Effects of vernalization duration control genes (Vrd) on agronomical traits in winter bread wheat

In monogenic dominant for Vrd1 or Vrd2 genes almost isogenic lines and cultivars the shortening of the period before hadding duration, plant height reduction, and decrease of frost resistance particularly in the second half of winter and in spring have been shown. As for the determined traits the greater effect was detected for Vrd1 gene, the less one--for Vrd2. Genes Vrd1 and Vrd2 did not significantly influence the quantitative characteristics of yield components except the 1000 kernel weight. The use of monogenic dominant for Vrd2 genotypes is recommended to develop new dwarf cultivars for South step of Ukraine.     

Effects of genes that control the length of vernalization (Vrd) from agronomic features in soft winter soft wheat

A reduction in the time to heading, a decrease in plant height, and a reduction in frost resistance, especially in the second half of winter and in spring, is demonstrated in near-isogenic lines and cultivars that are monogenic dominant for gene Vrd1 or gene Vrd2. A greater effect with respect to these traits is typical of the Vrd1 gene and a lesser effect for the Vrd2 gene. The two genes Vrd1 and Vrd2 have practically no influence on the quantitative characteristics of the structural elements of wheat, except for the 1000 kernel weight. It is recommended that genotypes that are monogenic dominant in the Vrd2 gene be used to develop new dwarf cultivars for the southern steppe of Ukraine.     

Differences in the effects of alleles of the genes Vrd1 and Ppd-D1 with respect to winter hardiness, frost tolerance and yield in winter wheat

The influence of allelic differences between the genes Vrd1 and Ppd-D1 and their interaction with respect to winter hardiness, frost tolerance, and yield and the components of the yield in recombinant-inbred F5 lines of Odesskaya 16/Bezostaya 1 is investigated. From 9 to 15% of the differences with respect to winter hardiness and frost tolerance in the recombinant-inbred lines are attributable to alternative alleles of the Vrd1 gene and 10–16% to the alternative alleles of the Ppd-D1 gene. Interaction between the alleles vrd1 and Ppd-D1a promotes the formation of the greatest winter hardiness and frost tolerance in tillered plants throughout winter. At the same time, a reliable increase in the time to heading and height of the plants as well as a tendency towards reduced yield of grain in lines with the genotype vrd1 vrd1 Ppd-D1a Ppd-D1a by comparison with lines with the genotype Vrd1 Vrd1 Ppd-D1a Ppd-D1a are discovered.     

Chromosomal location of genes for vernalization duration (Vrd) in winter bread wheat

In this study, we carried out monosomic analysis of two isogenic lines of cultivar Mironovskaya 808, monogenically dominant for genes Vrd1 and Vrd2 reducing the cultivar vernalization requirement duration from 50 to respectively 35 and 45 days, as well as analysis of substitution lines Cappelle Desperez/Bezostaya 1. Gene Vrdl is localized on chromosome 4A; Vrd2, on chromosome 5D. The third gene, which is not allelic to the former two, is present in cultivar Cappelle Desperez on either the IA, 6A, or 4B chromosome.     

Marking the Vrd1 gene in the bread winter wheat

PCR analysis was used to create DNA markers to the Vrd1 gene. DNA of almost isogenic lines with respect to Vrd genes of the cultivars Mironovskaya 808 and Erytrospermum 604 was used. It was shown that in the monogenic Vrd1 dominant genotypes the product of amplification (280 b.p.) is absent in comparison with the DNA of the vrd recessive and monogenic Vrd2 dominant genotypes. The linkage of the marker with the Vrd1 gene has been determined using DNA analysis of plant population obtained as a result of crossing of Erytrospermum 604 (vrd recessive) and Triple Dirk C (Vrd1vrd2). F2 population segragated in two groups on the character of 280 b.p. amplification product "presence/absence". The segregation significantly coincided to the theoretical one (by ?2 test) with 1:3 expectation. The revealed molecular marker identified homozygous dominant Vrd1 plants only. The DNA-marker to Vrd1 gene is nulle-allelic 280(-).     

Chromosomal location of genes for vernalization requirement duration (<Emphasis Type="Italic">Vrd</Emphasis>) in winter bread wheat

In this study, we carried out monosomic analysis of two isogenic lines of cultivar Mironovskaya 808, monogenically dominant for genes Vrd1 and Vrd2 reducing the cultivar vernalization requirement duration from 50 to respectively 35 and 45 days, as well as analysis of substitution lines Cappelle Desperez/Bezostaya 1. Gene Vrd1 is localized on chromosome 4A; Vrd2, on chromosome 5D. The third gene, which is not allelic to the former two, is present in cultivar Cappelle Desperez on either the 1A, 6A, or 4B chromosome.     

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.     

Effect of the 5R(5A) alien chromosome substitution on the growth habit and winter hardiness of wheat

The growth habit, ear emergence time, and frost tolerance of wheat/rye substitution lines have been studied in cultivars Rang and Mironovskaya Krupnozernaya whose chromosome 5A is substituted with chromosome 5R of Onkhoyskaya rye. Hybrid analysis has demonstrated that the spring habit of the recipient cultivars Rang and Mironovskaya Krupnozernaya is controlled by dominant gene Vrn-A1 located in chromosome 5A. Onokhoyskaya rye has a dominant gene for the spring habit (Sp1) located in chromosome 5R. It has been found that the resultant 5R(5A) alien-substitution lines have a winter type of development and ears do not emerge during summer in plants sown in spring. The change in growth habit has been shown to be related to the absence of the rye Spl gene expression in the substitution lines. The winter hardiness of winter 5R(5A) alien-substitution lines has been studied under the environmental conditions of Novosibirsk. Testing the lines in the first winter demonstrated that their winter survival is 20-27%. The possible presence of the frost resistance gene homeoallelic to the known genes Fr1 and Fr2 of the common wheat located on chromosomes 5A and 5D, respectively, is discussed.     

The detection of nonallelic to known genes of resistance to Tilletia caries (DC) Tul. in wheat strains from interspecific hybridization (Triticum aestivum x Aegilops cylindrica)

It was established by hybridological analysis that winter bread wheat lines 1/74-91, 3/36-91, 5/55-91 possess single dominant gene of resistance to bunt (Tilletia caries (DC) Tul.), but lines 8/2-91, 5/43-91, 4/11-91 and 8/16-91 have two independent dominant genes for this character. These genes originated from Aegilops cylindrica are not identical to Bt1-Bt17 genes and are unknown to date. The lines were obtained from crosses between winter bread wheat variety Odeskaya polukarlikovaya and Aegilops cylindrica.     

Current applications of wheat and wheat–alien precise genetic stocks

A comprehensive collection of wheat aneuploids, whole chromosome substitutions (both intervarietal and interspecific) and wheat–alien addition lines, along with various introgression and near-isogenic lines, has been created over a period of years, primarily to provide the means of localizing the genes underpinning traits and to introduce novel genes into the bread wheat genome. For a time, interest in this class of genetic material was on the wane, but more recently it has revived in the context, for example, of localizing DNA-based markers, designing chromosome-specific bacterial artificial chromosome libraries, and establishing functional differences between alleles and homoeoalleles. Here, a brief review is provided of recent applications of precise genetic stocks in the field of molecular genetics, functional genetics and genomics of the Triticeae species.     

Vernalization-induced changes of the DNA methylation pattern in winter wheat.

Vernalization is a cold treatment that induces or accelerates flowering and insures that temperate-zone plants will not flower until after winter. There is evidence that vernalization results in DNA demethylation that induces flowering. Differences in DNA methylation can be determined using methylation-sensitive amplified fragment length polymorphisms (AFLPs). Methylation-sensitive AFLPs utilize restriction enzyme isoschizomers that are differentially sensitive to methylation, producing polymorphisms related to methylation differences as opposed to sequence differences. Near-isogenic lines (NILs) have been developed for spring vs. winter habit in wheat (Triticum aestivum) and allow for the study of a single vernalization locus. In this study, differences in the methylation pattern were determined for spring and winter NILs, as well as for unvernalized and vernalized individuals. Winter wheat was more highly methylated than spring wheat and methylation-related AFLPs were produced between winter and spring wheat. Changes in the methylation pattern were observed at the end of vernalization, one week after the end of vernalization, and four weeks after the end of vernalization of winter wheat. However, the most methylation differences were observed one week after removal of winter wheat from cold treatment. Our data suggest that there is not only a vernalization-induced demethylation related to flower induction, but there is also a more general and non-specific demethylation of sequences unrelated to flowering. Two methylation-related AFLPs induced by vernalization were shared among all of the winter NILs.     

Effect of the 5R(5A) Alien Chromosome Substitution on the Growth Habit and Winter Hardiness of Wheat

The growth habit, ear emergence time, and frost tolerance of wheat/rye substitution lines have been studied in cultivars Rang and Mironovskaya Krupnozernaya whose chromosome 5A is substituted with chromosome 5R of Onkhoyskaya rye. Hybrid analysis has demonstrated that the spring habit of the recipient cultivars Rang and Mironovskaya Krupnozernaya is controlled by dominant gene Vrn-A1 located in chromosome 5A. Onokhoyskaya rye has a dominant gene for the spring habit (Sp1) located in chromosome 5R. It has been found that the resultant 5R(5A) alien-substitution lines have a winter type of development and ears do not emerge during summer in plants sown in spring. The change in growth habit has been shown to be related to the absence of the rye Sp1 gene expression in the substitution lines. The winter hardiness of winter 5R(5A) alien-substitution lines has been studied under the environmental conditions of Novosibirsk. Testing the lines in the first winter demonstrated that their winter survival is 20–27%. The possible presence of the frost resistance gene homeoallelic to the known genes Fr1 and Fr2 of the common wheat located on chromosomes 5A and 5D, respectively, is discussed.     

Identification of Ug99 stem rust resistance loci in winter wheat germplasm using genome-wide association analysis

The evolution of a new race of stem rust, generally referred to as Ug99, threatens global wheat production because it can overcome widely deployed resistance genes that had been effective for many years. To identify loci conferring resistance to Ug99 in wheat, a genome-wide association study was conducted using 232 winter wheat breeding lines from the International Winter Wheat Improvement Program. Breeding lines were genotyped with diversity array technology, simple sequence repeat and sequence-tagged site markers, and phenotyped at the adult plant stage for resistance to stem rust in the stem rust resistance screening nursery at Njoro, Kenya during 2009-2011. A mixed linear model was used for detecting marker-trait associations. Twelve loci associated with Ug99 resistance were identified including markers linked to known genes Sr2 and Lr34. Other markers were located in the chromosome regions where no Sr genes have been previously reported, including one each on chromosomes 1A, 2B, 4A and 7B, two on chromosome 5B and four on chromosome 6B. The same data were used for investigating epistatic interactions between markers with or without main effects. The marker csSr2 linked to Sr2 interacted with wPt4930 on 6BS and wPt729773 in an unknown location. Another marker, csLV34 linked to Lr34, also interacted with wPt4930 on 6BS and wPt4916 on 2BS. The frequent involvement of wPt4916 on 2BS and wPt4930 on 6BS in interactions with other significant loci on the same or different chromosomes suggested complex genetic control for adult plant resistance to Ug99 in winter wheat germplasm.     

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.     

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.     

Quantitative Trait Loci Associated with Phenological Development,Low-Temperature Tolerance,Grain Quality,and Agronomic Characters in Wheat (Triticum aestivum L.)

Plants must respond to environmental cues and schedule their development in order to react to periods of abiotic stress and commit fully to growth and reproduction under favorable conditions. This study was initiated to identify SNP markers for characters expressed from the seedling stage to plant maturity in spring and winter wheat (Triticum aestivum L.) genotypes adapted to western Canada. Three doubled haploid populations with the winter cultivar ‘Norstar’ as a common parent were developed and genotyped with a 90K Illumina iSelect SNP assay and a 2,998.9 cM consensus map with 17,541 markers constructed. High heritability’s reflected large differences among the parents and relatively low genotype by environment interactions for all characters considered. Significant QTL were detected for the 15 traits examined. However, different QTL for days to heading in controlled environments and the field provided a strong reminder that growth and development are being orchestrated by environmental cues and caution should be exercised when extrapolating conclusions from different experiments. A QTL on chromosome 6A for minimum final leaf number, which determines the rate of phenological development in the seedling stage, was closely linked to QTL for low-temperature tolerance, grain quality, and agronomic characters expressed up to the time of maturity. This suggests phenological development plays a critical role in programming subsequent outcomes for many traits. Transgressive segregation was observed for the lines in each population and QTL with additive effects were identified suggesting that genes for desirable traits could be stacked using Marker Assisted Selection. QTL were identified for characters that could be transferred between the largely isolated western Canadian spring and winter wheat gene pools demonstrating the opportunities offered by Marker Assisted Selection to act as bridges in the identification and transfer of useful genes among related genetic islands while minimizing the drag created by less desirable genes.     

Genetic diversity in European wheat and spelt breeding material based on RFLP data

Fifty-two winter wheat (Triticum aestivum L.), nine spring wheat, and 20 spelt (Triticum spelta L.) lines representing part of the European breeding germplasm, were assayed for RFLPs (restriction fragment length polymorphisms) with 56 wheat DNA clones and two barley cDNA clones. Objectives of this study were to (1) determine the level of variation for RFLPs in the wheat and spelt breeding lines, (2) characterize the genetic diversity within the European winter wheat germplasm, and (3) evaluate the usefulness of RFLP markers for pedigree analysis and the grouping of wheat and spelt lines of various origins. Seventy-three of the 166 RFLP loci detected with 58 probes and one restriction enzyme were polymorphic for the 81 lines. The percentage of polymorphic loci was greatest for the B genome (58%) and smallest for the D genome (21%). Among the 81 lines, 271 different RFLP bands were detected. RFLP band frequencies of the winter wheat lines differed considerably (0.5) from those of the spring wheat lines at five loci, and from those of the spelt lines at 17 loci. Eight cultivars that had a major impact as progenitors on the development of improved winter wheat cultivars accounted for 93% of the observed RFLP bands in winter wheat. Genetic distance (GD) estimates between two lines ranged between 0.01 and 0.21. Mean GD estimates within winter wheat (0.083), within spring wheat (0.108) and within spelt (0.096) were smaller than between spring and winter wheat (0.114), and greatest between winter wheat and spelt (0.132) and spring wheat and spelt (0.148). Principal coordinate analysis performed on GD estimates revealed a clear separation of wheat and spelt germplasm. Novel spelt lines with various proportions of wheat germplasm were positioned between wheat and traditional spelt lines. The spring wheat lines formed a distinct group at the periphery of the distribution of the winter wheat lines. Subgroupings of the winter wheat lines according to the cluster analysis were in good agreement with their origin, and lines with common ancestors were grouped together.