The endophytic fungi from wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

In order to study the species composition of endophytes from wheat healthy plants in Buenos Aires Province (Argentina) and to determine their infection frequencies from leaves, stems, glumes and grains, wheat plants were collected from five cultivars at five growth stages from crop emergence to harvest. A total of 1,750 plant segments (leaves, stems, glumes and grains) were processed from the five wheat cultivars at five growth stages, and 722 isolates of endophytic fungi recovered were identified as 30 fungal genera. Alternaria alternata, Cladosporium herbarum, Epicoccum nigrum, Cryptococcus sp., Rhodotorula rubra, Penicillium sp. and Fusarium graminearum were the fungi that showed the highest colonization frequency (CF%) in all the tissues and organs analysed. The number of taxa isolated was greater in the leaves than those in the other organs analysed.     

Characterization of a common wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) high-tillering dwarf mutant

Key message

A novel high-tillering dwarf mutant in common wheat Wangshuibai was characterized and mapped to facilitate breeding for plant height and tiller and the future cloning of the causal gene.

Abstract

Tiller number and plant height are two major agronomic traits in cereal crops affecting plant architecture and grain yield. NAUH167, a mutant of common wheat landrace Wangshuibai induced by ethylmethyl sulfide (EMS) treatment, exhibits higher tiller number and reduced plant height. Microscope observation showed that the dwarf phenotype was attributed to the decrease in the number of cells and their length. The same as the wild type, the mutant was sensitive to exogenous gibberellins. Genetic analysis showed that the high-tillering number and dwarf phenotype were related and controlled by a partial recessive gene. Using a RIL_2:6 population derived from the cross NAUH167/Sumai3, a molecular marker-based genetic map was constructed. The map consisted of 283 loci, spanning a total length of 1007.98 cM with an average markers interval of 3.56 cM. By composite interval mapping, a stable major QTL designated QHt.nau-2D controlling both traits, was mapped to the short arm of chromosome 2D flanked by markers Xcfd11 and Xgpw361. To further map the QHt.nau-2D loci, another population consisted of 180 F₂ progeny from a cross 2011I-78/NAUH167 was constructed. Finally, QHt.nau-2D was located within a genetic region of 0.8 cM between markers QHT239 and QHT187 covering a predicted physical distance of 6.77 Mb. This research laid the foundation for map-based cloning of QHt.nau-2D and would facilitate the characterization of plant height and tiller number in wheat.

     

Overexpression of <Emphasis Type="Italic">AtHDG11</Emphasis> enhanced drought tolerance in wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

Drought is one of the major abiotic stresses restricting the yield of wheat (Triticum aestivum L.). Breeding wheat varieties with drought tolerance is an effective and durable way to fight against drought. Here we reported introduction of AtHDG11 into wheat via Agrobacterium-mediated transformation and analyzed the morphological and physiological characteristics of T2 generation transgenic lines under drought stress. With drought treatment for 30 days, transgenic plants showed significantly improved drought tolerance. Compared with controls, the transgenic lines displayed lower stomatal density, lower water loss rate, more proline accumulation and increased activities of catalase and superoxide dismutase. Without irrigation after booting stage, the photosynthetic parameters, such as net photosynthesis rate, water use efficiency and efficiency of excitation energy, were increased in transgenic lines, while transpiration rate was decreased. Moreover, the kernel yield of transgenic lines was also improved under drought condition. Taken together, our data demonstrate that AtHDG11 has great potential in genetic improvement of drought tolerance of wheat.     

Genetic architecture of seed longevity in bread wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

The deterioration in the quality of ex situ conserved seed over time reflects a combination of both physical and chemical changes. Intraspecific variation for longevity is, at least in part, under genetic control. Here, the grain of 183 bread wheat accessions maintained under low-temperature storage at the IPK-Gatersleben genebank over some decades have been tested for their viability, along with that of fresh grain subjected to two standard artificial ageing procedures. A phenotype–genotype association analysis, conducted to reveal the genetic basis of the observed variation between accessions, implicated many regions of the genome, underling the genetic complexity of the trait. Some, but not all, of these regions were associated with variation for both natural and experimental ageing, implying some non-congruency obtains between these two forms of testing for longevity. The genes underlying longevity appear to be independent of known genes determining dormancy and pre-harvest sprouting.     

A high-density microsatellite consensus map for bread wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

A microsatellite consensus map was constructed by joining four independent genetic maps of bread wheat. Three of the maps were F₁-derived, doubled-haploid line populations and the fourth population was Synthetic × Opata, an F₆-derived, recombinant-inbred line population. Microsatellite markers from different research groups including the Wheat Microsatellite Consortium, GWM, GDM, CFA, CFD, and BARC were used in the mapping. A sufficient number of common loci between genetic maps, ranging from 52 to 232 loci, were mapped on different populations to facilitate joining the maps. Four genetic maps were developed using MapMaker V3.0 and JoinMap V3.0. The software CMap, a comparative map viewer, was used to align the four maps and identify potential errors based on consensus. JoinMap V3.0 was used to calculate marker order and recombination distances based on the consensus of the four maps. A total of 1,235 microsatellite loci were mapped, covering 2,569 cM, giving an average interval distance of 2.2 cM. This consensus map represents the highest-density public microsatellite map of wheat and is accompanied by an allele database showing the parent allele sizes for every marker mapped. This enables users to predict allele sizes in new breeding populations and develop molecular breeding and genomics strategies.Electronic Supplementary Material Supplementary material is available for this article at     

Flow karyotyping and chromosome sorting in bread wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

Previously, we reported on the development of procedures for chromosome analysis and sorting using flow cytometry (flow cytogenetics) in bread wheat. That study indicated the possibility of sorting large quantities of intact chromosomes, and their suitability for analysis at the molecular level. However, due to the lack of sufficient differences in size between individual chromosomes, only chromosome 3B could be sorted into a high-purity fraction. The present study aimed to identify wheat stocks that could be used to sort other chromosomes. An analysis of 58 varieties and landraces demonstrated a remarkable reproducibility and sensitivity of flow cytometry for the detection of numerical and structural chromosome changes. Changes in flow karyotype, diagnostic for the presence of the 1BL·1RS translocation, have been found and lines from which translocation chromosomes 5BL·7BL and 4AL·4AS-5BL could be sorted have been identified. Furthermore, wheat lines have been identified which can be used for sorting chromosomes 4B, 4D, 5D and 6D. The ability to sort any single arm of the hexaploid wheat karyotype, either in the form of a ditelosome or a isochromosome, has also been demonstrated. Thus, although originally considered recalcitrant, wheat seems to be suitable for the development of flow cytogenetics and the technology can be applied to the physical mapping of DNA sequences, the targeted isolation of molecular makers and the construction of chromosome- and arm-specific DNA libraries. These approaches should facilitate the analysis of the complex genome of hexaploid bread wheat.     

Structure and expression of the <Emphasis Type="Italic">TaGW7</Emphasis> in bread wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

OsGW7 (also known as OsGL7) is homologous to the Arabidopsis thaliana gene that encodes LONGIFOLIA protein, which regulates cell elongation, and is involved in regulating grain length in rice. However, our knowledge on its ortholog in wheat, TaGW7, is limited. In this study, we identified and mapped TaGW7 in wheat, characterized its nucleotide and protein structures, predicted the cis-elements of its promoter, and analysed its expression patterns. The GW7 orthologs in barley (HvGW7), rice (OsGW7), and Brachypodium distachyon (BdGW7) were also identified for comparative analyses. TaGW7 mapped onto the short arms of group 2 chromosomes (2AS, 2BS, and 2DS). Multiple alignments indicated GW7 possesses five exons and four introns in all but two of the species analysed. An exon–intron junction composed of introns 3–4 and exons 4–5 was highly conserved. GW7 has a conserved domain (DUF 4378) and two neighbouring low complexity regions. GW7 was mainly expressed in wheat spikes and stems, in barley seedling crowns, and in rice anthers and embryo-sacs during early development. Drought and heat significantly increased and decreased GW7 expression in wheat, respectively. In barley, GW7 was significantly down-regulated in paleae and awns but up-regulated in seeds under drought treatment and down-regulated under Fusarium and stem rust inoculation. In rice, OsGW7 expression differed significantly under drought treatments. Collectively, these results provide insights into GW7 structure and expression in wheat, barley and rice. The GW7 sequence structure and expression data are the foundation for manipulating GW7 and uncovering its roles in plants.     

Asymmetric somatic hybridization between wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis>) and <Emphasis Type="Italic">Avena sativa</Emphasis> L.

Protoplasts from cell suspensions of young-embryo-derived calli, whichwere non- regenerable for long-term subculture and protoplasts from embryogenic calli with the regeneration capacity of 75% of the same wheat Jinan 177, were mixed as recipient. Protoplasts from embryogenic calli of Avena sativa (with the regeneration capacity of less than 10%) irradiated with UV at an intensity of300 μW/cm2 for 30 s, 1 min, 2 min, 3 min, 5 min were used as the donor. Protoplasts of the recipient and the donor were fused by PEG method. Many calli and normal green plants were regenerated at high frequency, and were verified as somatic hybrids by chromosome counting, isozyme, 5S rDNA spacer sequence analysis and GISH (genomic in situ hybridization). Fusion combination between protoplasts either from the cell suspensions or from the calli and UV-treated Avena sativa protoplasts could not regenerate green plants.     

Cloning and characterization of microRNAs from wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

Background  

MicroRNAs (miRNAs) are a class of small, non-coding regulatory RNAs that regulate gene expression by guiding target mRNA cleavage or translational inhibition. So far, identification of miRNAs has been limited to a few model plant species, such as Arabidopsis, rice and Populus, whose genomes have been sequenced. Wheat is one of the most important cereal crops worldwide. To date, only a few conserved miRNAs have been predicted in wheat and the computational identification of wheat miRNAs requires the genome sequence, which is unknown.     

Evidence of intralocus recombination at the <Emphasis Type="Italic">Glu-3</Emphasis> loci in bread wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

Key message

Recombination at the Glu-3 loci was identified, and strong genetic linkage was observed only between the amplicons representing i-type and s-type genes located, respectively, at the Glu-A3 and Glu-B3 loci.

Abstract

The low-molecular weight glutenin subunits (LMW-GSs) are one of the major components of wheat seed storage proteins and play a critical role in the determination of wheat end-use quality. The genes encoding this class of proteins are located at the orthologous Glu-3 loci (Glu-A3, Glu-B3, and Glu-D3). Due to the complexity of these chromosomal regions and the high sequence similarity between different LMW-GS genes, their organization and recombination characteristics are still incompletely understood. This study examined intralocus recombination at the Glu-3 loci in two recombinant inbred line (RIL) and one doubled haploid (DH) population, all segregating for the Glu-A3, Glu-B3, and Glu-D3 loci. The analysis was conducted using a gene marker system that consists of the amplification of the complete set of the LMW-GS genes and their visualization by capillary electrophoresis. Recombinant marker haplotypes were detected in all three populations with different recombination rates depending on the locus and the population. No recombination was observed between the amplicons representing i-type and s-type LMW-GS genes located, respectively, at the Glu-A3 and Glu-B3 loci, indicating tight linkage between these genes. Results of this study contribute to better understanding the genetic linkage and recombination between different LMW-GS genes, the structure of the Glu-3 loci, and the development of more specific molecular markers that better represent the genetic diversity of these loci. In this way, a more precise analysis of the contribution of various LMW-GSs to end-use quality of wheat may be achieved.

     

The parameters of grain filling and yield components in common wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) and durum wheat (<Emphasis Type="Italic">Triticum turgidum</Emphasis> L. var. <Emphasis Type="Italic">durum</Emphasis>)

Final grain dry weight, a component of yield in wheat, is dependent on the duration and the rate of grain filling. The purpose of the study was to compare the grain filling patterns between common wheat, (Triticum aestivum L.), and durum wheat, (Triticum turgidum L. var. durum), and investigate relationships among grain filling parameters, yield components and the yield itself. The most important variables in differentiating among grain filling curves were final grain dry weight (W) for common wheat genotypes and grain filling rate (R) for durum wheat genotypes; however, in all cases the sets of variables important in differentiating among grain filling curves were extended to either two or all three parameters. Furthermore, in one out of three environmental conditions and for both groups of genotypes, the most important parameter in the set was grain filling duration (T). It indicates significant impact of environmental conditions on dry matter accumulation and the mutual effect of grain filling duration and its rate on the final grain dry weight. The medium early anthesis date could be associated with further grain weight and yield improvements in wheat. Grain filling of earlier genotypes occurs in more temperate environments, which provides enough time for gradual grain fill and avoids the extremes of temperature and the stress of dry conditions.     

A search for high-molecular-weight subunits of glutenin from <Emphasis Type="Italic">Triticum timopheevi</Emphasis> Zhuk. in the lines of common wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L. <Emphasis Type="Italic">Triticum timopheevi</Emphasis> Zhuk.)

The study is a continuation of investigation of prolamins in brown rust-resistant introgressive lines of common wheat, produced with participation of Triticum timopheeevi Zhuk. [1]. Two wheat lines with a substitution of the Glu-1 loci of T. timopheevi were identified. Line 684 had high-molecular-weight glutenin subunits encoded by 1Ax, as well as by 1Ay gene, which was silent in commercial lines. It was demonstrated that line 684 could serve as a source of the Glu-A _t ¹ locus. Line 186 carried the Glu-B1/Glu-G1 substitution. Comparative analysis of storage proteins from the introgression lines of common wheat Triticum aestivum L. with those from parental forms demonstrated polymorphism among the lines, resulted from natural varietal polymorphism, and introgression of the Glu-3 and Gli-1 loci from the genome of T. timopheevi.     

Formation of phenolic compounds in various cultivars of wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

The formation of soluble phenolic compounds, including flavonols, was studied in winter (Erythrospermum , Lutescens 230, and R 47-28) and spring cultivars (Lada) of wheat (Triticum aestivum L.). The contents of soluble phenolic compounds and flavonols were 1.8–2.6 and 0.5–1.3 mg/g fresh weight, respectively. These results illustrate the similarity of phenol metabolism in leaves of winter and spring wheat cultivars. The exception was the cultivar R 47-28 that accumulated the maximum amount of phenolic compounds (e.g., flavonols). In this cultivar the ratio of flavonols reached 50% of total soluble phenol content. In other cultivars, this parameter did not exceed 25–35%. The data indicate that the cultivar R 47-28 differs from other wheat cultivars in metabolism of phenolic compounds. The observed differences are probably related to genetic modifications of the cultivar R 47-28 during selection.Translated from Prikladnaya Biokhimiya i Mikrobiologiya, Vol. 41, No. 1, 2005, pp. 113–116.Original Russian Text Copyright © 2005 by Zagoskina, Olenichenko, Chzhou Yunvei, Zhivukhina.     

Assessing genetic diversity of wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) germplasm using microsatellite markers

A set of 24 wheat microsatellite markers, representing at least one marker from each chromosome, was used for the assessment of genetic diversity in 998 accessions of hexaploid bread wheat (Triticum aestivum L.) which originated from 68 countries of five continents. A total of 470 alleles were detected with an average allele number of 18.1 per locus. The highest number of alleles per locus was detected in the B genome with 19.9, compared to 17.4 and 16.5 for genomes A and D, respectively. The lowest allele number per locus among the seven homoeologous groups was observed in group 4. Greater genetic variation exists in the non-centromeric regions than in the centromeric regions of chromosomes. Allele numbers increased with the repeat number of the microsatellites used and their relative distance from the centromere, and was not dependent on the motif of microsatellites. Gene diversity was correlated with the number of alleles. Gene diversity according to Nei for the 26 microsatellite loci varied from 0.43 to 0.94 with an average of 0.77, and was 0.78, 0.81 and 0.73 for three genomes A, B and D, respectively. Alleles for each locus were present in regular two or three base-pair steps, indicating that the genetic variation during the wheat evolution occurred step by step in a continuous manner. In most cases, allele frequencies showed a normal distribution. Comparative analysis of microsatellite diversity among the eight geographical regions revealed that the accessions from the Near East and the Middle East exhibited more genetic diversity than those from the other regions. Greater diversity was found in Southeast Europe than in North and Southwest Europe. The present study also indicates that microsatellite markers permit the fast and high throughput fingerprinting of large numbers of accessions from a germplasm collection in order to assess genetic diversity.     

Quantitative trait loci for grain fructan concentration in wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

Fructans (fructo-oligosaccharides) are prebiotics that are thought to selectively promote the growth of colonic bifidobacteria, thereby improving human gut health. Fructans are present in the grain of wheat, a staple food crop. In the research reported here, we aimed to detect and map loci affecting grain fructan concentration in wheat using a doubled-haploid population derived from a cross between a high-fructan breeding line, Berkut, and a low-fructan cultivar, Krichauff. Fructan concentration was measured in grain samples grown at two locations in Australia and one in Kazakhstan. Fructan concentration varied widely within the population, ranging from 0.6 to 2.6% of grain dry weight, and was quite repeatable, with broad-sense heritability estimated as 0.71. With a linkage map of 528 molecular markers, quantitative trait loci (QTLs) were detected on chromosomes 2B, 3B, 5A, 6D and 7A. Of these, the QTLs on chromosomes 6D and 7A had the largest effects, explaining 17 and 27% of the total phenotypic variance, respectively, both with the favourable (high-fructan concentration) alleles contributed from Berkut. These chromosome regions had similar effects in another mapping population, Sokoll/Krichauff, with the favourable alleles contributed from Sokoll. It is concluded that grain fructan concentration of wheat can be improved by breeding and that molecular markers could be used to select effectively for favourable alleles in two regions of the wheat genome.     

Allelic variations in <Emphasis Type="Italic">Glu-1</Emphasis> and <Emphasis Type="Italic">Glu-3</Emphasis> loci of historical and modern Iranian bread wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) cultivars

Proline and glutamine-rich wheat seed endosperm proteins are collectively referred to as prolamins. They are comprised of HMW-GSs, LMW-GSs and gliadins. HMW-GSs are major determinants of gluten elasticity and LMW-GSs considerably affect dough extensibility and maximum dough resistance. The inheritance of glutenin subunits follows Mendelian genetics with multiple alleles in each locus. Identification of the banding patterns of glutenin subunits could be used as an estimate for screening high quality wheat germplasm. Here, by means of a two-step 1D-SDS-PAGE procedure, we identified the allelic variations in high and low-molecular-weight glutenin subunits in 65 hexaploid wheat (Triticum aestivum L.) cultivars representing a historical trend in the cultivars introduced or released in Iran from the years 1940 to 1990. Distinct alleles 17 and 19 were detected for Glu-1 and Glu-3 loci, respectively. The allelic frequencies at the Glu-1 loci demonstrated unimodal distributions. At Glu-A1, Glu-B1 and Glu-D1, we found that the most frequent alleles were the null, 7 + 8, 2 + 12 alleles, respectively, in Iranian wheat cultivars. In contrast, Glu-3 loci showed bimodal or trimodal distributions. At Glu-A3, themost frequent alleles were c and e. At Glu-B3 the most frequent alleles were a, b and c. At Glu-D3 locus, the alleles b and a, were the most and the second most frequent alleles in Iranian wheat cultivars. This led to a significantly higher Nei coefficient of genetic variations in Glu-3 loci (0.756) as compared to Glu-1 loci (0.547). At Glu-3 loci, we observed relatively high quality alleles in Glu-A3 and Glu-D3 loci and low quality alleles at Glu-B3 locus.     

An integrative genetic linkage map of winter wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

We constructed a genetic linkage map based on a cross between two Swiss winter wheat (Triticum aestivum L.) varieties, Arina and Forno. Two-hundred and forty F₅ single-seed descent (SSD)-derived lines were analysed with 112 restriction fragment length polymorphism (RFLP) anonymous probes, 18 wheat cDNA clones coding for putative stress or defence-related proteins and 179 simple-sequence repeat (SSR) primer-pairs. The 309 markers revealed 396 segregating loci. Linkage analysis defined 27 linkage groups that could all be assigned to chromosomes or chromosome arms. The resulting genetic map comprises 380 loci and spans 3,086 cM with 1,131 cM for the A genome, 920 cM for the B genome and 1,036 cM for the D genome. Seventeen percent of the loci showed a significant (P < 0.05) deviation from a 1:1 ratio, most of them in favour of the Arina alleles. This map enabled the mapping of QTLs for resistance against several fungal diseases such as Stagonospora glume blotch, leaf rust and Fusarium head blight. It will also be very useful for wheat genetic mapping, as it combines RFLP and SSR markers that were previously located on separate maps. S. Paillard and T. Schnurbusch contributed equally to the work