淀粉含量呈显著正相关(最终粘度r=0.797，低谷粘度r=0.910、反弹值r=0.954、峰值时间r=0.970、糊化温度r=0.962、起始糊化温度r=0.932)。以上结论可为糯小麦品种选育和淀粉品质改良提供理论依据。 Waxy wheat is very important in food processing industry, starch processing industry and the other industries, so it is a focus of wheat research in many countries these years. Foreign wheat breeders have not conquered the difficulty of high yield combined with waxy character, and there is no waxy wheat variety with high protein and strong gluten in China at present，all of which were caused by lacking proper breeding methods and effective, applied molecular markers-assisted selection technique at a certain extent. Until now, research about the effect of waxy genes mainly depended on nullisomic-tetrasomic lines, recombinant lines or near-isogenic lines, and it is lacking the reports of using improved BC5F2 backcross progenies under the common genetic background. Near-isogenic lines at the Wx loci are important materials for wheat starch quality breeding. However, there are no such lines under the Chinese cultivated wheat genetic background. To develop partial waxy wheats, waxy wheats and near-isogenic lines at the Wx loci under the Chinese cultivated wheat genetic background, we use SDS-PAGE of waxy proteins and effective, applied molecular marker-assisted selection technical system to identify the genotype of waxy wheat’s progenies. The results indicated that such a system is applicable in waxy wheat’s molecular marker-assisted selection effectively. A series of Chinese Spring Wx loci near-isogenic lines were used to identify the specific bands of six STS markers and one CAPS marker of Wx genes. After optimizing PCR amplification and separating of PCR products, three co-dominant and dominant STS-markers were identified at the Wx-A1, Wx-D1 and Wx-B1 loci, respectively, which were used to identify the genotype of waxy wheat’s progenies. Eight Wx genotypes were developed from the improved BC5F2 backcross progenies, which follows Mendelian segregation. Among them, there were two aabbdd waxy plants whose amylose content in the BC5F3 seeds were 1.81% and 0.82%, respectively. In addition, there were partial waxy plants (AAbbdd and aabbDD) whose amylose content in the BC5F3 seeds were 15.24 % and 17.57%, respectively. Most agronomic and quality traits of these four plants resembled those of the recurrent parent “Chuanyu 12”, and superior to waxy wheat parent “98Y1441”. This shows that backcross approach in combination with molecular marker-assisted selection of waxy genes is helpful to develop partial and full waxy wheat with good traits in the waxy wheat breeding program. At the same time, molecular marker-assisted selection technical system in this paper, also establish the base for breeding the near-isogenic lines at the Wx loci under the Chinese cultivated wheat genetic background. According to the results of genotype identification, we use waxy wheat’s improved BC5F2 backcross progenies to verify the effects of null alleles on reducing amylose content and determine the amylose synthesis capacity of each Wx gene independently, and investigate the relativity among amylose content with agonomic traits, quality traits, starch pasting properties respectively. There was significant difference in amylose content of the eight genotypes carrying different null Wx alleles. The reducing effect of the single null alleles was the most significant in Wx-B1b, followed by Wx-D1b and Wx-A1b, and there was no significant difference between Wx-B1b and Wx-D1b. The results of the double null lines further demonstrated that for the capacity of amylose synthesis, Wx-B1a was the highest, followed by Wx-D1a and Wx-A1a, and there was no significant difference between Wx-B1a and Wx-D1a. Amylose contents of the eight genotypes were not significantly correlated with plant height, spike length, spikelets per spike, grains per spike, 1000-grain weight, which showed that starch quality breeding could integrate with high yield breeding. Amylose contents of the eight genotypes were negatively significantly correlated with SDS-sedimentation value(r=-0.726), which suggested that reduction in amylose content is propitious to improve quality at a certain extent. Starch pasting properties of the full waxy type was significantly different from the other seven types, with the highest peak viscosity and breakdown, and lowest valley viscosity, final viscosity, setback, peak time, pasting temperature and starting pasting temperature. It indicated that waxy wheat starch has special use in food and industry. Breakdown was negatively significantly correlated with amylose contents (r=-0.969), and the other parameters were positively significantly correlated with amylose contents (r=0.797 for final viscosity, r=0.910 for trough viscosity, r =0.954 for setback, r =0.970 for peak time, r=0.962 for pasting temperature and r=0.932 for starting pasting temperature ). The results of the study are very useful for waxy wheat variety breeding and starch quality improvement.

水稻同源四倍体高代自交系农艺性状分析及遗传差异研究

课题组在不断地创制新的同源四倍体材料的同时，连续多年以提高结实率为目的培育、筛选自交系材料，已获得自交繁殖十二年的高代自交系材料。相对于诱导创制初期，材料表现出的结实率低，同种系单株间的差异较大；高代材料已表现出较显著的结实率提升和较一致的农艺性状表型。 本实验选取课题组多年培育的同源四倍体水稻高代自交系材料，通过形态学、农艺性状和细胞遗传学比较，研究水稻同源四倍体与二倍体之间的异同。结果显示，所有同源四倍体材料的染色体组成均为2N=4X=48，花粉母细胞(PMC)减数分裂行为较正常，99%以上的染色体都能在减数分裂中期I（MI）发生联会、配对，形成四价体和二价体，这与理论染色体组构成相符。在减数分裂过程中，结实率较高的材料染色体异常现象较少而结实率较低的材料染色体异常现象较严重。统计分析表明，二价体和四价体的比例对结实率没有显著影响，但是三价体的数目对结实率有一定影响。这一结果表明了结实率和细胞减数分裂行为可能存在相关性，同源四倍体的减数分裂行为为筛选高结实率的同源四倍体种系提供了依据。 然后，对同源四倍体水稻高代自交系材料进行农艺性状和品质性状的统计与分析。主要针对结实率、每穗实粒数、有效分蘖和穗长等主要农艺性状，以及直链淀粉含量这一重要的品质性状进行统计。将统计结果与1996年诱导加倍的初代材料的数据相对比分析，结果显示所有材料经过多代选育培养，其农艺性状已经有了较显著的提高，同时同源四倍体材料的农艺性状稳定性也有了较显著的提升。如结实率的提高幅度较大，所有材料的平均结实率均显著高于加倍初代，而同种材料不同单株间的结实率差异也显著地减少，变异系数（CV）的平均值由1996年的41.15%减少到了2008年的28.81%。其他重要农艺性状也有不同程度的改良，种内变异系数也相应地降低。此外，实验测量了同源四倍体材料和来源二倍体材料的直链淀粉含量。分析结果显示，部分材料的直链淀粉含量与二倍体亲本产生了较显著的差异，这可能是诱导加倍过程中的遗传变异造成的；同源四倍体材料的种内变异系数（CV）平均值由1996年的6%下降到了2008年的3.88%，显示出在品质性状方面，同源四倍体材料的遗传稳定性也有较显著的增加。同源四倍体材料农艺性状经过多年的选育，表现出一定的提升，同时，经过多年自交纯化，所有材料种系内的性状差异逐渐缩小，说明同源四倍体水稻的遗传稳定性随着自交纯化而增强，这为同源四倍体水稻的进一步选育打下了良好的基础。 最后，通过测量连续两年的自交系材料的遗传多态性，分析材料间遗传差异和种群遗传结构，深入研究连续两代材料间的遗传差异，研究同源四倍体水稻与二倍体材料遗传稳定性之间的差异。实验采用18对SSR微卫星标记对连续两代15个材料，共94份样本进行差异分析。通过扩增条带长度多态性分析，计算不同材料以及同种材料不同世代间的遗传距离，构建同源四倍体和二倍体水稻的分子指纹库，并绘制聚类图。结果显示，同源四倍体和二倍体不同材料间的遗传差异比较大，遗传距离处于0.4757至0.2816之间；而相同品种不同世代材料间的遗传差异较小，但也表现出一定的遗传差异。同种同源四倍体材料不同世代间的遗传差异比二倍体材料更大，两代四倍体材料间遗传距离处于0.1359至0.0485之间；而两代二倍体材料间的遗传距离处于均小于0.0388。结果表明，同源四倍体水稻高代材料具有一定的遗传稳定性，但与来源二倍体材料相比，其世代间的遗传变异性仍然较强。这种结果说明，经过多代的自交纯化培育，同源四倍体水稻材料能够建立起相对稳定的遗传结构，同时，其强于二倍体亲本的变异性有能够为新品种的选育，农艺性状、品质性状的改良提供一定的遗传基础。此外，分析结果表明通过分子标记辅助检验，水稻材料间的遗传多态性能够有效地区分不同的品种，这为水稻品种的分子鉴定提供了一定的依据。 本研究从细胞学鉴定，农艺性状统计分析以及分子标记辅助聚类分析多方面地对同源四倍体水稻高代系进行了研究，对探究同源四倍体水稻的遗传规律，进一步揭示其遗传特性、农艺性状的遗传构成，为进一步选育优质的多倍体水稻提供了一定的理论依据。 This group insists on creating new Autotetraploid Rice (Oryza sativa L.) materials, while improving the seed-setting of them for many years, cultivated and selected the inbred line materials, has obtained the high generation inbred lines after twelve years cultivation. Compared to the early induced materials, which shown the low seed setting, and the large difference between the different plants in the same germ-line; the high generation materials have shown significant improvement in seed setting and more uniform phenotype agronomic traits. The autotetraploid rice high generation inbred lines material, which has been cultivated for more than 12 years, was chose in this experiment. The similarities and differences between autotetraploid and diploid rice was studied through morphological, agronomic and cytogenetic ways. The results showed that all the chromosome of autotetraploid materials are composed of 2N=4X=48, the pollen mother cells (PMC) meiosis behavior is normal, more than 99% chromosomes in metaphase I(MI) were federated and paired to form tetravalents or bivalents, which constitutes a consistent theory of genome. In the meiosis process, the material with a higher seed setting showed less chromosome abnormal than the material whose seed setting is lower. However, statistical analysis showed that the bivalent and tetravalent rate had no significant impact on seed setting, but the number of trivalent had a certain impact on seed setting. The result shows that the seed setting may be related to the meiosis behavior, which provides a basis to cultivate new autotetraploid germ line with high seed setting through the meiotic behavior. Furthermore, the agronomic and quality traits of autotetraploid rice high generation inbred material were statistically analyzed. The statistically analysis was focused on major agronomic traits such as: seed setting, grains per panicle, effective tillers and panicle length, as well as the important quality trait amylose content. The statistic data was compared with the data in 1996, when the first induced generation of autotetraploid material, and the result shows that after a multi-generation breeding, the agronomic traits has been significantly improved in all the materials, while the stability of agronomic traits also significant upgraded. For instant, the seed setting increased significantly, the average seed setting of all materials was significantly higher than the first induced generation, and the differences between different plants in the same species also significantly reduced, the average of the coefficient of variation (CV) was reduced from 41.15% in 1996 to 28.81% in 2008. Other important agronomic traits had improved in different degrees; the coefficient of variation within species is also reduced accordingly. In addition, the amylose content of autotetraploid and diploid materials was measured in this experiment. The results shows that the amylose content of some of the material differed from diploid parents significantly, it may caused by the genetic change during the inducing, autotetraploid materials intra-specific coefficient of variation (CV) average reduced from 6% in 1996 to 3.88% in 2008, shows that this is a significant increase of quality traits stability in autotetraploid rice. Agronomic traits of autotetraploid material shows some improvement after years of breeding, at the same time, after years of purification, all material within the germ-line gradually narrow the differences in traits indicates that autotetraploid rice genetic stability was enhanced, which laid a good foundation for the further autotetraploid rice breeding. Finally, this experiment studied the genetic differences between materials of two generations and researched the difference of genetic stability between diploid and autotetraploid rice materials through investigating the genetic polymorphism, genetic differences between materials and population genetic structure of inbred line materials of two consecutive years.18 pairs of SSR microsatellite markers for 15 materials of two generations were used in this experiment, and the total of 94 samples were analyzed. Through the amplification length polymorphism analysis of different materials and materials in different generations, the genetic distance between materials and generations was analyzed, a diploid and autotetraploid rice molecular fingerprint database and map rendering cluster were constructed. The result shows that the genetic distance is between 0.4757 to 0.2816 among different autotetraploid and diploid materials; the genetic distance between different generations of same species was less, but also shows a certain degree of genetic differences. The inter-generational genetic differences of autotetraploid materials were greater than of the diploid materials, which are 0.1359 to 0.0485 as the genetic distance; comparing with the 0.0388 of diploid materials. The result shows that high generation inbred autotetraploid rice material has a certain genetic stability, but the genetic variation between generations is still strong comparing with the source diploid materials. It indicates that, after many generations of purification cultivation, autotetraploid rice materials established a relatively stable genetic structure, at the same time, stronger variability than its diploid parents are useful in the breeding of new varieties, provides a genetic foundation to the agronomic and quality traits improvement. In addition, the analysis result shows that the through the molecular marker-assisted testing, rice genetic polymorphism between materials can effectively distinguish different species, provides a certain basis for molecular identification of varieties of rice. A series of investigation such as cytological identification, statistical analysis of agronomic traits, molecular marker-assisted cluster analysis was applied in this experiment to research genetic pattern of autotetraploid rice high generation inbred lines, revealed the genetic characteristics and the genetic composition of agronomic traits, provides a theoretical basis for the further selection of high quality autotetraploid rice.

Localized Solid-State Amorphization at Grain Boundaries in a Nanocrystalline Al Solid Solution Subjected to Surface Mechanical Attrition

Using high-resolution electron microscopy, localized solid-state amorphization (SSA) was observed in a nanocrystalline (NC) Al solid solution (weight per cent 4.2 Cu, 0.3 Mn, the rest being Al) subjected to a surface mechanical attrition treatment. It was found that the deformation-induced SSA may occur at the grain boundary (GB) where either the high density dislocations or dislocation complexes are present. It is suggested that lattice instability due to elastic distortion within the dislocation core region plays a significant role in the initiation of the localized SSA at defective sites. Meanwhile, the GB of severely deformed NC grains exhibits a continuously varying atomic structure in such a way that while most of the GB is ordered but reveals corrugated configurations, localized amorphization may occur along the same GB.

Accommodation of large plastic strains and defect accumulation in nanocrystalline Ni grains

A transmission electron microscopy (TEM) study has been carried out to uncover how dislocations and twins accommodate large plastic strains and accumulate in very small nanocrystalline Ni grains during low-temperature deformation. We illustrate dislocation patterns that suggest preferential deformation and nonuniform defect storage inside the nanocrystalline grain. Dislocations are present in individual and dipole configurations. Most dislocations are of the 60 degrees type and pile up on (111) slip planes. Various deformation responses, in the forms of dislocations and twinning, may simultaneously occur inside a nanocrystalline grain. Evidence for twin boundary migration has been obtained. The rearrangement and organization of dislocations, sometimes interacting with the twins, lead to the formation of subgrain boundaries, subdividing the nanograin into mosaic domain structures. The observation of strain (deformation)-induced refinement contrasts with the recently reported stress-assisted grain growth in nanocrystalline metals and has implications for understanding the stability and deformation behavior of these highly nonequilibrium materials.

Hg~(2+)、Cd~(2+)及其联合胁迫对伊乐藻的生长及POD和SOD活性的影响

利用水族箱实验研究了伊乐藻的现存量以及POD和SOD活性在Hg2+、Cd2+及其联合胁迫下的响应特点.结果表明:Hg2+和Cd2+对伊乐藻的联合毒性大于单一的毒性;在Hg2+20μmol.L-1,或Cd2+80μmol.L-1,或Hg2++Cd2+50μmol.L-1([Hg2+]/[Cd2+]=1/4)时,植物现存量增加的百分比与金属离子浓度负相关;高于上述浓度时,植物现存量减少的速率明显降低.POD和SOD活性的变化趋势相似,在6 h时,其活性在低于40μmol.L-1的Hg2+、或160μmol.L

Hg~(2+)与POD复合处理对小麦萌发及幼苗生长的影响

通过水培实验研究了0、10、20、50、70和100 mg.L-1 Hg2+和65 U.mL-1的过氧化物酶(POD)混合浸种对小麦(Triticum aestivum L.)萌发及幼苗生长过程中的10个形态和生理生化指标的影响。结果表明:施加外源POD可明显提高种子发芽率、植株日均增重和幼苗叶片的可溶性蛋白含量,增加幼苗叶片内源超氧物歧化酶(SOD)和POD的活性,拮抗Hg2+胁迫对种子发芽率、苗高、日均增重及叶片可溶性蛋白含量的不利影响,Hg2+浓度较高时(≥50 mg.L-1),对种子发芽率和日均增

不同pH缓冲液处理下蚕豆幼苗叶片SOD、POD和CAT活性的变化

利用不同pH值的酸碱溶液处理蚕豆或者离体蚕豆叶片,研究酸碱胁迫下蚕豆叶片保护酶活性的变化。结果表明,离体蚕豆叶片处理10 min和30 min的SOD活性相差不大,整株处理5 h的蚕豆叶片SOD活性远大于处理12 h的SOD活性;离体蚕豆叶片和整株蚕豆处理,较长时间处理下的CAT活性基本上高于短时间处理的CAT活性,短时间处理下(10 min、5 h)POD活性均显著低于对照值,较长时间处理(30 min、12h)下POD活性变化的规律性不强,且变化幅度较小。

Strong visible photoluminescence from amorphous silicon grains in a-SiOx:H films

Two strong luminescence bands were observed from a-SiOx:H in the spectral range of 550-900 nm at room temperature. One is a main broad peak which blueshifts with oxygen content and the other is a shoulder fixed at about 835 nm. In conjunction with TR and micro-Raman spectra, we have proposed that the main band may originate from the amorphous silicon grains embedded in SiOx network, while the shoulder might be due to some defects induced by excess-silicon in these films. (C) 1997 Elsevier Science Ltd.