陆地棉和野生斯特提棉种间异源六倍体的合成与性状鉴定

陆地棉(Gossypiumhirsutum)是世界上重要的栽培棉种,野生斯特提棉(G.sturtianum)含有陆地棉所缺乏的许多优质基因。本研究通过陆地棉和斯特提棉的远缘杂交和染色体加倍,获得了自交可育的后代植株,对其进行流式细胞倍性检测和花粉母细胞减数分裂观察,筛选出2株染色体组完整的异源六倍体植株。统计鉴定表明,六倍体和亲本及三倍体比较,叶形介于双亲之间,叶面积增大,保卫细胞中叶绿体数明显增多;远缘杂种与亲本在花的表型性状方面差异明显,六倍体的花粉粒直径大于亲本和三倍体;六倍体棉纤维为白色,长度小于母本陆地棉,父本斯特提棉的种子腺体延缓发育性状在异源六倍体中得到表达。这些结果证明通过远缘杂交和加倍成功获得了陆地棉与斯特提棉间可育的异源六倍体新种质,为棉花遗传育种研究提供了有价值的材料。     

四倍体小麦与六倍体小麦杂种的染色体遗传特性

四倍体栽培小麦(Triticum turgidum L., AABB)和普通小麦(Triticum aestivum L., AABBDD)是两种目前主要的小麦栽培种。通过远缘杂交转移利用四倍体小麦(或六倍体小麦)基因是六倍体小麦(或四倍体小麦)遗传改良的重要方法。然而,两者杂种F1为基因组组成不平衡的五倍体,其中A和B基因组染色体均为两套,而D基因组染色体仅一套。亲本间的遗传差异,包括核基因组和细胞质基因组,可能影响五倍体杂种的染色体传递效率。本研究以多个不同遗传背景的四倍体小麦和六倍体小麦为亲本,配置正反交五倍体杂种F1,采用多色荧光原位杂交技术分析自交F2代植株的染色体组成规律。结果表明,杂交亲本的遗传背景对杂种F1自交结实率影响显著;不论是以四倍体小麦还是六倍体小麦做母本, AB基因组染色体在F1自交过程中相对稳定, F2后代的数目均接近28条(27.9 vs. 28.0);以四倍体小麦为母本F2平均保留的D基因组染色体数显著多于以六倍体小麦为母本的后代(7.0 vs. 2.9)。因此,以四倍体小麦为最终目标后代时,应优先以六倍体小麦为母本进行杂交组合的配置;以六倍体小麦为最终目标后代时,应优先以四倍体小麦为母本开始最初的杂交组合配置。     

半浸根法加倍小麦远缘杂交幼胚再生植株染色体

染色体加倍是小麦单倍体育种和克服远缘杂种不育的重要技术之一.多年来,应用秋水仙素对花培产生的单倍体植株的染色体加倍进行了大量研究[1～4],但对小麦远缘杂交幼胚再生植株的染色体加倍技术研究很少.传统的全浸根法染色体加倍技术成功率低,而且死苗严重.和现昌等[5]用半浸根法就地挖坑加倍小麦花粉植株,加倍率达80%以上,幼     

野生棉与陆地棉异源四倍体的合成与性状鉴定

棉属具有丰富的种质资源,将抗病性从野生棉转移到陆地棉中,以此提高陆地棉抗病性是一条理想的育种途经。本研究通过陆地棉和C组野生澳洲棉远缘杂交获得杂种F1,对其进行染色体加倍,将加倍的异源六倍体再与B组野生绿顶棉杂交,产生陆地棉、澳洲棉、绿顶棉的异源四倍体杂种。异源四倍体杂种继承了亲本的部分性状,同时也产生了如蔓生等特异性状;该杂种减数分裂后期染色体不能均等分离,四分体时期有多分体和微核出现;SSR结果发现,该杂种不仅具有三个亲本的特征条带,并且产生了新的重组成分。本研究不仅为该异源四倍体杂种不育提供了直接原因,也为进一步探讨有效的育性恢复方法及棉花新种质创制提供了依据,同时为利用野生棉资源控制棉花黄萎病育种探索培育了中间材料。     

组织培养中大葱染色体倍性变异的研究

采用大葱茎尖分生组织直接成苗及分化丛生苗、茎盘诱导愈伤组织培养再生植株,通过染色体压片,对大葱愈伤组织及幼苗染色体数目变化进行了研究。结果表明,茎尖分生组织培养的幼苗及丛生苗遗传稳定,其染色体未发生倍性变异,均为2n=16;愈伤组织及其再生苗遗传稳定性较差,愈伤组织染色体数变异率为43.4%,其中单倍体占6.7%、三倍体占2.5%、四倍体占10%、五倍体占4.2%、六倍体占3.3%、七倍体占4.2%、八倍体占3.3%、非整倍体占9.2%;愈伤组织分化苗染色体变异率为11.7%,其中单倍体占6.7%,三倍体占1.7%,四倍体占3.3%。     

由小麦×玉米获得的小麦DH系花粉母细胞减数分裂观察

研究了由小麦×玉米远缘杂交获得的小麦双单倍体DH2代花粉母细胞减数分裂过程。结果表明，大多数双单倍体小麦与异源六倍体普通小麦染色体数目相同，这是染色体经秋水仙素成功加倍的结果。同时在少数细胞中观察到了染色体的“块状移动”，在这些“块”中存在少数“染色体落后”现象，这可能是由于在染色体加倍过程中部分细胞染色体数目发生变异造成的。     

介绍两个棉花新种质系

中陆高衣分棉是河北省农科院棉花所于1972年从武安中棉中选出的一株中棉和陆地棉天然杂交不育株,1979年用秋水仙碱进行染色体加倍,获得六倍体杂种,后又与邢台6871杂交,经多年选择,于1984年育成。生育期132天,株高90厘米左右,铃长卵     

花椰菜与黑芥体细胞杂种的生物学特性

对经UV处理,PEG融合获得的79株花椰菜和黑芥的体细胞杂种进行了全生育期性状调查分析,包括细胞DNA含量测定、染色体计数、植株形态学观察、育性调查等.结果表明:杂种形态变异广泛,多数呈中间类型,少数呈偏亲性状;杂种细胞DNA含量不一致,呈现大于、等于、小于双亲细胞DNA含量之和的类型;DNA含量大于双亲之和的杂种与DNA含量等于或小于双亲之和的杂种相比,有较高比例的材料叶型出现畸形和(或)植株生长势弱,育性也更差.显示出杂种植株的生长势、育性与q细胞的DNA含量具有一定的相关性.通过染色体计数,发现所检测杂种为混倍体,同一植株的细胞有多种染色体数目构成.在79个杂种中,筛选出13个目标材料,生长势强,有较好或一定程度的育性,表明采用体细胞杂交技术手段来改良甘蓝类蔬菜的遗传多样性具有町行性.     

散穗高粱与白壳苏丹草杂交F1及其染色体加倍植株ISSR分析

为了明确散穗高粱与白壳苏丹草杂交F1及其染色体加倍植株遗传差异性及其遗传距离,为下一步新品种育成利用奠定基础和提供科学依据。试验利用ISSR标记技术对散穗高粱与白壳苏丹草杂交F1及其染色体加倍植株进行多态性位点比较分析。结果表明：6条适宜引物共扩增得到重复性好的清晰条带164条,其中144条多态性条带,多态性比率达到86.9%;材料间的遗传距离变幅为0.2690~0.5923,散穗高粱与散穗高粱×白壳苏丹草F1加倍植株之间的遗传距离最远;供试材料以遗传距离0.26为基准可分为散穗高粱和白壳苏丹草;散穗高粱×白壳苏丹草杂种F1;散穗高粱×白壳苏丹草杂种F1加倍植株这三类。     

节节麦×六倍体小黑麦杂种胚再生植株育性及其变异的细胞学研究

对节节麦(2n=2x=14)×六倍体小黑麦(2n=6x=42)杂种胚培养植株和胚愈伤组织再生植株的育性比较,发现杂种胚愈伤组织再生植株育性有较大的变异。8株胚培养杂种植株的平均育性为0.87％(0.39％～1.40％),同期抽穗的杂种胚愈伤组织再生植株的平均育性为0.75％(0～5.39％)。细胞学研究表明杂种F_1可育性是由于未减数配子产生的结果,在一些PMCs中,单价体中期Ⅰ集结到赤道板上,后期Ⅰ分裂失败形成再组核,再组核分裂产生二分体或细胞质提前分裂产生有核和无核子细胞,有核子细胞分裂产生未减数配子。细胞学研究揭示再生植株的育性和染色体数目和配对构型无关而和单价体中期Ⅰ在赤道板上的集结程度呈正相关。远缘杂种F_1再生植株的育性变异为克服杂种不育提供了技术途径。     

In vitro induction of hexaploid plants from triploid hybrids of Pennisetum purpureum and Pennisetum glaucum

This study describes an efficient in vitro method using colchicine-treated triploid seedlings of Napiergrass and Pearl millet hybrids to produce hexaploid hybrids and their subsequent identification with flow cytometry. It also describes chromosome count and stomatal morphology and their use to ploidy analysis. Four-hundred and eighty triploid seeds, representing 12 different hybrids were sterilized and transferred to MS media to induce chromosome doubling. Surviving plants were analysed by flow cytometry. From six triploid (control) and hexaploid plants, the stomata sizes and frequency were analysed. Chromosome count was performed only in the plants identified as hexaploid. Seventeen plants were identified as hexaploid by flow cytometry analysis. Further confirmation of the hexaploid condition was performed with stomatal morphology (stomatal frequency reduction and stomatal length increase) and chromosome count (2n = 6x = 42). Chromosome doubling has numerous applications in Pennisetum breeding. It can be used to restore the fertility of interspecific hybrids and to improve seed size.     

The production and behaviour of hexaploid hybrids between Hordeum vulgare and H. Bulbosum

Summary To produce hexaploid (or other polyploid) hybrids, diploid or tetraploid Hordeum vulgare was crossed with hexaploid or octoploid H. bulbosum, and perennial triploid hybrids between the two species were treated with colchicine. The crosses did not yield viable plants: seedset was low, the seed aborted and embryo culture was unsuccessful. The colchicine treatments geve rise to plants in which hexaploid chromosome numbers were observed. At the hexaploid level chromosomal instability occurred, resulting in chromosome elimination.The colchicine-treated triploid hybrids showed in the first years after the treatment better fertility after open flowering than untreated plants, but the level of fertility remained very low. The offspring consisted of haploid, diploid and approximately triploid plants like H. vulgare, tetraploid and approximately tetraploid plants like H. bulbosum, and plants with hybrid morphology and unstable chromosome number, which were highly sterile. Thus the crossing barrier between H. vulgare and H. bulbosum could not be broken down at higher ploidy level.     

Interspecific hybridization between Brassica carinata and Brassica rapa

The crossability between Brassica carinata (BBCC, 2n=34) and Brassica rapa (AA, 2n=20), and the cytomorphology of their F₁ hybrids were studied. Hybrids between these two species were only obtained when B. carinata was used as the female parent. The hybrid plants exhibited intermediate leaf and flower morphology, and were found to be free from white rust and Alternaria blight diseases. One of the four F₁ plants was completely male sterile, while the remaining plants had 4.8, 8.6, and 10.9% stainable pollen, respectively. No seed was produced on hybrid plants under self pollination or in backcrosses; but seed was obtained from open pollination. The occurrence of the maximum of 11 bivalents as well as up to 44.8%) of cells with multivalent associations in the form of trivalents (0‐2) and a quadrivalent (0‐1) in the trigenomic triploid hybrid (ABC, 2n = 27) revealed intergenomic homoeology among the A, B and C genomes. Meiotic analysis of F₁ hybrids indicated that traits of economic importance, such as disease resistance, could be transferred from B. carinata to B. rapa through interspecific crosses.     

Wide hybridization between wheat (Triticum L.) and lymegrass (Leymus Hochst.)

A total of 240 F₁ hybrids was made beween wheat (Triticum aestivum L. em. Thell. (2n = 6x = 42) and T. carthlicum Nevski (2n = 4x = 28)) and perennial lymegrass (North European Leymus arenarius (L.) Hochst. (2n = 8x = 56) and North American L. mollis (Trin.) Pilger (2n = 4x = 28)). The wide crosses yielded embryos in 20% of caryopses and 96% of the embryos developed into normal hybrid plants. The hybrids were vegetatively vigorous, with evidence of the Leymus rhizomatous habit. Those deriving from L. arenarius survived overwintering in Iceland, but the hybrids L. mollis did not, whereas in a milder environment, both showed perenniality. Cytogenetic analysis of root tip cells before the plants were treated with colchicine showed that 21 out of 28 hybrids investigated had chromosome mosaics, with a population of both amphihaploid and amphidiploid cells. This spontaneous doubling of somatic chromosomes occurred in all cross combinations, with the highest average frequency of diploid cells (28%) in T. carthlicum × L. arenarius crosses. A few selfed seeds have been obtained from a T. aestivum × L. arenarius hybrid. All the hybrids were treated twice with colchicine, but the treatment appeared to have little or no effect on the frequency of chromosome doubling in the hybrids deriving from T. aestivum. The frequency of diploid cells, however, increased significantly (e.g. to 80%) in the hybrids deriving from the T. carthlicum parent. Genomic in situ hybridization confirmed the hybridity of the plants and showed that the hybrids were amphiploids containing genomes of both wheat and lymegrass. In situ hybridization using ribosomal DNA probe differentiated chromosomes of L. mollis, L. arenarius from those of wheat. The hybrids are being backcrossed with lymegrass pollen, aiming to domesticate the wild, perennial species. This revised version was published online in July 2006 with corrections to the Cover Date.     

The transfer of triazine resistance from Brassica napus L. to B. oleracea L. III. First backcross to parental species

Summary Atrazine resistant Brassica napus × B. oleracea F₁ hybrids were backcrossed to both parental species. The backcrosses to B. napus produced seeds in both directions but results were much better when the F₁ hybrid was the pollen parent. Backcrosses to B. oleracea failed completely but BC₁s were rescued by embryo culture both from a tetraploid hybrid (2n = 4x = 37; A₁C₁CC) and sesquidiploid hybrids (2n = 3x = 8; A₁C₁C). Progeny of crosses between the tetraploid hybrid and B. oleracea had between 25 and 28 chromosomes. That of crosses between the sesquidiploid hybrid and B. oleracea had between 21 and 27. A few plants that had chromosome counts outside the expected range may have originated from either diploid parthenogenesis, unreduced gametes or spontaneous chromosome doubling during in vitro culture. Pollen stainability of the BC₁s ranged from 0% to 91.5%. All the BC₁s to B. oleracea were resistant to atrazine.     

Production of 27-, 28-, and 56-chromosome apomictic hybrid derivatives between pearl millet (2n=14) and Pennisetum squamulatum (2n=54)

Summary An interspecific hybridization program designed to transfer gene(s) controlling apomixis from Pennisetum squamulatum Fresen. (2n=6x=54) to induced tetraploid (2n=4x=28) cultivated pearl millet, Pennisetum americanum (L.) Leeke resulted in four offtype plants, two with 27 chromosomes and two with 28 chromosomes. These plants were found among 217 spaced plants established from open-pollinated seed of an apomictic 21-chromosome polyhaploid (2n=21) plant derived from an apomictic interspecific hybrid (2n=41) between tetraploid pearl millet and Pennisetum squamulatum. It appeared that a 21- (or 20-) chromosome unreduced egg from the apomictic polyhaploid united with a 7-chromosome pearl millet (2n=2x=14) gamete to produce a 28- (or 27-) chromosome offspring. Meiotic chromosome behavior was irregular averaging from 3.60 to 4.05 bivalents per microsporocyte in the 27- and 28-chromosome hybrids. The 27- or 28-chromosome hybrids, like the 21-chromosome female parent, shed no pollen, but set from 1.8 to 28 seed per panicle when allowed to outcross with pearl millet. Progeny of the 28-chromosome hybrids were uniform and identical to their respective female parents, indicating that apomixis had been effectively transferred through the egg. In addition, a 56-chromosome plant resulting from chromosome doubling of a 28-chromosome hybrid was identified. Pollen was 68 per cent stainable and the plant averaged 2.3 selfed seeds per panicle. Chromosomes of the 56-chromosome plant paired as bivalents (x=10.67) or associated in multivalents. Three to nine chromosomes remained unpaired at metaphase I. Multiple four-nucleate embryo sacs indicated the 56-chromosome hybrid was an obligate apomict. The production of 27-, 28-, and 56-chromosome hybrid derivatives were the results of interspecific hybridization, haploidization, fertilization of unreduced apomictic eggs, and spontaneous chromosome doubling. These mechanisms resulted in new unique genome combinations between x=7 and x=9 Pennisetum species.     

A synthetic hexaploid (2n = 42) oat from the cross of Avena strigosa (2n = 14) and domesticated A. magna (2n = 28)

A synthetic hexaploid oat was produced by chromosome doubling of a sterile triploid hybrid between cultivated Avena strigosa (2n = 14) cv. Saia and a domesticated form of A. magna (2n = 28). The synthetic hexaploid was intermediate between its parents in panicle shape and lemma color, similar to the tetraploid parent in spikelet structure, and to the diploid parent in having a single, albeit partially shriveled seed per spikelet, and low protein content. By the third generation, plants with yellowish lemmas, mostly two seeds per spikelet and better filled grains had been selected. Rust resistance of the diploid parent was retained in the synthetic hexaploid, but not tolerance to barley yellow dwarf virus disease (BYDV). Chromosome associations at meiosis in the triploid hybrid was low, with over 60% of them being univalents. Bivalent association was the rule in the synthetic hexaploid with an occasional one or two quadrivalents. Regular meiosis with 21 bivalents was observed in further generations. The preferential pairing of homologous chromosomes in the synthetic hexaploid was probably contributed by the A. strigosa genome which exhibits this tendency in artificial allopolyploid situations. Selection of yellow lemma color and two seeds per spikelet suggests that the genes controlling these traits are located on the chromosomes involved in quadrivalents in the synthetic hexaploid. The potential and limitations of utilizing the synthetic hexaploid in oat research and breeding are briefly discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Successful induction of trigenomic hexaploid <Emphasis Type="Italic">Brassica</Emphasis> from a triploid hybrid of <Emphasis Type="Italic">B.</Emphasis><Emphasis Type="Italic">napus</Emphasis> L. and <Emphasis Type="Italic">B. nigra</Emphasis> (L.) Koch

A triploid hybrid with an ABC genome constitution, produced from an interspecific cross between Brassica napus (AACC genome) and B. nigra (BB genome), was used as source material for chromosome doubling. Two approaches were undertaken for the production of hexaploids: firstly, by self-pollination and open-pollination of the triploid hybrid; and secondly, by application of colchicine to axillary meristems of triploid plants. Sixteen seeds were harvested from triploid plants and two seedlings were confirmed to be hexaploids with 54 chromosomes. Pollen viability increased from 13% in triploids to a maximum of 49% in hexaploids. Petal length increased from 1.3 cm (triploid) to 1.9 cm and 1.8 cm in the two hexaploids and longest stamen length increased from 0.9 cm (triploid) to 1.1 cm in the hexaploids. Pollen grains were longer in hexaploids (43.7 and 46.3 μm) compared to the triploid (25.4 μm). A few aneuploid offsprings were also observed, with chromosome number ranging from 34 to 48. This study shows that trigenomic hexaploids can be produced in Brassica through interspecific hybridisation of B. napus and B. nigra followed by colchicine treatment.     

Brassica napocampestris L. (2n=58). 1. Synthesis,cytology, fertility and general considerations

Summary The synthesis of leafy, forage forms of Brassica napocampestris (2n=58, aaaacc) by colchicine treatment of hybrids between B. napus (2n=38, aacc) and B. campestris (2n=20, aa) is described.The cytology of both triploid and hexaploid hybrids was studied. B. napocampestris proved fairly stable meiotically although multivalents were formed and some aneuploids detected in later generations. Seed fertility proved adequate for commercial production.The variation within the parental species and their easy crossability suggests that several distinct forms of B. napocampestris could be created, some of which may have agronomic potential. B. napocampestris may be used as a stepping stone in elaborating the range of variability within B. napus.     

Resynthesis of rapeseed (Brassica napus L.): A comparison of sexual versus somatic hybridization

Sexual and somatic Brassica napus hybrids produced from the same parental plants were compared. Sexual crosses between a white-flowered, self-compatible broccoli selection (B. oleracea var. italica, cc genome) as the maternal parent and a flowering pak choi accession (B. chinensis, aa genome) yielded one unique spontaneous hybrid and four hybrids through embryo rescue. Thirty-nine somatic hybrids were recovered from a protoplast fusion experiment. Hybridity was confirmed by morphology, isozyme expression, flow cytometry, and DNA hybridization. Sexual and somatic hybrids exhibited differences in leaf morphology, flower colour, flowering habit, and organellar inheritance. Sexual hybrids were all fertile amphidiploids (2n = 38, aacc) following spontaneous chromosome doubling. All somatic hybrids had high nuclear DNA contents; most were probably hexaploids (aaaacc or aacccc) from the fusion of three portoplasts. Two initially sterile hexaploid (aaaacc) regenerates eventually set selfed seed after the loss of the putative extra aa genome following regrowth from axillary buds. A bias toward inheritance of B. chinensis chloroplasts was observed with somatic hybrids.