四部体小麦“简阳矮兰麦”与黑麦可杂交性及其在六倍体水平上的遗传特性

中国六倍体普通小麦地方品种有一个比较独特的特征-存在丰富的高亲和性材料。因此,研究中国四倍体小麦的亲和性问题具有特殊的意义。“简阳矮兰麦”是来源于四川省的一个四倍体小麦地方品种,它与黑麦有高的可杂交性,其杂交结实率达60%。遗传分析表明,“简阳矮兰麦”与黑麦的高可杂交性是受2-3对隐性基因所控制,但3对基因的可能性更大。而且,这些隐性基因的作用在合成六倍体小麦后仍能比较完全的表达。通过与六倍体普通小麦相比较,结果表明四倍体小麦的可杂交性系统与六倍体小麦的可杂交性系统的作用方式是类似的。 Abstract:It is a special characteristic that many Chinese common wheat landraces showed a high crossability with rye.Thus,it is important that elucidate the genetic control of the crossability of Chinese tetraploid wheat with rye.Triticum turgidum cv.Jianyangailanmai native to Sichuan,China has high crossability with rye,up to 60%.In this study,it is indicated that the crossability of Jianyangailanmai with rve is controlled by two or more probably three recessive genes,which was almost totally expressed in the hexaploid wheat level.The operation of these recessive genes influencing crossability with rye was similar to that of hexaploid common wheat.     

小麦新材料“J—11”与黑麦可杂交性的遗传研究

新材料“J－11”比众所周知的高亲和性品系“中国春”具有明显更高的与黑麦的可杂交性,遗传分析表明,“J－11”与“中国春”的可杂交性基因一样表现为完全隐性,但控制“J－11”和“中国春”与黑麦可杂交性的基因型确实不相同,“J－11”除具有“中国春”的3对可杂交性基因,即5B上的kr1,5A上的kr2和5D上的kr3,外,还具有1个新的可杂交性基因kr4,位于1A染色体上,新基因kr4表现为强效,其效应比kr1的弱,但在kr2和kr3的强。小麦可杂交性基因间存在互作,表现为纯合隐性等位基因对其它显性等位基因的抑制作用,而纯合隐性等位基因的效应可加性。     

Meiotic behaviour of tetraploid wheats (<Emphasis Type="Italic">Triticum turgidum</Emphasis> L.) and their synthetic hexaploid wheat derivates influenced by meiotic restitution and heat stress

Meiotic restitution is considered to be a common mechanism of polyploidization in plants and hence is one of the most important processes in plant speciation. Meiotic behaviour of plant chromosomes is influenced by both genetic and environmental factors. In this study, the meiotic behaviour of cereal crops was investigated, which includes tetraploid wheat genotypes (with and without the meiotic restitution trait) and their derivates (synthetic hexaploid wheats and a doubled haploid (DH) line), grown at two planting dates in the field. In addition, two local landraces of emmer wheat (Triticum turgidum ssp. dicoccum), one wheat cultivar (Chinese spring), one DH triticale cultivar (Eleanor) and one rye accession were included. Immature spikes of mid-autumn and end-winter sowing plants were collected in April and May 2008, respectively, fixed in Carnoy’s solution and stained with hematoxylin. Pollen mother cells (PMCs) from anthers at different stages of meiotic process were analysed for their chromosomal behaviour and irregularities. Meiotic aberrations such as laggards, chromosome bridges, micronuclei, abnormal cytokines, chromatin pulling and meiotic restitution were observed and the studied genotypes were accordingly ranked as follows: triticale > synthetic hexaploid wheats > tetraploid wheats possessing meiotic restitution > tetraploid wheats lacking meiotic restitution > rye. The results indicated that the samples that had been planted in the autumn, thus experiencing an optimum temperature level at the flowering stage, exhibited less meiotic irregularities than winter planting samples that encountered heat stress at the flowering period.     

Development and assessment of DArT markers in triticale

Triticale (X Triticosecale Wittm.) is a hybrid derived by crossing wheat (Triticum sp.) and rye (Secale sp.). Till date, only a limited number of simple sequence repeat (SSRs) markers have been used in triticale molecular analyses and there is a need to identify dedicated high-throughput molecular markers to better exploit this crop. The objective of this study was to develop and evaluate diversity arrays technology (DArT) markers in triticale. DArT marker technology offers a high level of multiplexing. Development of new markers from triticale accessions was combined with mining the large collection of previously developed markers in rye and wheat. Three genotyping arrays were used to analyze a collection of 144 triticale accessions. The polymorphism level ranged from 8.6 to 23.8% for wheat and rye DArT markers, respectively. Among the polymorphic markers, rye markers were the most abundant (3,109) followed by wheat (2,214) and triticale (719). The mean polymorphism information content values were 0.34 for rye DArT markers and 0.37 for those from triticale and wheat. High correlation was observed between similarity matrices derived from rye, triticale, wheat and combined marker sets, as well as for the cophenetic values matrices. Cluster analysis revealed genetic relationships among the accessions consistent with the agronomic and pedigree information available. The newly developed triticale DArT markers as well as those originated from rye and wheat provide high quality markers that can be used for diversity analyses and might be exploited in a range of molecular breeding and genomics applications in triticale.     

Genetic diversity in wild wheats and goat grass

The genetic structure of 35 populations of wild relatives of cultivated wheats, all collected in Syria and Lebanon, was assessed using ten isozymes. The populations consisted of diploid goat grass, Aegilops speltoides, diploid wild wheats, Triticum monococcum spp. aegilopoides and T. urartu, and tetraploid wild wheat, T. turgidum ssp. dicoccoides. The majority of the populations were polymorphic (P=0–70%) having low within-population mean genetic diversity (H_ep=0.05–0.10) and relatively high within-species genetic diversity (H_es=0.14–0.31). The linkage between loci did not seem to be one of the causes for the observed polymorphism. All four species showed significant inbreeding at both the population (0.31–0.64) and species (0.77–0.96) levels, and the extent of inbreeding did not correlate with mating systems. Despite their apparent common ecological and evolutionary history, between-population or between-species level genetic identity was low (I=0.43–0.86). Among the diploid species, populations of Ae. speltoides clustered distinctly from those overlapping clusters of T. monococcum ssp. aegilopoides and T. urartu. The tetraploid species T. turgidum ssp. dicoccoides had relatively less genetic diversity (H_es=0.14) and was highly homozygous (F=0.96). The results suggest that these wild progenitors of cultivated wheats have undergone extensive local differentiation and inbreeding. We discuss the implications of our results on the management of wild wheat and goat grass populations. Received: 12 September 1999 / Accepted: 10 November 1999     

Polyphenol oxidase genes as integral part of the evolutionary history of domesticated tetraploid wheat

Studying and understanding the genetic basis of polyphenol oxidases (PPO)-related traits plays a crucial role in genetic improvement of crops.A tetraploid wheat collection (T. turgidum ssp., TWC) was analyzed using the 90K wheat SNP iSelect assay and phenotyped for PPO activity. A total of 21,347 polymorphic SNPs were used to perform genome-wide association analysis (GWA) in TWC and durum wheat sub-groups, detecting 23 and 85 marker-trait associations (MTA). In addition, candidate genes responsible for PPO activity were predicted. Based on the 23 MTAs detected in TWC, two haplotypes associated with low and high PPO activity were identified. Four SNPs were developed and validated providing one reliable marker (IWB75732) for marker assisted selection. The 23 MTAs were used to evaluate the genetic divergence (F_ST > 0.25) between the T. turgidum subspecies, providing new information important for understanding the domestication process of Triticum turgidum ssp. and in particular of ssp. carthlicum.     

Genes WHEAT FRIZZY PANICLE and SHAM RAMIFICATION 2 independently regulate differentiation of floral meristems in wheat

Background

Inflorescences of wheat species, spikes, are characteristically unbranched and bear one sessile spikelet at a spike rachis node. Development of supernumerary spikelets (SSs) at rachis nodes or on the extended rachillas is abnormal. Various wheat morphotypes with altered spike morphology, associated with the development of SSs, present an important genetic resource for studies on genetic regulation of wheat inflorescence development.

Results

Here we characterized diploid and tetraploid wheat lines of various non-standard spike morphotypes, which allowed for identification of a new mutant allele of the WHEAT FRIZZY PANICLE (WFZP) gene that determines spike branching in diploid wheat Ttiticum monococcum L. Moreover, we found that the development of SSs and spike branching in wheat T. durum Desf. was a result of a wfzp-A/TtBH-A1 mutation that originated from spontaneous hybridization with T. turgidum convar. сompositum (L.f.) Filat. Detailed characterization of the false-true ramification phenotype controlled by the recessive sham ramification 2 (shr2) gene in tetraploid wheat T. turgidum L. allowed us to suggest putative functions of the SHR2 gene that may be involved in the regulation of spikelet meristem fate and in specification of floret meristems. The results of a gene interaction test suggested that genes WFZP and SHR2 function independently in different processes during spikelet development, whereas another spike ramification gene(s) interact(s) with SHR2 and share(s) common functions.

Conclusions

SS mutants represent an important genetic tool for research on the development of the wheat spikelet and for identification of genes that control meristem activities. Further studies on different non-standard SS morphotypes and wheat lines with altered spike morphology will allow researchers to identify new genes that control meristem identity and determinacy, to elucidate the interaction between the genes, and to understand how these genes, acting in concert, regulate the development of the wheat spike.

     

Patterns and impacting factors of gene evolutionary rate between wild and cultivated emmer wheat (Triticum turgidum)

Tetraploid emmer wheat (Triticum turgidum L., BBAA) is the founder progenitor of bread wheat, providing the valuable genetic resource and gene pool for wheat improvement. However, the evolutionary trajectory of tetraploid wheat, especially the evolutionary fate of different types of genes has not been well studied. In this study, the rate of non-synonymous substitution (d_N) and synonymous substitution (d_S) was calculated by comparing the orthologs between the wild emmer and cultivated durum wheat at the whole genome and subgenome levels to obtain the positively selected genes (PSGs) and negatively selected genes (NSGs). Then, mutation rate, gene length, exon number, GC content, codon bias, and expression level were comprehensively investigated and compared between the PSGs and NSGs. Within both wild emmer and cultivated durum wheat, PSGs between A and B subgenome displayed shorter gene and exon lengths as well as fewer exon numbers compared with NSGs, whereas from wild emmer to cultivated durum wheat, PSGs showed longer gene length and more exon numbers. Furthermore, PSGs displayed much higher expression levels and stronger codon usage bias, but lower genetic diversity compared with NSGs. Finally, two PSGs TdER1-6B, and TdLC7-2A, were found to play the crucial roles in regulating grain width and plant height of tetraploid wheat, respectively. This study systematically investigated the evolutionary, structural, and functional difference between PSGs and NSGs in tetraploid wheat, which will contribute to a better understanding of the selective mode and evolutionary trajectory during wheat domestication and evolution.     

The inheritance of tetraploid wheat seed peroxidases

Summary Embryo and endosperm peroxidases from dry mature seeds of three subspecies of tetraploid wheat (Triticum turgidum L.) were subjected to genetic analysis. The inheritance of eight isozymes (embryo isozymes a₂, d₁, d₂, e and f; and endosperm isozymes b, d and 4) were studied in F₂'s obtained from different wheat accessions. Simple monogenic inheritance producing three banded: one null segregation and two epistatic segregations (97 and 151) were found. In the case of isozymes b, d and 4, monogenic or epistatic segregation depended on the F₂ analyzed. Segregation data indicated that at least 9 different loci would determine the peroxidase isozymes of tetraploid wheat seed, all the loci studied containing null alleles. Furthermore, several loci determining embryo peroxidases were noticed to be mutually linked. All these data are discussed in context of the inheritance of seed peroxidases in hexaploid wheat and rye.     

Alien DNA introgression and wheat DNA rearrangements in a stable wheat line derived from the early generation of distant hybridization

Polyploidy has been found to be common in plants. Bread or common wheat (Triticum aestivum L., 2n=42) is a good example of allopolyploid made up of three diploid genomes A, B and D. In recent years, by the study of mimicking the origination of common wheat, it was found that changes of DNA sequence and gene expression occurred at the early stages of artificial allohexaploid between tetraploid wheat and Aegilops tauschii, which was probably favorable to genetic diploidization of new synthetic hexaploid wheat. Common wheat 99L2 is a new line stable in genetic, which was derived from the early self-pollinated generation of wide hybrids between common wheat and rye. In this study, it was found that at least two rye DNA segments had been introgressed into 99L2. This result suggested that a mechanism of alien DNA introgression may exist, which was different from the traditional mechanism of chromosome pairing and DNA recombination between wheat and alien species. Meanwhile, during the introgression process of alien rye DNA segments, the changes in DNA sequences of wheat itself occurred.     

A genetic linkage map of durum wheat

 A genetic linkage map of tetraploid wheat [Triticum turgidum (L.) Thell.] was constructed using segregation data from a population of 65 recombinant inbred lines (RILs) derived from a cross between the durum wheat cultivar Messapia and accession MG4343 of T. turgidum (L.) Thell. ssp dicoccoides (Korn.) Thell. A total of 259 loci were analysed, including 244 restriction fragment length polymorphisms (RFLPs), one PCR (polymerase chain reaction) marker (a sequence coding for a LMW (low-molecular-weight) glutenin subunit gene located at the Glu-B3 locus), seven biochemical (six seed-storage protein loci and one isozyme locus) and seven morphological markers. A total of 213 loci were mapped at a LOD≥3 on all 14 chromosomes of the A and B genomes. The total length of the map is 1352 cM and the average distance between adjacent markers is 6.3 cM. Forty six loci could not be mapped at a LOD≥3. A fraction (18.6%) of the markers deviated significantly from the expected Mendelian ratios; clusters of loci showing distorted segregation were found on chromosomes 1B, 3AL, 4AL, 6AL and 7AL. The durum wheat map was compared with the published maps of bread wheat using several common RFLP markers and general features are discussed. The markers detected the known structural rearrangements involving chromosomes 4A, 5A and 7B as well as the translocation between 2B-6B, but not the deletion on 2BS. This map provides a useful tool for analysing and breeding economically important quantitative traits and for marker-assisted selection, as well as for studies of genome organisation in small grain cereal species. Received: 5 January 1998 / Accepted: 31 March 1998     

Development of consistently crossable wheat genotypes for alien wheat gene transfer through fine-mapping of the <Emphasis Type="Italic">Kr1</Emphasis> locus

Breeders can force sexual hybridisation between wheat and related grass species to produce interspecific hybrids containing a dihaploid set of wheat and related chromosomes. This facilitates the introgression of desirable genes into wheat from the secondary gene pool. However, most elite European wheat varieties carry genes that suppress crossability, making the transfer of novel traits from exotic germplasm into elite wheat varieties difficult or impossible. Previous studies have identified at least five crossability loci in wheat. Here, the crossability locus with the largest effect, Kr1 on chromosome arm 5BL, was fine-mapped by developing a series of recombinant substitution lines in which the genome of the normally non-crossable wheat variety ‘Hobbit sib’ carries a recombinant 5BL chromosome arm containing segments from the crossable variety ‘Chinese Spring’. These recombinant lines were scored for their ability to cross with rye over four seasons. Analysis revealed at least two regions on 5BL affecting crossability, including the Kr1 locus. However, the ability to set seed is highly dependent on prevailing environmental conditions. Typically, even crossable wheat lines exhibit little or no seed set when crossed with rye in winter, but show up to 90% seed set from similar crosses made in summer. By recombining different combinations of the two regions affecting crossability, wheat lines that consistently exhibit up to 50% seed set, whether crossed in the UK winter or summer conditions, were generated, thus creating a very important tool for increasing the efficiency of alien wheat transfer programmes.     

Genetic diversity for drought resistance in wild emmer wheat and its ecogeographical associations

Wild emmer wheat (Triticum turgidum spp. dicoccoides (Körn.) Thell.), the tetraploid progenitor of cultivated wheat, is a potential source for various agronomical traits, including drought resistance. The objectives of this study were to characterize (1) the genetic diversity for drought resistance in wild emmer wheat, and (2) the relationship between drought responses of the wild emmer germplasm and the ecogeographical parameters of its collection sites. A total of 110 wild emmer accessions consisting of 25 populations and three control durum wheat cultivars were examined under two irrigation regimes, well-watered (’wet’) and water-limited (’dry’). Wide genetic diversity was found both between and within the wild emmer populations in most variables under each treatment. A considerable number of the wild emmer accessions exhibited an advantage in productivity (spike and total dry matter) over their cultivated counterparts. Most wild emmer wheat accessions exhibited a greater carbon isotope ratio (δ¹³C, indicating higher water-use efficiency) under the dry treatment and higher plasticity of δ¹³C relative to the cultivated controls, which may have contributed to the drought adaptations in the former. The most outstanding drought-tolerance capacity (in term of productivity under the dry treatment and susceptibility indices) was detected in wild emmer populations originated from hot dry locations. The results suggest that wild emmer has the potential to improve drought resistance in cultivated wheat.     

Genetic dissection of a major Fusarium head blight QTL in tetraploid wheat

The devastating effect of Fusarium head blight (FHB) caused by Fusarium graminearum has led to significant financial losses across the Upper Midwest of the USA. These losses have spurred the need for research in biological, chemical, and genetic control methods for this disease. To date, most of the research on FHB resistance has concentrated on hexaploid wheat (Triticum aestivum L.) lines originating from China. Other sources of resistance to FHB would be desirable. One other source of resistance for both hexaploid wheat and tetraploid durum wheat (T. turgidum L. var. durum) is the wild tetraploid, T. turgidum L. var. dicoccoides (T. dicoccoides). Previous analysis of the `Langdon'-T. dicoccoides chromosome substitution lines, LDN(Dic), indicated that the chromosome 3A substitution line expresses moderate levels of resistance to FHB. LDN(Dic-3A) recombinant inbred chromosome lines (RICL) were used to generate a linkage map of chromosome 3A with 19 molecular markers spanning a distance of 155.2 cM. The individual RICL and controls were screened for their FHB phenotype in two greenhouse seasons. Analysis of 83 RICL identified a single major quantitative trait locus, Qfhs.ndsu-3AS, that explains 37% of the phenotypic or 55% of the genetic variation for FHB resistance. A microsatellite locus, Xgwm2, is tightly linked to the highest point of the QTL peak. A region of the LDN (Dic-3A) chromosome associated with the QTL for FHB resistance encompasses a 29.3 cM region from Xmwg14 to Xbcd828.     

Wheat germ agglutinin evidence for a genetic basis of multiple forms

Germ from hexaploid wheat (Triticum aestivum L.) contained three forms of agglutinin separable by ion-excahnge column chromatography at pH 3.8, while germ from tetraploid wheat (Triticum turgidum L. (durum group)) contained only two such forms. The different number of forms, not due to protein modification occuring during the purification process, was demonstrable in commercial germ and in bran fractions containing germ from single wheat varieties. This evidence for a genetic basis of lectin multiple forms in wheat indicates the advisability of using genetically identified plant varieties in lectin research.     

Comparative responses of tetraploid wheats pollinated with Zea mays L. and Hordeum bulbosum L.

Ten different tetraploid wheat (Triticum turgidum) genotypes were pollinated with maize (Zea mays). Fertilization was achieved in all ten genotypes and no significant difference in fertilization frequency between the tetraploid wheat genotypes was detected. A mean of 41.1% of pollinated ovaries contained an embryo. All these crosses were characterized by the elimination of the maize chromosomes, and the resulting embryos were haploids. Six of the tetraploid wheat genotypes were also pollinated with Hordeum bulbosum. Fertilization frequencies with H. bulbosum were much lower (mean=13.4%), and significant differences between the tetraploid wheat genotypes were detected. Observation of pollen tube growth revealed that part of the incompatibility reaction between tetraploid wheats and H. bulbosum was due to an effect similar to that of the Kr genes, namely pollen tube growth inhibition. These results indicate that pollinations with maize may have potential as a broad spectrum haploid production system for tetraploid wheats. Present address: Agriculture Canada, Research Branch, Central Experimental Farm, Bldg 50, Ohawa, Ontario, Canada K1A OC6     

Phylogenetic analysis of tetraploid wheat based on nuclear DMC1 gene

Tetraploid wheat (AABB or AAGG, 2n = 4x = 28) holds an important place in Triticum. It includes two allopolyploid species, Triticum turgidum and Triticum timopheevii. Many problems concerning the phylogenetic relationships among tetraploid wheat species remain unresolved. In this study, sequences data for the nuclear DMC1 gene from 61 accessions of Triticum and Aegilops species, representing diploid and tetraploid species, were used to examine the phylogenetic relationships among tetraploid wheat. Phylogenetic trees were constructed using maximum-likelihood and neighbor-joining approaches, and gene flow and genetic differentiation values were computed. The results indicated that the A genome of tetraploid wheat originated from T. urartu rather than T. monococcum, and Aegilops speltoides was the donor of the B and G genomes. Hulled tetraploid wheat accessions formed a subclade, and naked tetraploid wheat got other subclade, indicating that at least two intermediary subspecies were involved in the evolution of T. turgidum. Triticum turgidum and T. timopheevii might have simultaneously originated from a hybridization events. These results indicated that the DMC1 gene sequences are useful for resolution of the molecular phylogenetic relationships of tetraploid wheat.     

Map-based analysis of the tenacious glume gene Tg-B1 of wild emmer and its role in wheat domestication

The domestication of wheat was instrumental in spawning the civilization of humankind, and it occurred through genetic mutations that gave rise to types with non-fragile rachises, soft glumes, and free-threshing seed. Wild emmer (Triticum turgidum ssp. dicoccoides), the tetraploid AB-genome progenitor of domesticated wheat has genes that confer tenacious glumes (Tg) that underwent genetic mutations to give rise to free-threshing wheat. Here, we evaluated disomic substitution lines involving chromosomes 2A and 2B of wild emmer accessions substituted for homologous chromosomes in tetraploid and hexaploid backgrounds. The results suggested that both chromosomes 2A and 2B of wild emmer possess genes that inhibit threshability. A population of recombinant inbred lines derived from the tetraploid durum wheat variety Langdon crossed with a Langdon — T. turgidum ssp. dicoccoides accession PI 481521 chromosome 2B disomic substitution line was used to develop a genetic linkage map of 2B, evaluate the genetics of threshability, and map the gene derived from PI 481521 that inhibited threshability. A 2BS linkage map comprised of 58 markers was developed, and markers delineated the gene to a 2.3 cM interval. Comparative analysis with maps containing the tenacious glume gene Tg-D1 on chromosome arm 2DS from Aegilops tauschii, the D genome progenitor of hexaploid wheat, revealed that the gene inhibiting threshability in wild emmer was homoeologous to Tg-D1 and therefore designated Tg-B1. Comparative analysis with rice and Brachypodium distachyon indicated a high level of divergence and poorly conserved colinearity, particularly near the Tg-B1 locus. These results provide a foundation for further studies involving Tg-B1, which, together with Tg-D1, had profound influences on wheat domestication.     

Development of a wheat genotype combining the recessive crossability alleles kr1kr1kr2kr2 and the 1BL.1RS translocation, for the rapid enrichment of 1RS with new allelic variation

The main objective of the present work was to develop a wheat genotype containing both the recessive crossability alleles (kr1kr1kr2kr2), allowing high crossability between 6x wheat and diploid rye, and the 1BL.1RS wheat/rye translocation chromosome. This wheat genotype could be used as a recipient partner in wheat–rye crosses for the efficient introduction of new allelic variation into 1RS in translocation wheats. After crossing the wheat cultivars ‘Mv Magdaléna’ and ‘Mv Béres’, which carry the 1BL.1RS translocation involving the 1RS chromosome arm from ‘Petkus’, with the line ‘Mv9 kr1’, 117 F₂ plants were analysed for crossability, ten of which had higher than 50% seed set with rye and thus presumably carried the kr1kr1kr2kr2 alleles. Four of the ten plants contained the 1BL.1RS translocation in the disomic condition as detected by genomic in situ hybridization (GISH). The wheat × rye F₁ hybrids produced between these lines and the rye cultivar ‘Kriszta’ were analysed in meiosis using GISH. 1BL.1RS/1R chromosome pairing was detected in 62.4% of the pollen mother cells. The use of fluorescent in situ hybridization (FISH) with the repetitive DNA probes pSc119.2, Afa family and pTa71 allowed the 1R and 1BL.1RS chromosomes to be identified. The presence of the 1RS arm from ‘Kriszta’ besides that of ‘Petkus’ was demonstrated in the F₁ hybrids using the rye SSR markers RMS13 and SCM9. In four of the 22 BC₁ progenies analysed, only ‘Kriszta’-specific bands were observed with these markers, though the presence of the 1BL.1RS translocation was detected using GISH. It can be concluded that recombination occurred between the ‘Petkus’ and ‘Kriszta’ 1RS chromosome arms in the translocated chromosome in these plants.