Chromosome banding in Triticum aestivum cv. chinese spring and Aegilops variabilis

N-banding has been used to identify each of the fourteen chromosomes of Aegilops variabilis Eig. These patterns differ from the patterns of the nine wheat chromosomes that band with this technique. The banding pattern of Aegilops variabilis chromosome G was the same when examined in the parent species and in the wheat-variabilis addition line. — Banding analysis can be reliably carried out on both mitotic and meiotic chromosomes of wheat. Nine pairs of wheat chromosomes can be identified at meiosis.     

Identification of cytokinins in young wheat spikes (Triticum aestivum cv. Chinese spring)

Cytokinins in young wheat (Triticum aestivum cv. Chinese spring) spikes (2–15 mm) were isolated by immunoaffinity chromatography. High-performance liquid chromatography-radioimmunoassay and gas chromatography-mass spectrometry indicated that major cytokinins present weretrans-zeatin, ribosyl-trans-zeatin, ribosyldihydrozeatintrans-zeatin-9-glucoside, and the glucosides oftrans-zeatin, ribosyl-trans-zeatin, andtrans-zeatin-9-glucoside. Dihydrozeatin,iso-pentenyladenosine, andiso-pentenyladenine were also present but at lower concentrations.Mention of a trade name, proprietary product, or specific equipment does not constitute a guarantee or warranty by the U.S. Department of Agriculture and does not imply approval to the exclusion of other products that may also be suitable. R. C. Durley's present address is Biological Sciences, Monsanto Company, St. Louis, Missouri 63167.     

中国春双端二体中端体的配对研究

21个中国春双端二体与中国春品种杂交,观察了杂种F_1减数分裂中期Ⅰ端体与相应染色体的配对。结果表明:14个组合的中期Ⅰ具有1个异形三价体的PMC的百分数超过90%;有3个组合(6A、5B和6D)分别为89.87%、83.56%和85.71%;2个组合(4A和1B)低于80%。在4A、1B和5B的3个组合中,具有1个异形二价体和1个单价端体的PMC超过15%。在4A、1B和4D的组合中,还有一定频率的PMC具有2个单价端体。用21个组合中端体配对频率计算的二价体频率与中国春品种中期Ⅰ构型频率基本一致。这些结果表明,染色体臂作为端体时和它作为双臂染色体的一部分时,是以同样的方便程度配对的。     

137Cs uptake in spring wheat (Triticum aestivum L.cv. Tonic) at varying K supply

Spring wheat (Triticum aestivum L. cv. Tonic) was grown for 16 days in a sandy loam soil which was contaminated with ¹³⁷Cs. The soil was fertilised with K at three rates (0,1 and 2 mmol K per 950 g dry soil) and with NO₃ ^--N at two rates (0 and 2 mmol per 950 g dry soil) in a factorial design. The ¹³⁷Cs Activity Concentration (AC) in the shoot tissue significantly reduced 8.2-fold (nil N treatment, p<0.001) and 9.3-fold (highest N dose, p<0.001) with increasing K supply. In contrast, the K application increased the ¹³⁷Cs AC in soil solution 1.7 fold (nil N treatment) or had no significant effect (highest N dose). At similar K application, the application of N increased the ¹³⁷Cs AC in the shoot compared to the control. This effect is most probably due to the increased NH₄ ⁺ concentration in soil solution which increased the ¹³⁷Cs AC in soil solution. The soil solution composition (¹³⁷Cs and K concentration) in the rhizosphere was estimated from the average soil solution composition at day 16 and solute transport calculations. The ¹³⁷Cs AC in the shoot tissue was predicted from the estimated soil solution composition in the rhizosphere and the relationship between K concentration and ¹³⁷Cs uptake derived from a nutrient solution experiment. The predictions of ¹³⁷Cs AC's in the shoot are qualitatively correct for the fertiliser effects but underestimate the observations between 1.4 and 9.9 fold.     

Plant regeneration from protoplasts of Triticum aestivum L. cv. Nakasoushu

A fast-growing, small, granular, embryogenic callus was selected from primary calli induced from the Japanese wheat cultivar Nakasoushu and the Australian wheat cultivar Bodallin. Regenerable and fine suspension cultures were induced three to six months after liquid culture was initiated and were characterized by dense cytoplasm and active division. These suspension cultures routinely provided high yields of protoplasts with about 90% viability when incubated in a modified KMP (Kao and Michayluk, 1975) medium containing 1 mg l^-1 2,4-D (2,4-dichlorophenoxyacetic acid), and 1 mg l^-1 zeatin. Nakasoushu and Bodallin protoplasts divided at frequencies of 8.6% and 11.1%, respectively, in agarose-solidified media. When Nakasoushu protoplasts were cultured with effective nurse cells of sorghum and wheat, protoplast division increased to 16.9% and 12.6%, respectively. Plating efficiencies varied from 0.03% to 2.5%. After subculture, protocolonies yielded embryogenic calli and somatic embryos, from which green plants were eventually regenerated. Whole plants obtained from Nakasoushu protoplasts were fertile, demonstrating the first report of Japanese cultivars in wheat protoplast cultures. This revised version was published online in June 2006 with corrections to the Cover Date.     

Chinese spring wheat (Triticum aestivum L.) chloroplast genome: Complete sequence and contig clones

Libraries of plasmid clones covering the entire chloroplast (cp) genome of the common wheat,Triticum aestivum cv. Chinese Spring were constructed and assembled into contig-clones. From these, we obtained the complete nucleotide sequence of wheat chloroplast DNA—a 134,540 bp circular DNA (DDBJ accession no. AB042240) containing four species of ribosomal RNA, 30 genes for 20 species of transfer RNA, and 71 protein coding genes. Additionally, we detected five unidentified open reading frames conserved among grasses. Plasmid clones are available on request.     

Optical maps refine the bread wheat Triticum aestivum cv. Chinese Spring genome assembly

Until recently, achieving a reference-quality genome sequence for bread wheat was long thought beyond the limits of genome sequencing and assembly technology, primarily due to the large genome size and > 80% repetitive sequence content. The release of the chromosome scale 14.5-Gb IWGSC RefSeq v1.0 genome sequence of bread wheat cv. Chinese Spring (CS) was, therefore, a milestone. Here, we used a direct label and stain (DLS) optical map of the CS genome together with a prior nick, label, repair and stain (NLRS) optical map, and sequence contigs assembled with Pacific Biosciences long reads, to refine the v1.0 assembly. Inconsistencies between the sequence and maps were reconciled and gaps were closed. Gap filling and anchoring of 279 unplaced scaffolds increased the total length of pseudomolecules by 168 Mb (excluding Ns). Positions and orientations were corrected for 233 and 354 scaffolds, respectively, representing 10% of the genome sequence. The accuracy of the remaining 90% of the assembly was validated. As a result of the increased contiguity, the numbers of transposable elements (TEs) and intact TEs have increased in IWGSC RefSeq v2.1 compared with v1.0. In total, 98% of the gene models identified in v1.0 were mapped onto this new assembly through development of a dedicated approach implemented in the MAGAAT pipeline. The numbers of high-confidence genes on pseudomolecules have increased from 105 319 to 105 534. The reconciled assembly enhances the utility of the sequence for genetic mapping, comparative genomics, gene annotation and isolation, and more general studies on the biology of wheat.     

Isolation and identification of Triticum aestivum L. em. Thell. cv Chinese Spring-T. peregrinum Hackel disomic chromosome addition lines

Analyses of RFLPs, isozymes, morphological markers and chromosome pairing were used to isolate 12 Triticum aestivum cv Chinese Spring (genomes A, B, and D)-T. peregrinum (genomes S^v and U^v) disomic chromosome addition lines. The evidence obtained indicates that each of the 12 lines contains an intact pair of T. peregrinum chromosomes. One monosomic addition line, believed to contain an intact 6S^v chromosome, was also isolated. A CS-7U^v chromosome addition line was not obtained. Syntenic relationships in common with the standard Triticeae arrangement were found for five of the seven S^v genome chromosomes. The exceptions were 4S^v and 7S^v. A reciprocal translocation exists between 4S¹ and 7S¹ in T. longissimum and evidence was obtained that the same translocation exists in T. peregrinum. In contrast, evidence for syntenic relationships in common with the standard Triticeae arrangements were found for only one U^v chromosome of T. peregrinum.; namely, chromosome 2U^v. All other U^v genome chromosomes are involved in at least one translocation, and the same translocations were found in the U genome of T. umbellulatum. Evidence was also obtained indicating that the centromeric regions of 4U and 4U^v are homoeologous to the centromeric regions of Triticeae homoeologous group-6 chromosomes, that the centromeric regions of 6U and 6U^v are homoeologous to the centromeric regions of group-4 chromosomes, and that 4U and 4U^v are more closely related overall to Triticeae homoeologous group-6 chromosomes than they are to group-4 chromosomes.     

Molecular and biochemical characterization of cytosolic phosphoglucomutase in wheat endosperm (Triticum aestivum L. cv. Axona)

Evidence from a number of plant tissues suggests that phosphoglucomutase (PGM) is present in both the cytosol and the plastid. The cytosolic and plastidic isoforms of PGM have been partially purified from wheat endosperm (Triticum aestivum L. cv. Axona). Both isoforms required glucose 1,6-bisphosphate for their activity with K(a) values of 4.5 micro M and 3.8 micro M for cytosolic and plastidic isoforms, respectively, and followed normal Michaelis-Menten kinetics with glucose 1-phosphate as the substrate with K(m) values of 0.1 mM and 0.12 mM for the cytosolic and plastidic isoforms, respectively. A cDNA clone was isolated from wheat endosperm that encodes the cytosolic isoform of PGM. The deduced amino acid sequence shows significant homology to PGMs from eukaryotic and prokaryotic sources. PGM activity was measured in whole cell extracts and in amyloplasts isolated during the development of wheat endosperm. Results indicate an approximate 80% reduction in measurable activity of plastidial and cytosolic PGM between 8 d and 30 d post-anthesis. Northern analysis showed a reduction in cytosolic PGM mRNA accumulation during the same period of development. The implications of the changes in PGM activity during the synthesis of starch in developing endosperm are discussed.     

cDNA encoding a wheat (Triticum aestivum cv. Chinese Spring) glycine-rich RNA-binding protein

A wheat cDNA encoding a glycine-rich RNA-binding protein, whGRP-1, was isolated. WhGRP-1 contains two conserved domains, the RNA-binding motif (RNP motif) combined with a series of glycine-rich imperfect repeats, characteristic of a conserved family of plant RNA-binding proteins. Northern analysis revealed that whGRP-1 mRNA accumulates to high levels in roots and to lower levels in leaves of wheat seedlings. whGRP-1 mRNA accumulation is not enhanced by exogenous abscisic acid in seedlings and accumulates to very high levels during wheat embryo development, showing a pattern different from that of the ABA-inducible wheat Em gene.     

Cytological and anatomical observations on the awn and lemma of wheat (Triticum aestivum L. cv. Ofanto)

Abstract

The anatomy and cytology of the awn and lemma of Triticum aestivum cv. Ofanto was studied. Transverse sections of awns showed five vascular bundles, elongated and branched chlorenchyma cells containing protein bodies are lacking in starch; therefore sugars are supposed rapidly translocated. Starch is abundant in the spike. Phytoliths are present.     

Production of near-isogenic lines and marked monosomic lines in common wheat (Triticum aestivum) cv. Chinese Spring.

Sixteen near-isogenic lines (NILs) carrying a marker gene were produced by the recurrent backcrossing method in the genetic background of common wheat (Triticum aestivum) cv. Chinese Spring (CS). Three genes from alien species showed segregation distortion. In NILs carrying a marker gene of rye (Secale cereale) or Aegilops caudata, the alien chromosome segments were detected by fluorescence in situ hybridization (FISH). The NILs were grown with replications and the effect of marker genes on plant morphology in the genetic background of CS was investigated. These NILs were further crossed with the corresponding monosomics of CS and 13 monosomic lines whose monosome carries a respective marker gene were established and named "marked monosomics." Many of the marked monosomics were distinguishable from the disomic NILs because of the different dosage effect of the genes. The NILs are utilized for studies on gene isolation or gene regulation. Marked monosomics are useful not only for monosomic analysis but also for production of homologous chromosome substitution lines because chromosome observation is not required.     

Molecular cloning and characterization of an up-regulated UDP-glucosyltransferase gene induced by DON from Triticum aestivum L. cv. Wangshuibai

Fusarium head blight, also called scab, is a serious disease of small grain cereals and maize. Scab can not only cause yield loss, more seriously is that it can also deteriorate seed quality by contaminating the infected grains with trichothecenes toxins harmful to human and animal health. Deoxynivalenol (DON) is one of the most important toxin members. It was proposed that DON acted first as a virulence factor during fungal pathogenesis and then accumulated in grain to levels posing a threat to human and animal health. In the present research, by expression analysis of DON-induced samples using GeneChip^® Wheat Genome Array (http://www.affymetrix.com/products/arrays/specific/wheat.affx), a DON-resistance related gene TaUGT3 (GenBank accession FJ236328) was cloned and characterized from a scab resistant wheat (Triticum aestivum L.) variety Wangshuibai. The full-length cDNA of TaUGT3 was 1,755 bp and contained a putative open reading frame (ORF) with 496 amino acids encoding a UDP-glucosyltransferase (UGT). TaUGT3 showed high similarity in amino acid level with DOGT1 gene in Arabidopsis, which is able to detoxify DON. TaUGT3 was located on the group 3 chromosomes of wheat using nulli-tetrasomic lines and deletion lines of Chinese Spring. Co-transformed of TaUGT3 with GFP genes to onion epidermis cells using transient transformation technique by microprojectile bombardment indicated the subcellular location of the protein encoded by TaUGT3 was in the plasma membrane and nuclear. Transformation and overexpression of the TaUGT3 gene in Arabidopsis could enhance tolerance against DON.     

Effect of population structure on protein-yield improvements in spring wheat (Triticum aestivum L. em Thell)

Summary In a study designed to develop a more efficient breeding method for concurrent protein-yield improvements in wheat (Triticum aestivum L. em. Thell), 7 base populations [2 F₂'s, 1 intermated F₂ (IF₂) and 4 partial backcross (PBC) populations] developed from biparental crosses involving 2 Canadian hard red spring (CHRS) and 2 Canadian utility (CU) wheat cultivars were evaluated in Winnipeg, Manitoba, Canada. The IF₂ and PBC populations were generated for comparison with conventional F₂ populations and to determine which of the 4 methods of population development would provide a more efficient means of producing potentially superior genetic recombinants. Parameters pertaining to means, variances, correlations, heritabilities and frequencies of desirable and undesirable progenies were used to evaluate the limitations to genetic gain that may be expected from selection for GY and GPC in F₂, IF₂, CHRS-PBC and CU-PBC populations. Analysis of protein and yield data from 105 S₁ lines derived from each of the 7 populations showed the CU-PBC's to have the highest grain yield (GY) and the lowest grain protein concentration (GPC) means; and the CHRS-PBC's, the lowest GY and the highest GPC means. The F₂ and IF₂ populations were intermediate for both characteristics. Populations developed from the same biparental cross did not differ significantly with respect to the majority of genetic parameters. However, desirable progenies combining high GY with high GPC were more frequent in the CU-PBC, and least frequent in the CHRS-PBC populations. The observed superiority of the CU-PBC populations appeared to be related to the advantage the system has in preserving the genetic integrity of a proven cultivar, while adding desirable genetic factors from another cultivar, thus capitalizing on introgression and upgrading simultaneously.Contribution No. 549 from Agriculture Canada, Lacombe Research Station. Research was supported by a grant from the Natural Sciences and Engineering Research Council of Canada     

Hybridization between Triticum aestivum L. and Agropyron michnoi Roshev.

Summary Intergeneric hybrids between Triticum aestivum cv Chinese Spring (2n=6x=42, AABBDD) and Agropyron michnoi Roshev. (2n=4x=28, PPPP) were obtained by embryo culture. Their spike characteristics were similar to those of common wheat but, unlike their parents, they were long-awned. The average meiotic chromosome pairing at MI of F₁ hybrids was: 6.39 I +3.75 rodII+8.64 ringII+0.81 III+0.30 IV+0.04 V, the bivalent and multivalent formation of which was much higher than expected from the genomic formulae. It is especially worthwhile to note that the F₁ hybrids were self-fertile, self set being 0.15%, and seeds were easily obtained from the backcross of f₁ plants with hexaploid and tetraploid wheats; here the seed set was more than 20.0%. The polyploid taxa and the position of A. Michnoi in Agropyron are discussed.     

Aqueous silicate complexes in wheat, Triticum aestivum L.

The chemical speciation of silicon in xylem exudate from wheat (Triticum aestivum L.) was examined by ²⁹Si NMR spectroscopy. Wheat plants were grown to maturity in silicon‐free nutrient medium, and then transferred to a solution containing 0.02 mm ²⁹Si‐enriched silicic acid. After 30 min the shoots were excised and xylem exudate was collected. Within 10 min the Si concentration of the xylem exudate reached values greatly in excess of that of the starting nutrient solution, eventually reaching levels as high as 8 mm . Silicon‐29 nuclear magnetic resonance spectra indicated the existence of only two Si‐containing species in the xylem exudate, mono and disilicic acid (H₄SiO₄^o and (HO)₃Si(µ‐O)Si(OH)₃^o) in a ratio of approximately 7 : 1. Significantly, there was no evidence of organosilicate complexes. Nevertheless, the efficiency by which the plant concentrates aqueous silicon indicates active mechanisms of silicon transport across root cell membranes.