Comparative RFLP mapping of Hordeum vulgare and Triticum tauschii

Hordeum vulgare (barley) and Triticum tauschii are related, but sexually incompatible, species. This study was conducted to determine the extent of homology between the genomes of barley and T. tauschii using a common set of restriction fragment length polymorphism (RFLP) markers. Results showed that >95% of low-copy sequences are shared, but 42% of the conserved sequences showed copy-number differences. Sixty-three loci were mapped in T. tauschii using RFLP markers previously mapped in barley. A comparison of RFLP marker order showed that, in general, barley and T. tauschii have conserved linkage groups, with markers in the same linear orders. However, six of the seven linkage groups of T. tauschii contained markers which mapped to unrelated (i.e., non-homoeologous) barley chromosomes. Additionally, four of the T. tauschii linkage groups contained markers that were switched in order with respect to barley. All the chromosome segments differing between T. tauschii and barley contained markers that were detected by multi-copy probes. The results suggest that the observed differences between the T. tauschii and barley genomes were brought about by duplications or deletions of segments in one or both species. The implications of these findings for genetic mapping, breeding, and plant genome evolution are discussed.Published with the approval of the Director of the Colorado State University/Agricultural Experiment Station     

节节麦细胞不同分裂时期和阶段的G—带核型及其变动性分析

采用改良的ASG法获得了中期和3个染色体凝缩程度不同的早中期阶段（分别称为早中期Ⅰ、Ⅱ、Ⅲ）染色体的G-带,并进行了G-带核型和变动性分析。所分析的分裂时期和阶段,每条染色体的全长显示出了密切邻近的多重的带纹,带纹细窄、大小较相近,带间区小,带纹分布较密集而均匀。随着有丝分裂进程推进,染色体的带纹数目减少,早中期Ⅰ、Ⅱ、Ⅲ于中期单倍染色体组的G-带带纹总数分别减少41%、36%、28%,而染色体组的绝对长度分别缩短43%、37%、27%,带数减少幅度与染色体长度缩短的幅度几乎相等。早中期Ⅰ至早中期Ⅱ、Ⅲ和早中期Ⅱ至早中期Ⅲ的带纹减少幅度与染色体长度缩短幅度也基本一致。染色体组中各染色体之间带纹减少和染色体缩短的比例不尽相同,有一定的变幅。早中期Ⅰ、Ⅱ、Ⅲ和中期染色体组中每单位绝对长度的带数（带/μm）分别为2.19、2.22、2.32和2.29,差异不大。对节节麦G-带的特性等问题进行了讨论。     

Chromosomal location of isozyme and seed storage protein genes in Dasypyrum villosum (L.) Candargy

Summary The zymogram phenotypes of glucose-phosphate isomerase (GPI), alcohol dehydrogenase-1 (ADH-1), glutamate oxaloacetate transaminase (GOT), superoxide dismutase (SOD), lipoxygenase (LPX), esterase (EST) and the banding patterns of gliadin and glutenin seed storage proteins were determined for Triticum aestivum cv. Chinese Spring (CS), Dasypyrum villosum, the octoploid amphiploid T. aestivum cv. Chinese Spring D. villosum (CS × v) (2n=8x=56; AABBDDVV), and for five CS-D. villosum disomic addition lines. The genes Gpi-V1, Adh-V1, Got-V2, and Sod-V2 coding for GPI-1, ADH-1, GOT-2, and SOD-2 isozymes were located in D. villosum on chromosome 1V, 4V, 6V, and 7V, respectively. Genes coding for gliadin- and glutenin-like subunits are located in D. villosum chromosomes 1V. There are no direct evidence for chromosomal location of genes coding for GOT-3, EST-1 and LPX-2 isozymes. The linkage between genes coding for glutenin-like proteins and GPI-1 isozymes in chromosome 1V is evidence of homoeology between chromosome 1V and the chromosomes of homoeologous group 1 in wheat.Research supported by the National Research Council (Italy) and National Science Foundation (USA). International cooperative project, Grant No. 85.01504.06 (CNR)     

Phylogenetic relationships of Triticum tauschii,the D genome donor to hexaploid wheat

Summary Isoelectric focusing of seed esterase (Est-5) isozymes in 79 T. tauschii accessions from diverse sources revealed the presence of six different seed esterase phenotypes. In one of these phenotypes, exclusive to a var. meyeri accession (AUS 18989), no detectable enzymatic activity was observed. Segregation in crosses between T. tauschii (D^t) accessions confirmed three of the seed esterase phenotypes to be alleles of the designated Est-D ^t5 gene locus; the inheritance pattern of these isozymes was not affected by the subspecies differences between the parents. On the bases of variation in Est-5 and their Glu-1 and Gli-1 gene loci (in a previous study in this series), only three strangulata accessions showed consistent homology with their prevalent gene expression in the D genome of hexaploid wheat. The implications of these observations for further interpreting the phyletic nature of the D genome donor in natural hexaploid wheat synthesis are also reported.     

Use of winter wheat x Triticum tauschii backcross populations for germplasm evaluation

The wild diploid goatgrass, Triticum tauschii (Coss.) Schmal., is an important source of genes for resistance to both diseases and insects in common wheat (Triticum aestivum L.) We have evaluated grain yield, kernel weight, protein concentration, and kernel hardness of 641 BC₂ F₁-derived families from direct crosses involving four T. aestivum cultivars and 13 T. tauschii accessions over 2 years and at two Kansas, USA, locations. On average, T. tauschii germplasm depressed grain yield and increased protein concentration, whereas kernel weight was affected either positively or negatively, depending on the T. tauschii parent. Three T. tauschii parents produced a large proportion of families with very soft endosperm. Some variation among progeny of different T. tauschii parents resulted from the segregation of genes for resistance to leaf rust (caused by Puccinia recondita Rob. ex Desm.). This study confirmed that random BC₂-derived families can be used to evaluate the effects of T. tauschii genes in the field. This methodology, although laborious, can provide useful information which is not obtainable by the screening of T. tauschii accessions themselves.Joint contribution of USDA-ARS, the Kansas Agricultural Experiment Station, and the Wheat Genetics Resource Center. Contribution no. 94-242-J. Mention of a proprietary name in the article does not imply approval to the exclusion of other suitable products     

Seed set after pollination with in-vitro-matured,isolated pollen of Triticum aestivum

Summary Immature pollen of two varieties of Triticum aestivum, at the stage right after the first pollen mitosis, was isolated from individual anthers and cultured in microcultures of microliter droplets. In a specifically designed medium, some of the pollen grains developed to maturity. These were applied to excised stigmas on agar, where they produced pollen tubes. Application to flowers in vivo led to seed set. Pollen was matured in vitro from a variety that produced a different protein banding pattern on SDS-PAGE as compared to the variety that was pollinated. The protein banding in the produced seeds showed the hybrid pattern, demonstrating that the seeds were not produced by self-pollination in this in-breeding species but by pollination with the in-vitro-matured pollen.     

Cloning and molecular characterization of a novel x-type glutenin gene Glu-D(t)1 from Aegilops tauschii

A novel gene encoding an x-type high molecular weight glutenin subunit (HMW-GS), designated 1Dx1.1 ^t , was isolated from Aegilops tauschii. It is the largest HMW-GS gene reported so far in this species and its product has a slower mobility than that of subunit 1Ax1 in SDS-PAGE. The open reading frame (ORF) of the gene was 2,628 bp, encoding a protein of 874 amino acid residues. Comparisons of amino acid sequences showed that subunit 1Dx1.1^t had high similarity with other 1Dx subunits but also had two unique characteristics. Firstly, a tripeptide of consensus LQE present in the N-terminal domains of other 1Dx subunits was absent from subunit Dx1.1^t. Secondly, three copies of tandem duplications of the tripeptide motif GQQ and a novel tripeptide sequence (GQL) were present in its central repetitive domain. Phylogenetic analysis showed that subunit 1Dx1.1^t clustered with other known 1Dx subunits.     

D genome doners for Aegilops cylindrica (CCDD) and Triticum aestivum (AABBDD) deduced from esterase isozyme analysis

Summary Putative D genome donors for Aegilops cylindrica (2n = 28, CCDD) and Triticum aestivum (2n = 42, AABBDD) were studied with the isoelectric focusing patterns of esterase isozymes. 103 strains of Ae. cylindrica were uniform in their isozyme pattern. 30 strains of the putative parent, Ae. caudata, showed no zymogram variation, whereas the other parent, Ae. squarrosa, comprised 3 phenotypes. Natural Ae. cylindrica had an isozyme pattern which corresponded to a mixture of esterases from Ae. caudata and type 3 Ae. squarrosa. Therefore, it is concluded that the D genome donor of Ae. cylindrica is derived from type 3 Ae. squarrosa. These results suggest that Ae. cylindrica originated with a single amphiploidy event, and the C and D genomes have remained remarkably constant regarding esterase isozyme composition.On the other hand, T. aestivum comprised three zymogram phenotypes. These phenotypes contain bands which can be ascribed to the D genome of type 2 Ae. squarrosa. These results suggest that the D genome of Ae. cylindrica differs from that of T. aestivum. Evolution of the AB and D genomes of T. aestivum is indicated by the zymogram polymorphism. The origin of Ae. cylindrica is possibly more recent than that of T. aestivum.Contribution No. 433 of the Laboratory of Genetics, Faculty of Agriculture, Kyoto University     

Cytogenetic identification of Aegilops squarrosa chromosome additions in durum wheat

Summary A set of four normal chromosomes (1D, 2D, 3D, and 6D), and three translocation chromosomes (4DS·5DS, 5DL·7DS, and 7DL·4DL) involving all 14 chromosome arms of the D-genome were obtained as monosomic additions from Aegilops squarrosa (genome D, n=7) in Triticum durum Desf. cv PBW114 (genome AB, n=14). The cyclical translocation occurred during the synthesis of the amphiploid probably as a result of misdivision and reunion of the univalents during meiosis of the F₁ hybrid T. durum x A. Squarrosa. The amphiploid was backcrossed twice with the durum parent to obtain monosomic addition lines. The monosomic addition chromosomes were identified by C-banding and associated phenotypic traits. All monosomic addition lines were fertile. The development of disomic and ditelosomic addition lines is underway, which will be useful for cytogenetic analysis of individual D-genome chromosomes in the background of T. Durum.Contribution No. 90-117-J from the Wheat Genetics Resource Center and Kansas Agricultural Experiment Station, Kansas State University, Manhattan     

Resistance to Meloidogyne spp. in Allohexaploid Wheat Derived from Triticum turgidum and Aegilops squarrosa

Expression of resistance to Meloidogyne incognita and M. javanica from Aegilops squarrosa was studied in a synthetic allohexaploid produced from Triticum turgidum var. durum cv. Produra and Ae. squarrosa G 3489. The reproductive rate of different races of M. incognita and M. javanica, expressed in eggs per gram of fresh root, was low (P < 0.05) on the synthetic allohexaploid and the resistant parent, Ae. squarrosa G 3489, compared with different bread and durum wheat cultivars. Reproduction of race 2 and race 3 of M. incognita and an isolate of M. javanica was studied on the synthetic allohexaploid and seven cultivars of T. aestivum: Anza, Coker 747, Coker 68-15, Delta Queen, Double Crop, McNair 1813, and Southern Bell. The latter six cultivars are grown in the southeastern United States and reportedly were resistant to M. incognita. Significant differences (P < 0.05) were detected in nematode reproduction on the seven bread wheat cultivars. Reproduction of M. incognita race 3 and M. javanica was highest on Anza. Reproductive rates on the six southeastern United States bread wheat cultivars varied both within and among nematode isolates. The lowest reproductive rates of the three root-knot isolates were detected in the synthetic allohexaploid.     

Consistency of population genetics parameters estimated from isozyme and RAPDs dataset in species of genus <Emphasis Type="Italic">Prosopis</Emphasis> (Leguminosae,Mimosoideae)

Genetic variability, population structure and differentiation among 17 populations of 5 species and 2 natural interspecific hybrids of section Algarobia of genus Prosopis were analyzed from data of 23 isozyme and 28 RAPD loci. Both markers indicated that the studied populations are highly variable. P. alba populations in average showed lower values of genetic variability estimates from isozyme data, but this trend was not observed for RAPD markers. The hierarchical analyses of the distribution of genetic variability showed that the highest proportion of variation occurred within populations, the differentiation among species was intermediate and the lowest component was observed among populations within species. The consistency between results from both dataset implies that they are not biased and reflect the actual genetic structure of the populations analyzed. The matrices of Euclidean distances obtained from the two sets of markers were highly correlated according to Mantel test. In both cases the corresponding phenogram and MDS plot tended to cluster conspecific populations while hybrid populations were not intermediate between putative parents. Some disagreements between isozyme and RAPD phenograms were observed mainly in the affinities of hybrid populations. Such inconsistencies might result from reticular rather than dichotomic evolutionary relationships. The phenetic associations retrieved gave no support to the division of the section Algarobia into series.     

Catalogue of alleles of gliadin-coding loci in durum wheat (Triticum durum Desf.)

Gliadins are seed storage proteins which are characterized by high intervarietal polymorphism and can be used as genetic markers. As a result of our work, a considerably extended catalogue of allelic variants of gliadin component blocks was compiled for durum wheat; 74 allelic variants for four gliadin-coding loci were identified for the first time. The extended catalogue includes a total of 131 allelic variants: 16 for locus Gli-A1(d), 19 for locus Gli-B1(d), 41 for locus Gli-A2(d), and 55 for locus Gli-B2(d). The electrophoretic pattern of the standard cultivar and a diagram are provided for every block identified. The number of alleles per family is quite small for loci Gli-A1(d) and Gli-B1(d) of durum wheat, as contrasted to loci Gli-A2(d) and Gli-B2(d) that are characterized by large families including many alleles. The presence of large block families determines a higher diversity of durum wheat for loci Gli-A2(d) and Gli-B2(d) as compared to Gli-A1(d) and Gli-B1(d). The catalogue of allelic variants of gliadin component blocks can be used by seed farmers to identify durum wheat cultivars and evaluate their purity; by breeders, to obtain homogenous cultivars and control the initial stages of selection; by gene bank experts, to preserve native varieties and the original biotypic composition of cultivars.     

Extent of genetic variability of endosperm esterases in Triticum aestivum L. 2n=6x=42

Summary Genetic variability of endosperm esterase has been studied in 42 cultivars of Triticum aestivum L. 2n=6x=42. Different techniques, including sequential electrophoresis and electrofocusing, have been used with various substrates and esterase inhibitors. The electrophoretic patterns in each cultivar are described. Chromosomal location using the nullitetrasomic and ditelosomic lines of Chinese Spring was carried out in order to relate and/or locate the esterase genes to specific chromosomes. Most of the esterase isozymes located were in the long arm of the chromosomes of the homoeology group 3; but we have found six located in the short arms, five of them in the chromosome 3AS and one in the 3DS. This location increases the number of esterase genes described, because no esterase genes had been described so far in short arms of chromosomes of the homoeology group 3. The genetic control is discussed and, according to our results, between 12 and 15 loci, organized in five compound loci, control the endosperm esterases in wheat. Also one modifier gene modifying the mobility of two esterase bands and present in all the cultivars studied is postulated.This work was supported by a personal grant (L. Rebordinos) from the P.F.P.I. and by an institutional grant from the C.A.I.C.Y.T. (PB85-0153)     

Phylogenetic relationships of Triticum tauschii the D genome donor to hexaploid wheat

Summary In crosses between T. tauschii (D ^t) accesions, their polymorphic gliadin forms were inherited as blocks of gliadin components -Gli-D ^t1, Gli-D ^t2 — as single Mendelian characters. From the progeny of four tri-parental crosses (test-crosses), HMW glutenin subunits derived from T. tauschii (Glu-D ^t1) segregated as alleles of the Glu-D1 locus in bread wheat. In three of the tri-parental crosses, a small proportion (2.5%) of the progeny with atypical segregation patterns, were identified through somatic chromosome counts, to be aneuploids (1.9% hypoploids and 0.6% hyperploids). Chromosomal mapping studies revealed that the synteny of genes for HMW glutenin subunits and gliadins in T. tauschii are conserved in the D genome homologue (chromosome 1D) of T. aestivum. The map distance between the Glu-D1/-D ^t1 and Gli-D1/-D ^t1 loci was calculated to be 63.5 cM, while a linkage to the centromere of 7.7–9.7 cM was estimated for the Glu-D1/-D ^t1 locus.     

Control of lectins in Triticum aestivum and Aegilops umbellulata by homoeologous group 1 chromosomes

Summary Each of the three genomes in hexaploid wheat controls the expression of a specific lectin in the embryo. The chromosomes which control their synthesis were determined using nullisomic-tetrasomic and inter-varietal chromosome substitution lines of Chinese Spring. All three wheat lectins were shown to be controlled by the homoeologous group 1 chromosomes. Using ditelosomic lines of Chinese Spring the lectin genes could be localized on the long arms of chromosomes 1A and 1D. Inter-specific addition and substitution lines of Aegilops umbellulata chromosomes to Chinese Spring indicated that chromosome 1U, which is homoeologous to the group 1 chromosomes of wheat, controls lectin synthesis.     

RELP markers linked to two Hessian fly-resistance genes in wheat (Triticum aestivum L.) from Triticum tauschii (coss.) Schmal

Summary Restriction fragment length polymorphism (RFLP) markers linked to genes controlling Hessian fly resistance from Triticum tauschii (Coss.) Schmal. were identified for two wheat (Triticum aestivum L.) germ plasm lines KS89WGRC3 (C3) and KS89WGRC6 (C6). Forty-six clones with loci on chromosomes of homoeologous group 3 and 28 clones on those of group 6 were surveyed for polymorphisms. Eleven and 12 clones detected T. tauschii loci in the two lines, respectively. Analysis of F₂ progenies indicated that the Hessian fly resistance gene H23 identified in C3 is linked to XksuH4 (6.9 cM) and XksuG48 (A) (15.6 cM), located on 6D. The resistance gene H24 in C6 is linked to XcnlBCD451 (5.9 cM), XcnlCD0482 (5.9 cM) and XksuG48 (B) (12.9 cM), located on 3DL.Paper No. 810 of the Cornell Plant Breeding Series     

Relationships among tetraploid wheat (Triticum turgidum L.) landrace populations revealed by isozyme markers and agronomic traits

Diversity and relationships among ten tetraploid wheat landrace populations, collected from different localities in the central highlands of Ethiopia, were studied using isozyme markers and agronomic traits. This type of analysis in crop species is fundamental for designing optimal germ plasm collection, management practices and for developing an index for parental selection. The populations differed in allelic frequencies. Gene-diversity estimates showed that the populations encompass an appreciable amount of variation. However, differentiation between them was low, as was also confirmed by the presence of gene flow. Much of the diversity (85%), was attributable to the within-population level. The genetic distances were mostly small with the exception of those between a few pairs of populations. Thus, the relationships discerned among the populations were more of a similarity nature which could be ascribed to sharing a common ancestral population and/or adaptation to similar climatic conditions. The pattern of genetic divergence appeared to be independent of geographic distance. Considerable divergence in the agronomic traits was observed for certain populations. Cluster analyses of the isozyme and agronomic data produced different patterns and memberships of groupings. This lack of agreement could be ascribed to the different forces of evolution acting on isozyme markers and agronomic traits since agronomic traits, are the prime target of artificial selection. The clustering based on agronomic traits resulted in grouping together populations with similar agronomic performance. The results of this study suggest that taking more samples within a locality or population would be a better approach to capture the range of variation in the landrace populations of the central highlands of Ethiopia.     

Lack of detectable isozyme variability in British populations of Potamogeton epihydrus (Potamogetonaceae)

Outside North America Potamogeton epihydrus Raf. is confined to two areas of Britain. An investigation of British material from apparently native sites in the Outer Hebrides and from a canal in northern England (where it is believed to be introduced) revealed only a single isozyme genotype. Ten putative loci were resolved. The IDH phenotype was uniform and three-banded, consistent with heterozygosity (possibly caused by a duplicated locus or preserved by clonal growth). All other enzyme loci were homozygous.     

Grain protein variability among species of Triticum and Aegilops: quantitative SDS-PAGE studies

Summary Total proteins were extracted from degermed seeds of various species of Triticum and Aegilops with solutions containing sodium dodecyl sulfate (SDS) and mercaptoethanol. The reduced, dissociated proteins were fractionated according to molecular weight (MW) by high-resolution polyacrylamide gel electrophoresis in buffers containing SDS (SDS-PAGE). Stained SDS-PAGE patterns were measured by densitometric scanning over a suitable range of optical density. The data were normalized to equivalent total areas for each of the densitometric scans by means of a computer program that also permitted the construction of patterns of hypothetical amphiploids by averaging patterns of two or three diploid species. The grain proteins of most species examined had distinctive qualitative and quantitative aspects that were characteristic of the species even though nearly every accession or cultivar of a species exhibited at least minor differences in pattern from other accessions or cultivars. The main protein components (probably prolamins) of Triticum monococcum ssp. monococcum, T. monococcum ssp. boeoticum, T. urartu, and Aegilops squarrosa had MW's in the range 29–36 X 10³ whereas the most important components of Ae. speltoides, Ae. longissima, and Ae. searsii had MW's in the range 37–55 × 10³. Changes in the quantitative expression of particular genes, especially those coding for storage protein components, may have been associated with speciation. The strong predominance of proteins with MW's in the range 29–36 × 10³ in some accessions of AB genome tetraploids, such as T. turgidum ssp. dicoccoides, may indicate contributions to the B genome of these tetraploids by T. monococcum ssp. boeoticum, T. urartu, or Ae. squarrosa.     

Variation at isozyme loci in wildVigna unguiculata (Fabaceae,Phaseoleae)

An electrophoretic comparison of variation at 37 presumptive isozyme gene loci was performed for 55 wildVigna unguiculata accessions. The analysis included seven subspecies, covering the whole range of variation available in wildVigna unguiculata. The results of the isoenzymatic study broadly confirmed the previous infraspecific classification inferred from morphological data. Although the southern taxa (e.g., subsp.tenuis, subsp.stenophylla) are as yet too poorly sampled to discuss in depth, wildVigna unguiculata can be divided into one mainly autogamous annual group (including subsp.pubescens and var.spontanea) and several widely divergent perennial subspecies.