VE161小麦的外源染色体鉴定

通过染色体原位杂交、ＲＦＬＰ分析和染色体重双端体分析,对在小麦遗传育种研究中具有重要理论和应用价值的ＶＥ１６１小麦不育异代换系及其附加系进行了染色体鉴定。结果表明,ＶＥ１６１小麦代换的或附加的外源染色体为来自长穗偃麦草的４Ｅ染色体,被代换的小麦染色体为４Ｂ。过去曾鉴定为７Ｂ,可能是由于ＶＥ１６１早代染色体易位较多所致。同时发现,ＶＥ１６１小麦在５Ｂ,７Ｂ和１Ｄ所在的３个部分同源群中仍有染色体相互易     

小麦的外源染色体鉴定

通过染色体原位杂交、RFLP分析和染色体重双端体分析,对在小麦遗传育种研究中具有重要理论和应用价值的VE161小麦不育异代换系及其附加系进行了染色体鉴定.结果表明,VE161小麦代换的或附加的外源染色体为来自长穗偃麦草的4E染色体,被代换的小麦染色体为4B.过去曾鉴定为7B,可能是由于VE161早代染色体易位较多所致.同时发现,VE161小麦在5B,7B和1D所在的3个部分同源群中仍有染色体相互易位存在,为进一步研究VE161小麦促进部分同源染色体配对的机制、不育的机制和应用奠定了基础.     

VE161小麦促进部分同源染色体配对的遗传

ＶＥ１６１小麦包括具有一对长穗偃麦草染色体的雄性不育代换系、可育附加系和杂育系,杂育系由其代换系×附加系产生。ＶＥ１６１小麦在与其它小麦品系的杂交Ｆ１中,具有促进部分同源染色体配对的作用,但其本身部分同源配对频率较低。研究结果表明,ＶＥ１６１小麦本身部分同源染色体配对水平较低,是因其小麦染色体组中存在有一对纯合隐性上位基因,它能够抑制Ｅ染色体（Ｅｐｈ基因）,促进部分同源染色体配对作用的表达,而一般小麦品系中具有该基因的相对显性基因。同时,在促进小麦部分同源染色体配对作用上,Ｅ染色体（Ｅｐｈ基因）具有剂量效应     

小麦VE161雄性不育异代换系的染色体分析

VE161是一个具有一对长穗偃麦草(Agropyron elongatum)染色体的小麦雄性不育异代换系。由于不能用做父本,采用一般单体分析法确定其被代换的染色体比较困难。因此用一套中国春缺-四体和重双端体对其进行了分析,并以F_1花粉母细胞MI单价体的N-显带技术进行了验证。结果表明,VE161代换系所代换的染色体为7B,该方法对确定雄性不育代换系所代换的染色体是一个简单易行的方法。染色体行为观察说明,该代换系的一对长穗偃麦草染色体可能与小麦的染色体7B没有部分同源关系,除了引起雄性不育以外,有时与小麦染色体分裂不同步而表现落后,并有抑制Ph基因的作用,能强烈促进小麦部分同源染色体的联会配对,致使在中期Ⅰ出现很高频率的各种多价体。     

硬粒小麦 长穗偃麦草2E和4E附加系及E染色体传递

为探讨长穗偃麦草E染色体在硬粒小麦背景中的传递特点,利用染色体特异分子标记、基因组原位杂交(GISH)、非变性荧光原位杂交(ND FISH)等方法,对小偃麦8801(AABBEE)与硬粒小麦(AABB)杂交后代中选育的株系Du_No.2和Du_No.4进行了分析。结果表明：(1)分子标记检测株系Du_No.2及Du_No.4分别能扩增出长穗偃麦草2E、4E染色体特异条带。(2)GISH和ND FISH分析显示,株系Du_No.2和Du_No.4分别附加了1条2E和4E染色体,表明株系Du_No.2 和Du_No.4分别为硬粒小麦 长穗偃麦草2E和4E单体附加系。(3)2个株系的减数分裂过程观察发现,后期Ⅰ、Ⅱ和末期Ⅱ都有E染色体分离异常现象,且株系Du_No.2和 Du_No.4的异常率分别为22.24%和36.18%。(4)2个株系分别与硬粒小麦进行正反杂交的后代PCR分析表明, 2E和4E染色体经雄配子的传递率分别为4.41%和2.17%,而通过雌配子的传递率都为零,表明2E和4E染色体在硬粒小麦背景中能通过雄配子传递,但不通过雌配子的传递。该研究为创建全套硬粒小麦 长穗偃麦草双体附加系及代换系提供基础。     

四倍体小麦背景中长穗偃麦草E染色体传递特征

通过细胞学方法和染色体特异分子标记鉴定六倍体小偃麦(AABBEE)与硬粒小麦(AABB)杂交的自交后代F₂和F₃植株,探讨长穗偃麦草染色体在硬粒小麦背景中世代间的传递特征,并筛选硬粒小麦-长穗偃麦草E染色体附加系。对218个F₂单株染色体数检测表明,2n=28植株占41.7%,2n=29植株占18.3%,其余40.0%植株的染色体数在2n=31~42范围内。分子标记鉴定表明,在F₂代2n=29单体附加植株中,不同的长穗偃麦草染色体传递率之间存在明显差异,1E传递率最高,3E和6E传递率最低。在F₂代2n=30单株中,1E、4E、7E和5E染色体相互组合产生的双单体多,6E参与组合较少,未检测到2E或3E与其他染色体的组合单株。在1E~7E单体附加株自交后代F₃中,E染色体传递率变化范围为9.1%~27.5%,1E传递率最高,6E传递率最低,与F₂的传递率一致。从F₃代中选育出1E~7E单体附加及少数二体附加,所有单体附加均可育。这些附加E染色体材料将对小麦代换系和易位系的创制提供有益的中间材料。     

黑麦6R染色体在小麦背景中的传递

带有６Ｒ的配子传递率普通显著下降。６Ｒ通过雌配子的传递率为８．８％,通过雄配子的传递率为１０．３％,通过花药培养的传递率较高,为２３．３％,但均低于理论值。进一步分析各种配子经花药离体培养的传递率,发现附加型提高最多,正常型次之,缺失型减少最多,代换型次之,说明离体培养对各种配子具有选择作用。另外,还观察到６Ｒ单体附加,６Ｒ＾Ｌ端体单附加和６Ｒ＾Ｌ等臂单附加自交传递率差异不显著。对于影响传递率的各     

利用电离辐射创造普通小麦外源染色体易位系

电离辐射是诱导染色体结构变异尤其是易位系的常用方法。介绍了电离辐射的原理、种类及方法,阐述了电离辐射的生物学效应,分析了辐射的材料、时期和适宜剂量,最后论述了电离辐射创造的普通小麦外源易位系在育种上的应用价值。     

利用生化及分子标记确定长穗偃麦草（Elytrigia elongatum,EE.2n=14） …

利用限制性片段长度多态性（ＲＦＬＰ）及等电聚焦（ＩＥＦ）技术确定普通小麦中国春－二倍体长穗偃麦草７个异附加系所附加的外源染以体与小麦染色体的部分同源性,共有８个生化标记,１３个ＲＦＬＰ标记在亲本间揭示了多态性,结果表明：长穗偃麦草的１Ｅ,２Ｅ,３Ｅ,４Ｅ,５Ｅ,６Ｅ,７Ｅ７条染色体分别与小麦染色体的１、２、３、４、５、６、７７个部分同源群具有部分同源关系,偃麦草的１Ｅ与７Ｅ、５Ｅ与７Ｅ染色体间可能     

一个超矮秆核质杂种小麦的初步研究

在用普通小麦对长穗偃麦草(Etytrigia elongata=Agropyron elongatum,2n=70)的核代换回交过程中,在BC_9F_1发现了一个超矮秆核质杂种小麦,株高35厘米左右,定名为小偃矮。细胞学观察和与普通小麦正反杂交的遗传分析,证明:(1) 小偃矮是一个异源胞质单体附加系(21″W+1′Ag);(2) 长穗偃麦草细胞质和附加的外来染色体没有携带矮秆基因;(3) 矮秆遗传主要受细胞核内一对显性矮化基因控制。     

小麦染色体轴结构的观察

对普通小麦 ( Triticum aestivum L.)中期染色体进行常规制片银染的结果显示 ,染色体中存在着染色深的轴结构 ,每个染色单体一条 ,轴在有些部位似乎是螺旋的。研究结果对染色体轴结构的真实性提供了证据     

Comparative analysis of Stowaway-like miniature inverted repeat transposable elements in wheat group 7 chromosomes: Abundance,composition, and evolution

Miniature inverted repeat transposable elements (MITEs) are the most ubiquitous transposable elements in eukaryotic genomes; they play a prominent role in sequence divergence and genome evolution. There are many well-characterized Stowaway-like MITE families in wheat, but their distribution, abundance, and composition at the chromosome level are still not well understood. In this study, we systematically investigated the Stowaway-like MITEs in wheat group 7 chromosomes based on the survey sequences of isolated wheat chromosomes, to compare them at the chromosome level and to reveal their evolutionary role on wheat polyploidization. In summary, 2026 MITEs were identified, of which 587, 714, and 725 were distributed on 7A, 7B, and 7D chromosomes, respectively. There are more MITEs present on 7D, compared to 7A and 7B, suggesting A and B subgenomes eliminated some repetitive elements during two hybridization processes. Furthermore, some chromosome/arm-specific MITEs were also identified, providing information on the function and evolution of MITEs in wheat genomes. The sequence diversity of the MITE insertions was also investigated. This study for the first time investigated the abundance and composition of MITEs at the chromosome level, which will be beneficial to improve our understanding of the distribution of wheat MITEs and their evolutionary role in polyploidization.     

Characterizing the composition and evolution of homoeologous genomes in hexaploid wheat through BAC-end sequencing on chromosome 3B

Bread wheat (Triticum aestivum) is one of the most important crops worldwide. However, because of its large, hexaploid, highly repetitive genome it is a challenge to develop efficient means for molecular analysis and genetic improvement in wheat. To better understand the composition and molecular evolution of the hexaploid wheat homoeologous genomes and to evaluate the potential of BAC-end sequences (BES) for marker development, we have followed a chromosome-specific strategy and generated 11 Mb of random BES from chromosome 3B, the largest chromosome of bread wheat. The sequence consisted of about 86% of repetitive elements, 1.2% of coding regions, and 13% remained unknown. With 1.2% of the sequence length corresponding to coding sequences, 6000 genes were estimated for chromosome 3B. New repetitive sequences were identified, including a Triticineae-specific tandem repeat (Fat) that represents 0.6% of the B-genome and has been differentially amplified in the homoeologous genomes before polyploidization. About 10% of the BES contained junctions between nested transposable elements that were used to develop chromosome-specific markers for physical and genetic mapping. Finally, sequence comparison with 2.9 Mb of random sequences from the D-genome of Aegilops tauschii suggested that the larger size of the B-genome is due to a higher content in repetitive elements. It also indicated which families of transposable elements are mostly responsible for differential expansion of the homoeologous wheat genomes during evolution. Our data demonstrate that BAC-end sequencing from flow-sorted chromosomes is a powerful tool for analysing the structure and evolution of polyploid and highly repetitive genomes.     

The contribution of distant hybridization with decaploid Agropyron elongatum to wheat improvement in China

Wheat is a staple food crop in the world as well as in China. Because of the progress of wheat breeding and other agricultural sci-technologies, the wheat grain yield per unit area has increased more than five folds from 1952 to 2006 in China. The first part of this article briefly reviews the history of wheat breeding in China. Second, the establishment of "Triticum aestivum-Agropyron" distant hybridization system and its contribution to wheat production and breeding in China are summarized. Finally, the future challenges of wheat breeding are discussed, which include how to increase the utilization efficiencies of water, soil nutrient and light energy through breeding.As an example, our research progress on how to increase light use efficiency in wheat through breeding is introduced and discussed.     

Genetic control of B chromosome transmission rate in Zea mays ssp. mays (Poaceae)

We selected genotypes of high and low B chromosome transmission rate (TR) in a native race of maize (Pisingallo) from northwest Argentina. We made 20 female OB male IB and 20 f.IB m.OB crosses. The former (GOm) showed a large variation of B TR, with a mean of TR ± SE = 0.52 ± 0.06, ranging from 0.17 to 0.98. In the latter (GOf) the mean was TR = 0.47 ± 0.02 ranging from 0.31 to 0.58. Plants showing the highest and the lowest TR were selected to constitute the progenitors of the G1 generations. We made 19 f.0B m.2B crosses, studying 24–30 plants per cross. The TR of the high (H) and low (L) lines in Glm (GlmH and GlmL) significantly differed (TRH = 0.65 ± 0.03, TRL = 0.40 ± 0.01), indicating that the H and L lines are different groups. The large variation in male TR suggests that preferential fertilization of gametes carrying B chromosomes does not always occur. We also selected plants showing high and low TR in the progenies of f.lB m.OB crosses (GOf), and made 24 f.1B m.0B crosses, studying 23–30 plants per cross. The TRs of the H and L lines in G1f (GlfH and GlfL) were significantly different (TRH = 0.48 ± 0.025, TRL = 0.40 ± 0.02). The TRs in G0f and G1fL were significantly different (TR = 0.47 ± 0.02 and 0.40 ± 0.02, respectively), while this was not the case between G0f and G1fH. Our results demonstrate the existence of genotypes controlling B TR in this native population of maize.     

Morphological and cytological characteristics of some wheat x barley hybrids

As initial step in the transfer of dwarf bunt resistance from barley into wheat, the two cereal crops were hybridized. Using the wheat cultivars Fukuhokomugi and Chinese Spring (AABBDD genomes) as female parents and barley cultivar Luther (II genome) as male, we synthesized 9 euploid hybrids (2n = 4x = 28; ABDI genomes). The hybrids were vigorous, but highly sterile. Meiotic analyses of seven hybrids showed considerable variation in chromosome pairing. Of the hybrids involving Fukuhokomugi 3 had high pairing with a mean of 5.08–6.72 chiasmata per cell, while others had 2.16–3.52 chiasmata per cell. As many as 12 bivalents in some pollen mother cells would suggest at least some pairing between wheat and barley chromosomes. This level of homoeologous pairing, coupled with some, albeit low, female fertility of the F₁ hybrids, could offer an opportunity for intergeneric gene transfers from barley into wheat and vice versa.     

小麦-簇毛麦属间染色体易位系的高效诱导

利用60Coγ射线以不同剂量照射硬粒小麦-簇毛麦双二倍体即将成熟的花粉,将其授于母本中国春,创造出一批包含小麦-簇毛麦易住染色体的材料,对这些材料用中国春进行连续回交或自交,可有效保留簇毛麦染色体片段,实现外源基因的转移.研究结果表明,60Coγ射线照射花粉后产生易位染色体的频率因剂量不同而有显著差异,12 Gy和8 Gy剂量照射后杂交的M1群体中,产生小麦-簇毛麦易位染色体的单株分别占调查总数的76.7%和50.0%,均显著高于用其他方法创造易住的频率,并且12 Gy较8 Gy产生了更优的易住类型;创制的易位染色体有67.6%可以从M1传递到BC1,BC1的易位染色体有96.4%可传递到BC,;在回交后代中,加以人为选择,整条簇毛麦染色体很快丢失,至BC2F2即有纯合易位株出现.     

Homoeologous chromosome pairing between the A and B genomes of Musa spp. revealed by genomic in situ hybridization

Background and Aims

Most cooking banana and several desert bananas are interspecific triploid hybrids between Musa acuminata (A genome) and Musa balbisiana (B genome). In addition, M. balbisiana has agronomical characteristics such as resistance to biotic and abiotic stresses that could be useful to improve monospecific acuminata cultivars. To develop efficient breeding strategies for improving Musa cultivars, it is therefore important to understand the possibility of chromosome exchange between these two species.

Methods

A protocol was developed to prepare chromosome at meiosis metaphase I suitable for genomic in situ hybridization. A series of technical challenges were encountered, the main ones being the hardness of the cell wall and the density of the microsporocyte''s cytoplasm, which hampers accessibility of the probes to the chromosomes. Key parameters in solving these problems were addition of macerozyme in the enzyme mix, the duration of digestion and temperature during the spreading phase.

Results and Conclusions

This method was applied to analyse chromosome pairing in metaphase from triploid interspecific cultivars, and it was clearly demonstrated that interspecific recombinations between M. acuminata and M. balbisiana chromosomes do occur and may be frequent in triploid hybrids. These results provide new insight into Musa cultivar evolution and have important implications for breeding.