Articles
One of the largest world wheat collections maintained in a living state at the N.I. Vavilov Research Institute of Plant Industry, St. Petersburg, is described, and studies conducted with the collection are reviewed. The history of pre-breeding studies and results of genetic diversity evaluation of wheat samples by means of DNA markers is surveyed.
The results of the work on the development of the gene pool of Siberian spring common wheat and spring and winter triticale are reported. Collections of traits and genes and working collections of these cereals are described. The gene pool includes almost all landraces of Siberian origin. All accessions are registered in the certificate database and have numbers of the Siberian Institute of Plant Industry and Breeding. Atypical forms collected from heterogeneous populations also have their accession numbers. In addition, a collection of spontaneous spring mutants isolated from populations of winter crops is being developed. Twenty two spring common wheat varieties and two winter triticale varieties have been created on the base of the Siberian gene pool developed at the Institute.
Pilot experiments on molecular marker application in breeding of winter wheat at the Krasnodar Lukyanenko Research Institute of Agriculture (KNIISH) are described. The most efficient ways of marker application in creating new cultivars are outlined. A variety of genes responsible for valuable agronomic traits in KNIISH varieties have been detected.
The results of investigation and exploitation of the synthetic genome addition line T. miguschovae (Triticum militinae /Aegilops tauschii) and genome substitution lines Avrodes, Avrosis, Avrolata, Avrotata, Avroale, and Avrocum are reported. In the genome substitution forms, genomes of Ae. speltoides, Ae. sharonensis, Ae. umbellulata, Ae. uniaristata, Secale cereale and Agropyron glaucum are substituted for the D-genome of common wheat cultivar Avrora. The synthetic forms provide a unique genetic basis for preservation and use of the gene pool of wild relatives in wheat breeding. These forms have been used to produce secondary recombination synthetic forms (RS forms) with genome constitutions BBAADS, BBAASR and BBAASSsh. These cytologically stable introgression lines combine disease resistance and high protein content. Five common winter wheat cultivars have been developed on the base of the introgression lines obtained.
Plant genetic resources (PGR) have been used in breeding programs for many decades to produce modern varieties by introducing genes of interest, in particular, resistance genes. Nevertheless, these resources remain underestimated if we focus on abiotic stress tolerance or new agricultural techniques, which consider productivity with regard to the environment. In recent years, new users, such as scientists and farmers, have discovered diverse sources of interest for screening and exploiting natural diversity conserved in PGR collections.
In the case of the French cereals PGR Network, a share of the responsibility, based on the knowledge and ability of network members, has been decided in order to better promote the use of PGR. The main species of Triticum (wheat), Hordeum (barley), Secale (rye), ×Triticosecale (triticale), Avena (oat) genera and their wild relatives are held in the collection. By combining phenotypic and genotypic data, the whole genetic resource collection has been structured into smaller functional groups of accessions, in order to facilitate the access and meet the increasing number of different requirements for the distribution of adapted samples of accessions.
New panels are being processed to give breeders and scientists new useful tools to study, for instance, stress resistance or to develop association studies. All these data obtained from the French small grain cereal Network will be progressively available through the INRA Genetic Resource Website (http://urgi.versailles.inra.fr/siregal/siregal/welcome.do).
With the expected development of thousands of molecular markers in most crops, the marker-assisted selection theory has recently shifted from the use of a few markers targeted in QTL regions (or derived from candidate or validated genes) to the use of many more markers covering the whole genome. These genome-wide markers are already used for association analysis between polymorphisms for anonymous markers and qualitative or quantitative traits. The condition for success is that a sufficient level of linkage disequilibrium (LD) exists between the adjacent markers used for genotyping and the true genes or QTLs. This LD is known to vary among species and type of genetic material. In selfing species, particularly among breeding lines, LD has been reported to range up to 1 cM or more. In such conditions, uncharacterized markers can be used to predict the breeding value of a trait without referring to actual QTLs. We present an example applying DArT markers to the INRA wheat breeding material in an attempt to implement whole genome selection as an alternative to phenotypic selection. This study assesses different models (GBLUP, Ridge Regression BLUP, Bayesian Ridge Regression and Lasso) and their ability to predict the yields of genotypes evaluated in a multi-site network from 2000 to 2009 in a highly unbalanced design. The prediction coefficients obtained by cross-validation techniques are encouraging, given the small size of the training population.
Heading time of substitution and near-isogenic lines (NILs) with Vrn-B1a and Vrn-B1c alleles was studied without vernalization and after 30-day vernalization in a greenhouse and in the field. Without vernalization, both in a greenhouse and in the field, plants with the Vrn-B1c allele headed several days earlier than plants with Vrn-B1a. However, plants with Vrn-B1a responded to vernalization by more pronounced heading acceleration than Vrn-B1c plants. The weak Vrn-B1a allele dominated in F1 hybrids from the cross between two NILs with the Vrn-B1c and Vrn-B1a alleles. These observations confirm the multiple allelism of the Vrn-B1 gene, responsible for the spring growth habit in wheat.
Allele combinations of the Ppd-D1, Vrn-A1, Vrn-B1 and Vrn-D1 genes have been investigated with allele-specific primers in 56 wheat cultivars and breeding lines raised at the Lukyanenko Krasnodar Research Institute of Agriculture. A significant association between the allele combinations and heading dates has been detected, as well as an interaction between the genotype and day length. Allele-specific markers allow breeders to manipulate plant material and to choose allele combinations most suitable for particular growth conditions.
The paper presents an overview of studies of genetic polymorphism of loci determining bread-making quality among Ukrainian wheat varieties by means of electrophoretic analysis of storage proteins (Gli and Glu) and PCR. The results of analysis of polymorphism in the Gli-A1, Gli-B1, Gli-D1, Glu-A3 loci, as well as the allelic compositions of the Pina-D1 and Pinb-D1 genes, determining grain hardness, and Wx genes, controlling amylose content in the starch of the endosperm, are presented. Comparison of the results obtained with allele-specific primers to the γ gliadin loci and by storage protein electrophoresis shows that the former method can identify some alleles, but the level of polymorphism revealed by this method is lower than that revealed by electrophoresis of storage proteins. Most of the varieties under consideration have PCR alleles characteristic for hard wheat, and only three varieties have alleles specific for soft wheat. Varieties originating from different Ukrainian breeding-centers differ in grain hardness. PCR analysis has not revealed the presence of null alleles of Wx genes in the studied Ukrainian genetic pool but allowed selection of breeding material for further development of low-amylose varieties.
The transition from vegetative to reproductive development in wheat is regulated by seasonal cues, including vernalization and photoperiod. Here we present a simple logical model of the wheat development gene network. Vernalization accelerates flowering in winter cereals. It is regulated mainly by the vernalization genes VRN1, VRN2, and VRN3. After vernalization, VRN1 downregulates the VRN2 flowering repressor, thereby increasing the VRN3 level. The expression of VRN3 promotes further increases in the VRN1 transcription level, generating a positive feedback loop, which enhances VRN1 transcription to a threshold level required to initiate flowering. The products of the PPD1 and CO2 photoperiod genes increase VRN3 expression under long daylight conditions. Seasonal changes in day length are perceived by plant photoreceptors and transmitted to the circadian clock to modulate flowering time. Here we integrate data on vernalization and photoperiod genes in a gene network. Using a synchronous Boolean model, we have simulated the network dynamics. This model can be useful to test the coherence of experimental data and to hypothesize gene interactions that remain to be discovered.
Antimicrobial peptides (AMPs) are low-molecular-weight defense polypeptides, produced in all living organisms either constitutively or upon perception of signals from pathogenic microorganisms. They are important components of the immune system in both animals and plants. AMPs differ in structure and mode of action. Most of them belong to cysteine-rich peptides; their molecules contain even numbers of cysteine residues involved in the formation of disulphide bonds, which stabilize the peptide structure. A number of families of plant AMPs have been isolated on the base of amino acid sequence similarity and 3D structure. Plant AMP genes can be used in the engineering of pest resistance in crops and development of novel antibiotics and antimycotics. We provide a concise review of properties and gene structures of major AMP families discovered by the authors in Triticum kiharae seeds, including glycine-rich peptides, defensins, hevein-like peptides and the so-called 4-Cys peptides.
DNA samples of wild relatives, synthetic forms and introgression lines of common wheat (Triticum aestivum L.) have been genotyped with diagnostic molecular markers linked to known leaf rust resistance genes Lr9, Lr35 and Lr47. The Lr9 gene is present identified in Aegilops umbellulata, and Lr35 and Lr47, in Ae. speltoides. The synthetic forms Avrolata and Avrodes, with the substitution of the genomes of A е. umbellulata and Aе. speltoides, respectively, for the wheat D-genome, possess Lr9 and Lr35 genes. The genomes of the introgression lines developed using Aе. umbellulata lack Lr9. The Lr35 gene is present in one of the introgression lines derived from Avrodes. Some of the wild relatives and the introgression lines are suggested to have additional leaf rust resistance genes.
The effect of genes for adult plant resistance to leaf rust has been explored in southern West Siberia by the examples of common wheat cv. Thatcher (Tc), carrying the Lr22b gene, and its near-isogenic lines TcLr34 and TcLr37. Lr22b is ineffi cient, Lr34 slows down the disease development at a mean daily temperature below 16 ºС, but is poorly efficient at temperatures above 20 ºС. Lr37 confers high resistance under all conditions. At the heading stage, TcLr34 and TcLr37 show similar components of partial resistance to rust: reduction in the number and sizes of spots and sporogenesis suppression. Cytological examination has revealed partial suppression of the formation of Puccinia triticina infection signs (appressoria and haustorium) without hypersensitive reaction (HR). Additional defense mechanisms include an oxidative burst induced by contacts of appressoria with stomata and callose-lignine appositions on the wall. Auto fluorescence of lignins in TcLr34 and TcLr37 lines differs from the glow typical of HR-accompanied combinations. The Lr34 and Lr37 genes exert a pleiotropic action on pathogenesis.
Puccinia graminis f. sp. tritici induces stem rust, which is the cause of a considerable crop loss. Race Ug99 of P. graminis f. sp. tritici (pathotype TTKS) is virulent to the majority of wheat varieties. According to FAO reports, major wheat-producing countries to the east of Iran (Afghanistan, India, Pakistan, Turkmenistan, Uzbekistan and Kazakhstan) are greatly endangered. It is necessary to seek resistance sources to stem rust with identified Sr genes. Screening with PCR SSR and STS markers associated with effective Sr genes (Sr2, Sr22, Sr24 and Sr46) was undertaken to identify Sr gene sources. Twelve accessions with the Sr2-gene were identified. Seven resistant lines were found to possess Sr24/Lr24 genes. Sr46 was identified in one line. PCR analysis revealed the presence of Sr22 in six promising lines. The results are used in wheat breeding programs for stem rust resistance with marker-assisted selection.
The effects of introgression fragments from Triticum timopheevii Zhuk. (2n = 28, AtAtGG) and their combinations on resistance to leaf rust, stem rust, powdery mildew, and some quantitative traits were assessed in 15 common wheat introgression lines. Molecular and cytological analyses of the lines demonstrated an advantage of combined use of various marker types in comprehensive characterization of hybrids and detection of translocations and substitutions. Resistance tests to various fungal diseases showed that the lines containing introgression fragments of chromosome 5G were completely resistant to the West Siberian populations of leaf rust and to the stem rust population of the Omsk region. Lines 3862-5 and 3862-15, containing a fragment of the long arm of chromosome 2G, were resistant to West Siberian stem rust populations. No negative effects of the alien genetic material on yield and other quantitative traits were noted. In addition, positive effect of the 2G chromosome fragments of Triticum timopheevii on ear grain number was established. Thus, the introgression lines can be used in breeding programs as donors of resistance genes to fungal diseases.
The states of the 18S/5S mitochondrial (mt) repeat and some chloroplast DNA regions have been studied in alloplasmic lines of common wheat with cytoplasm from barley species Hordeum marinum subsp. gussoneanum Hudson and H. vulgare L., and in progenies of reciprocal hybrids between Triticum aestivum L. and Secale cereale L. The heteroplasmic state of the 18S/5S repeat, which was a result of biparental mtDNA transmission, is observed in rye × wheat hybrids and in their progenies possessing rye cytoplasm. For the first time, the heteroplasmic state of chloroplast DNA associated with heteroplasmy of the 18S/5S mt repeat has been detected in cereals by using alloplasmic wheat lines. It has been found that the transition of mt- and cpDNA heteroplasmy, barley homoplasmy of chloroplast regions to wheat homoplasmy is associated with complete fertility restoration and barley chromosome elimination from the newly developed nuclear genomes of alloplasmic lines.
DELLA proteins are a subfamily of transcriptional regulators from the GRAS protein family. They act as growth repressors. Gibberellins (GA) promote growth by overcoming the DELLA-mediated growth restraint. A number of dominant mutations in highly conserved orthologous DELLA genes are known in various plant species. These mutations reduce plant height owing to production of more active forms of growth repressors. The aim of the current study is to estimate the genetic similarity of DELLA nucleotide and amino acid sequences stored in GenBank and to identify mutant and wild type alleles that encode DELLAs in modern Ukrainian winter bread wheat varieties. We have performed nucleotide and amino acid sequence search and alignment of the Rht-D1 wheat dwarfing gene and DELLA-encoding genes of other plant species with BLAST and MUSCLE software. A dendrogram illustrating phylogenetic relations among DELLA sequences of 35 plant species has been constructed using MEGA v5. In addition, PCR-based genotyping for the major wheat dwarfing genes Rht-B1 and Rht-D1 has been performed in wheat cultivars from different regions of Ukraine. It is shown that the mutant Rht-D1b allele is the commonest dwarfing allele among those tested in Ukrainian wheat cultivars (68 %), but its distribution over Ukraine is not random.
Lines derived from spring bread wheat Omskaya 37 and possessing wheat-rye translocation 1RS.1BL have been studied and tested for resistance to fungal pathogens, drought, crop yield, and parameters characterizing ecological plasticity and stability. Three lines have been studied with the use of the C-banding technique. It is shown that these lines, in addition to wheat-rye translocation 1RS.1BL possess wheat-wheatgrass translocation 7DL-7Ai, where a segment of chromosome 7Ai of Agropyron elongatum (= Thinopyrum elongatum ; = Thinopyrum ponticum) is translocated to the long arm of wheat chromosome 7D. It is concluded that the complex stability of Omskaya 37 and its promising lines is related to the influence of a cluster of genes located on segments of rye and Agropyron chromosomes involved in the respective wheat–alien translocations. Several promising lines are recommended for further use in breeding programs. One of the lines we consider here, Lutescens 242/97-2-10, is submitted to state variety trial for registration as spring wheat variety Omskaya 41.
Molecular marker-based identification of allelic variants of Wx genes has been performed in the collection of 99 common wheat cultivars and breeding lines developed at the Krasnodar Lukyanenko Research Institute of Agriculture.
Use of two molecular markers to the Wx-А1 gene shows that cultivars ‘Starshina’ and ‘Sila’ carry null alleles of Wx-А1. Studies with four systems of molecular markers indicate that cultivars ‘Nota’ and ‘Lastochka’ possess the Wx-B1e allele. No cultivars with null-alleles of Wx-B1 have been found. Only wild-type alleles are present in the Wx-D1 locus.
Studies of several generations of common wheat lines carrying changes induced by nonionic detergent Triton X-100 (TX-100) are reported. It is shown that the induced changes recorded in the first generations are also observed in the fourth, fifth and sixth generations.
Coloration of some wheat organs may be of adaptive significance. Coloration traits are widely used in wheat taxonomy and variety identification. They also provide a suitable model for genetic and molecular studies. Here, data on chromosome location, genetic mapping, and structural and functional organization of all known genes determining coloration in wheat are reviewed. To date, thirty genes determining coloration in wheat have been mapped. These genes are represented mainly by homoeologous loci in the A, B and D genomes, and most of them are located in the 1S0.8 and 7S0.4 gene-rich regions of wheat genome. Comparative mapping in cereals shows that some orthologous genes determining coloration occur in a few species (homoeologous series Rg has been found in wheat and Aegilops only, and R, in wheat, Aegilops and rye), whereas others (genes determining anthocyanin pigmentation) widely occur in Poaceae. The data on comparative mapping together with the results of recent studies dedicated to cloning and functions of genes determining coloration in wheat suggest that these genes belong to the Myb- and Myc-like families of genes, encoding transcriptional activators for structural genes involved in plant flavonoid pigments biosynthesis.
The (1B) 1R wheat-rye chromosome substitution and 1BL.1RS translocation have been identified in original introgression stocks using cytological and molecular marker analysis. The pairing between short arms of chromosomes 1BL.1RS and bread wheat chromosome 1B is observed at a very low frequency (in 0,2–0,3 % of pollen mother cells). The translocation stocks are resistant to leaf and stem rusts, and the substitution stocks are susceptible because of the different origins of the chromosomes 1R involved in the translocation or substitution. The Hg1 gene for glume hairiness, inherited from cv. Hostianum 237, has been detected in some introgression stocks. Several stocks show hairiness on the leaf upper surface, lower surface and leaf margin. The character, probably originating from Ae. tauschii, was inherited from the synthetic wheat T. timopheevii Zhuk./Aegilops tauschii Coss.
Gene engineering techniques and transgenic plants are frequently used in plant molecular genetics. Promoters from wheat genes with verified patterns of activity (annotated in TransGene Promoters Database, TGP) are discussed. The TGP database can be used as an information resource for planning various genetic engineering experiments.
High winter hardiness requires two features: (1) a duration of deep rest comparable to the duration of wintering and (2) high frost resistance. An interdisciplinary approach to studying the mechanisms governing the formation of winter hardiness permits one to develop new methods for increasing genetic diversity, to improve well-known ones, and to compare their efficiencies. Such diversity, in particular, is essential for breeding wheat varieties that would meet the conditions of Siberia. Treatment of shoots of winter varieties with gibberellin A 3 yielded families (lines) with 85–100 % survival under deep snow cover in the foreststeppe zone. The survival of original varieties under the same conditions was lower by an order of magnitude. Gibberellin stress in two consecutive generations induced a long deep rest in some survivors, comparable to the duration of wintering, which ensured high survival of their offspring. These changes were inherited. The harder was the selection for the duration of deep rest in «gibberellic» lines, the higher proportion of them was constituted by highly frost-resistant forms that survived under conditions of poor snow cover in the steppe. When both parents had at least one component of high winter hardiness, the crosses yielded the highest proportion of highly frost-resistant forms. Inbred clones of intermediate wheatgrass Agropyron glaucum were good donors of both components of winter hardiness when crossed to wheat. Hereditary changes in wheat accessions in two consecutive generations both in the forest-steppe under the influence of gibberellins and in the steppe under the effect of moderate to severe frosts are likely to have a regulatory epigenetic nature.
One way of obtaining high-frost-resistant varieties of winter wheat is a wide hybridization with wild relatives, in particular, certain species of wheatgrass. The most promising frost resistance donor is Agropyron glaucum (Desf. ex DC) Roem. & Schult. (=Syn. Thinopyrum intermedium (Host) Barkworth & D.R. Dewey). A large collection of Agropyron glaucum genotypes was derived from the original material collected in Eastern Kazakhstan, at an elevated site with little snow, which suggested that they had high frost resistance. A biotechnological approach to obtaining pure androgenous wheatgrass lines via anther culture and an efficient method for rapid analysis of frost resistance in winter wheat, wheatgrass and other crops were developed. The said approach gave rise to androgenous lines with various wheat cultivars, and subsequent backcrossing yielded a diversity of wheat-wheatgrass hybrids. This material is currently being used for creation of frost-resistant varieties of winter wheat and for increasing wheat biodiversity. The described technology shortens the time for production of frost resistant wheat-wheatgrass hybrids to 2–3 years. In addition, experiments on frost resistance transfer from wheatgrass to wheat by means of the leaf nurse method were conducted. When ripe, a few frost-resistant lines of winter wheat obtained displayed elevated productivity and altered morphology of ears, which had long awns, inherited in the progeny. This material is now being studied and propagated.
Antifreeze proteins are a class of proteins synthesized by poikilothermic organisms under cold stress. These proteins have random phylogenetic distribution, differ in primary and secondary structures, have different regulatory pathways, but they all display a common feature: the ability to be adsorbed onto the surface of ice crystals and to modify their growth. The review summarizes data on the origin of antifreeze proteins, activities and mechanisms mediating their action with emphasis on cereals, including wheat.
Satellite DNA, consisting of tandem repeats, forms heterochromatic regions packed into nucleosomes. Sequence and conformational DNA features responsible for the high efficiency of this package have been sought with a Fourier transform. The curvature profiles in tandem repeats differ significantly from a random model. As many as 50 % of the monomers have a periodicity of DNA bends in the vicinity of 170 bp, fitting the wrapping length of a single nucleosome within two highest-order harmonics in the DNA curvature profile. The nucleosome positioning scheme in subtelomeric satellites in plants differs from that in centromeric satellites.
Molecular heterogeneity was studied in 20 spring triticale accessions by using ISSR and RAPD markers. The study revealed a high level of polymorphism (80,2 % and 89,9 %, respectively, on the average), which allowed the studied triticale accessions to be grouped according to the degree of genetic relationship and to choose genetically distant parental pairs for crosses to obtain heterotic hybrids.
