An integrated molecular linkage map of diploid wheat based on a <Emphasis Type="Italic">Triticum boeoticum</Emphasis> × <Emphasis Type="Italic">T. monococcum</Emphasis> RIL population

Diploid A genome species of wheat harbour immense variability for biotic stresses and productivity traits, and these could be transferred efficiently to hexaploid wheat through marker assisted selection, provided the target genes are tagged at diploid level first. Here we report an integrated molecular linkage map of A genome diploid wheat based on 93 recombinant inbred lines (RILs) derived from Triticum boeoticum × Triticum monococcum inter sub-specific cross. The parental lines were analysed with 306 simple sequence repeat (SSR) and 194 RFLP markers, including 66 bin mapped ESTs. Out of 306 SSRs tested for polymorphism, 74 (24.2%) did not show amplification (null) in both the parents. Overall, 171 (73.7%) of the 232 remaining SSR and 98 (50.5%) of the 194 RFLP markers were polymorphic. Both A and D genome specific SSR markers showed similar transferability to A genome of diploid wheat species. The 176 polymorphic markers, that were assayed on a set of 93 RILs, yielded 188 polymorphic loci and 177 of these as well as two additional morphological traits mapped on seven linkage groups with a total map length of 1,262 cM, which is longer than most of the available A genome linkage maps in diploid and hexaploid wheat. About 58 loci showed distorted segregation with majority of these mapping on chromosome 2A^m. With a few exceptions, the position and order of the markers was similar to the ones in other maps of the wheat A genome. Chromosome 1A^m of T. monococcum and T. boeoticum showed a small paracentric inversion relative to the A genome of hexaploid wheat. The described linkage map could be useful for gene tagging, marker assisted gene introgression from diploid into hexaploid wheat as well as for map based cloning of genes from diploid A genome species and orthologous genes from hexaploid wheat.     

不同倍性小麦对盐胁迫的适应性差异

植物染料在工业化应用过程中存在着资源限制,目标色相不丰富、色牢度不理想、植物染料本身的鉴别和成品的鉴别等问题。为了丰富染料植物资源的来源和提高染料植物资源的利用效率,该研究对西双版纳傣族利用的染料植物及其染色工艺涉及的相关植物进行了系统调查。2014年10月到2016年1月,采用半结构式访谈法对西双版纳14个村寨的56个关键信息人进行访谈,收集信息包括使用着色植物、媒染植物和助染植物的种类、傣名、利用部位和资源来历,以及预处理和染色过程工艺条件与技术步骤;采用参与式观察法对4种色相的10个染色工艺过程进行了记录,采集了凭证标本和图像资料;对调查信息进行了整理编目。结果表明：西双版纳地区的傣族使用11种着色植物和17种助染植物;目标色相有红、黄、蓝和绿。分析了傣族染料植物资源的发掘潜力、傣族利用植物染色对于染料植物利用的应用启发。该研究详细深入地记录了西双版纳傣族使用的染料植物的种类及其相关的组合和染色的过程。该研究结果对民族民间染料植物与染色工艺的产业化应用具有重要借鉴意义,为染料植物资源筛选及其染色工艺条件优化提供了参考。     

Cloning and characterization of a gene encoding wheat starch synthase I

 A cDNA clone, and a corresponding genomic DNA clone, containing full-length sequences encoding wheat starch synthase I, were isolated from a cDNA library of hexaploid wheat (Triticum aestivum) and a genomic DNA library of Triticum tauschii, respectively. The entire sequence of the starch synthase-I cDNA (wSSI-cDNA) is 2591 bp, and it encodes a polypeptide of 647 amino-acid residues that shows 81% and 61% identity to the amino-acid sequences of SSI-type starch synthases from rice and potato, respectively. In addition, the putative N-terminal amino-acid sequence of the encoded protein is identical to that determined for the N-terminal region of the 75-kDa starch synthase present in the starch granule of hexaploid wheat. Two prominent starch synthase activities were demonstrated to be present in the soluble fraction of wheat endosperm by activity staining of the non-denaturing PAGE gels. The most anodal band (wheat SSI) shows the highest staining intensity and results from the activity of a 75-kDa protein. The wheat SSI mRNA is expressed in the endosperm during the early to mid stages of wheat grain development but was not detected by Northern blotting in other tissues from the wheat plant. The gene encoding the wheat SSI (SsI-D1) consists of 15 exons and 14 introns, similar to the structure of the rice starch synthase-I gene. While the exons of wheat and rice are virtually identical in length, the wheat SsI-D1 gene has longer sequences in introns 1, 2, 4 and 10, and shorter sequences in introns 6, 11 and 14, than the corresponding rice gene. Received: 5 June 1998 / Accepted: 29 September 1998     

Performance of wheat crops with different chromosome ploidy: root-sourced signals, drought tolerance, and yield performance

Pot-culture experiments were carried out to estimate the role of non-hydraulic root signals (nHRS) and the relation of these signals to drought tolerance and grain yield formation under drought stress in six wheat varieties. These were two modern hexaploid wheat (Triticum aestivum L., AABBDD) Plateau602 and Longchun8139-2, two diploid wheat (Triticum monococcum L., AB) MO1 and MO4, and two tetraploid wheat (Triticum dicoccum Schuebl L., AABB) DM22 and DM31. In the two diploid relatives, the nHRS was switched on and off at a soil water content (SWC) of approximately 53–45% field water capacity (FWC). In contrast, in the modern hexaploid varieties, Longchun8139-2 and Plateau602 the nHRS occurred between a SWC of about 71 and 35% FWC, a much wider soil moisture range. The two tetraploid relatives, DM22 and DM31, were generally intermediate. The nHRS threshold range in SWC also narrowed as all six varieties went through successive developmental stages from shooting to grain filling. The two hexaploid wheat varieties had the longest duration of survival after the water supply ceased, and the best yield stability under drought stress, similar to with tetraploid wheat varieties; the diploid wheat varieties were least robust. These two parameters were both significantly correlated with the nHRS soil moisture threshold range (r=0.9456** and 0.8608*, respectively). Based on these patterns, we propose a ‘triple Z’ model to describe the features of non-hydraulic stomatal sensitivity versus soil drought in wheat growth.     

Effects of Soil Flooding on Growth and Grain Yield of Populations of Tetraploid and Hexaploid Species of Wheat

Single populations of three hexaploid species of wheat, Triticumaestivum, Triticum spelta and Triticum macha, and two populationsof the tetraploid wheat, Triticum dicoccum (Pontus and Bordeaux),were grown in a greenhouse experiment at a range of soil floodingregimes: free draining, two levels of transient flooding andcontinuous flooding. Increasing severity of flooding treatment resulted in increasedsoil reduction and an increase in the concentration of reducediron and manganese in the experimental soil, and also resultedin a reduction in vegetative growth, number of inflorescences,grain number and grain weight. There were, however, large differencesbetween the wheat populations in the degree of reduction inyield caused by flooding. The population of T. macha was muchmore flooding-tolerant than the other hexaploid species andthe ‘Pontus’ population of the emmer wheat, T. dicoccum,was more tolerant than the ‘Bordeaux’ populationof this species and than T. spelta and T. aestivum. The results are discussed in relation to the origin of the populations. Soil flooding, Triticum aeslivum, Triticum macha, Triticum spelta, Triticum dicoccum     

Expression of high zinc efficiency of Aegilops tauschii and Triticum monococcum in synthetic hexaploid wheats

The effect of varied zinc (Zn) supply on shoot and root dry matter production, severity of Zn deficiency symptoms and Zn tissue concentrations was studied in two Triticum turgidum (BBAA) genotypes and three synthetic hexaploid wheat genotypes by growing plants in a Zn-deficient calcareous soil under greenhouse conditions with (+Zn=5 mg kg^-1 soil) and without (−Zn) Zn supply. Two synthetic wheats (BBAADD) were derived from two different Aegilops tauschii (DD) accessions using same Triticum turgidum (BBAA), while one synthetic wheat (BBAAAA) was derived from Triticum turgidum (BBAA) and Triticum monococcum (AA). Visible symptoms of Zn deficiency, such as occurrence of necrotic patches on leaves and reduction in shoot elongation developed more rapidly and severely in tetraploid wheats than in synthetic hexaploid wheats. Correspondingly, decreases in shoot and root dry matter production due to Zn deficiency were higher in tetraploid wheats than in synthetic hexaploid wheats. Transfer of the DD genome from Aegilops tauschii or the AA genome from Triticum monococcum to tetraploid wheat greatly improved root and particularly shoot growth under Zn-deficient, but not under Zn-sufficient conditions. Better growth and lesser Zn deficiency symptoms in synthetic hexaploid wheats than in tetraploid wheats were not accompanied by increases in Zn concentration per unit dry weight, but related more to the total amount of Zn per shoot, especially in the case of synthetic wheats derived from Aegilops tauschii. This result indicates higher Zn uptake capacity of synthetic wheats. The results demonstrated that the genes for high Zn efficiency from Aegilops tauschii (DD) and Triticum monococcum (AA) are expressed in the synthetic hexaploid wheats. These wheat relatives can be used as valuable sources of genes for improvement of Zn efficiency in wheat. This revised version was published online in June 2006 with corrections to the Cover Date.     

The expression of salt tolerance from Triticum tauschii in hexaploid wheat

Summary Accessions of Triticum tauschii (Coss.) Schmal. (D genome donor to hexaploid wheat) vary in salt tolerance and in the rate that Na⁺ accumulates in leaves. The aim of this study was to determine whether these differences in salt tolerance and leaf Na⁺ concentration would be expressed in hexaploid wheat. Synthetic hexaploids were produced from five T. tauschii accessions varying in salt tolerance and two salt-sensitive T. turgidum cultivars. The degree of salt tolerance of the hexaploids was evaluated as the grain yield per plant in 150 mol m^-3 NaCl relative to grain yield in 1 mol m^-3 NaCl (control). Sodium concentration in leaf 5 was measured after the leaf was fully expanded. The salt tolerance of the genotypes correlated negatively with the concentration of Na⁺ in leaf 5. The salt tolerance of the synthetic hexaploids was greater than the tetraploid parents primarily due to the maintenance of kernel weight under saline conditions. Synthetic hexaploids varied in salt tolerance with the source of their D genome which demonstrates that genes for salt tolerance from the diploid are expressed at the hexaploid level.     

Differential expression of manganese superoxide dismutase sequence variants in near isogenic lines of wheat during cold acclimation

Numerous sequence variants of wheat (Triticum aestivum L.) manganese superoxide dismutase (MnSOD) genes have been found. Quantitative real-time PCR was used to measure the expression levels of three MnSOD genes distinguished by a variable amino acid, and three genes distinguished by sequence variation in the 3′ untranslated region (3′ UTR), in wheat plants grown at 20°C and cold-acclimated for 1–4 weeks at 2°C. The amino acid variants did not differ significantly in expression levels, however, differential expression of genes differing in the 3′ UTR was observed. Diploid wheat-related species also carried sequence variants of MnSOD, with differing levels of expression, suggesting diversification of the MnSOD gene family occurred prior to the polyploidization events of hexaploid wheat.     

Allopolyploidy alters gene expression in the highly stable hexaploid wheat

Hexaploid wheat (Triticum aestivum) contains triplicated genomes derived from three distinct species. To better understand how different genomes are coordinated in the same nucleus of the hexaploid wheat, we globally compared gene expression of a synthetic hexaploid wheat with its diploid (Aegilops tauschii) and tetraploid (T. turgidum) parents by cDNA-AFLP display. The results suggested that the expression of a significant fraction of genes was altered in the synthetic hexaploid; most appeared to be diminished and some were activated. We characterized nine cDNA clones in details. Cytogenetic as well as genomic sequence analyses indicated that the gene silencing was not due to chromosome/DNA loss but was caused by gene regulation. Northern and RT-PCR divided these genes into three groups: (I) four genes were down-regulated nonspecifically, likely involving both parental orthologues; (II) four genes were down-regulated in an orthologue-dependent manner; (III) one gene was activated specifically in the synthetic hexaploid wheat. These genes were often altered non-randomly in different synthetic hexaploids as well as natural hexaploid wheat, suggesting that many of the gene expression changes were intrinsically associated with polyploidy.     

Intraspecific divergence in wheats of the Timopheevi group as revealed by in situ hybridization with tandem repeats of the Spelt1 and Spelt52 families

Fluorescent in situ hybridization (FISH) was used to study the distribution of the Spelt1 and Spelt52 repetitive DNA sequences on chromosomes of ten accessions representing three polyploid wheat species of the Timopheevi group: Triticum araraticum (7), T. timopheevii (2), and T. kiharae (1). Sequences of both families were found mostly in the subtelomeric chromosome regions of the G genome. The total number of Spelt1 sites varied from 8 to 14 in the karyotypes of the species under study; their number, location, and size differed among the seven T. araraticum accessions and were the same in the two T. timopheevii accessions and T. kiharae, an amphidiploid T. timopheevii-Aegilops tauschii hybrid. The Spelt52 tandem repeat was detected in the subtelomeric regions of chromosomes 1-4; its sites did not coincide with the Spelt1 sites. The chromosome distribution and signal intensity of the Spelt52 repeats varied in T. araraticum and were the same in T. timopheevii and T. kiharae. The chromosome distributions of the Spelt1 and Spelt52 repeats were compared for the polyploid wheats of the Timopheevi group and diploid Ae. speltoides, a putative donor of the G genome. The comparison revealed a decrease in hybridization level: both the number of sites per genome and the size of sites were lower. The decrease was assumed to result from repeat elimination during polyploidization and subsequent evolution of wheat and from the founder effect, since the origin of Timopheevi wheats might involve the genotype of Ae. speltoides, which is highly polymorphic for the distribution of Spelt1 and Spelt52 sequences and is similar in the chromosome location of the repeats to modern wheat.     

The presence of the enhanced K/Na discrimination trait in diploid Triticum species

Summary A number of accessions of the three species of diploid wheat, Triticum boeoticum, T. monococcum, and T. urartu, were grown in 50 mol m^-3 NaCl+2.5 mol m^-3 CaCl₂. Sodium accumulation in the leaves was low and potassium concentrations remained high. This was not the case in T. durum grown under the same conditions, and indicates the presence in diploid wheats of the enhanced K/Na discrimination character which has previously been found in Aegilops squarrosa and hexaploid wheat. None of the accessions of diploid wheat showed poor K/Na discrimination, which suggests that if the A genome of modern tetraploid wheats was derived from a diploid Triticum species, then the enhanced K/Na discrimination character became altered after the formation of the original allopolyploid. Another possibility is that a diploid wheat that did not have the enhanced K/Na discrimination character was involved in the hybridization event which produced tetraploid wheat, and that this diploid is now extinct or has not yet been discovered.     

About the origin of European spelt (<Emphasis Type="Italic">Triticum spelta</Emphasis> L.): allelic differentiation of the HMW Glutenin B1-1 and A1-2 subunit genes

To investigate the origin of European spelt (Triticum spelta L., genome AABBDD) and its relation to bread wheat (Triticum aestivum L., AABBDD), we analysed an approximately 1-kb sequence, including a part of the promoter and the coding region, of the high-molecular-weight (HMW) glutenin B1-1 and A1-2 subunit genes in 58 accessions of hexa- and tetraploid wheat from different geographical regions. Six Glu-B1-1 and five Glu-A1-2 alleles were identified based on 21 and 19 informative sites, respectively, which suggests a polyphyletic origin of the A- and B-genomes of hexaploid wheat. In both genes, a group of alleles clustered in a distinct, so-called beta subclade. High frequencies of alleles from the Glu-B1-1 and Glu-A1-2 beta subclades differentiated European spelt from Asian spelt and bread wheat. This indicates different origins of European and Asian spelt, and that European spelt does not derive from the hulled progenitors of bread wheat. The conjoint differentiation of alleles of the A- and B-genome in European spelt suggests the introgression of a tetraploid wheat into free-threshing hexaploid wheat as the origin of European spelt.Electronic Supplementary Material Supplementary material is available in the online version of this article at Communicated by J. Dvorak     

The mechanisms of variation of subtelomeric repeats Spelt1 in the progeny of introgressive line <Emphasis Type="Italic">Triticum aestivum</Emphasis> L. × <Emphasis Type="Italic">Aegilops speltoides</Emphasis> Tausch.

Quantitative variation of species-specific subtelomeric repeat Spelt1 was studied in the progeny of an individual plant from the introgressive line Triticum aestivum × Aegilops speltoides. In the progeny, no cases of the Spelt1 increased content were observed. On the contrary, in some cases statistically significant decrease of the repeat copy number was detected. It seems likely that the mechanisms of the Spelt1 elimination involve either the selection at the gamete level versus the increase of the satellite DNA content in the telomeres, or intramolecular (within one chromatid) homologous recombination.     

Genome identification of the Triticum crassum complex (Poaceae) with the restriction patterns of repeated nucleotide sequences

Species of the Triticum crassum complex, tetraploid and hexaploid T. crassum, hexaploid T. juvenale, and hexaploid T. syriacum, share a similar morphology. Variation in the restriction profiles of nuclear repeated nucleotide sequences is employed in identification of genomes of these species. The data show that hexaploid T. crassum originated from hybridization of the tetraploid cytotype of T. crassum with T. tauschii. Triticum juvenale and T. syriacum originated from hybridization of tetraploid T. crassum with T. umbellulatum and T. searsii, respectively. Tetraploid T. crassum appears to be an ancient allotetraploid that originated from hybridization of primitive T. tauschii with an ancient species in the evolutionary lineage leading to the section Sitopsis of the genus Triticum.     

Hessian fly-resistance gene transferred from chromosome 4Mv of Aegilops ventricosa to Triticum aestivum

 A new Hessian fly (Mayetiola destructor) resistance gene from Aegilops ventricosa and its transfer to hexaploid wheat is described. The 4D(4M^v) substitution line H-93-33 derived from the cross [(Triticum turgidum H-1-1×Aegilops ventricosa no. 11)×Triticum aestivum H-10-15] was highly resistant to the Spanish population tested. Resistance seemed to be inherited as a single dominant factor in the F₂ generation resulting from a cross of H-93-33 with its susceptible parent (H-10-15). Resistance in Ae. venticosa no. 10 was located on chromosome 4M^v using M^v wheat/Ae. ventricosa addition lines. The resistance gene transferred from Ae. ventricosa no. 11 to H-93-33 (H27) is allelic with respect to that of Ae. ventricosa no. 10 and is non-allelic with respect to the genes H3 and H6 from Monon and Caldwell respectively. The assignment of H27 gene to chromosome 4M^v is further supported by its linkage to a gene encoding isozyme Acph-M^v1, previously located on chromosome 4M^v in the line H-93-33. A new marker from homoeologous chromosome group 4 (Amp-M^v2) present in H-93-33 and the 4M^v addition line is described. Received: 12 October 1996 / Accepted: 22 November 1996     

An unusual wheat insertion sequence (WIS1) lies upstream of an alpha-amylase gene in hexaploid wheat, and carries a "minisatellite" array

Summary Comparison of the 5′ flanking regions of three α-amylase genes from chromosome 6B of hexaploid wheat by heteroduplex and sequence analysis revealed the presence of a 1.6 kb stem-loop insertion sequence (WIS1) in one of them. Polymorphism among hexaploid wheat varieties suggests the relatively recent insertion/excision of this sequence from its present position. The complete sequence of the stem-loop insertion shows that it has many of the features found in transposable elements, including target site duplication and terminal inverted repeats. One unusual feature is a tandem array of direct repeats comprising a wheat “minisatellite” sequence. Both the insertion sequence and the minisatellite are found at multiple locations in the wheat genome, but the functional significance of their association in WIS1 is unknown. The minisatellite arrays share a common core structure, and long arrays are polymorphic between different hexaploid varieties.     

Photosynthetic response of tetraploid and hexaploid wheat to water stress

Photosynthetic characteristics of ear and flag leaves of wheat species, tetraploid Triticum dicoccoides Kom and hexaploid Bima1, were studied in plants grown under well-watered (WW) and water-stressed (WS) conditions. Compared to ears, flag leaves exhibited higher photosynthetic rate (P _N) at the filling stage, but more severe decrease under WS. P _N in the tetraploid wheat ear remained higher than that in the hexaploid wheat during the grain-filling stage. Water stress decreased PN in both the organs; this decline was caused by a reduction in Rubisco activity, not by drought-induced stomatal limitation. Tetraploid wheat ears exhibited higher relative water content and water-use efficiency than that of hexaploid wheat, under WS. The change in phosphoenolpyruvate carboxylase activity and carbon isotope composition indicated the absence of C₄ metabolism in the ears of both species under both conditions. The improved performance of the tetraploid wheat ears under WS was associated with better water relations.     

Molecular analysis of the D-genome of the Triticeae

Summary The chromosome of three tetraploid Aegilops L. species containing the D-genome were analyzed by in situ hybridization with a repeated DNA sequence clone pAS1 isolated from Aegilops squarrosa and observed to be D-genome specific. This sequence is found on all seven D-genome chromosome pairs of A. squarrosa and hexaploid wheat. Two distinct D-genome patterns were observed in the tetraploid species. The D-genome of A. cylindrica was similar to hexaploid wheat. Seven pairs of chromosomes having large amounts and numerous sites of the sequence were observed. Five chromosome pairs with fewer and smaller sites of the repetitive sequence were observed in the D-genomes of A. crassa and A. ventricosa. In addition to these major repeated sequence differences, chromosomal modifications appear to have occurred between T. aestivum and A. cylindrica and between A. crassa and A. ventricosa resulting in changes with respect to location of the sequence between the respective species. D-genome divergence with respect to pAS1 sequence appears to have occurred at least in two forms, one characterized by the changes in amount of repetitive sequence and the second by changes in location of the sequence.     

The origin of spelt and free-threshing hexaploid wheat

It is widely believed that hexaploid wheat originated via hybridization of hulled tetraploid emmer with Aegilops tauschii (genomes DD) and that the nascent hexaploid was spelt, from which free-threshing wheat evolved by mutations. To reassess the role of spelt in the evolution of Triticum aestivum, 4 disomic substitution lines of Ae. tauschii chromosome 2D in Chinese Spring wheat were developed and one of them was used to map the Tg locus, which controls glume tenacity in Ae. tauschii, relative to simple sequence repeat (SSR) and expressed sequence tag loci on wheat chromosome 2D. The segregation of SSR markers was used to assess the presence of Tg alleles in 11 accessions of spelt, both from Europe and from Asia. Ten of them had an inactive tg allele in the D genome and most had an active Tg allele in the B genome. This is consistent with spelt being derived from free-threshing hexaploid wheat by hybridization of free-threshing wheat with hulled emmer. It is proposed that the tetraploid parent of hexaploid wheat was not hulled emmer but a free-threshing form of tetraploid wheat.     

Comparative analysis in cereals of a key proline catabolism gene.

Proline accumulation and catabolism play significant roles in adaptation to a variety of plant stresses including osmotic stress, drought, temperature, freezing, UV irradiation, heavy metals and pathogen infection. In this study, the gene Δ¹ -pyrroline-5-carboxylate dehydrogenase (P5CDH), which catalyzes the second step in the conversion of proline to glutamate, is characterized in a number of cereal species. P5CDH genes from hexaploid wheat, Triticum turgidum (durum wheat), Aegilops tauschii, Triticum monococcum, barley, maize and rice were shown to be conserved in terms of gene structure and sequence, present as a single copy per haploid, non-polyploid genome and located in evolutionarily conserved linkage groups. A wheat cDNA sequence was shown by yeast complementation to encode a functional P5CDH activity. A divergently-transcribed rab7 gene was identified immediately 5′ of P5CDH in all grasses examined, except rice. The rab7/P5CDH intergenic region in these species, which presumably encompasses 5′ regulatory elements of both genes, showed a distinct pattern of sequence evolution with sequences in juxtaposition to each ORF conserved between barley, wheat, A. tauschii and T. monococcum. More distal 5′ sequence in this intergenic region showed a higher rate of divergence, with no homology observed between these regions in the wheat and barley genomes. Maize and rice showed no similarity in regions 5′ of P5CDH when compared with wheat, barley, and each other, apart from a 22 bp region of conserved non-coding sequence (CNS) that is similar to a proline response element identified in the promoter of the Arabidopsis proline dehydrogenase gene. A palindromic motif similar to this cereal CNS was also identified 5′ of the Arabidopsis AtP5CDH gene showing conservation of this sequence in monocot and dicot lineages.