大鹅观草与蛇河披碱草属间杂种的细胞遗传学研究

为探讨大鹅观草(Roegneria grandis,2n=4x=28)的染色体组组成,为其正确的分类处理提供细胞学依据。该研究通过人工远缘杂交,成功获得3株大鹅观草与蛇河披碱草(Elymus wawawaiensis,2n=4x=28)属间杂种F1植株。杂种植株形态介于两亲本之间,不育。亲本及杂种经I2-IK溶液染色后进行花粉育性检测,结果显示Roegneria grandis和Elymus wawawaiensis的花粉可育,育性高达94.6%和90.5%;杂种F1不育。花粉母细胞减数分裂中期I染色体配对结果显示,亲本花粉母细胞配对正常,均形成14个二价体,以环状二价体为主,Roegneria grandis有频率很低(0.04/细胞)的单价体出现;杂种F1平均每个花粉母细胞形成6.46个二价体,变化范围为5~8;在观察的83个花粉母细胞中,有35.2%的花粉母细胞形成了7个二价体,形成6个二价体的细胞占42.59%,较少细胞形成8个二价体;平均每个细胞形成14.66个单价体,变化范围为10~18;平均每细胞观察到0.14个三价体;杂种花粉母细胞染色体构型为14.66 I+6.46 II+0.14 III;平均每细胞交叉数为9.83,C值为0.35。结果表明:(1)R.grandis与Elymus wawawaiensis有一组染色体组同源的St染色体组,另外一组染色体组不是St或者H染色体组,Roegneria grandis的染色体组组成不是St Stg;(2)较低频率的三价体(平均0.14个/细胞),可能是由于R.grandis的St和Y染色体组间具有一定的同源性,也可能是染色体易位等原因导致,对于Y染色体组的起源还需深入地研究;(3)在不同地理来源的披碱草属和鹅观草属物种中St染色体组同源性不同,R.grandis与来自于北美的Elymus lanceolatus与E.wawawaiensis的St染色体组较与分布于亚洲的E.sibiricus和E.caninus的St染色体组同源性反而更高,其原因还需要进一步地研究。     

部分菊属植物及其种间杂种减数分裂异常现象观察

对不同倍数性菊属植物及其部分种间杂种的减数分裂异常现象进行观察统计,并分析其形成机制以及在菊属系统演化中的作用。结果表明,菊属减数分裂异常现象包括分裂不同步、二价体提前解离、二价体互锁、染色体桥、落后染色体等。减数分裂不同步现象普遍存在于菊属植物减数分裂过程。二倍体的菊花脑、甘菊、异色菊的部分二价体在终变期提前解离为单价体。菊花脑及其部分杂种中观察到了互锁二价体。四倍体菊花脑、南京野菊、‘黄英’、‘滁菊’在AI和AII都出现了染色体桥,毛华菊有1.5%的PMC在AI出现染色体桥。四倍体菊花脑AI、AII期出现落后染色体的频率分别为10.6%和7.3%;毛华菊AI期出现落后染色体的频率为4.4%;栽培菊‘黄英’和‘滁菊’在AI、AII期出现落后染色体的频率高于毛华菊。杂种出现染色体桥及落后染色体的频率普遍高于亲本。倒位以及由其引起的各种染色体结构变异可能在菊属系统演化过程中起着重要作用。     

辣椒属种间杂种F_1植株的细胞遗传学研究

本文分析了南京早椒（ＣａｐｓｉｃｕｍｆｒｕｔｅｓｃｅｎｓＬ．ｖａｒ．ＣｏｎｏｉｄｅｅｓＢａｉｌｅｙ）和Ｃ．ｃｈｉｎｅｎｓｅ二亲本及Ｆ１杂种花粉母细胞减数分裂终变期和中期Ｉ染色体配对的构型。结果表明：二亲本花粉母细胞减数分裂染色体配对均正常,为１２个二价体（双单倍体２ｎ＝２４）。Ｆ１杂种花粉母细胞减数分裂染色体配对很不规则。其平均频率分别为单价体０．０３６,二价体９．１８,三价体０．０３６,四价体０．８０,六价体０．３８。南京早椒和Ｃ．ｃｈｉｎｅｎｓｅ染色体间存在着相互易位,因此,二亲本间彼此有差异。单价体出现极少,这可断定南京早椒与Ｃ．ｃｈｉｎｅｎｓｅ染色体间是部分同源的,但染色体组结构上存在着差异。由于染色体结构上差异,所以Ｆ１杂种的育性较低。     

phKL基因和Ph2基因缺失重组体的创制及其与小麦外源物种杂种的染色体减数分裂观察

以小麦(Triticum aestivum L.)双端体3DL为细胞学标记,用具有phKL基因的小麦地方品种“开县罗汉麦”为受体连续回交,将促进小麦外源部分同源染色体西己对的phKL基因和Ph2基因缺失重组在一起获得了重组体phKL Ph2^-。这种重组体有正常的育性。与只有phKL基因的小麦材料相比,重组体与外源物种Aegilops variabilis Eig．或黑麦(Secale cereale L.)杂种的部分同源染色体配对水平显著增加,表明Ph2基因的缺失体与phKL基因可能存在加性效应。部分同源染色体配对水平的增加农现在棒状二价体、环状二价体和三价体的数量变多而单价体数量减少。单价体的减少主要足由于棒状二价体的增加所造成的。在小麦外源遗传转移中,运用重组体phKL Ph2^-可能比单纯应用Ph2缺铁或phKL基因材料更理想。当与具有phlb基因的材料比较时发现,重组体phKL Ph2^-与Ae,variabilis(或黑麦)杂种的部分同源染色体配对水平显著降低,这丰要是由环状二价体和多价体的减少造成的,但是棒状二价体数量表现增加(与Ae.variabilis杂种)或达到类似水平(与黑麦杂种),这一有趣的发现从表现型上证明了Ph1基因与Ph2或phKL基因在诱导部分同源染色体配对时的遗传作用机制存在差异。     

鹅观草和簇毛麦属间杂种的形态学和细胞遗传学研究

通过幼胚离体拯救培养,成功地获得鹅观草Roegneria kamoji Ohwi(2n=6x=42,StStHHYY)和簇毛麦Dasypyrum villosum(L．)Candargy(2n=2x=14,VV)属间杂种,对这两个种及其杂种F_l的形态学、繁育学和减数分裂配对行为进行了研究。结果表明：(1)鹅观草和簇毛麦形态差异极大,杂种F1的形态特征介于父母本之间;(2)杂交结实率低,为11．63％;经幼胚组织培养,获2株杂种苗;杂种F_l高度不育,表明亲本间存在极强的生殖隔离,是独立的生物学种;(3)杂种F_l体细胞染色体数目为稳定的28条,减数分裂中期I染色体配对很低,其构型为：26．72Ⅰ+0．62Ⅱ+0．02Ⅲ。表明鹅观草的St、H、Y染色体组与簇毛麦的V染色体组部分同源性很低,它们的亲缘关系较远。     

披碱草属与大麦属系统关系的研究

禾本科中,披碱草属Elymus L.为多倍体属,约含150余种;大麦属Hordeum L.具二倍体和多倍体,约有40余种,该两属均广泛地分布于全球温带地区。该两属,尤其是披碱草属的系统分类较为困难。基于形态学的传统研究认为这两个属的系统关系较远,而细胞学研究的资料却表明,披碱草属的H染色体组起源于大麦属。笔者对来源不同的披碱草属和大麦属的物种进行了远缘杂交,并对其属间杂种F1的减数分裂中期I染色体配对行为进行了分析。结果表明,若以披碱草属作母本,该两属有相对较高的杂交亲合力,通过对杂种幼胚进行分割和离体培养,也能获得杂种F1植株。属间杂种植株的形态介于双亲之间,但更接近于披碱草属,杂种的生殖器官发育不健全,而且所有的杂种F1均完全不育。细胞学的观察结果表明,这两个属间的杂种F1通常具有较低的减数分裂中期I染色体配对数,但有较大的变异。通过笔者的工作及掌握的形态学和细胞学的资料分析认为：披碱草属和大麦属的亲缘关系较为复杂,不能一概而论。含H染色体组的披碱草属和大麦属物种有着较近的亲缘关系,但这两个属中所含的H染色体组已产生了程度不同的分化;不含H染色体组的披碱草属及大麦属的物种具有较远的亲缘关系。     

节节麦-簇毛麦属间杂种的形态学和细胞遗传学研究

通过远缘杂交,结合杂种幼胚离体培养,获得了节节麦（Aegilops tauschii,2n=14,DD）和簇毛麦（Dasypyrum villosum,2n=14,VV）的属间杂种F1。对杂种F1花粉母细胞减数(PMC)分裂中期Ⅰ (MⅠ)染色体配对行为进行观察发现,“节节麦×簇毛麦”杂种F1平均每PMC有1.25个棒状二价体, 染色体的平均构型为2n=14=11.49Ⅰ+1.25Ⅱ (Xta=1.25), 大部分被观察的细胞出现1～5个二价体, 表明节节麦D染色体与簇毛麦V染色体间具有相对较高的部分同源配对, D和V染色体之间存在一定的部分同源性。F1植株高度自交不育,经染色体加倍处理后能够自交结实。Abstract: ‘Aegilops tauschii×Dasypyrum villosum’ F1 hybrids were obtained by the combination of hybridization and embryo culture in vitro. Chromosome pairing behavior in meiosis of the hybrid F1 was carried out. Results showed that in an average , 1.25 rod bivalents were observed in one PMC, meiotic configuration was 2n=14=11.49Ⅰ+1.25Ⅱ(Xta=1.25) and most of PMCs possessed 1～5(rod) bivalens, indicating that the relatively high homeology was detected between the D genome of Ae.tauschii and the V genome of D.villosum. The morphological differences between F1 hybrids and their parents were significant. F1 plants were highly self-sterile, but partially self-fertile after treated by chromosome doubling technique.     

10种披碱草属植物的RAPD分析及其系统学意义

利用随机扩增多态性DNA(RAPD)技术分析了10种披碱草属植物,即：Elymus sibiricus L.,E．caninus(L．)L¨E．lanceolatus(Scribner et Smith)Gould,E．nutans Griseb,E．dahuricus Turcz,,E．tangutorum(Nevski)Hand．-Mazz., E．brachyaristatus ALöve,E.submuticus(Keng)Keng f.,E．cylidricus(Franch)Honda和E．excelsus Turcz. 。对34个OPRON公司十聚体随机引物进行多态性筛选,25个(75．53％)能产生多态性。16个引物产生的136个DNA片断,用于计算种间Nei氏遗传相似性系数分析,在NTSYS程序中利用UPGMA构建系统发育树状图。分析结果表明：(1)四倍体和六倍体物种各自聚为一支,它们之间的亲缘关系较远;(2)E．sibiricus和E. caninus;亲缘关系较近,支持把Roegneria caninus (L．)Nevski归入Elymus;(3)E．nutans和E．dahuricus亲缘关系密切;(4)形态相似、地理分布一致的E．brachyaristatus和E．submuticus存在着一定程度的核苷酸序列的差异,它们与E．nutans和E．dahuricus有一定的亲缘关系;(5)E．excelsus 与 E．cylindricus的亲缘关系较近,它们又与E．tangutorum有亲缘关系;(6)RAPD结果与形态学和细胞学等分析结果基本一致,RAPD分析方法将为Elymus系统分类提供DNA水平上丰富的资料。     

青海高原披碱草属种间天然杂种的细胞学鉴定

利用重复序列探针染色体荧光原位杂交（FISH）和基因组原位杂交（GISH）技术,对采自青海高原披碱草属种间天然杂种进行细胞学鉴定,同时结合物种分布及形态学特征,共揭示6种不同天然杂种的类型。第一类为垂穗披碱草（Elymus nutans Griseb.）和鹅观草属（Roegneria C.Koch）物种间的天然杂种,染色体数为35,染色体组成为StStYYH;第二类为垂穗披碱草和达乌力披碱草种（Elymus dahuricus Turcz.ex Griseb.）间杂种,染色体数为42,染色体组成为StStHHYY;第三类为达乌力披碱草和老芒麦（Elymus sibiricus L.）种间杂种,染色体数为35,染色体组成为StStHHY;第四类为垂穗披碱草和糙毛以礼草（Kengilia hirsuta Keng）种间杂种,染色体数为42,染色体组成为StStYYHP;第五类为垂穗披碱草和大颖草（Kengilia grandiglumis Keng）种间杂种,染色体数为42,染色体组成为StStYYHP;第六类为糙毛以礼草和赖草（Leymus secalinus（Georgi） Tzvel.）种间杂种,染色体数为35,染色体组成为StYPNsXm。研究结果为进一步研究披碱草属种间杂交渐渗提供了重要参考资料;同时鉴定出的天然杂种可以作为潜在的种质资源在牧草或生态草育种中加以利用。     

Y基因组分化及其进化意义

在同倍体（homoploid）植物杂交－分化的物种形成（speciation）过程中,杂交后代与亲本之间的有效生殖隔离是新物种形成的关键。杂种与亲本在时间、空间、生态环境和基因水平上的隔离,保证了杂种后代的分化和稳定,并逐渐形成新物种。为了研究披碱草属（Elymus）含S_tY基因组四倍体物种的系统演化关系,本文对来自亚洲不同地理分布区的26种披碱草属植物进行了大规模的种间杂交和杂种F₁减数分裂染色体配对行为的分析。结果表明各物种之间有不同程度的杂交亲合力,杂交结实率在各杂交组合之间有较大的变异（在4.8%-100%之间）;但各物种之间的杂种F₁完全不育。证明各物种之间形成了明显的生殖隔离。种间杂种F₁减数分裂中期-I染色体配对分析的结果进一步表明,S_tY基因组随各披碱草属物种地理分布的不同而有不同程度的分化。来自同一分布区（如东亚或西亚分布区之内）物种的S_tY基因组分化程度较低,但来自不同分布区（如东亚和西亚）物种之间相同的S_tY基因组具有显著的分化。表明地理隔离对含S_tY基因组物种的分化起到了十分重要的作用。通过对种间和种内杂种F₁的减数分裂异常现象和染色体配对频率变化规律的分析,作者认为细胞学水平的变化,如基因组同源性的分化和染色体结构的变异等都在杂种后代与亲本之间产生生殖隔离并逐渐形成新物种的进化过程中起到了积极的作用。     

Review. Hybrid trait speciation and Heliconius butterflies

Homoploid hybrid speciation (HHS) is the establishment of a novel species through introgressive hybridization without a change in chromosome number. We discuss different routes by which this might occur and propose a novel term, 'hybrid trait speciation', which combines the idea that hybridization can generate adaptive novelty with the 'magic trait' model of ecological speciation. Heliconius butterflies contain many putative examples of hybrid colour patterns, but only recently has the HHS hypothesis been tested explicitly in this group. Molecular data has shown evidence for gene flow between many distinct species. Furthermore, the colour pattern of Heliconius heurippa can be recreated in laboratory crosses between Heliconius melpomene and Heliconius cydno and, crucially, plays a role in assortative mating between the three species. Nonetheless, although the genome of H. heurippa shows evidence for hybridization, it is not a mosaic of the two parental species. Instead, ongoing hybridization has likely blurred any signal of the original speciation event. We argue that where hybridization leads to novel adaptive traits that also cause reproductive isolation, it is likely to trigger speciation.     

Genetic divergence, range expansion and possible homoploid hybrid speciation among pine species in Northeast China

Although homoploid hybrid speciation in plants is probably more common than previously realized, there are few well-documented cases of homoploid hybrid origin in conifers. We examined genetic divergence between two currently widespread pines in Northeast China, Pinus sylvestris var. mongolica and Pinus densiflora, and also whether two narrowly distributed pines in the same region, Pinus funebris and Pinus takahasii, might have originated from the two widespread species by homoploid hybrid speciation. Our results, based on population genetic analysis of chloroplast (cp), mitochondrial (mt) DNA, and nuclear gene sequence variation, showed that the two widespread species were divergent for both cp- and mtDNA variation, and also for haplotype variation at two of eight nuclear gene loci surveyed. Our analysis further indicated that P. sylvestris var. mongolica and P. densiflora remained allopatric during the most severe Quaternary glacial period that occurred in Northeast China, but subsequently exhibited rapid range expansions. P. funebris and P. takahasii, were found to contain a mixture of chlorotypes and nuclear haplotypes that distinguish P. sylvestris var. mongolica and P. densiflora, in support of the hypothesis that they possibly originated via homoploid hybrid speciation following secondary contact and hybridization between P. sylvestris var. mongolica and P. densiflora.     

加拿大披碱草、老芒麦及其杂种F1代的RAPD分析

加拿大披碱草和老芒麦是披碱草属地理性远缘的2个种。采用RAPD技术,筛选了16个随机引物对这2个种及其F1代进行遗传多态性检测。在获得的186个位点中,114个为多念性位点,占61．29％。从种群内的遗传多态性来看,加拿大披碱草的多态性位点百分率最高(242．04%),其次是老芒麦(9．14%),杂种F1(1．61％)。从种群间的遗传关系来看,加拿大披碱草和老芒麦的遗传距离为0．4979,杂种F1与母本加拿大披碱草的遗传距离(0．2720)较近,而与父本老芒麦的遗传距离(0.4074)相对较远。     

Genomic collinearity and the genetic architecture of floral differences between the homoploid hybrid species Iris nelsonii and one of its progenitors,Iris hexagona

Hybrid speciation represents a relatively rapid form of diversification. Early models of homoploid hybrid speciation suggested that reproductive isolation between the hybrid species and progenitors primarily resulted from karyotypic differences between the species. However, genic incompatibilities and ecological divergence may also be responsible for isolation. Iris nelsonii is an example of a homoploid hybrid species that is likely isolated from its progenitors primarily by strong prezygotic isolation, including habitat divergence, floral isolation and post-pollination prezygotic barriers. Here, we used linkage mapping and quantitative trait locus (QTL) mapping approaches to investigate genomic collinearity and the genetic architecture of floral differences between I. nelsonii and one of its progenitor species I. hexagona. The linkage map produced from this cross is highly collinear with another linkage map produced between I. fulva and I. brevicaulis (the two other species shown to have contributed to the genomic makeup of I. nelsonii), suggesting that karyotypic differences do not contribute substantially to isolation in this homoploid hybrid species. Similar to other studies of the genetic architecture of floral characteristics, at least one QTL was found that explained >20% variance in each color trait, while minor QTLs were detected for each morphological trait. These QTLs will serve as hypotheses for regions under selection by pollinators.     

木兰科5个种间杂种减数分裂行为观察

对木兰科5个二倍体人工杂交后代的减数分裂行为进行观察。结果表明,各杂交F1代的减数分裂行为基本正常,在减数分裂中期I有个别二价体提前分开形成单体;中期I还存在异型二价体,说明杂交亲本间（种间）都有一定的遗传分化,但这种变异仅停留在基因水平上;后期I偶有染色体桥出现。杂种F1代的减数分裂过程基本正常,能形成生活力正常的生殖孢子。可预期的是自然界中木兰科属内种间的自然二倍体杂种可自行繁衍,经过一定繁衍周期后,即可形成具有相对稳定种群的新种。     

Increasing evidence of the role of gene flow in animal evolution: hybrid speciation in the yellow-rumped warbler complex

In this issue of Molecular Ecology, Brelsford et al. (2011) present strong evidence for a case of hybrid speciation within the yellow-rumped warbler complex. Although homoploid hybrid speciation has now been documented in many animals (Mallet 2007), it seems rare in tetrapods (Mavárez & Linares 2008) and it has barely even been mentioned in birds (Price 2008). Brelsford and colleagues thus present the first detailed molecular evidence suggesting that hybrid speciation can occur in birds. Brelsford et al. (2011) posit that Audubon's warbler (Dendroica auduboni) constitutes a hybrid species originating from the admixture of two distinct parental lineages, represented today by myrtle warbler (D. coronata) and black-fronted warbler (D. nigrifrons). The authors present three major lines of molecular evidence suggesting that this is not simply a case of a hybrid swarm or limited introgression.     

红砂基因组大小变异及物种分化

红砂(Reaumuria soongarica, 柽柳科)是广泛分布于亚洲内陆干旱区温带荒漠的建群灌木, 该物种内部经历过分化和杂交事件, 是研究荒漠植物多样性发生和杂交物种形成的理想模型。然而, 红砂不同群体的倍性水平尚不清楚, 制约了对其物种形成机制的深入研究。为了确定红砂不同支系的倍性及基因组大小变异模式, 本研究以红砂幼苗根尖为实验材料, 以野生番茄(Solanum pimpinellifolium)作为内标物种, 利用流式细胞术对分别来自北疆支系及其可能的亲本支系(东部和西部支系)的共8个红砂群体进行了DNA 1C-值测定和分析。结果显示: 红砂东部支系的DNA 1C-值(1.149 ± 0.012 pg)略小于西部支系的1C-值(1.195 ± 0.031 pg)。北疆支系中阜康(FK)和沙湾(SW)群体的DNA 1C-值处于东、西支系的1C-值之间, 而火烧山(HSS)和五彩城(WCC)群体的1C-值接近东、西支系1C-值的2倍。结合之前的分子标记结果, 我们推测北疆支系中阜康和沙湾群体为东、西部支系的同倍体杂交种群, 而火烧山和五彩城群体属于异源四倍体杂交种群。不同倍性的北疆群体起源于不同的杂交事件, 可以划归为不同的物种。     

Hybrid speciation in sparrows I: phenotypic intermediacy,genetic admixture and barriers to gene flow

Homoploid hybrid speciation is thought to require unusual circumstances to yield reproductive isolation from the parental species, and few examples are known from nature. Here, we present genetic evidence for this mode of speciation in birds. Using Bayesian assignment analyses of 751 individuals genotyped for 14 unlinked, nuclear microsatellite loci, we show that the phenotypically intermediate Italian sparrow (Passer italiae) does not form a cluster of its own, but instead exhibits clear admixture (over its entire breeding range) between its putative parental species, the house sparrow (P. domesticus) and the Spanish sparrow (P. hispaniolensis). Further, the Italian sparrow possesses mitochondrial (mt) DNA haplotypes identical to both putative parental species (although mostly of house sparrow type), indicating a recent hybrid origin. Today, the Italian sparrow has a largely allopatric distribution on the Italian peninsula and some Mediterranean islands separated from its suggested parental species by the Alps and the Mediterranean Sea, but co‐occurs with the Spanish sparrow on the Gargano peninsula in southeast Italy. No evidence of interbreeding was found in this sympatric population. However, the Italian sparrow hybridizes with the house sparrow in a sparsely populated contact zone in the Alps. Yet, the contact zone is characterized by steep clines in species‐specific male plumage traits, suggesting that partial reproductive isolation may also have developed between these two taxa. Thus, geographic and reproductive barriers restrict gene flow into the nascent hybrid species. We propose that an origin of hybrid species where the hybrid lineage gets geographically isolated from its parental species, as seems to have happened in this system, might be more common in nature than previously assumed.     

大鹅观草与阿拉善鹅观草杂种的形态学和细胞学研究

为探讨阿拉善鹅观草 ( R.alashanica( Keng) S.L.Chen)的染色体组组成 ,进行了大鹅观草 ( R.grandisKeng( 2 n=2 4 ,St St YY) )和阿拉善鹅观草种间杂交 ,对这两个种及其杂种 F1的形态学、繁育学和减数分裂染色体配对行为进行了研究。结果表明 :杂种 F1的形态特征介于父母本之间 ,其花粉母细胞减数分裂染色体平均构型为 :2 0 .4 0 +3.6 9 +0 .0 9 +0 .0 4 。表明阿拉善鹅观草含有一个修饰的 St基因组 ,即 Sta。