Introgression of QTL from Aegilops tauschii enhances yield-related traits in common wheat

To break the narrow diversity bottleneck of the wheat D genome, a set of Aegilops tauschii-wheat introgression(A-WI) lines was developed by crossing Ae. tauschii accession T015 with common wheat elite cultivar Zhoumai 18(Zhou18). A high-density genetic map was constructed based on Single Nucleotide Polymorphism(SNP) markers and 15 yield-related traits were evaluated in 11 environments for detecting quantitative trait loci(QTL). A total of 27 environmentally stable QTL were identified in at least five environments, 20 of which were derived from Ae. tauschii T015, explaining up to 24.27% of the phenotypic variations. The major QTL for kernel length(KL), QKl-2D.5, was delimited to a physical interval of approximately 2.6 Mb harboring 52 candidate genes. Three Kompetitive Allele Specific PCR(KASP)markers were successfully developed based on nonsynonymous nucleotide mutations of candidate gene AetT093_2Dv1G100900.1 and showed that A-WI lines with the T015 haplotype had significantly longer KL than the Zhou18 haplotype across all 11 environments. Four primary valuable A-WIs with good trait performance and carrying yield-related QTL were selected for breeding improvement. The results will facilitate the efficient transfer of beneficial genes from Ae. tauschii into wheat cultivars to improve wheat yield and other traits.

Tolerant Mechanism and Chromosome Location of Gene Controlling Sprouting Tolerance in Aegilops Tauschii Cosson

An artificial amphiploid RSP (2n = 42, AABBDD) between tetraploid landrace Ailanmai (Triticum turgidum L., 2n= 28, AABB) and Aegllops tauschii (DD, 2n = 14) expressed high tolerance to preharvest sprouting which derived from Ae. tauschii. Tolerance to preharvest sprouting of RSP was examined by four ways in six varying periods after anthesis. The germination percentages of preharvest intact spikes were only 6.06% in its high peak period of germination. Its tolerance was mainly decided by the seed dormancy. It was showed that the tolerance to sprouting in ' RSP' derived from Ae. tauschii was inherited as a recessive trait which was controlled by one gene, located on chromosome 2D.

硬粒小麦-节节麦人工合成种Decoy1/Aegilops tauschii 510抗条锈性状(条中30,条中31)的遗传分析

硬粒小麦、节节麦人工合成种Ｄｅｃｏｙ１／Ａｅ．ｔａｕｓｃｈｉ５１０成株期对中国条锈病新小种条中３０（ＣＹＲ３０）和条中３１（ＣＹＲ３１）高抗－免疫。将Ｄｅｃｏｙ１／Ａｅ．ｔａｕｓｃｈｉ５１０与高感品种川育１２杂交，获得杂种Ｆ１和Ｆ２群体。对杂种Ｆ１和Ｆ２群体分小种（ＣＹＲ３０和ＣＹＲ３１）接种鉴定表明，杂种Ｆ１抗性反应型与抗病亲本Ｄｅｃｏｙ１／Ａｅ．ｔａｕｓｃｈｉ５１０一致，为免疫－高抗；杂种Ｆ２群体中免疫－高抗单株与抗－高感单株之比符合两对显性互补基因分离比例即９∶７。分析表明，Ｄｅｃｏｙ１／Ａｅ．ｔａｕｓｃｈｉ５１０对条中３０、条中３１的抗性受两对显性互补基因控制。

A Unique Aegilops tauschii Genotype Needless to Immature Embryo Culture in Cross with Wheat

Common or bread wheat ( Triticum aestivum L., AABBDD, 2n=42) originated ca. 8 000 years ago from hybridization of tetraploid wheat ( Triticum turgidum L., AABB, 2n=28) and diploid Aegilops tauschii Coss. (DD, 2n=14). An essential prerequisite for this evolutionary step is that the natural hybrids between tetraploid wheat and diploid Aegilops tauschii can produce relatively many filled seeds which germinated well. In this study, without special techniques, e.g. immature embryo culture, out of 22 Ae. tauschii accessions, the genotype AS60 produced relatively many filled seeds which germinated well. The seed germination percentages in the crosses of Ae. tauschii ×tetraploid wheat, tetraploid wheat× Ae. tauschii and Ae. tauschii ×common wheat were, respectively, 50.0%, 57.1% and 45.5%. It seems that Ae. tauschii accession AS60 has a unique genotype which facilitate hybrid seed development and viability, and which meets with the prerequisite for wheat evolutionary. Furthermore, the significance of this finding for common wheat improvement and evolution was discussed.

粗山羊草(Aegilops tauschii)遗传多样性的研究进展

概述了粗山羊草（Ａｅ．ｔａｕｓｃｈｉｉ （Ｃｏｓｓ．）Ｓｃｈｍａｌ．）的类别和地理分布以及其在山羊草属（Ａｅｇｉｌｏｐｓ）分类中的地位。并从个体、细胞、生化和分子水平上对粗山羊草遗传多样性的研究进展作了系统的综述。这些结果对进一步研究和利用粗山羊草以及其它小麦近缘植物具有重要意义。

粗山羊草(Aegilops tauschii)有效利用的研究进展

粗山羊草（Ａｅ．ｔａｕｓｃｈｉ（Ｃｏｓｓ．）Ｓｃｈｍａｌ．）Ｄ染色体组不仅是普通小麦（Ｔｒｉｔｉｃｕｍａｅｓ－ｔｉｖｕｍＬ．）Ｄ染色体组的供体，而且它在山羊草属（Ａｅｇｉｌｏｐｓ）的进化过程中，起着关键性染色体组的作用。除此之外，本文还对利用粗山羊草细胞质与普通小麦细胞核结合所形成的核质杂种以及粗山羊草在改良普通小麦抗病、虫等方面的利用现状作了全面的综述。

粗山羊草(Aegilops tauschii)抗纹枯病的鉴定

通过土壤人工接种,采用相对抗病指数法对收集到的56份粗山羊草的抗纹枯病性能在大田成株期进行了鉴定和评价.结果表明,这些粗山羊草的纹枯病抗性普遍较好.8个品系为免疫,15个品系为高抗,26个品系为中抗,7个品系为中感或高感.这些抗病材料可以作为小麦抗纹枯病的资源.

粗山羊草(Aegilops tauschii)中Pinb基因的克隆和表达分析

puroindoline a(Pina)和puroindoline b(Pinb)是控制小麦籽粒硬度的主效基因。根据已报道的小麦Pinb基因的保守序列,设计合成了一对特异性引物,对粗山羊草Aegilops tauschii(DD)的基因组DNA进行Pinb基因扩增、克隆和序列分析,发现了一个新型Pinb等位基因。该基因长447 bp,编码148个氨基酸残基,具有麦类作物PinB蛋白所特有的WPTKWWK色氨酸结构域和10个半胱氨酸所形成的5个二硫键结构。与软粒小麦cv.Capitole的Pinb-D1a相比较,该基因含有14个氨基酸变异位点,其中包括一个紧邻色氨酸结构域的变异位点(Val66Phe),其核苷酸和氨基酸同源性分别为93.3%和90.5%。RT-PCR和Western Blot证实了Pinb基因在籽粒胚乳中的表达。Southern Blot分析结果表明,粗山羊草中Pinb基因为单拷贝。研究结果表明,粗山羊草中包含着与小麦差异较大的籽粒硬度控制基因,对此基因的进一步研究将加深对小麦籽粒硬度形成分子机制的了解。

Production of aneuhaploid and euhaploid sporocytes by meiotic restitution in fertile hybrids between durum wheat Langdon chromosome substitution lines and Aegilops tauschii

Fertile F1 hybrids were obtained between durum wheat （Triticum durum Desf.） Langdon （LDN） and its 10 disomic substitution （LDN DS） lines with Aegilops tauschii accession AS60 without embryo rescue. Selfed seedset rates for hybrids of LDN with AS60 were 36.87% and 49.45% in 2005 and 2006, respectively. Similar or higher selfed seedset rates were observed in the hybrids of 1D （1A）, 1D （1B）, 3D （3A）, 4D （4B）, 7D （7A）, and 2D （2B） with AS60, while lower in hybrids of 3D （3B） ＋ 3BL, 5D （5A） ＋ 5AL, 5D （5B） ＋ 5B and 6D （6B） ＋ 6BS with AS60 compared with the hybrids of LDN with AS60. Observation of male gametogenesis showed that meiotic restitution, both first-division restitution （FDR） and single-division meiosis （SDM） resulted in the formation of functional unreduced gametes, which in turn produced seeds. Both euhaploid and aneuhaploid gametes were produced in F1 hybrids. This suggested a strategy to simultaneously transfer and locate major genes from the ancestral species T. turgidum or Ae. tauschii. Moreover, there was no significant difference in the aneuhaploid rates between the F1 hybrids of LDN and LDN DS lines with AS60, suggesting that meiotic pairing between the two D chromosomes in the hybrids of LDN DS lines with AS60 did not promote the formation of aneuhaploid gametes.

Association analysis of grain traits with SSR markers between Aegilops tauschii and hexaploid wheat(Triticum aestivum L.)

Seven important grain traits, including grain length（GL）, grain width（GW）, grain perimeter（GP）, grain area（GA）, grain length/width ratio（GLW）, roundness（GR）, and thousand-grain weight（TGW）, were analyzed using a set of 139 simple sequence repeat（SSR） markers in 130 hexaploid wheat varieties and 193 Aegilops tauschii accessions worldwide. In total, 1 612 alleles in Ae. tauschii and 1 360 alleles in hexaploid wheat（Triticum aestivum L.） were detected throughout the D genome. 197 marker-trait associations in Ae. tauschii were identified with 58 different SSR loci in 3 environments, and the average phenotypic variation value（R2） ranged from 0.68 to 15.12%. In contrast, 208 marker-trait associations were identified in wheat with 66 different SSR markers in 4 environments and the average phenotypic R2 ranged from 0.90 to 19.92%. Further analysis indicated that there are 6 common SSR loci present in both Ae. tauschii and hexaploid wheat, which are significantly associated with the 5 investigated grain traits（i.e., GA, GP, GR, GL, and TGW） and in total, 16 alleles derived from the 6 aforementioned SSR loci were shared by Ae. tauschii and hexaploid wheat. These preliminary data suggest the existence of common alleles may explain the evolutionary process and the selection between Ae. tauschii and hexaploid wheat. Furthermore, the genetic differentiation of grain shape and thousand-grain weight were observed in the evolutionary developmental process from Ae. tauschii to hexaploid wheat.

Genomewide association study of Aegilops tauschii traits under seedling-stage cadmium stress

Aegilops tauschii Ais a wild relative of common wheat(Triticum aestivum) and acts as an important resource of elite genes including genes for resistance to biotic and abiotic stresses. To improve the cadmium(Cd) tolerance of wheat varieties using A. tauschii resources, we investigated the genetic variation of biomass-based Cd tolerance in 235 A. tauschii accessions treated with 0(control) and100 μmol L-1CdC l2(as Cd stress). Simultaneously, we performed a genomewide association study(GWAS) using a single-nucleotide polymorphism chip containing 7185 markers. Six markers were found to be significantly associated with Cd tolerance by a general linear model and a mixed linear model. These markers were close to several candidate/flanking genes associated with Cd tolerance according to results in public databases, including pdil5-1, Acc-1, DME-5A,TaA P2-D, TaA P2-B, Vrn-B1, and FtsH-like protein gene. The A. tauschii accessions were classified as high, moderate, and low Cd-tolerant according to a secondary index, the synthetic index(SI), in proportions of 9%, 57%, and 34%, respectively. By the average SI, accessions from Afghanistan,Turkey, Azerbaijan, and Iran showed relatively high Cd tolerance.

Molecular mapping of the hybrid necrosis gene NetJingY176 in Aegilops tauschii using microsatellite markers

The rich genetic variation preserved in collections of Aegilops tauschii can be readily exploited to improve common wheat using synthetic hexaploid wheat lines. However,hybrid necrosis, which is characterized by progressive death of leaves or plants, has been observed in certain interspecific crosses between tetraploid wheat and Ae. tauschii. The aim of this study was to construct a fine genetic map of a gene(temporarily named Net Jing Y176)conferring hybrid necrosis in Ae. tauschii accession Jing Y176. A triploid F1 population derived from distant hybridization between Ae. tauschii and tetraploid wheat was used to map the gene with microsatellite markers. The newly developed markers Xsdau K539 and Xsdau K561 co-segregated with Net Jing Y176 on chromosome arm 2DS. The tightly linked markers developed in this study were used to genotype 91 Ae. tauschii accessions. The marker genotype analysis suggested that 49.45% of the Ae. tauschii accessions carry Net Jing Y176. Interestingly, hybrid necrosis genotypes tended to appear more commonly in Ae. tauschii ssp. tauschii than in Ae. tauschii ssp. strangulata.

Comparing two approaches for introgression of germplasm from Aegilops tauschii into common wheat

Allelic diversity in the wild grass Aegilops tauschii is vastly greater than that in the D genome of common wheat(Triticum aestivum), of which Ae. tauschii is the source. Since the 1980 s,there have been numerous efforts to harness a much larger share of Ae. tauschii^ extensive and highly variable gene pool for wheat improvement. Those efforts have followed two distinct approaches: production of amphiploids, known as "synthetic hexaploids," between T. turgidum and Ae. tauschii,and direct hybridization between 丁. aestiuum and Ae. tauschii;both approaches then involve backcrossing to 丁. aestiuum. Both synthetic hexaploid production and direct hybridization have led to the transfer of numerous new genes into common wheat that confer improvements in many traits. This work has led to release of improved cultivars in China, the United States, and many other countries. Each approach to D-genome improvement has advantages and disadvantages. For example, production of synthetic hexaploids can incorporate useful germplasm from both T. turgidum and Ae.tauschii, thereby enhancing the A, B, and D genomes; on the other hand, direct hybridization rapidly restores the recurrent parent's A and B genomes and avoids incorporation of genes with adverse effects on threshability, hybrid necrosis, vernalization response, milling and baking quality, and other traits, which are often transferred when T. turgidum is used as a parent. Choice of method will depend in part on the type of wheat being developed and the target environment. However, more extensive use of the so-far underexploited direct hybridization approach is especially warranted.

Mapping of the heading date gene HdAey2280 in Aegilops tauschii

An optimum heading date is essential for sustainable crop productivity and ensuring high yields. In the present study, F2：3 populations were generated by crossing an early-heading accession, Y2280, with a late-heading accession, Y2282. The heading dates of the F2 and F3 populations were investigated in a field study. Using publicly available simple sequence repeat （SSR） markers, the early heading date gene HdAey2280 was mapped onto Aegilops tauschfi chromosome 7DS between the flanking markers wmc438 and barc126 at distances of 15 and 9.1 cM, respectively. Further analysis indicated that HdAey2280 is a novel heading date gene. New SSR markers were developed based on the Ae. tauschfi draft genome sequence, resulting in four new markers that were linked to the heading date gene HdAey2280. The closest distance of these markers was 1.9 cM away from the gene. The results collected in this study will serve as a framework for map-based cloning and marker-assisted selection in wheat breeding programs in the future.

Characterization of WAP2 gene in Aegilops tauschii and comparison with homoeologous loci in wheat

The Q/q gene, also known as WAP2, is an important gene for wheat domestication and is a member of the AP2 （APETALA2） class of transcription factors. In the present study, we first isolated the WRAP2 allele （where the superscript ＂t＂ refers to the speciese source, in this case ＂tauschii＂） on chromosome 5D from Aegilops tauschii Coss., the D-genome donor species of common wheat. We found that WRAP2 and the AP2 gene from Arabidopsis share a central core of the AP2 polypeptide, a highly basic 10-amino acid domain, and an AASSGF box, although there are many differences in the 37-amino acid serine-rich acidic domain and the remaining regions. In addition, WRAP2 was highly homologous to the homoeologous loci on 5A and 5B of wheat at both the nucleotide and amino acid level. However, there were some variations that are probably related to gene function. In the first AP2 domain, the amino acids VYL on the 5D and 5A loci were replaced with LLR on 5B. In the 37-amino acid serine-rich acidic domain, WRAP2 on 5D had an extra amino acid insertion. There was also a variation at the 329 amino acid position, which is thought to be related to the appearance of free-threshing wheat. At this position, the amino acid is isoleucine on 5A for the Q allele and valine for the q allele, whereas the amino acid is leucine on 5D and 5B. Furthermore, a Stowaway miniature terminal inverted repeat element （MITE） insertion was present in the ninth intron of WAP2 on 5B of all common wheats and partial tetraploid Triticum turgidum wheats. These results provide new clues for studies into the evolutionary biology of WAP2 and the origin of common wheat.

Genetic Characterization of Genetic Resources of <i>Aegilops tauschii</i>, Wheat D Genome Donor, Newly Collected in North Caucasia

For the purpose of broadening the available genetic resources to improve wheat breeding and to elucidate wheat evolution, 16 accessions of Aegilops tauschii newly collected in North Caucasia named NCT accessions were characterized genetically based on morphology, chloroplast SSR variation and AFLP. Ae. tauschii is one of the most important wild wheat genetic resources because it is the progenitor of the D genome of hexaploid wheat. Since Caucasia is considered to be a center of diversity of both cultivated and wild wheat, a lot of studies have been conducted to evaluate the diversity of Caucasian genetic resources including Ae. tauschii. Such kind of analyses, however, focused on Transcaucasia but little attention has been paid to North Caucasia because of the lack of available genetic resources. Based on the molecular analyses in this study, the 16 NCT accessions were generally divided into two groups although morphologically those are classified into the same subspecies. The grouping also represented geographical distribution, that is, the northern part group and Derbent group. This division is consistent with the two major genepools in Ae. tauschii reported in previous studies. The northern part and Derbent groups correspond to Eurasian wide genepool (called Tauschii genepool) and Caucasia and Caspian coast limited genepool (Strangulata genepool), respectively. Regarding to chloroplast, all the 16 accessions were genotyped as HG7, the most major haplogroup of the species. Although all the 16 NCT accessions were categorized into ssp. tauschii morphologically, accessions of Derbent group showed a tendency to have larger spikelets. Among them, especially NCT3 had the quite large size of spikelets and grains that are at almost the largest level in ssp. tauschii. The results of this study filled the missing information of Ae. tauschii and will be helpful for future utilization.

Genome-wide characterization of early response genes to abscisic acid coordinating multiple pathways in Aegilops tauschii

The diploid wild goat grass Aegilops tauschii(Ae. tauschii, 2 n = 14;DD), as the D-sub genome of common wheat, provides rich germplasm resources for many aspects of wheat breeding. Abscisic acid(ABA) is an essential phytohormone that plays a pivotal role in plant adaptation to abiotic stresses. However,the gene regulation network of Ae. tauschii in response to ABA stress remains unclear. Here, we conducted a time-course strand-specific RNA-sequencing study to globally profile the transcriptome that responded to ABA treatment in Ae. tauschii. We identified 4818 differentially expressed transcription units/genes with time-point-specific induction/repression patterns. Using functional annotation, one-to-one ortholog and comparative transcriptome profiling analyses, we identified 319 ABA-responsive Ae. tauschii orthologs that were also induced/repressed under ABA treatment in hexaploid wheat. On the quantitative trait loci(QTL) used in wheat marker-assisted breeding, we found that the ABA-responsive expression patterns of eight Ae. tauschii orthologs were associated with drought stress tolerance, flowering process and/or grain quality. Of them, the ABA-responsive gene encoding sucrose:sucrose 1-fructosyltransferase in fructan and glucose metabolism pathways showed the most significant association with wheat drought tolerance. The characterization of ABA early-responsive genes in this study provides valuable information for exploring the molecular functions of the regulatory genes and will assist in wheat breeding.

土壤养分异质性入侵植物节节麦种内竞争的影响

自然生境中的土壤异质性普遍存在,而且被认为在促进外来植物成功入侵方面发挥着重要作用。通过盆栽试验,研究了在不同种植密度(1、2、4、8株/盆)和恒定土壤养分的条件下,入侵植物节节麦对土壤养分异质性的响应。结果表明:(1)植物形态、生物量指标的变化特征验证了土壤养分异质性在一定程度上促进了节节麦的生长,但未达到显著水平,而这可能与试验设置的土壤斑块大小有关。(2)节节麦可以通过增加根系生物量、降低根冠比的方式来适应异质性土壤环境。(3)结合相对竞争强度(RCI)及自然对数响应比值(lnRR),土壤类型与种植密度之间不存在交互作用,土壤养分异质性对节节麦种内竞争的影响较小。

节节麦对甲基二磺隆的抗性水平及其靶标基因突变分析

采用室内整株生物测定法测定了采自河南省不同地区的28个节节麦种群对甲基二磺隆的抗性水平,同时对高抗和敏感节节麦种群的靶标乙酰乳酸合成酶(ALS)基因已报道的突变位点进行对比分析,为节节麦的化学防除提供理论依据。结果表明,低抗、中抗、高抗甲基二磺隆的节节麦种群分别有15个[2≤RI(相对抗性倍数)<5]、7个(5≤RI≤10)、3个(RI>10)。其中,对甲基二磺隆抗性最高的种群是TXLZ(采自通许县厉庄乡),抑制中剂量(ED_(50))为126.11 g/hm^(2),RI为31.85。对3个高抗和1个敏感种群的靶标ALS基因已报道的突变位点进行对比分析,并未发现突变。综上,河南省大部分地区的节节麦种群对甲基二磺隆产生了抗性,节节麦产生抗性的原因并不是由靶标基因位点突变引起的,可能是由代谢作用等引起的非靶标抗性。

过表达粗山羊草AetHIPP28增强拟南芥的耐镉性

小麦(Triticum aestivum)D基因组供体粗山羊草(Aegilops tauschii)具有多种抵御生物和非生物胁迫的基因,是小麦遗传改良的主要基因库;重金属相关异戊二烯化植物蛋白(heavy metal-associated isoprene plant protein,HIPP)在调控植物的金属离子平衡和解毒过程中具有重要作用。通过农杆菌介导获得过表达粗山羊草AetHIPP28的转基因拟南芥,并利用一系列生理生化分析研究转基因拟南芥对镉(Cd)胁迫的响应。结果表明,AetHIPP28定位于细胞核和质膜上。过表达AetHIPP28可以显著增强拟南芥对Cd的耐受性,促进Cd胁迫下的拟南芥根系生长。在Cd的胁迫下,转基因拟南芥的活性氧(reactive oxygen species,ROS)积累显著低于野生型,而抗氧化酶活性显著高于野生型。过表达AetHIPP28明显抑制了Cd 2+的跨膜内流,并增加了Cd在根部的积累。以上结果表明,过表达AetHIPP28通过调节拟南芥中ROS的积累和抗氧化酶的活性,并改变Cd 2+在根部的内流和分布,提高拟南芥对Cd的耐受性。上述结果为了解AetHIPP28应对Cd胁迫的反应机制提供了一定参考。