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PubMed1998

Effect of the pairing gene Ph1 and premeiotic colchicine treatment on intra- and interchromosome pairing of isochromosomes in common wheat.

The analysis of the pattern of isochromosome pairing allows one to distinguish factors affecting presynaptic alignment of homologous chromosomes from those affecting synapsis and crossing-over. Because the two homologous arms in an isochromosome are invariably associated by a common centromere, the suppression of pairing between these arms (intrachromosome pairing) would indicate that synaptic or postsynaptic events were impaired. In contrast, the suppression of pairing between an isochromosome and its homologous chromosome (interchromosome pairing), without affecting intrachromosome pairing, would suggest that homologous presynaptic alignment was impaired. We used such an isochromosome system to determine which of the processes associated with chromosome pairing was affected by the Ph1 gene of common wheat-the main gene that restricts pairing to homologues. Ph1 reduced the frequency of interchromosome pairing without affecting intrachromosome pairing. In contrast, intrachromosome pairing was strongly reduced in the absence of the synaptic gene Syn-B1. Premeiotic colchicine treatment, which drastically decreased pairing of conventional chromosomes, reduced interchromosome but not intrachromosome pairing. The results support the hypothesis that premeiotic alignment is a necessary stage for the regularity of meiotic pairing and that Ph1 relaxes this alignment. We suggest that Ph1 acts on premeiotic alignment of homologues and homeologues as a means of ensuring diploid-like meiotic behavior in polyploid wheat.

Base Pairing↗
PubMed2026

Comparative Genome-Wide Association Studies of Metabolites and Grain-Related Traits in Common Wheat.

The metabolome is highly diverse and the closest layer to phenotype; therefore, it is commonly regarded as a bridge between the genome and phenome in plants. Here, we performed large-scale metabolome analysis using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and 33 grain-related traits in a diverse panel of natural accessions and a recombinant inbred line (RIL) population. We identified a new network of 2286 associations between 947 metabolites and 33 grain-related traits. Systematic integration of metabolic genome-wide association study (mGWAS) and metabolic quantitative trait locus (mQTL) analyses identified 33 566 significant single-nucleotide polymorphisms (SNPs) and 3128 mQTL. Thirteen annotated metabolites co-localized within a physical interval on 7A. Integration of metabolite-based and phenotype-based GWAS and QTL revealed an overlapped region for gibberellin A4 (GA4) content and grain roundness on 4A. Phenotyping of an ethyl methanesulfonate (EMS)-induced mutant confirmed the role of TaSDR in regulating GA4 content and grain morphology. These findings provide novel insights into the metabolic pathways influencing key grain-related traits and advance our understanding of the complex molecular mechanisms regulating grain metabolites and phenotypes in wheat. The identified metabolic markers and candidate genes provide valuable targets for molecular breeding programs aimed at improving wheat yield and quality.

QTL↗
PubMed2003

Powdery mildew resistance gene Pm22 in cultivar Virest is a member of the complex Pm1 locus in common wheat ( Triticum aestivum L. em Thell.).

The powdery mildew resistance gene Pm22, identified in the Italian wheat cultivar Virest and originally assigned to wheat chromosome 1D, was mapped to chromosome 7A with the aid of molecular markers. Mapping of common AFLP and SSR markers in two wheat crosses segregating for Pm22 and Pm1c, respectively, indicated that Pm22 is a member of the complex Pm1 locus. Pm22 also showed a pattern of resistance reaction to a differential set of Blumeria graminis f. sp. tritici isolates that was distinguishable from those from other Pm1 alleles in lines Axminster/8*Cc ( Pm1a), MocZlatka ( Pm1b), Weihenstephan Stamm M1N ( Pm1c) and Triticum spelta var. duhamelianum TRI 2258 ( Pm1d). Based on these results, the gene symbol Pm1e is proposed for the powdery mildew resistance gene in cv. Virest.

Chromosome Mapping↗
PubMed1991

Two-dimensional electrophoresis of 1D-encoded B and D glutenin subunits in common wheats with similar omega gliadins.

Gli-D1-encoded omega gliadins of bread wheats show little variation; their electrophoretic patterns can be classified into two main groups which broadly resemble the patterns found in the cultivars Chinese Spring and in Cheyenne. B and D subunits of low molecular weight glutenin encoded by the chromosome 1D loci Glu-D3 and Gli-D1, respectively, also showed little variation. D subunits were found only in bread wheats with "Chinese Spring-type" omega gliadins and they all exhibited the same electrophoretic pattern. This material also showed very similar B subunits. "Cheyenne-type" bread wheats displayed the same electrophoretic distribution of chromosome 1D-encoded B subunits, although they were slightly different from that found in Cheyenne itself.

Electrophoresis, Gel, Two-Dimensional↗
PubMed1994

Introgression of Elymus trachycaulus chromatin into common wheat.

A number of wheat-Elymus trachycaulus (2n = 4x = 28, genomically StStHtHt) chromosome addition, substitution, and translocation lines were isolated from the derivatives of an E. trachycaulus x wheat hybrid. Eighteen out of a total of 28 chromosome arms of E. trachycaulus were recovered in the addition lines. The genomic affinity of individual E. trachycaulus chromosomes was analysed by comparative chromosome banding and in situ hybridization using genome-specific repetitive DNA sequences as probes. The homoeology of the E. trachycaulus chromosomes added to wheat was determined by storage protein, isozyme, and restriction fragment length polymorphism analysis. Alloplasmic wheat-E. trachycaulus chromosome additions were isolated which only involved chromosome 1Ht and 1St that carry fertility restoration gene Rf-Ht1 and Rf-St1, respectively. Based on the results of production and characterization of a wheat-E. trachycaulus 5Ht(5B) substitution line, it is likely that some wheat chromosomes can be well compensated genetically by E. trachycaulus chromosomes. Several spontaneous wheat-E. trachycaulus chromosome translocation lines were detected. All the translocation lines involved either 1Ht or 1St. To estimate the potential of recombination between wheat and E. trachycaulus chromosomes, a backcross population derived from a plant which was double monosomic for chromosomes 7A and 7AL.7AS-1StS and a ph1b gene was developed. The plants from this population were analysed for 1St-specific genetic markers and no recombinant was recovered.

Chromosome Banding↗
PubMed2004

Localization of a novel recessive powdery mildew resistance gene from common wheat line RD30 in the terminal region of chromosome 7AL.

Segregation analysis of resistance to powdery mildew in a F(2) progeny from the cross Chinese Spring (CS) x TA2682c revealed the inheritance of a dominant and a recessive powdery mildew resistance gene. Selfing of susceptible F(2) individuals allowed the establishment of a mapping population segregating exclusively for the recessive resistance gene. The extracted resistant derivative showing full resistance to each of 11 wheat powdery mildew isolates was designated RD30. Amplified fragment length polymorphism (AFLP) analysis of bulked segregants from F(3)s showing the homozygous susceptible and resistant phenotypes revealed an AFLP marker that was associated with the recessive resistance gene in repulsion phase. Following the assignment of this AFLP marker to wheat chromosome 7A by means of CS nullitetrasomics, an inspection of simple sequence repeat (SSR) loci evenly spaced along chromosome 7A showed that the recessive resistance gene maps to the distal region of chromosome 7AL. On the basis of its close linkage to the Pm1 locus, as inferred from connecting partial genetic maps of 7AL of populations CS x TA2682c and CS x Virest ( Pm1e), and its unique disease response pattern, the recessive resistance gene in RD30 was considered to be novel and tentatively designated mlRD30.

Ascomycota↗
PubMed2004

A cytogenetic method for stacking gene pairs in common wheat.

The potential for non-reciprocal Robertsonian translocations of wheat (Triticum aestivum L.) to assist in the stacking of genes was assessed from a study of their cytological and genetic behaviour. To obtain translocations, a double monosomic (3B+5A; 2n=40=19ii+2i) was crossed reciprocally with a contrasting disomic. Individuals inheriting a broken monosome were identified from the loss of one arm-specific DNA marker coupled with retention of a marker for the opposite arm. No double breaks (potential translocations) were found in 180 cross progeny recovered from pollen of the double monosomic but two instances (loss of 5AL plus 3BS; loss of 5AL plus 3BL) were found in 251 progeny recovered from ovules. Meiotic pairing and multi-color genome-specific fluorescence in situ hybridization (mcGISH) showed that each plant with a double break contained one translocated chromosome between the A and B genomes that had rejoined at the centromere and that formed a trivalent (19ii+ liii) in about 83% of PMC. Most trivalents (approximately 92%) aligned at metaphase in a 'V' configuration(alternate disjunction) while the rest aligned in linear 'I'(adjacent disjunction) or ambiguous 'L' configurations. Genetic analysis of a testcross of these 'fusion monosomics' showed that this preferential co-orientation of the trivalent influenced the assortment of the chromosome arms involved. Loci that were located in the hemizygous ends of the 'V' trivalent showed strong quasi-linkage in that most ovules from the female testcross carried relevant DNA markers either from both standard chromosomes or from neither. This shows that, in most cases, the two standard chromosomes assorted to the same pole while the fused monosome segregated to the opposite pole. For heterozygous loci (present both on the fusion monosome and the standard chromosomes) assortment was either independent or showed partial linkage to the hemizygous arm depending on the reported recombination distance from centromere. Marker assortment was further distorted in male testcrosses and in doubled haploids (made from the fusion monosomics by the maize method) by the strong selective advantage of pollen or haploids that inherited the standard chromosomes rather than the deficiencies. This genetic data shows that under the combined influence of alternate disjunction and natural selection, progeny of fusion monosomics will revert to the standard disomic arrangement, fixing the gene content of both hemizygous arms in the process. Thus, any pair of genes could be targeted for joint fixation by isolating the fusion monosome that will link them temporarily in a segregating population.

Chromosome Mapping↗
PubMed2005

Genetic characterization and molecular mapping of a Hessian fly-resistance gene transferred from T. turgidum ssp. dicoccum to common wheat.

A gene (temporarily designated Hdic) conferring resistance to the Hessian fly (Hf) [Mayetiola destructor (Say)] was previously identified from an accession of German cultivated emmer wheat [Triticum turgidum ssp. dicoccum (Schrank ex Schübler) Thell] PI 94641, and was transferred to the Hf-resistant wheat germplasm KS99WGRC42. The inheritance of Hdic resistance exhibited incomplete penetrance because phenotypes of some heterozygous progenies are fully resistant and the others are fully susceptible. Five simple sequence repeat (SSR) markers (Xgwm136,Xcfa2153, Xpsp2999,Xgwm33, and Xbarc263) were linked to the Hdic gene on the short arm of wheat chromosome 1A in the same region as the H9, H10, and H11 loci. Flanking markers Xgwm33 and Xcfa2153 were mapped at distances 0.6 cM proximal and 1.4 cM distal, respectively. Marker analysis revealed that a very small intercalary chromosomal segment containing Hdic was transferred from emmer wheat to KS99WGRC42. This is the first emmer-derived Hf-resistance gene that has been mapped and characterized. The Hdic gene confers a high level of antibiosis to biotypes GP and L, as well as to strains vH9 and vH13 of the Hf, which is different from the biotype reaction patterns of the known Hf-resistance genes on chromosome 1A (H5 and H11 susceptible to biotype L, H9 and H10 susceptible to strain vH9). These results suggested that Hdic is either a new gene or a novel allele of a known H gene on chromosome 1A. The broad spectrum of resistance conferred by the Hdic gene makes it valuable for developing Hf resistant wheat cultivars.

Animals↗
PubMed2005

Application of a new IBD-based QTL mapping method to common wheat breeding population: analysis of kernel hardness and dough strength.

Mapping quantitative trait loci (QTL) in plants is usually conducted using a population derived from a cross between two inbred lines. The power of such QTL detection and the estimation of the effects highly depend on the choice of the two parental lines. Thus, the QTL found represent only a small part of the genetic architecture and can be of limited economical interest in marker-assisted selection. On the other hand, applied breeding programmes evaluate large numbers of progeny derived from multiple-related crosses for a wide range of agronomic traits. It is assumed that the development of statistical techniques to deal with pedigrees in existing plant populations would increase the relevance and cost effectiveness of QTL mapping in a breeding context. In this study, we applied a two-step IBD-based-variance component method to a real wheat breeding population, composed of 374 F6 lines derived from 80 different parents. Two bread wheat quality related traits were analysed by the method. Results obtained show very close agreement with major genes and QTL already known for those two traits. With this new QTL mapping strategy, inferences about QTL can be drawn across the breeding programme rather than being limited to the sample of progeny from a single cross and thus the use of the detected QTL in assisting breeding would be facilitated.

Breeding↗
PubMed2005

Characterization of low-molecular-weight glutenin subunit genes and their protein products in common wheats.

To characterize the low-molecular-weight glutenin subunit (LMW-GS), we developed specific PCR primer sets to distinguish 12 groups of LMW-GS genes of Norin 61 and to decide their loci with nullisomic-tetrasomic lines of Chinese Spring. Three, two, and ten groups were assigned to Glu-A3, Glu-B3, and Glu-D3 loci, respectively. To identify the proteins containing the corresponding amino acid sequences, we determined the N-terminal amino acid sequence of 12 spots of LMW-GSs of Norin 61 separated by two-dimensional gel electrophoresis (2DE). The N-terminal sequences of the LMW-GS spots showed that 10 of 12 groups of LMW-GSs were expressed as protein products, which included LMW-i, LMW-m, and LMW-s types. Four spots were encoded by Glu-A3 (LMW-i). Three spots were encoded by Glu-B3 (LMW-m and LMW-s). Five spots were encoded by Glu-D3 (LMW-m and LMW-s). A minor spot of LMW-m seemed to be encoded by the same Glu-B3 gene as a major spot of LMW-s, but processed at a different site. Comparing among various cultivars, there were polymorphic and non-polymorphic LMW-GSs. Glu-A3 was highly polymorphic, i.e., the a, b, and c alleles showed one spot, the d allele showed four spots, and the e allele had no spot. Insignia used as one of the Glu-A3 null standard cultivars had a LMW-GS encoded by Glu-A3. We also found that Cheyenne had a new Glu-D3 allele. Classification of LMW-GS by a combination of PCR and 2DE will be useful to identify individual LMW-GSs and to study their contribution to flour quality.

Amino Acid Sequence↗
PubMed2005

Fine genetic mapping fails to dissociate durable stem rust resistance gene Sr2 from pseudo-black chaff in common wheat (Triticum aestivum L.).

The broad-spectrum stem rust resistance gene Sr2 has provided protection in wheat against Puccinia graminis Pers. f. sp. tritici for over 80 years. The Sr2 gene and an associated dark pigmentation trait, pseudo-black chaff (PBC), have previously been localized to the short arm of chromosome 3B. In a first step towards the positional-based cloning of Sr2, we constructed a high-resolution map of this region. The wheat EST (wEST) deletion bin mapping project provided tightly linked cDNA markers. The rice genome sequence was used to infer the putative gene order for orthologous wheat genes and provide additional markers once the syntenic interval in rice was identified. We used this approach to map six wESTs that were collinear with the physical order of the corresponding genes on rice chromosome 1 suggesting there are no major re-arrangements between wheat and rice in this region. We were unable to separate by recombination the tightly linked morphological trait, PBC from the stem rust resistance gene suggesting that either a single gene or two tightly linked genes control both traits.

Basidiomycota↗
PubMed2006

Identification and characterization of stripe rust resistance gene Yr34 in common wheat.

An uncharacterized source of seedling resistance to Puccinia striiformis f.sp. tritici was identified in an advanced wheat breeding line WAWHT2046. Genetic analysis based on a WAWHT2046/Carnamah-derived double haploid (DH) population demonstrated monogenic inheritance of seedling stripe rust resistance in WAWHT2046. The gene controlling stripe rust resistance in line WAWHT2046 was tentatively designated YrWA. The chromosome 5AL located awn inhibitor gene B1, possessed by WAWHT2046, also showed monogenic inheritance when the DH population was scored for the presence and absence of awns. Joint segregation analysis at the B1 and YrWA loci indicated genetic linkage between the two loci. A recombination value of 12.2 cM was computed using Mapmanager. This association located YrWA in the chromosome arm 5AL. Molecular mapping using microsatellite markers placed YrWA distal to B1. All molecular markers mapped proximal to the awn inhibitor locus B1. As no other stripe rust resistance gene is reported to be located in the chromosome arm 5AL, YrWA was permanently designated as Yr34. Yr34 produced an intermediate (23C) seedling infection type and expressed very low stripe rust response (10R-MR) on adult plants in the field, similar to the resistance gene Yr17. In addition to Yr34, this mapping population segregated for three genetically independent adult plant stripe rust resistance genes. The detection of DH lines with completely susceptible response, higher than that shown by the Yr34-lacking parent Carnamah, suggested that both parents contributed adult plant resistance. The use of WAWHT2046 as a parent in breeding programs would also contribute APR in addition to Yr34.

Chromosome Mapping↗
PubMed2006

Pm34: a new powdery mildew resistance gene transferred from Aegilops tauschii Coss. to common wheat (Triticum aestivum L.).

Powdery mildew is a major fungal disease in wheat growing areas worldwide. A novel source of resistance to wheat powdery mildew present in the germplasm line NC97BGTD7 was genetically characterized as a monogenic trait in greenhouse and field trials using F(2) derived lines from a NC97BGTD7 X Saluda cross. Microsatellite markers were used to map and tag this resistance gene, now designated Pm34. Three co-dominant microsatellite markers linked to Pm34 were identified and their most likely order was established as: Xbarc177-5D, 5.4cM, Pm34, 2.6cM, Xbarc144-5D, 14cM, Xgwm272-5D. These microsatellite markers were previously mapped to the long arm of the 5D chromosome and their positions were confirmed using Chinese Spring nullitetrasomic Nulli5D-tetra5A and ditelosomic Dt5DL lines. Pm2, the only other known Pm gene on chromosome 5D, has been mapped to the short arm and its specificity is different from that of Pm34.

Ascomycota↗
PubMed2004

Preferential expression of a HLP homolog encoding a mitochondrial L14 ribosomal protein in stamens of common wheat.

Interaction between nucleus and cytoplasm has essential roles in plant development, including that of floral organs. We isolated a wheat homolog Whlp of Arabidopsis HUELLENLOS PARALOG (HLP) gene encoding a mitochondrial (mt) ribosomal protein L14. Transient expression analysis using the green fluorescent protein (GFP) fusion protein showed that 50 amino residues located on the N-terminal of the wheat HLP homolog (WHLP) protein acted as a mt-targeting signal (MTS). Expression patterns of the Whlp gene were compared among floral organs of alloplasmic lines of wheat, in which intrinsic cytoplasms were replaced by the cytoplasm of a wild relative Aegilops crassa. In these alloplasmic lines, pistillody (homeotic transformation of stamens into pistil-like organs) is induced by the alien cytoplasm in the absence of nuclear restorer genes. The Whlp transcripts preferentially accumulated in stamens compared with pistils, leaves, and roots. The expression level of Whlp in the pistillate stamens of the alloplasmic lines was similar to that in genuine pistils of both euplasmic lines and fertile alloplasmic lines. The result suggested that the elevated expression of the Whlp gene plays a role in aiding the development of male reproductive organ but not in the determination of its whorl identity. A comparable expression pattern was observed in another nuclear-encoded mt ribosomal protein gene but not in a mt-encoded gene. The different expression patterns of different mt ribosomal protein genes suggest that the abundance of mt ribosomal proteins is differentially regulated in the organ/tissue development in wheat.

Amino Acid Sequence↗
PubMed1999

Distribution and structural variation of arabinoxylans in common wheat mill streams.

In 19 wheat-milling fractions total pentosan content, calculated as 0.88 x (% L-arabinose + % D-xylose), varied between 1.44 and 30.66% on dry matter (dm). It increased with ash content once the latter exceeded 0.6% (dm basis). Water-extractable arabinoxylans were recovered by saturating water extracts to 65% ethanol. Their contents in the milling fractions varied between 0.35 and 1.38%, and above 0.6% ash content also increased with this parameter. Their L-arabinose-to-D-xylose ratios ranged between 0.65 and 0.39, with the lowest values found for the fractions with highest ash content, indicating that the ash-rich tissues contain more arabinoxylans that are less branched. (1)H NMR spectroscopy revealed that the decrease in L-arabinose-to-D-xylose ratio was accompanied by an increase in unsubstituted xylose residues and a decrease in disubstituted xylose residues, while the contents of monosubstituted xyloses were virtually constant.

Industry↗
PubMed2000

Gametocidal factor-induced structural rearrangements in rye chromosomes added to common wheat.

The gametocidal factor on the Aegilops cylindrica chromosome 2Cc was used to induce and analyze the nature of chromosomal rearrangements in rye chromosomes added to wheat. For this purpose we isolated plants disomic for a given rye chromosome and monosomic for 2Cc and analyzed their progenies cytologically. Rearranged rye chromosomes were identified in 7% of the progenies and consisted of rye deficiencies (4.6%), wheat rye dicentric and rye ring chromosomes (1.8%), and terminal translocations (0.6%). The dicentric and ring chromosomes initiated breakage-fusion-bridge cycles (BFB) that ceased within a few weeks after germination as the result of chromosome healing. Of 56 rye deficiencies identified, after backcrossing and selfing, only 33 were recovered in either homozygous or heterozygous condition covering all rye chromosomes except 7R. The low recovery rate is probably caused by the presence of multiple rearrangements induced in the wheat genome that resulted in poor plant vigor and seed set, low transmission, and an underestimation of the frequency of wheat rye dicentric chromosomes. Genomic in-situ hybridization (GISH) analysis of the 33 recovered rye deficiencies revealed that 30 resulted from a single break in one chromosome arm followed by the loss of the segment distal to the breakpoint. Only three had a wheat segment attached distal to the breakpoint. Although some of the Gc-induced rye rearrangements were derived from BFB cycles, all of the recovered rye rearrangements were simple in structure. The healing of the broken chromosome ends was achieved either by the de-novo addition of telomeric repeats leading to deficiencies and telocentric chromosomes or by the fusion with other broken ends in the form of stable monocentric terminal translocation chromosomes.

Chromosomes↗