Genealogic analysis of the resistance of winter wheat to common bunt

Comparative genealogical analysis of North American (the United States and Canada) and Eastern European (Russia and Ukraine) winter wheat cultivars resistant and susceptible to common bunt has been performed. Analysis of variance applied to North American wheats has demonstrated that resistant and susceptible cultivars significantly differ from each other with respect to the contributions of common ancestors. The contributions of Oro (Bt4 and Bt7), Rio (Bt6), White Odessa (Bt1), and Florence (Bt3) to the resistant cultivars are significantly higher than their contributions to the susceptible ones. This demonstrates that the use of these resistance donors in wheat breeding for several decades has been effective. The contribution of PI-178383 (Bt8, Bt9, and Bt10) is considerably higher in the group of resistant cultivars bred after 1965. The mean contributions of Federation (Bt7) and Nebred (Bt4) are significantly higher in the group of resistant cultivars obtained before 1965; however, the differences in the contributions of these donors between new resistant and susceptible cultivars became nonsignificant. Among the Russian and Ukrainian cultivars, there are differences between groups of resistant and susceptible cultivars from different regions determined by the differences between the regional populations of the pathogen in racial composition. In the northern region, the contributions of the wheat grass (Agropyron glaucum) and the rye cultivar Eliseevskaya are significantly higher in the resistant cultivars; in the southern region, a local cultivar of the Odessa oblast is the prevalent resistant cultivar. In addition, cultivar Yaroslav Emmer is likely to be effective in the northern region; and foreign sources (Oro, Florence, Federation, and Triticum timopheevii), in the southern region. Very few sources of vertical resistance to common bunt are used for winter wheat breeding in Russia and Ukraine. The decrease in genetic diversity in favor of a few identical genes may cause adequate changes in the pathogen population and subsequent proliferation of the pathogen on the genetically identical substrate. A new interpretation of the resistance of line Lutescens 6028 as a source of new genes, Bt12 and Bt13, is suggested. Both genealogical and segregation analyses have shown that the genes determining the resistance of this line may be identical to those described earlier (Bt1, Bt3, Bt4, Bt6, and Bt7); and the high resistance of this line is determined by a combination of these genes.     

Use of winter wheat x Triticum tauschii backcross populations for germplasm evaluation

The wild diploid goatgrass, Triticum tauschii (Coss.) Schmal., is an important source of genes for resistance to both diseases and insects in common wheat (Triticum aestivum L.) We have evaluated grain yield, kernel weight, protein concentration, and kernel hardness of 641 BC₂ F₁-derived families from direct crosses involving four T. aestivum cultivars and 13 T. tauschii accessions over 2 years and at two Kansas, USA, locations. On average, T. tauschii germplasm depressed grain yield and increased protein concentration, whereas kernel weight was affected either positively or negatively, depending on the T. tauschii parent. Three T. tauschii parents produced a large proportion of families with very soft endosperm. Some variation among progeny of different T. tauschii parents resulted from the segregation of genes for resistance to leaf rust (caused by Puccinia recondita Rob. ex Desm.). This study confirmed that random BC₂-derived families can be used to evaluate the effects of T. tauschii genes in the field. This methodology, although laborious, can provide useful information which is not obtainable by the screening of T. tauschii accessions themselves.Joint contribution of USDA-ARS, the Kansas Agricultural Experiment Station, and the Wheat Genetics Resource Center. Contribution no. 94-242-J. Mention of a proprietary name in the article does not imply approval to the exclusion of other suitable products     

Use of genomic in situ hybridization for the genetic study of common wheat Triticum aestivum L. and its close relatives

The literature data on use of genomic in situ hybridization (GISH) for genetic studying of common wheat and its close relatives are reviewed. The conclusions as to the necessity of complex investigation of genetic material using GISH and other modern methods are drawn.     

Meta-QTL analysis of the genetic control of ear emergence in elite European winter wheat germplasm

Variation in ear emergence time is critical for the adaptation of wheat (Triticum aestivum L.) to specific environments. The aim of this study was to identify genes controlling ear emergence time in elite European winter wheat germplasm. Four doubled haploid populations derived from the crosses: Avalon × Cadenza, Savannah × Rialto, Spark × Rialto, and Charger × Badger were selected which represent diversity in European winter wheat breeding programmes. Ear emergence time was recorded as the time from 1st May to heading in replicated field trials in the UK, France and Germany. Genetic maps based on simple sequence repeat (SSR) and Diversity Arrays Technology (DArT) markers were constructed for each population. One hundred and twenty-seven significant QTL were identified in the four populations. These effects were condensed into 19 meta-QTL projected onto a consensus SSR map of wheat. These effects are located on chromosomes 1B (2 meta-QTL), 1D, 2A (2 meta-QTL), 3A, 3B (2 meta-QTL), 4B, 4D, 5A (2 meta-QTL), 5B, 6A, 6B 7A (2 meta-QTL), 7B and 7D. The identification of environmentally robust earliness per se effects will facilitate the fine tuning of ear emergence in predictive wheat breeding programmes. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Comparative genetic analysis of the Aegilops longissima and Ae. sharonensis genomes with common wheat

Aegilops longissima Schw. et Musch. (2n= 2x=14, S^lS^l) and Aegilops sharonensis Eig. (2n=2x=14, S^lS^l) are diploid species belonging to the section Sitopsis in the tribe Triticeae and potential donors of useful genes for wheat breeding. A comparative genetic map was constructed of the Ae. longissima genome, using RFLP probes with known location in wheat. A high degree of conserved colinearity was observed between the wild diploid and basic wheat genome, represented by the D genome of cultivated wheat. Chromosomes 1S^l, 2S^l, 3S^l, 5S^l and 6S^l are colinear with wheat chromosomes 1D, 2D, 3D, 5D and 6D, respectively. The analysis confirmed that chromosomes 4S^l and 7S^l are translocated relative to wheat. The short arms and major part of the long arms are homoeologous to most of wheat chromosomes 4D and 7D respectively, but the region corresponding to the distal segment of 7D was translocated from 7S^lL to the distal region of 4S^lL. The map and RFLP markers were then used to analyse the genomes and added chromosomes in a set of ’Chinese Spring’ (CS)/Ae. longissima chromosome additions. The study confirmed the availability of disomic CS/Ae. longissima addition lines for chromosomes 1S^l, 2S^l, 3S^l, 4S^l and 5S^l. An as yet unpublished set of Ae. sharonensis chromosome addition lines were also available for analysis. Due to the gametocidal nature of Ae. sharonensis chromosomes 2S^l and 4S^l, additions 1S^l, 3S^l, 5S^l, 6S^l and 7S^l were produced in a (4D)4S^l background, and 2S^l and 4S^l in a euploid wheat background. The analysis also confirmed that the 4/7 translocation found in Ae. longissima was not present in Ae. sharonensis although the two wild relatives of wheat are considered to be closely related. The phenotypes of the Ae. sharonensis addition lines are described in an Appendix. Received: 28 September 2000 / Accepted: 19 January 2001     

Synthetic hexaploid wheat and its utilization for wheat genetic improvement in China

Synthetic hexaploid wheat （Triticum turgidum x Aegilops tauschii） was created to explore for novel genes from T. turgidum and Ae. tauschii that can be used for common wheat improvement. In the present paper, research advances on the utilization of synthetic hexaploid wheat for wheat genetic improvement in China are reviewed. Over 200 synthetic hexaploid wheat （SHW） accessions from the International Maize and Wheat Improvement Centre （CIMMYT） were introduced into China since 1995. Four cultivars derived from these, Chuanmai 38, Chuanmai 42, Chuanmai 43 and Chuanmai 47, have been released in China. Of these, Chuanmai 42, with large kernels and resistance to stripe rust, had the highest average yield （〉 6 t/ha） among all cultivars over two years in Sichuan provincial yield trials, outyielding the commercial check cultivar Chuanmai 107 by 22,7%. Meanwhile, by either artificial chromosome doubling via colchicine treatment or spontaneous chromosome doubling via a union of unreduced gametes （2n） from T. turgidum-Ae, tauschii hybrids, new SHW lines were produced in China. Mitotic-like meiosis might be the cytological mechanism of spontaneous chromosome doubling. SHW lines with genes for spontaneous chromosome doubling may be useful for producing new SHW-alien amphidiploids and double haploid in wheat genetic improvement.     

Molecular genetic characteristics of the Wx-B1e allele from common wheat and applicability of the DNA markers for its identification

Molecular genetic characterization of the Wx-B1e allele identified by the authors of the study in the common wheat cultivar Korotyshka was performed. The 804-bp Wx-B1e fragment was cloned and sequenced. Comparison of the sequence obtained with that for the wild-type allele of common wheat (Wx-B1a) demonstrated that Wx-B1e carried the 34-bp insertion, 8-bp deletion, and 23 nucleotide substitutions. BLAST analysis revealed the highest homology with the nucleotide sequences of Wx genes from Triticum spelta and Triticum durum. The amplification variants of four Wx-B1 molecular markers, applied worldwide for testing the collections for different Wx allelic variants, are demonstrated.     

行距对晚播冬小麦群体的调节效应

为了明确行距对晚播冬小麦群体的调节效应,在2011—2013年度,以"济麦22"为试验材料,在晚播条件下设置3个行距处理(12、20、30 cm),比较了不同行距类型群体生育后期的冠层结构和冠层下部环境的差异、群体内植株个体性状及变异程度、产量和产量构成因素的变化。结果表明:行距缩小至12 cm,群体生育后期的叶面积指数显著提高,中上部冠层的光能截获显著增加、冠层下部的漏光损失显著减小;与20 cm和30 cm行距相比,12 cm行距群体内部的最高温度分别降低0.9和2.5℃,相对湿度增加0.3%和0.9%;行距缩小后,群体内单株性状的变异程度缩小,穗长和小穗数显著增加,单株穗粒重变异系数缩小,群体产量的稳定性提高,产量增加7.8%~24.5%。研究认为,窄行距(12 cm)播种有利于提高华北平原干旱缺水地区晚播冬小麦的群体产量。     

AB-QTL analysis in winter wheat: II. Genetic analysis of seedling and field resistance against leaf rust in a wheat advanced backcross population

The present study aimed to localize exotic quantitative trait locus (QTL) alleles for the improvement of leaf rust (P. triticina) resistance in an advanced backcross (AB) population, B22, which is derived from a cross between the winter wheat cultivar Batis (Triticum aestivum) and the synthetic wheat accession Syn022L. The latter was developed from hybridization of T. turgidum ssp. dicoccoides and T. tauschii. Altogether, 250 BC₂F₃ lines of B22 were assessed for seedling resistance against the leaf rust isolate 77WxR under controlled conditions. In addition, field resistance against leaf rust was evaluated by assessing symptom severity under natural infestation across multiple environments. Simultaneously, population B22 was genotyped with a total of 97 SSR markers, distributed over the wheat A, B and D genomes. The phenotype and genotype data were subjected to QTL analysis by applying a 3-factorial mixed model analysis of variance including the marker genotype as a fixed effect and the environments, the lines and the marker by environment interactions as random effects. The QTL analysis revealed six putative QTLs for seedling resistance and seven for field resistance. For seedling resistance, the effects of exotic QTL alleles improved resistance at all detected loci. The maximum decrease of disease symptoms (−46.3%) was associated with marker locus Xbarc149 on chromosome 1D. For field resistance, two loci had stable main effects across environments and five loci exhibited marker by environment interaction effects. The strongest effects were detected at marker locus Xbarc149 on chromosome 1D, at which the exotic allele decreased seedling symptoms by 46.3% and field symptoms by 43.6%, respectively. Some of the detected QTLs co-localized with known resistance genes, while others appear to be as novel resistance loci. Our findings indicate, that the exotic wheat accession Syn022L may be useful for the improvement of leaf rust resistance in cultivated wheat.     

Beginning and duration of expression of photoperiodic response genes in winter common wheat

The influence of various Ppd genes on the beginning and duration of photoperiodic responce has been investigated in near isogenic lines of winter bread wheat Mironovskaya 808. During ontogenesis the photoperiodic responce is ascertained from the middle 2nd stage of ontogenesis according to Kuperman (usually a week later after vernalization completion in winter genotypes) and it is completed to the late 5th stage (2-3 weeks before heading). Different Ppd alleles do not affect the photoreaction intensity however they have an influence on its duration through the rate of development. Ppd-A1a and Ppd-B1a genes manifest shorter duration of expression when compared to the recessive alleles in the initial Mironovskaya 808 cultivar. Effect of the Ppd-B1a gene is stronger and of the Ppd-A1a is weaker.     

Use of DNA fingerprinting for human population genetic studies

DNA fingerprinting techniques have been used in population genetic studies on many different kinds of organisms. Here, we present new applications for multilocus DNA fingerprint probes in population studies and demonstrate the applicability of DNA fingerprinting to human population genetics, using M13 phage DNA as a probe. The new approach, which is based on a factor method of numerical coding of non-quantitative data (factor correspondence analysis-FCA), shows good agreement between population position, as indicated by the three principal factors, and ethnogenetic proximity.     

Dynamics of genetic diversity in winter common wheat Triticum aestivum L. cultivars released in Russia from 1929 to 2005

Genealogical analysis was used to study the dynamics of genetic diversity in Russian cultivars of winter common wheat from 1929 to 2005. The Shannon diversity index of the total set of released cultivars remained almost unchanged, although the number of original ancestors (landraces and genetic lines) increased almost tenfold in the period under study. This was explained in terms of the dependence of the modified Shannon diversity index on two parameters, the number of original ancestors and the mean coefficient of parentage. Significant direct effects were revealed: a positive effect of the former parameter and a negative of the latter. As a result, the increase in the number of original ancestors was compensated by the increase in relatedness of cultivars. Genetic erosion of released diversity was observed, as a half of Russian landraces were lost. Although the mean coefficient of parentage did not reach its critical value $(\bar R = 0.25)$ , cultivars of some regions (Central and Volga-Vyatka) proved to be closely related. A favorable gradual decrease in the mean coefficient of parentage was observed in the past 15 years. A set of modern winter wheat cultivars, which were introduced in the Russian Official List from 2002 to 2005, displayed a cluster structure. The overwhelming majority of cultivars formed two clusters originating from Bezostaya 1 (67% of cultivars) and Mironovskaya 808 (31%).     

Molecular genetic analysis of grain protein content and flour whiteness degree using RILs in common wheat

Grain protein content (GPC) and flour whiteness degree (FWD) are important qualitative traits in common wheat. Quantitative trait locus (QTL) mapping for GPC and FWD was conducted using a set of 131 recombinant-inbred lines derived from the cross ‘Chuan 35050 × Shannong 483’ in six environmental conditions. A total of 22 putative QTLs (nine GPC and 13 FWD) were identified on 12 chromosomes with individual QTL explaining 4.5–34.0% phenotypic variation. Nine QTLs (40.9%) were detected in two or more environments. The colocated QTLs were on chromosomes 1B and 4B. Among the QTLs identified for GPC, QGpc.sdau-4A from the parent Shannong 483 represented some important favourable QTL alleles. QGpc.sdau-2A.1 and QFwd.sdau-2A.1 had a significant association with both GPC and FWD. The markers detected on top of QTL regions could be potential targets for marker-assisted selection.     

Dynamics of genetic diversity in winter common wheat Triticum aestivum L. cultivars released in Russia from 1929 to 2005

Genealogical analysis was used to study the dynamics of genetic diversity in Russian cultivars of winter common wheat from 1929 to 2005. The Shannon diversity index of the total set of released cultivars remained almost unchanged, although the number of original ancestors (landraces and genetic lines) increased almost tenfold in the period under study. This was explained in terms of the dependence of the modified Shannon diversity index on two parameters, the number of original ancestors and the mean coefficient of parentage. Significant direct effects were revealed: a positive effect of the former parameter and a negative of the latter. As a result, the increase in the number of original ancestors was compensated by the increase in relatedness of cultivars. Genetic erosion of realized diversity was observed, as a half of Russian landraces were lost. Although the mean coefficient of parentage did not reach its critical value (R = 0.25), cultivars of some regions (Central and Volga-Vyatka) proved to be closely related. A favorable gradual decrease in the mean coefficient of parentage was observed in the past 15 years. A set of modem winter wheat cultivars, which were introduced in the Russian State Catalog from 2002 to 2005, displayed a cluster structure. The overwhelming majority of cultivars formed two clusters originating from Bezostaya 1 (67% of cultivars) and Mironovskaya 808 (31%).     

Choosing probe genotypes for the analysis of genotype-environment interaction in winter wheat trials

Genotype-environment interaction was analyzed in French multi-environment wheat (Triticum aestivum L.) trials using probe genotypes and bi-additive factorial regression. Probe genotypes are specific genotypes in which the comparisons of yield components to reference values describe the most-important environmental factors that limited grain yield. The time-period until flowering was described by the deviation of kernel number from a threshold number while the grain-filling period was described by the reduction of thousand-kernel weight from a potential value. The aim of this paper was to determine the convenient number and the characteristics of probe genotypes to include in wheat breeding trials. Two sets of genotypes were used to model genotype-environment interaction: set 1 with 12 varieties tested in 18 environments and set 2 with ten lines tested in 14 environments. Set 2 was used for validation. Seven probe genotypes described the environments by providing environmental covariates, namely differences in yield components, for further analysis of interaction in set 1 and set 2. Interaction was modelled with bi-additive factorial regressions including differences in yield components. Several rounds of models were fitted to determine the optimal number of probe genotypes (i.e. environmental covariates) to introduce. From the seven probe genotypes, all the possible combinations including one to seven genotypes were studied. Significance of the combinations was tested with critical values obtained from simulations through 1,000 random permutations. Taking into account the information available on the probe genotypes, one would think that two, three or four probe genotypes would be sufficient, otherwise the number should reach four or five genotypes. In all cases, these numbers will provide models more-parsimonious than the classical AMMI model. The important information to be known on the probe genotypes prior their first multilocation experiment is: interaction pattern, earliness, and differences in yield component. Tested for the first time, a quadruplet is better than a triplet because the probability of choosing complementary genotypes increases with their number.     

Genetic control system of the differences in duration of vernalization in winter common wheat

Hypotheses of differences in genetic control on duration of vernalization for winter wheat have been considered. It has been shown that differences in this character are controlled by independent Vrd gene system. Monogenic dominant near-isogenic lines have been created. They differ in two non-allelic Vrd1 and Vrd2 genes with unequal expression. The response of created lines to photoperiodic changes and Vrd genes effects on various agronomic traits have been characterized. Vrd genotypes have been identified in a number of winter common wheat cultivars.     

Differences in the genetic systems controlling photoreaction and vernalization requirements in winter wheat]

Comparing of vernalization requirement and photoperiodic sensitivity in various winter genotypes and F4 lines was carried out. The results of genetic analysis of Ppd genotypes in the crosses of winter wheat cultivars differing in photosensitivity and duration of vernalization requirement are described. It has been shown that differences in duration of vernalization requirement are under control of independent genetic system, distinctive from Ppd gene system regulating level of photosensitivity. This independence does not deny the opposite possibility of Ppd genes to modify duration of vernalization requirement in winter wheat.     

Standardizing selection and its consequences for genetic population structure

Type of selection for total fitness, specific for domestic animals and termed by us standardizing selection, is discussed. Consequences of such selection for the population structure genetic are considered taking a population of domestic pigs as an example. Examples of effective and ineffective standardizing selection are presented. Specific features of genetic determination of ten quantitative traits detected in analysis of standardizing selection are discussed.     

The response of spring barley and winter wheat to Avena fatua population density

Populations of Avena fatua were established in crops of spring barley and winter wheat, and relationships derived between yield and other crop parameters, and weed density. Competitive effects of A. fatua, which were similar to those found in other countries, were greatest at low crop densities. Crop head numbers were reduced proportionately less than crop yield, indicating that competition was affecting other yield components. Competition increased the proportion of thin grain of barley but not of wheat. Competition had little effect on the moisture content and the contamination of the harvested grain by A. fatua, suggesting that at threshold populations these factors are unlikely to be of economic significance. It was concluded that at average crop densities, low infestations of A. fatua are likely to result in cereal yield losses in the region of 1 % for each A. fatua plant m^-2.