【作者】 张连全；

【导师】 刘登才；

【作者基本信息】 四川农业大学 ， 作物遗传育种， 2007， 博士

【摘要】 多倍化在真核生物的进化中发挥了重要作用。可以通过同一染色体组加倍产生同源多倍体，或由不同物种杂交后染色体组加倍产生异源多倍体。普通小麦（Triticum aestivum L.，染色体组为AABBDD，2n=6x=42）是异源多倍体物种的一个典型代表。它是一个异源六倍体，由A、B、D三个具有部分同源关系的染色体组组成，每个染色体组由7条染色体构成。普通小麦的起源，曾经历了两次异源多倍化过程。第一次异源多倍化过程产生了四倍体小麦（T. turgidum），第二次异源多倍化是以栽培四倍体小麦为母本与节节麦（Aegilops tauschii）为父本天然杂交，然后通过染色体自然加倍，形成具有42条染色体和AABBDD染色体组的新兴异源六倍体小麦。人们可以模拟小麦的起源过程，合成新六倍体小麦（人工合成小麦）。近年来，围绕人工合成小麦进行的相关研究，为异源多倍化遗传机制探讨和异源多倍体作物种质资源开发及遗传育种研究提供了十分重要的参考价值。尽管普通小麦起源、进化的基本轮廓已比较清楚，但是许多细节问题还有待于进一步研究。普通小麦的异源六倍化起源包括两个重要过程：一是杂交过程（杂交世代），通过在共同分布区的四倍体小麦和节节麦远缘杂交，产生天然杂种F₁，从而把不同、但亲缘关系较近的A、B和D染色体组（异源染色体组）聚合在同一个细胞核内，实现“异源”，形成具有ABD染色体组的异源三倍体；二是染色体加倍过程（加倍世代），杂种F₁的染色体发生了自然加倍，产生了具有AABBDD染色体组的六倍体小麦（F₂或S₁代），从而实现“六倍化”（Hexaploidization）。本文围绕这两个过程进行相关研究。在不使用幼胚培养等辅助条件下，在大田自然环境中，通过属间杂交研究了四倍体小麦与节节麦之间的可杂交性及杂种F₁植株染色体自然加倍过程；以微卫星（Microsatellite，SSR）产物为例，研究了异源六倍化过程对基因组的影响及其在分子标记应用中的参考价值；通过该研究发现了一些新的自然加倍种质，包括我国的两份蓝麦地方品种AS2255和AS313，并利用它们为小麦遗传研究和育种改良创制了一批新材料。主要结果如下：1．利用属于7个不同亚种（波斯小麦ssp．carthlicum、硬粒小麦ssp．durum、波兰小麦ssp．polonicum、东方小麦ssp．turanicum、圆锥小麦ssp．turgidum、栽培二粒小麦ssp．dicoccon、野生二粒小麦ssp．dicoccoides）的196份四倍体小麦与13份节节麦配制了372个杂交组合。从66220朵授粉小花中，获得了3713粒杂交种子，杂交结实率平均为5.61％（0～75％）。许多杂种能够发芽并成长为植株。不同的四倍体小麦亚种与节节麦的可杂交性存在差异，野生二粒小麦亚种和栽培二粒小麦亚种与节节麦的可杂交性最高，而波兰小麦最低。在13份节节麦中，AS2405和AS2404与四倍体小麦的杂交结实率高于10％，而AS65、AS77和AS82的杂交结实率低于2％。利用硬粒小麦品种Langdon以及Langdon的D-染色体组代换系对可杂交性进行了遗传研究。代换系Langdon 7D（7A）和Langdon 4D（4B）的杂交结实率显著高于对照，表明Langdon的7A和4B染色体携带可杂交性的抑制基因。2．未经幼胚拯救及激素处理，获得了圆锥小麦（T．turgidum ssp．turgidum）与节节麦的F₁杂种。该杂种高度可育，F₁植株的平均自交结实率达25％。大约96％的F₂代种子能够正常发芽，其中，大约67％的F₂植株为自发双二倍体（2n=42，AABBDD）。对F₁植株雄配子形成的细胞学分析表明，一种“类有丝分裂减数分裂”途径产生了未减数配子，使得F₁杂种高度可育。圆锥小麦-节节麦（T．t．turgidum-Ae．tauschii）双二倍体与易变山羊草（Ae．variabilis）和黑麦（rye）的测交表明，“类有丝分裂减数分裂”受核基因控制并在其衍生后代起作用。这一发现暗示着该基因在加倍单倍体方面有重要的潜在应用价值。3．四倍体小麦与节节麦自发产生的三倍体F₁杂种产生有功能的配子是普通小麦起源的关键性步骤。第一次分裂核再组（first-division restitution，FDR）或发生在第一次分裂过程中的单次减数分裂（single division meiosis，SDM），导致了有功能的未减数配子产生。未使用幼胚拯救和激素处理，得到了硬粒小麦Langdon及二体代换系Langdon 1D（1B）与节节麦的杂种F₁，这些杂种F₁都高度可育。观察了F₁植株未减数雄配子的产生，同时预测了F₁未减数雌配子的产生。SDM是未减数配子产生的主要减数分裂途径。环境、基因型或环境与基因型互作都会影响未减数配子的产生。除整倍单倍体配子外，SDM产生了许多非整倍单倍体配子。4．以异源六倍体小麦为例，比较了四倍体小麦与节节麦合成六倍体小麦前后，位于普通小麦D染色体组不同染色体臂上的特异性引物揭示的微卫星位点变化特点。结果表明，在从四倍体小麦与节节麦杂交，将A、B与D染色体组结合在一起并加倍得到AABBDD的六倍体小麦这一异源六倍化过程中：（1）微卫星的侧翼序列发生了变化导致：出现了供体物种没有的新带纹或供体物种的带纹消失。其中，供体物种的带纹消失是主要的。（2）供体物种的带纹消失不是随机的，而是四倍体小麦消失频率远高于节节麦的频率，即发生在A、B染色体组的消失频率比发生在D染色体组的频率高得多。（3）微卫星侧翼序列的变化在多倍化的早期（F₁代或S₁代）就开始发生。由此看来，微卫星两边的侧翼区域在多倍化过程中很活跃，是容易发生变化的区域。微卫星的生物学功能可能与多倍体进化过程有关，微卫星两边的侧翼区域在多倍化过程的早期迅速发生有方向性的改变可能有利于新形成异源多倍体的迅速进化，从而使不同染色体组在遗传上迅速达到协调。5．微卫星分子标记已广泛用于普通小麦遗传和进化研究。由于人工合成小麦与小麦品种之间存在高的遗传多样性，人工合成小麦已被大量应用于小麦分子标记工作中。但是，目前还缺乏人工合成小麦的异源六倍化过程对微卫星影响的研究。本研究直接比较了四倍体小麦与节节麦远缘杂交并经染色体加倍获得人工合成小麦前后，位于普通小麦A／B染色体组不同染色体臂上的66个特异引物揭示的微卫星位点的保守性和可转移性。结果表明，除了一个引物在新合成小麦中扩增出供体亲本没有的新带，一个引物在节节麦扩增出的产物在新合成小麦中消失，其它的所有微卫星引物的扩增产物在小麦合成前后是保守的，没有变异发生。所有的引物能够在四倍体小麦中扩增出微卫星产物，四倍体小麦中的扩增产物也出现在新的人工合成小麦中；有70％的引物能够在节节麦扩增出产物，其中的绝大多数产物也出现在新的人工合成小麦中。因此，普通小麦A／B染色体组的这些微卫星引物除了在人工合成小麦的A／B染色体组中扩增出产物，还能在其D染色体组中扩增出产物，也就是说，这些引物对人工合成小麦而言，并非是A／B染色体组特异的。根据该研究结果，讨论了小麦微卫星的可转移性和特异性问题，重点讨论了在应用人工合成小麦构建的遗传群体进行微卫星分子标记中的应用价值及其应该注意的问题。6．利用5个四倍体小麦与节节麦杂交，通过形成未减数配子进行染色体自然加倍，得到了新合成六倍体材料，并通过形态学和细胞学观察对这些材料进行了鉴定。创制了编号为Syn-SAU-N-X-Y的231个新合成小麦株系。除了遗传育种研究价值，这些材料的创制过程中未使用幼胚培养及秋水仙碱染色体加倍处理技术等可能诱发遗传变异的化学药品，因此它们是小麦异源多倍化过程研究的理想材料。这套材料为准确和精确地进行相关研究提供了基础。7．利用Langdon D-染色体组代换系与节节麦杂交，通过形成未减数配子进行染色体自然加倍，得到了6个新的缺体-四体材料（Syn-SAU N1AT1D、Syn-SAU N1BT1D、Syn-SAU N2BT2D、Syn-SAU N3AT3D、Syn-SAU N4BT4D和Syn-SAU N7AT7D）。通过形态学、细胞学和分子标记对这些材料进行了鉴定。这些缺体-四体材料与中国春对应的缺体-四体不同，是一种新型的遗传工具材料。主要表现在：（1）对某一四体中的4条D染色体，2条来自节节麦，2条来自中国春；（2）用人工合成小麦途径获得，除了涉及相应四体的1对D染色体来自中国春外，其它遗传背景全部来自四倍体小麦和节节麦。8．通过使用秋水仙碱处理圆锥小麦与节节麦的杂种植株，人工合成了一个具有56条染色体的可育小麦材料（SHW-L2）。在花粉母细胞减数分裂中期Ⅰ，新合成小麦SHW-L2的56条染色体的配对构型为2.82个单价体、6.18个棒状二价体、19.39个环状二价体、0.5个三价体和0.14个四价体。细胞学分析表明，除了普通小麦的42条染色体外，SHW-L2还有7对染色体分别来自于A和D染色体组。SHW-L2特殊的染色体构成可能源自秋水仙碱处理幼苗进行染色体加倍和随后的雌雄配子自然加倍。对目前的结果及其在理论及应用方面的特殊价值进行了讨论。9．运用中国四倍体蓝麦AS2255与中东节节麦AS60创制的SHW-L1进行了小麦育种改良的应用研究，初步表明节节麦和蓝麦在小麦产量性状育种上有价值。更多还原

【Abstract】 Polyploidy has been found to be very common in plants. Polyploids can be formed viathe duplication of genomes, either of the same genomes （autopolyploid） or of divergedgenomes with homoeologous relationships （allopolyploid）. Bread or common wheat（Triticum aestivum L., 2n=42） is a good example of allopolyploid made up of three diploidgenomes A, B and D. Bread wheat has undergone two polyploidizations during itsevolution. T. turgidum L. （2n=28, AABB） was formed in the first intercrossingbetween T. urartu and Aegilops speltoides. Then bread wheat was formed bysecond polyploidization after the intercrossing between T. turgidum （maternal） andAe. tauschii followed by chromosome doubling. By the mimic of common wheatevolution, many synthetic hexaploid wheats have been produced. The syntheticwheat is very useful for genetic improvement of modern wheat. Moreover,common wheat has many distinctive scientific characteristics which make it aninteresting model for the study of the organization and evolution of plant genomes.Allopolyploidization generates two "shocks". One is hybridity, by which twodiverged genomes are joined together to form one nucleus. The other is polyploidy,resulting in duplicated genomes. Allohexaploidization of wheat also include thetwo events, hybridization between T. turgidum and Ae. tauschii andautoduptication of the hybrid. However, some details about the events are stillunclear. In this study, we studied the allohexaploidization by analyzing the processof artificially synthetic hexaploid wheat with emphasis on its application in genetics and breeding. The results were as follows:1. Two experiments to investigate the crossability of Triticum turgidum with Aegilopstauschii are described. In the first, 372 wide hybridization combinations were done bycrossing 196 T. turgidum lines belonging to seven subspecies with 13 Ae. tauschiiaccessions. From the 66220 florets pollinated, 3713 seeds were obtained, with a meancrossability percentages of 5.61% ranged from 0 to 75%. A lot of hybrid seeds couldgerminate and produce plants. Out of 372 combinations, 272 （73.12%） showed a very lowcrossability lower than 5%, 87 （23.39%） showed the crossability of 5-30%, ten （2.69%）showed the crossability of 30-50%, three （0.81%） showed hitch crossability more than 50%,respectively. All the crossability percentages more than 30% were obtained from thecrossing of ssp. dicoccoides or dicoccon with Ae. tauschii. Among the seven T. turgidumsubspecies, there were significant differences in crossability. The ssp. dicoccoides anddicoccon showed the highest crossability, while polonicum showed the lowest. Among the13 Ae. tauschii accessions, AS2405 and AS2404 showed a crossability more than10%,while AS65, AS77 and AS82 showed a crossability less than 2%, respectively. Thegenetics of crossability was investigated using T. turgidum ssp. durum cultivar Langdonand the D-genome chromosome substitution lines of Langdon. The higher crossabilitiescompared with the control in lines 7D（7A） and 4D（4B） suggested that 7A and 4B intetraploid wheat cv. Langdon carried dominant crossability alleles inhibiting crossabilitywith Ae. tauschii. The relationships of present results with previously reported crossabilitygenes of wheat are discussed.2. Highly fertile F₁ hybrids were made between Triticum turgidum L. ssp. turgidum（2n=28, AABB） and Aegilops tauschii Coss. （2n=14, DD） without embryo rescue andhormone treatment. The F₁ plants had an average seedset of 25%. Approximately 96% ofthe F₂ seeds were able to germinate normally and about 67% of the F₂ plants werespontaneous amphidiploid （2n=42, AABBDD）. Cytological analysis of malegametogenesis of the F₁ plants showed that meiotic restitution is responsible for the highfertility. It seems that a mitosis-like meiosis led to meiotic restitution at either of the twomeiotic divisions resulting in unreduced gametes. Test crosses of the T. t. turgidum-Ae. tauschii amphidiploid with Ae. variabilis and rye suggested that the mitosis-like meiosis iscontrolled by nuclear gene（s） that are functional in the derived lines. This discoveryimplicates a potential application of such genes in production of double haploids.3. The production of functional gametes in the triploid F₁ hybrids between Triticumturgidum L. （2n=28, AABB） and Aegilops tauschii Coss. （2n=14, DD） was a significantbiological step that led to the emergence of bread wheat. The meiotic restitution at either offirst-division restitution （FDR） or single equational division at the first division （SDM） isthe cytological mechanism responsible for the production of functional gametes. In thisstudy, highly fertile F₁ hybrids were made between T. turgidum L. ssp. durum cultivarLangdon and its disomic substitution 1D（1B） and Ae. tauschii without embryo rescue andhormone treatment. Observation of male gametogenesis and prediction of female gameteof the F₁ plants showed that the production of unreduced gametes was responsible for thehigh fertility. SDM was the major meiotic pathways for the production of unreducedgametes. Environments or genotypes, or both affected the production of unreducedgametes. Besides euhaploids, SDM produced a lot of aneuhaploid gametes. Therelationships between FDR and SDM and the implications of present results for the originstatus of bread wheat in cytology were discussed.4. It was suggested that the rapid changes of DNA sequence and gene expressionoccurred at the early stages of allopolyploid formation. In this study, we revealed themicrosatellite （SSR） differences between newly formed allopolyploids and their donorparents by using 21 primer sets specific for D genome of wheat. It was indicated that rapidchanges had occurred in the "shock" process of the allopolyploid formation betweentetraploid wheat and Aegilops tauschii. The changes of SSR flanking sequence resulted inappearance of novel bands or disappearance of parental bands. The disappearance of theparental bands showed much higher frequencies in comparison with that of appearance ofnovel bands. Disappearance of the parental bands was not random. The frequency ofdisappearance in tetraploid wheat was much higher than in Ae. tauschii, i. e. thedisappearance frequency in AABB genome was much higher than in D genome. Changesof SSR flanking sequence occurred at the early stage of F₁ hybrid or just after chromosomedoubling. From the above results, it can be inferred that SSR flanking sequence region was very active and was amenable to change in the process of polyploidization. This suggestedthat SSR flanking sequence probably had special biological function at the early stage ofpolyploidization. The rapid and directional changes at the early stage of polyploidizationmight contribute to the rapid evolution of the newly formed allopolyploid and allow thedivergent genomes to act in harmony.5. Microsatellites or SSRs as powerful genetic markers have widely been used ingenetics and evolutionary biology in common wheat. Because of the high polymorphism,newly synthesized hexaploid wheat has been used in the construction of geneticsegregation-population for SSR markers. However, data on the evolution of microsatellitesduring the polyploidization event of hexaploid wheat are limited.In this study, 66 pairs of primers specific to A/B genome SSR patterns among newlysynthesized hexaploid wheat, the donor tetraploid wheat and Ae. tauschii were compared.The results indicated that most SSR markers were conserved during the polyploidizationevents of newly synthetic hexaploid wheat, from T. turgidum and Ae. tauschii. Over 70%A/B genome specific SSR markers could amplify the SSR sequences from the D genomeof Ae. tauschii. Most amplified fragments from Ae. tauschii were detected in synthetichexaploid at corresponding positions with the same sizes and patterns as in its parental Ae.tauschii. This suggested that these SSR markers, specific for A/B genome in commonwheat, could amplify SSR products of D genome besides A/B gen0me in the newlysynthesized hexaploid wheat, that is, these SSR primers specific for A/B genome incommon wheat were nonspecific for the A/B genome in the synthetic hexaploid wheat. Inaddition, one amplified Ae. tauschii product was not detected in the newly synthetichexaploid wheat. An extra-amplified product was found in the newly synthetic hexaploidwheat. These results suggested that caution should be taken when using SSR marker togenotype newly synthetic hexaptoid wheat.6. New synthetic hexaptoid wheats were obtained from crosses of five T. turgidum L.lines with Ae. tauschii, which were formed by chromosome autoduplication throughunreduced gametes. Identifications were made by morphological and cytologicalobservation. Two hundred and thirty-one new synthetic wheat lines were coded by "Syn-SAU-N-X-Y". Besides the values in wheat improvement, they are desirable materials for study of allohexaploidization due to without the using of chemical materials, such asembryo rescue and colchicine treatment during the synthetic process.7. Six new nullisomic-tetrasomic lines （Syn-SAU N1AT1D, Syn-SAU N1BT1D, Syn-SAU N2BT2D, SYn-SAU N3AT3D, SYn-SAU N4BT4D and Syn-SAU N7AT7D） wereobtained from crosses of Langdon D-genome substitution lines with Ae. tauschii, whichwere formed by chromosome autoduplication through unreduced gametes. Identificationswere made by morphological, cytological and molecular analysis. They are different fromprevious Chinese Spring nullisomic-tetrasomic lines. The main differences were as follows:（1） for each of tetrasomics, there were four D chromosomes, two from Ae. tauschii and twofrom Chinese Spring; （2） they were obtained by manner of synthetic wheat, other geneticbackgrounds were from T. turgidum L. and Ae. tauschii except that their two Dchromosomes of the corresponding tetrasomics were from Chinese Spring.8. By colchicine treatment of the hybrid plants between Triticum turgidum andAegilops tauschii, a fertile wheat plant （SHW-L2） carrying 56 chromosomes wasartificially synthesized. At metaphaseⅠof pollen mother cells, the 56 chromosomes of newwheat SHW-L2 showed a pairing configuration of 2.82 univalents, 6.18 rod bivalents,19.39 ring bivalents, 0.5 trivalents and 0.14 quadrivalents. Cytological analysis suggestedthat SHW-L2 had additional 7 pairs of chromosomes from A and D genome besides the 42chromosomes as common wheat has. The special chromosome constitute of SHW-L2 maybe derived from the chromosome doubling by colchicine treatment for seedlings and thenspontaneous doubling for gametes. Present results were discussed with reference to specialvalues at both the theoretical and applied levels.9. The primary utilization of synthetic wheat SHW-L1 between T. turgidum ssp.turgidum line AS2255 and Ae. tauschii AS60 on bread wheat improvement indicated thepotential usefulness of synthetic wheat for yield characters, 1000-grain weight and spikeletnumber.更多还原