小麦一周文献推荐（12.17）

1、QTL analysis of falling number and seed longevity in wheat (Triticum aestivum L.)

Pre-harvest sprouting (PHS) and seed longevity (SL) are complex biological processes of major importance for agricultural production. In the present study, a recombinant inbred line (RIL) population derived from a cross between the German winter wheat (Triticum aestivum L.) cultivars History and Rubens was used to identify genetic factors controlling these two physiological seed traits. A falling number (FN) test was employed to evaluate PHS, while SL was measured using a germination test (and the speed of germination) after controlled deterioration. FN of the population was assessed in four environments; SL traits were measured in one environment. Four major quantitative trait loci (QTL) for FN were detected on chromosomes 4D, 5A, 5D, and 7B, whereas for SL traits, a major QTL was found on chromosome 1A. The FN QTL on chromosome 4D that coincided with the position of the dwarfing gene Rht-D1b only had effects in environments that were free of PHS. The remaining three QTL for FN were mostly pronounced under conditions conducive to PHS. The QTL on the long arm of chromosome 7B corresponded to the major gene locus controlling late maturity α-amylase (LMA) in wheat. The severity of the LMA phenotype became truly apparent under sprouting conditions. The position on the long arm of chromosome 1A of the QTL for SL points to a new QTL for this important regenerative seed trait.

2、RNA-seq facilitates development of chromosome-specific markers and transfer of rye chromatin to wheat

Transcriptome shotgun sequencing (RNA-seq) provides an abundant resource for developing molecular markers specifically related to functional genes. In this study, transcriptomes of Chinese rye cultivar Jingzhouheimai (JZHM) challenged with powdery mildew pathogen Bgt(Blumeria graminis f. sp. tritici) were obtained and used to develop expressed sequence tag (EST)-based simple sequence repeat (SSR) and sequence-tagged site (STS) markers. A total of 866 primer sets for EST-SSRs and STSs were designed, from which we developed 401 rye-specific markers. The highest level of polymorphism was observed in EST-SSRs (56.73%) followed by STS2 (49.07%) designed via rye-specific contigs and STS1 (35.90%) primers designed from upregulated contigs. Genotyping with newly developed markers along with cytogenetic techniques allowed us to identify nine wheat alien chromosome lines from the cross of Zhoumai 18/Jinghui 1 (Jinghui 1 is an amphiploid of wheat landrace Huixianhong and JZHM) carrying rye chromosome 6R or 6R segments of different length, which permitted preliminary location of the powdery mildew resistance gene PmJZHM6RL and 12 specific markers to 6RL FL 0.51–1.0. 5R-specific markers and genomic in situ hybridization/fluorescence in situ hybridization detected MtA5RL and T5AS·5AL-5RL chromosomes among 41 F5 plants from the cross CS ph1bph1b/MA5R, and aberrations permitted the location of the hairy peduncle gene (Hp) and marker XLFZ3473 to the region 5RL FL 0.78–1.0 with another nine markers locating to 5RL 0.0–0.78. The chromosome-specific markers and chromosome aberrations developed in this study will facilitate the introgression of rye chromatin into wheat.

3、Genome-wide identification and characterization of NB-ARC resistant genes in wheat (Triticum aestivum L.) and their expression during leaf rust infection

Wheat (Triticum aestivum L.) is an important cereal crop; however, its production is affected severely by numerous diseases including rusts. An efficient, cost-effective and ecologically viable approach to control pathogens is through host resistance. In wheat, high numbers of resistance loci are present but only few have been identified and cloned. A comprehensive analysis of the NB-ARC-containing genes in complete wheat genome was accomplished in this study. Complete NB-ARC encoding genes were mined from the Ensembl Plants database to predict 604 NB-ARC containing sequences using the HMM approach. Genome-wide analysis of orthologous clusters in the NB-ARC-containing sequences of wheat and other members of the Poaceae family revealed maximum homology with Oryza sativa indica and Brachypodium distachyon. The identification of overlap between orthologous clusters enabled the elucidation of the function and evolution of resistance proteins. The distributions of the NB-ARC domain-containing sequences were found to be balanced among the three wheat sub-genomes. Wheat chromosome arms 4AL and 7BL had the most NB-ARC domain-containing contigs. The spatio-temporal expression profiling studies exemplified the positive role of these genes in resistant and susceptible wheat plants during incompatible and compatible interaction in response to the leaf rust pathogen Puccinia triticina. Two NB-ARC domain-containing sequences were modelled in silico, cloned and sequenced to analyze their fine structures. The data obtained in this study will augment isolation, characterization and application NB-ARC resistance genes in marker-assisted selection based breeding programs for improving rust resistance in wheat.

4、High-density SNP mapping reveals closely linked QTL for resistance to Stagonospora nodorum blotch (SNB) in flag leaf and glume of hexaploid wheat

The genetic control of adult plant resistance to Stagonospora nodorum blotch (SNB) is complex consisting of genes with minor effects interacting in an additive manner. Earlier studies detected quantitative trait loci (QTL) for flag leaf resistance in successive years on chromosomes 1B, 2A, 2D, 5B using SSR- and DArT-based genetic maps of progeny from the crosses EGA Blanco/Millewa, 6HRWSN125/WAWHT2074 and P92201D5/P91193D1. Similarly, QTL for glume resistance detected in successive years and multiple environments were identified on chromosomes 2D and 4B from genetic maps of P92201D5/P91193D1 and 6HRWSN125/WAWHT2074, respectively. The SSR- and DArT-based genetic maps had an average distance of 6.5, 7.8 and 9.7 cM between marker loci for populations EGA/Millewa, P92201D5/P91193D1 and 6HRWSN125/WAWHT2074, respectively. This study used single nucleotide polymorphism (SNP) markers from the iSelect Infinium 90K genotyping array to fine map genomic regions harbouring QTL for flag leaf and glume SNB resistance reducing the average distance between markers to 2.9, 3.3 and 3.4 -3.4 cM for populations P92201D5/P91193D1, EGA/Millewa and 6HRWSN125/WAWHT2074, respectively. Increasing the marker density of the genetic maps with SNPs did not identify any new QTL for SNB resistance but discriminated previously identified co-located QTL into separate but closely linked QTL.

5、Review on resistance to wheat blast disease (Magnaporthe oryzae Triticum) from the breeder point-of-view: use of the experience on resistance to rice blast disease

This review on the resistance to wheat blast disease focus on the latest knowledge useful for the breeders, but also takes into account the lacks in these knowledge. To tackle this disease, it is relevant to apply a breeding strategy which has previously proven its efficacy for obtaining rice varieties with a high level of partial and durable resistance to blast. But, incomplete information is available on wheat blast resistance. Therefore, firstly, it is necessary to adjust this breeding strategy considering the worst hypothesis corresponding to every lack of knowledge. Next, the possible invalidation of every hypothesis can allow simplifying the breeding schema and its implementation. For every lack of knowledge, the practical consequences of the corresponding worst hypothesis, the study of its validity and the consequences of its possible invalidation are explained. Scientific arguments, materials and methods details are provided with the latest available references.

6、Wheat genetic resources in the post-genomics era: promise and challenges

7、B genome specific polymorphism in the TdDRF1 gene is in relationship with grain yield

A and B genome copies of DRF1 gene in durum wheat were isolated and sequenced using gene variability. B genome specific polymorphism resulted, in a RIL population, in relationship with grain yield mainly in drought condition. Drought tolerance is one of the main components of yield potential and stability, and its improvement is a major challenge to breeders. Transcription factors are considered among the best candidate genes for developing functional markers, since they are components of the signal transduction pathways that coordinate the expression of several downstream genes. Polymorphisms of the Triticum durum dehydration responsive factor 1 (TdDRF1) gene that belongs to DREB2 transcription factor family were identified and specifically assigned to the A or B genome. A panel of primers was derived to selectively isolate the corresponding gene copies. These molecular information were also used to develop a new molecular marker: an allele-specific PCR assay discriminating two genotypes (Mohawk and Cocorit) was developed and used for screening a durum wheat recombinant inbred line population (RIL-pop) derived from the above genotypes. Phenotypic data from the RIL-pop grown during two seasons, under different environmental conditions, adopting an α-lattice design with two repetitions, were collected, analyzed and correlated with molecular data from the PCR assay. A significant association between a specific polymorphism in the B genome copy of the TdDRF1 gene and the grain yield in drought conditions were observed.

8、QTL for stay-green traits in wheat in well-watered and water-limited environments

“Stay-green” plants retain green leaf area longer after flowering than senescent types. This can prolong carbon assimilation during grain filling, increasing yield, particularly under terminal drought stress. A population of doubled haploid wheats (Triticum aestivum L.) derived from a cross between stay-green SeriM82 and senescent Hartog was grown in eight environments with varying degrees of water limitation. The dynamics of normalised difference vegetative index (NDVI) was followed post-flowering to evaluate change in leaf greenness. Quantitative trait loci (QTL) were identified for components of stay-green including i) maximum NDVI (Nmax), ii) an indicator of the maximum rate of senescence (SR), iii) thermal time from flowering to commencement of senescence (OnS), iv) thermal time from flowering to mid-senescence (MidS), and v) the integral of NDVI from flowering to 1500 °Cd after flowering (SGint). Genetic regions associated with QTL for stay-green traits were identified (i) in both wet and dry environments on chromosomes 4A, 4B, 4D (constitutive stay-green); (ii) primarily in wetter environments on 2A and (iii) primarily in dryer environments on 5B. Other regions associated with QTL for stay-green were identified on 3B and 7B in a mixture of environment types. In some environments, stay-green QTL co-located with QTL for seminal root angle, seedling root number and/or for yield. Other stay-green QTL were co-located with yield but not seminal root angle and seedling root number. This suggests genetic regions associated with seminal root angle and seedling root number are not solely responsible for the high yielding, stay-green phenotype. Selection for stay-green traits will increase the rate of genetic progress for adaptation of wheat to both well-watered and water-limited environments.

9、An Advanced Backcross Population through Synthetic Octaploid Wheat as a “Bridge”: Development and QTL Detection for Seed Dormancy

The seed dormancy characteristic is regarded as one of the most critical factors for pre-harvest sprouting (PHS) resistance. As a wild wheat relative species, Aegilops tauschii is a potential genetic resource for improving common wheat. In this study, an advanced backcross population (201 strains) containing only Ae. tauschiisegments was developed by means of synthetic octaploid wheat (hexaploid wheat Zhoumai 18 × Ae. tauschii T093). Subsequently, seed dormancy rate (Dor) in the advanced backcross population was evaluated on the day 3, 5 and 7, in which 2 major QTLs (QDor-2D and QDor-3D) were observed on chromosomes 2D and 3D with phenotypic variance explained values (PVEs) of 10.25 and 20.40%, respectively. Further investigation revealed significant correlation between QDor-3D and Tamyb10 gene, while no association was found between the former and TaVp1 gene, implying that QDor-3D site could be of closer position to Tamyb10. The obtained quantitative trait locus sites (QTLs) in this work could be applied to develop wheat cultivars with PHS resistance.

10、miR430: the novel heat-responsive microRNA identified from miRNome analysis in wheat (Triticum aestivum L.)

11、Genetic and Molecular Characterization of Leaf Rust Resistance in Two Durum Wheat Landraces

Leaf rust, caused by Puccinia triticina, is a constraint to durum wheat (Triticum turgidum subsp. durum) production, and landraces are reported to be an important source of resistance. Two Portuguese landraces (Aus26582 and Aus26579) showed resistance against durum-specific P. triticina races and were crossed with a susceptible landrace (Bansi) to develop recombinant inbred line (RIL) populations. Monogenic segregation for leaf rust resistance was observed among both RIL populations. The underlying locus, temporarily named LrAW2, was mapped to the short arm of chromosome 6B in the Aus26582/Bansi population and five DArTseq markers cosegregated with LrAW2. Simple sequence repeat markers sun683 and sun684, developed from the chromosome survey sequence (CSS) contig 6BS2963854, identified through BlastN search of cosegregating DArTseq markers in the International Wheat Genome Sequencing Consortium database, cosegregated with LrAW2. Comparison of the CSS contig 6BS2963854-based sequences amplified from parental genotypes led to the development of marker sunKASP60, which also showed close linkage with LrAW2. Markers sun684 and sunKASP60 showed close association with LrAW2 in both RIL populations. The amplification of LrAW2-specific products by linked markers in Aus26582, Aus26579, and Guayacan (Lr61) indicated that LrAW2 may be Lr61. The alternate amplicon or haplotype produced with LrAW2-linked markers in Australian durum cultivars demonstrated their effectiveness in marker-assisted selection.

12 Genetic Diversity, Population Structure and Ancestral Origin of Australian Wheat

Since the introduction of wheat into Australia by the First Fleet settlers, germplasm from different geographical origins has been used to adapt wheat to the Australian climate through selection and breeding. In this paper, we used 482 cultivars, representing the breeding history of bread wheat in Australia since 1840, to characterize their diversity and population structure and to define the geographical ancestral background of Australian wheat germplasm. This was achieved by comparing them to a global wheat collection using in-silico chromosome painting based on SNP genotyping. The global collection involved 2,335 wheat accessions which was divided into 23 different geographical subpopulations. However, the whole set was reduced to 1,544 accessions to increase the differentiation and decrease the admixture among different global subpopulations to increase the power of the painting analysis. Our analysis revealed that the structure of Australian wheat germplasm and its geographic ancestors have changed significantly through time, especially after the Green Revolution. Before 1920, breeders used cultivars from around the world, but mainly Europe and Africa, to select potential cultivars that could tolerate Australian growing conditions. Between 1921 and 1970, a dependence on African wheat germplasm became more prevalent. Since 1970, a heavy reliance on International Maize and Wheat Improvement Center (CIMMYT) germplasm has persisted. Combining the results from linkage disequilibrium, population structure and in-silicopainting revealed that the dependence on CIMMYT materials has varied among different Australian States, has shrunken the germplasm effective population size and produced larger linkage disequilibrium blocks. This study documents the evolutionary history of wheat breeding in Australia and provides an understanding for how the wheat genome has been adapted to local growing conditions. This information provides a guide for industry to assist with maintaining genetic diversity for long-term selection gains and to plan future breeding programs.

13 Natural variation in photoperiodic flowering pathway and identification of photoperiod-insensitive accessions in wild wheat, Aegilops tauschii

The D-genome progenitor of hexaploid wheat, Aegilops tauschii Coss., has a wide natural species range in central Eurasia and possesses wide natural variation in heading and flowering time. Here, we report identification of two Ae. tauschii accessions insensitive to short day length. Similarly to a loss or reduced degree of vernalization requirement, the photoperiod-insensitive mutations were found only in the early flowering sublineage (TauL1b) of Ae. tauschii. Quantitative trait locus (QTL) analyses using two F2 mapping populations showed that a QTL for heading time on the long arm of chromosome 5D was related to the early heading phenotype of the photoperiod-insensitive accessions under short-day conditions. In the photoperiod-insensitive accession, expression patterns of two flowering-related genes were altered under short-day conditions compared with the patterns in photoperiod-sensitive accessions. This study indicates that analysis of natural variations in the Ae. tauschiipopulation is useful to find novel genetic loci controlling agronomically important traits.

14 Genetic and physical mapping of a putative Leymus mollis-derived stripe rust resistance gene on wheat chromosome 4A | Plant Disease

Wheat stripe rust is one of the most damaging diseases of wheat worldwide. The wheat–Leymus mollis introgression line M8664-3 exhibits all-stage resistance to Chinese stripe rust races. Genetic analysis of stripe rust resistance was performed by crossing M8664-3 with the susceptible line Mingxian169. Analysis of the disease resistance of F2 and F2:3 populations revealed that its resistance to Chinese stripe rust race 33(CYR33) is controlled by a single dominant gene, temporarily designated as YrM8664-3. Genetic and physical mapping showed that YrM8664-3 is located in bin 4AL13-0.59-0.66 close to 4AL12-0.43-0.59 on chromosome 4AL and is flanked by SNP markers AX111655681 and AX109496237 with genetic distances of 5.3 and 2.3 cM, respectively. Resistance spectrum and position analyses indicated that YrM8664-3 may be a novel gene. Molecular detection using the markers linked to YrM8664-3 with wheat varieties which commonly cultivated and wheat–L. mollis derived lines showed that YrM8664-3 is also present in other wheat–L. mollis introgression lines, but absent in commercial common wheat cultivars. YrM8664-3 is thus a potentially valuable source of stripe rust resistance for breeding.

15 A novel wheat cysteine-rich receptor-like kinase gene CRK41 is involved in the regulation of seed germination under osmotic stress in Arabidopsis thaliana

The bread wheat gene TaCRK41 encodes a cysteine-rich receptor kinase. It is down-regulated by various abiotic stresses and by exposure to abscisic acid. A transient expression experiment in Arabidopsis thaliana protoplasts involving a fusion between the sequence encoding green fluorescence protein and the TaCRK41 allele from either the salinity tolerant bread wheat cultivar Shanrong No. 3 (SR3) or its salinity sensitive progenitor cultivar Jinan 177 (JN177) showed that the TaCRK41 product is deposited in the cytoplasm. Recombinant TaCRK41 originating from both SR3 and JN177 displayed no kinase activity in vitro. The constitutive expression of TaCRK41 in A. thalianaresulted in a marked reduction in the plants’ sensitivity to both exogenous abscisic acid and to salinity during germination. The level of ABA-induced transcription of ABI3, ABI5 and the ABI5-controlled genes EM1 and EM6 was significantly reduced in plants subjected to stress. The data support the idea that TaCRK41 is involved in the regulation of ABA-dependent germination under conditions of osmotic stress.

16 Characterization of QTLs for Root Traits of Wheat Grown under Different Nitrogen and Phosphorus Supply Levels

Root is important in acquiring nutrients from soils. Developing marker-assisted selection for wheat root traits can help wheat breeders to select roots desirable for efficient acquisition of nutrients. A recombinant inbred line (RIL) population derived from wheat varieties Xiaoyan 54 and Jing 411 was used to detect QTLs for maximum root length and root dry weight (RDW) under control, low nitrogen and low phosphorus conditions in hydrophobic culture (HC). We totally detected 17 QTLs for the investigated root traits located at 13 loci on 11 chromosomes. These loci differentially expressed under different nutrient supplying levels. The RILs simultaneously harboring positive alleles or negative alleles of the most significant three QTLs for RDW, qRDW.CK-2A, qRDW.CK-2D, and qRDW.CK-3B, were selected for soil column culture (SC) trial to verify the effects of these QTLs under soil conditions. The RILs pyramiding the positive alleles not only had significantly higher shoot dry weight, RDW, nitrogen and phosphorus uptake in all the three treatments of the HC trial, but also had significantly higher RDW distribution in both the top- and sub-soils in the SC trial than those pyramiding the negative alleles. These results suggested that QTL analysis based on hydroponic culture can provide useful information for molecular design of wheat with large and deep root system.

17 A wheat MYB transcriptional repressor TaMyb1D regulates phenylpropanoid metabolism and enhances tolerance to drought and oxidative stresses in transgenic tobacco plants

MYB transcription factors are involved in the regulation of plant development and response to biotic and abiotic stress. In this study, TaMyb1D, a novel subgroup 4 gene of the R2R3-MYB subfamily, was cloned from wheat (Triticum aestivum L.). TaMyb1D was localized in the nucleus and functioned as a transcriptional repressor. The overexpression of TaMyb1D in tobacco (Nicotiana tabacum) plants repressed the expression of genes related to phenylpropanoid metabolism and down-regulated the accumulation of lignin in stems and flavonoids in leaves. These changes affected plant development under normal conditions. The expression of TaMyb1D was ubiquitous and up-regulated by PEG6000 and H2O2 treatments in wheat. TaMyb1D-overexpressing transgenic tobacco plants exhibited higher relative water content and lower water loss rate during drought stress, as well as higher chlorophyll content in leaves during oxidative stress. The transgenic plants showed a lower leakage of ions as well as reduced malondialdehyde and H2O2 levels during conditions of drought and oxidative stresses. In addition, TaMyb1D up-regulated the expression levels of ROS- and stress-related genes in response to drought stress. Therefore, the overexpression of TaMyb1D enhanced tolerance to drought and oxidative stresses in tobacco plants. Our study demonstrates that TaMyb1D functions as a negative regulator of phenylpropanoid metabolism and a positive regulator of plant tolerance to drought and oxidative stresses.

18 Characterization of the CCT family and analysis of gene expression in Aegilops tauschii

Flowering is crucial for reproductive success in flowering plant. The CCT domain-containing genes widely participate in the regulation of flowering process in various plant species. So far, the CCT family in common wheat is largely unknown. Here, we characterized the structure, organization, molecular evolution and expression of the CCT genes in Aegilops tauschii, which is the D genome donor of hexaploid wheat. Twenty-six CCT genes (AetCCT) were identified from the full genome of A. tauschii and these genes were distributed on all 7 chromosomes. Phylogenetic analysis classified these AetCCT genes into 10 subgroups. Thirteen AetCCT members in group A, C, H and G achieved rapid evolution based on evolutionary rate analysis. The AetCCT genes respond to different exogenous hormones and abiotic treatments, the expression of AetCCT4, 7, 8, 11, 12, 16, 17, 19, 21 and 22 showed a significant 24 h rhythm. This study may provide a reference for common wheat's evolution, domestication and evolvement rules, and also help us to understand the ecological adaptability of A. tauschii.

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