赖草属种子胚乳细胞多样性研究

对赖草属21个物种的胚乳细胞特征进行了解剖观察,发现赖草属植物种子胚乳细胞存在丰富的多样性,不同物种的胚乳细胞在大小、形状和数量上均表现出明显的差异,其胚乳细胞的特征具有类群鉴分的价值。属于较原始的sect．Leymus Hochst．组的沙生赖草、大赖草和滨麦具有较大而多的胚乳细胞,属于较进化的sect. Anisopyrum(Griseb．)Tzvel．组的多枝赖草和灰赖草具有较小而少的胚乳细胞。     

赖草属植物的遗传学研究与利用

赖草属植物具有广泛的适应性和丰富的抗逆性,作为麦类作物的重要基因资源愈来愈受到人们的重视。介绍了赖草属植物的种类及分布,分析了赖草属植物的优良特性及潜在利用价值,探讨了赖草属植物的核型、染色体带型及分子细胞遗传学研究,重点论述了赖草属植物在小麦遗传改良中的应用．阐明挖掘利用小麦近缘野生植物是未来小麦品种改良的有效途径。     

燕麦属细胞遗传学研究进展

整理燕麦属(Avena L.)细胞遗传学研究文献,总结相关研究进展。燕麦属有7组29种植物,分属5个基因组类型(A、C、AB、AC、ACD)。基于荧光原位杂交技术和种间杂交实验表明,A、C基因组染色体结构差异较大,A基因组二倍体物种具有等臂染色体,C基因组二倍体物种具有不等臂染色体。燕麦属植物D基因组和A基因组间分化程度较小,B基因组有可能是A基因组的变型——A′基因组。普遍观点认为A基因组二倍体物种可能是燕麦属六倍体物种母系亲本,砂燕麦(A.strigosa)为该属多倍体物种A基因组祖先的假说备受争议,有学者认为加那利燕麦(A.canariensis)可能是多倍体物种A或D基因组的供体。燕麦属多倍体物种基因组互换及染色体重排事件,增加燕麦属种间亲缘关系、多倍体物种基因组起源研究的困难。结合基因组学、分子细胞遗传学技术,有望为上述问题提供新证据。     

鹅观草属、披碱草属、猬草属和仲彬草属物种的RAMP分析及系统学意义

对鹅观草属、披碱草属、猬草属和仲彬草属4属23个物种进行了RAMP分析。结果表明属间变异极大,多态性极高。31个引物组合产生的286条DNA扩增片段均具有多态性。聚类分析显示鹅观草属、披碱草属、猬草属和仲彬草属物种各自聚为一类;Roegneria alashanica、R．elytrigioides和R．magnticaespes聚类在一起;猬草属的模式种Hystrix patula与披碱草属物种聚类在一起,而Hystrix duthiei和H．longearistata单独聚为一类;形态相似、染色体组相同、地理分布一致的物种聚类在一起。本研究结果基本上同形态学和细胞学研究结果相吻合,将鹅观草属、披碱草属和仲彬草属作为属分类等级处理比较恰当,而猬草属的系统地位有待进一步确认。RAMP标记可作为评价多年生小麦族物种遗传多样性和亲缘关系的一种分子标记技术。     

四川藁本属植物果实和叶柄解剖学研究

对四川省藁本属5种植物的叶柄及果实进行了解剖研究,结果表明:藁本属植物的果实分为近两侧压扁和背腹压扁两种类型,背棱每棱槽内油管总数多为1~4个,合生面油管总数4~8个,在少数种间有一定的差异;胚乳背面微微隆起,腹面平直或微凹,如多管藁本,胚乳向内微凹;在蕨叶藁本中,胚乳占很大的比重,胚乳形状有很明显的个体差异.果实的压扁程度、油管特征、胚乳的形状等特征可以作为确定本属植物种间关系的依据.叶柄横切面类型多样,包括圆型、U型和V型,其中U型植物3种,占60%;近轴面除蕨叶藁本外,都具有沟槽;膜苞藁本和抽葶藁本中不具有髓腔,其他种类具髓腔,且大小、形状略有不同;横切面上维管束的数目多为5~14个,排列类型为圆型、U型、V型.以上叶柄等特征比较稳定,并且具有明显的种间差异,可以作为本属分类的重要依据.     

同域分布垂穗披碱草和达乌力披碱草遗传多样性和遗传结构分析

披碱草属(Elymus L.)是禾本科(Poaceae)小麦族(Triticeae)中的一个多年生属,该属在青藏高原地区有广泛分布,多数物种是草原和草甸的组成成分,许多种类为品质优良的牧草.垂穗披碱草(E.nutans)和达乌力披碱草(E.dahuricus)同为禾本科小麦族披碱草属异源六倍体物种,染色体组组成皆为St...     

披碱草属(Elymus L.)两个物种之订正

披碱草属Elymus L．是小麦族Triticeae Dumort．中最大的属,全世界共有150多个种,广泛分布于 温带地区。我国约有80余种(包括鹅观草属Roegneria C．Koch),是披碱草属的重要分布区和多样性分 化中心。由于披碱草属植物种类繁多、分布广泛、生境多样以及形态变异较为复杂,导致该属在分类上 存在许多问题。同时,由于地域的局限和地区间交流的缺乏,致使同一种披碱草属植物被不同的学者多 次发表及同物异名现象的出现。本文对E．antiquus和E．burchan-buddae这两个曾多次被订名的披碱草 属物种进行了分类订正。     

披碱草属3组植物叶片解剖特征及其系统关系

采用石蜡切片法对披碱草属中小颖组、宽颖组和长颖组主要代表种的叶片横切面形态学特征进行观察。结果显示:(1)披碱草属3个组植物的叶片均为等面叶,由表皮、叶肉和维管束三部分构成,表现为典型的狐茅型,即表皮细胞形状、大小和排列不均,叶肉无栅栏组织和海绵组织之分,具有双层维管束鞘,周围叶肉细胞呈不规则排列,厚壁组织与表皮相接;但3个组植物在上表皮细胞形状、大小、沟的深浅,以及大型导管数目等叶片横切面特征上存在明显差异。(2)根据3个组植物叶片横切面性状的演化趋势,对各组的演化关系和系统位置分析表明,小颖组最原始,宽颖组较进化,长颖组最高级;小颖组可能直接派生了较进化的宽颖组,并在宽颖组的基础上进而产生了最高级的长颖组;小颖组、宽颖组和长颖组的这一系统关系与利用外部形态特征所获得的演化趋势基本一致。     

小麦族披碱草属、鹅观草属和猬草属模式种的C带研究

采用改良的Giemsa C带技术,分析了小麦族披碱草属、鹅观草属和猬草属模式种的染色体C带带型。Elymus sibiricus、Roegneria caucasica和Hysrix patula的染色体在Giemsa C带带型上存在明显的差异,显示了这3个属模式种的物种特异性。3个模式种的Giemsa C带核型表明,C带带纹主要分布在染色体的末端和着丝粒附近,而中间带相对较少。对E.sibiricus、R.caucasica和H.patula的St、H、Y染色体组C带带型与其它物种的St、H、Y染色体组C带带型的差异进行了讨论。     

冰草属研究进展

冰草属(Agropyron Gaertn.)作为重要的小麦野生近缘属之一,一直受到包括牧草育种家在内的许多学者的重视。冰草属在过去指包括现今形态分类上的冰草属,披碱草属(Elymus L.)和偃麦草属(Elytrigia Desv.),是一个相当复杂的庞大属。现在无论根据形态分类系统或染色体组分类系统,冰草属都已有了明确的概念,是指仅含P染色体组的冠状冰草复合群(crested wheatgrass complex),即包括冰草(A.cristatum Gaertn.),沙生冰草     

II. Cereal disease: the interplay between resistance and pathogenicity: Inheritance of pathogenicity in Gaeumannomyces graminis var. tritici

Variation in host response of isolates of the eyespot pathogen from different sources was examined over a number of years. Pathogen types were found in intensively-cropped couch-infested cereal sites that were almost as virulent on Agropyron repens (couch) as on wheat or barley. The commonly occurring wheat (W) type isolates from couch-free cereal crops were virulent on wheat and barley but avirulent on couch. Couch (C) types were isolated not only from couch but also from wheat, barley and oat crops with couch infestation. In pathogenicity tests on rye, C. types did not differ in virulence from the more commonly occurring W types. Aegilops ventricosa was equally resistant to both types. W type isolates from wheat and barley were examined to assess differential pathogenicity on wheat and barley. Sequential cropping with single cereal crops was used to separate out possible specific types. Isolates from fourth wheat and fourth barley crops were more pathogenic on the original than on the alternative host. When comparisons were made between isolates from third and fifth consecutive wheat and barley crops only those from barley showed a preference for the original host. An experiment comparing isolates from third and seventh consecutive wheat and barley crops showed a decline in virulence from the short to the longer sequences on the alternative but not on the original host.     

Phylogeny of a Genomically Diverse Group of Elymus (Poaceae) Allopolyploids Reveals Multiple Levels of Reticulation

The grass tribe Triticeae (=Hordeeae) comprises only about 300 species, but it is well known for the economically important crop plants wheat, barley, and rye. The group is also recognized as a fascinating example of evolutionary complexity, with a history shaped by numerous events of auto- and allopolyploidy and apparent introgression involving diploids and polyploids. The genus Elymus comprises a heterogeneous collection of allopolyploid genome combinations, all of which include at least one set of homoeologs, designated St, derived from Pseudoroegneria. The current analysis includes a geographically and genomically diverse collection of 21 tetraploid Elymus species, and a single hexaploid species. Diploid and polyploid relationships were estimated using four molecular data sets, including one that combines two regions of the chloroplast genome, and three from unlinked nuclear genes: phosphoenolpyruvate carboxylase, β-amylase, and granule-bound starch synthase I. Four gene trees were generated using maximum likelihood, and the phylogenetic placement of the polyploid sequences reveals extensive reticulation beyond allopolyploidy alone. The trees were interpreted with reference to numerous phenomena known to complicate allopolyploid phylogenies, and introgression was identified as a major factor in their history. The work illustrates the interpretation of complicated phylogenetic results through the sequential consideration of numerous possible explanations, and the results highlight the value of careful inspection of multiple independent molecular phylogenetic estimates, with particular focus on the differences among them.     

Phylogenetic and evolutionary relationships between<Emphasis Type="Italic"> Elymus humidus</Emphasis> and other<Emphasis Type="Italic"> Elymus</Emphasis> species based on sequencing of non-coding regions of cpDNA and AFLP of nuclear DNA

Species of the genus Elymus are closely related to some important cereal crops and may thus serve as potential alien genetic resources for the improvement of these crops. E. humidus is indigenous to Japan and is well adapted to a humid climate. However, the phylogenetic and evolutionary relationships between E. humidus and other Elymus species are unclear. To elucidate these relationships, we examined the sequences of three non-coding regions of chloroplast DNA (cpDNA) and the amplified fragment length polymorphism (AFLP) variation of nuclear DNA in E. humidus and other related species. A total of 15 sequence mutations from the three non-coding regions, trnL-trnF, trnF-ndhJ(C), and atpB-rbcL, covering approximately 1,800 bp, were detected in the Elymus species. A phylogenic tree resulting from the cpDNA sequence data revealed that all the species containing the St nuclear genome (St, StH, StY, and StHY) formed a well-supported clade that is remote from the Hordeum species (H). This result strongly supports the finding that Pseudoroegneria is the maternal genome donor to the genus Elymus. In addition, E. humidus showed the closest relationship with the cpDNA genome of the Pseudoroegneria species. The AFLP analysis detected 281 polymorphic bands with 11 AFLP primer combinations. The AFLP result showed that E. humidus is relatively closer to E. tsukushiensis. However, the cpDNA sequencing results indicated that E. humidus and E. tsukushiensis have different cytoplasmic origins. Our results suggest that the evolutionary process between E. humidus and E. tsukushiensis is not monophyletic, although the two species have similar morphological characters and adaptability.Communicated by J. Dvorak     

Phylogenetic analysis of the genus Pseudoroegneria and the Triticeae tribe using the rbcL gene

The Pseudoroegneria species are perennial grasses in the Triticeae tribe, whose St genome has been linked to several important polyploid species. Due to frequent hybridization and complex genetic mechanism, the relationships within Pseudoroegneria, and within the Triticeae have been heavily disputed. Using the chloroplast rbcL gene we estimated the nucleotide diversity of 8 Pseudoroegneria species. We also examined the phylogenetic relationships within Pseudoroegneria and of Pseudoroegneria within the Triticeae. The estimates of nucleotide diversity indicated that Pseudoroegneria tauri and Pseudoroegneria spicata species had the highest diversity, while Pseudoroegneria gracillima had the lowest diversity. The phylogenetic analysis of Pseudoroegneria placed all P. spicata species into a clade separate from the other Pseudoroegneria species, while the relationship of the other Pseudoroegneria species could not be determined. Due to the groupings of Pseudoroegneria with the polyploid Elymus, our results strongly supported Pseudoroegneria as the maternal genome donor to Elymus. There was also weak support that P. spicata may be the maternal donor to the StH Elymus species.     

Immunogold localization of prolamines in developingHaynaldia villosa endosperm

Summary Haynaldia villosa is a wild grass belonging to the tribe Triticeae, which includes important crops such as wheat, barley, and rye. The alcohol-soluble proteins ofH. villosa have extensive immunological relatedness with wheat prolamines as visualized by Western blot analysis. Amorphous protein inclusions surrounded by a limiting membrane are commonly found in the vacuoles of endosperm and subaleurone layers ofH. villosa seeds. A layer of cells just beneath the aleurone layer is rich in ER. Unlike that in other cell types, the ER in these cells is highly dilated and contains materials at its swollen distal ends. These materials are structurally similar to substances found in the protein bodies. Protein A-gold immunocytochemical localization studies employing antibodies against wheat prolamine confirmed that the inclusions found in the lumen of the ER do not contain prolamines. This observation indicates that the ER does not act as the site of prolamine accumulation inH. villosa. Protein bodies found in the vacuoles and the vesicles associated with the Golgi complexes were specifically labeled. This suggests that Golgi complexes mediate the transport of prolamines into vacuoles ofH. villosa endosperm cells, in a fashion analogous to that of other vacuolar proteins of dicotyledonous plants.     

Phylogenetic relationships in Elymus (Poaceae: Triticeae) based on the nuclear ribosomal internal transcribed spacer and chloroplast trnL-F sequences

To estimate the phylogenetic relationship of polyploid Elymus in Triticeae, nuclear ribosomal internal transcribed spacer (ITS) and chloroplast trnL-F sequences of 45 Elymus accessions containing various genomes were analysed with those of five Pseudoroegneria (St), two Hordeum (H), three Agropyron (P) and two Australopyrum (W) accessions. The ITS sequences revealed a close phylogenetic relationship between the polyploid Elymus and species from the other genera. The ITS and trnL-F trees indicated considerable differentiation of the StY genome species. The trnL-F sequences revealed an especially close relationship of Pseudoroegneria to all Elymus species included. Both the ITS and trnL-F trees suggested multiple origins and recurrent hybridization of Elymus species. The results suggested that: the St, H, P, and W genomes in polyploid Elymus were donated by Pseudoroegneria, Hordeum, Agropyron and Australopyrum, respectively, and the St and Y genomes may have originated from the same ancestor; Pseudoroegneria was the maternal donor of the polyploid Elymus; and some Elymus species showed multiple origin and experienced recurrent hybridization.     

Characterization of a novel variant HMW-glutenin gene from Elymus canadensis

High molecular weight (HMW) glutenin subunits (GS) play a key role in the determination of end-use quality of wheat and other cereal crops. In this study, we report the isolation and characterization of both promoter region and ORF of novel HMW-GS allele 1St1.3 from a perennial Triticeae species, Elymus canadensis. The amino acid (AA) sequences of E. canadensis 1St1.3 were deduced as 434 aa. Its protein primary structure comprises a signal peptide with a conserved N-terminal domain, a central repetitive domain and a C-terminal domain. E. canadensis 1St 1.3 possesses several distinct characteristics which are different from those of wheat HMW-GSs. The N-terminal domains of E. canadensis 1St 1.3 resemble that of y-type subunits, while their C-terminal domains are more similar to x-type subunits. The deletion of 85 bp fragment has been observed in promoter region of 1St 1.3, however which has not interrupted the expression of this gene. Our results indicate that 1St 1.3 is novel HMW-GS variants which will be valuable for enhancing our understanding of structural differentiation and the evolutionary relationship among HMW-GSs in Triticeae species.     

Identification of <Emphasis Type="Italic">Elymus</Emphasis> (Triticeae,Poaceae) and its related genera genomes by RFLP analysis of PCR-amplified <Emphasis Type="Italic">Adh</Emphasis> genes

Elymus L. is the largest genus in Triticeae, containing about 150 species with four recognized genome donors (St, H, P, and W). Traditionally, the genome compound of this genus is identified based on cytological data. Recently, molecular phylogenetic analysis was used to investigate its genomic combination. Here we describe a restriction fragment length polymorphism (RFLP) assay based on digesting alcohol dehydrogenase (Adh) amplicons with two restriction enzyme combinations, EcoRI–HindIII and EcoRI–PstI, which easily can be used to distinguish Elymus and its closely related genera genomes. The method includes only four steps: (1) amplifying nuclear Adh genes with universal primers; (2) purifying and cloning PCR products; (3) digesting plasmids with restriction enzymes that identify a given genome; (4) running the digested products on an agarose gel and identify the sample based on the restriction profiles. Results showed that: (1) PCR products ranged from 1,200 to 2,000 bp; (2) Adh2 gene was amplified from all the tested genomes; Adh1 gene was amplified from almost all of the tested genomes except the W genome; Adh3 gene was amplified only from the St genome; (3) the EcoRI–HindIII combination was effective to distinguish different Adh gene types (Adh1, Adh2, and Adh3); (4) the Adh2–EcoRI–PstI fragments could be used to distinguish Elymus and its closely related genera genomes. Therefore, This RFLP assay provides an inexpensive and simple means of identifying Elymus genomes.     

Cereal asparagine synthetase genes

Asparagine synthetase catalyses the transfer of an amino group from glutamine to aspartate to form glutamate and asparagine. The accumulation of free (nonprotein) asparagine in crops has implications for food safety because free asparagine is the precursor for acrylamide, a carcinogenic contaminant that forms during high‐temperature cooking and processing. Here we review publicly available genome data for asparagine synthetase genes from species of the Pooideae subfamily, including bread wheat and related wheat species (Triticum and Aegilops spp.), barley (Hordeum vulgare) and rye (Secale cereale) of the Triticeae tribe. Also from the Pooideae subfamily: brachypodium (Brachypodium dIstachyon) of the Brachypodiae tribe. More diverse species are also included, comprising sorghum (Sorghum bicolor) and maize (Zea mays) of the Panicoideae subfamily and rice (Oryza sativa) of the Ehrhartoideae subfamily. The asparagine synthetase gene families of the Triticeae species each comprise five genes per genome, with the genes assigned to four groups: 1, 2, 3 (subdivided into 3.1 and 3.2) and 4. Each species has a single gene per genome in each group, except that some bread wheat varieties (genomes AABBDD) and emmer wheat (Triticum dicoccoides; genomes AABB) lack a group 2 gene in the B genome. This raises questions about the ancestry of cultivated pasta wheat and the B genome donor of bread wheat, suggesting that the hybridisation event that gave rise to hexaploid bread wheat occurred more than once. In phylogenetic analyses, genes from the other species cluster with the Triticeae genes, but brachypodium, sorghum and maize lack a group 2 gene, while rice has only two genes, one group 3 and one group 4. This means that TaASN2, the most highly expressed asparagine synthetase gene in wheat grain, has no equivalent in maize, rice, sorghum or brachypodium. An evolutionary pathway is proposed in which a series of gene duplications gave rise to the five genes found in modern Triticeae species.     

Taxonomic separation ofKengyilia (Poaceae: Triticeae) in relation to nearest relatedRoegneria,Elymus, andAgropyron,based on some morphological characters

Based on 100 species representative of the four genera, we scored 290 herbarium specimens for a number of morphological characters. The data were subjected to canonical discriminant analysis using characters different from those in the identification key to these genera byBaum, Yen, andYang (1991). These characters collectively support the four groupsAgropyron, Kengyilia, Roegneria, andElymus as previously defined. The four groups are also supported by the linear discriminant function with an overall rate of 83% correct classification. Length of lemma awn was found to be an additional diagnostic character asAgropyron andKengyilia have lemma awns shorter than 5 mm, whereasRoegneria andElymus have longer lemma awns with very few exceptions. Length of glume awns is also a useful supplementary generic diagnostic.Agropyron andElymus have glume awns, whereas the majority of species ofKengyilia and more than half of the species ofRoegneria lack them. If a glume awn is present it is usually not longer than 1 mm.