New genetic resources in wheat breeding for an increased grain protein content

The present review offers an overview of genetic research on grain protein content (GPC) in various Triticum L. and Aegilops L. species. Regularities in geographic variability of GPC and the results of a longterm screening of accessions from the VIR collection for this trait are considered. On the basis of these assessments, a core-collection of genetic sources with high GPC has been formed. It includes the diploid Aegilops species as donors of B, G and D genomes for allopolyploid wheats, as well as accessions of di-, tetra- and hexaploid wheat species. The use of highprotein sources in wheat breeding in the United States and Canada in the 1970’s–1980’s resulted in the bread wheat GPC increase by 0.5–3.0 %; however, further purposeful attempts at increasing GPC by traditional breeding methods failed. A breakthrough in increasing the total GPC has been achieved as a result of molecular genetics methods and molecular markers development. For the first time, a functional locus, or the Gpc-B1 gene (chromosome 6BS) affecting the accumulation of protein, Zn and Fe in grain, was identified in T. dicoccoides, cloned and studied in detail. The application of molecular markers has revealed the active allele of this gene in some landraces and old cul-tivars of T. dicoccum, T. durum, T. spelta and T. aestivum. Moreover, Gpc-A1, Gpc-D1, and Gpc-2 wheat genes have been found in chromosomes 6A, 6D and homeologous group 2, respectively. All these genes have been identified as NAC transcription factors, which play an important role in the accelerated senescence of plants and remobilization of nutrients from leaves to grain. The genes related to Gpc-B1 from T. dicoccoides were found in the G genome of T. timopheevii and B (=S) genome of different species of Aegilops sect. sitopsis. Functional Gpc-B1 alleles have been introduced into commercial tetra- and hexaploid wheat cultivars, and it resulted in the creation of new highprotein and high-yield cultivars and series of nearly isogenic lines in different countries. They are promising sources for research and wheat breeding purposes

Molecular markers in the genetic analysis of crossability of bread wheat with rye

Bread wheat (Triticum aestivum L.), the varieties of which are widely used for the grain production, is difficultly crossable with related species of Triticeae Dum. This factor limits the chance of introduction of alien genetic material into the wheat gene pool and the possibility of new varieties breeding with good adaptation to adverse environmental factors. The crossability between wheat and related species is controlled by Kr1-Kr4 genes (Crossability with Rye, Hordeum and Aegilops spp.) and the SKr gene (Suppressor of crossability). SKr and Kr1 have the largest influence on the trait. In the case of the recessive alleles, these genes do not function and the quantity of hybrid seeds after pollination with alien species can achieve more than 50 %. SKr is located on 5BS between the GBR0233 and Xgwm234 markers, closely linked with the markers Xcfb341, TGlc2 and gene12. Kr1 was mapped on 5BL, proximally to the Ph1 gene, between the EST-SSR markers Xw5145 and Xw9340. The markers of SKr were used to control the transfer of its recessive allele into other wheat genotypes, which made it possible to obtain highly crossable forms. However, the advantages of using the SKr and Kr1 markers in marker-assisted selection and in the screening of ex situ collections are not sufficiently studied. The published Kr1 sequence for varieties with different crossability offers great prospects, because it will be possible to create allele-specific markers. In this review, the following issues are considered: genetic resources created by wheat and rye hybridization, the geographical distribution of easy-to-cross forms of wheat, genetic control of the wheat and rye compatibility, advances of the use of molecular markers in the mapping of Kr-genes and their transmission control

A system of molecular markers to identify alleles of the Rht-B1 and Rht-D1 genes controlling reduced height in bread wheat

Mutant alleles of the Rht-B1 and Rht-D1 (Reduced height) genes are widely used in bread wheat breeding for the development of intensive-type cultivars. These genes and their f lanking regions have been sequenced and the point mutations leading to the nonsense codons (Rht-B1b, Rht-B1e, Rht-B1p and Rht-D1b alleles) and various insertions (Rht-B1c, Rht-B1h and Rht-B1i-1) associated with a change in plant height have been described. DNA-markers based on the allele-specif ic PCR have been developed to identify single-nucleotide changes. However, the use of such technique imposes stringent PCR conditions, and the resulting data are not always unambiguous. An alternative can be found in the CAPS technology: it detects differences in sequences by digesting PCR products. In the absence of restrictases capable of digesting DNA at the point mutation site, restriction sites can be introduced into the primer sequence (derived CAPS). The aim of this study was to propose a system of CAPS-, dCAPS- and STS-markers for identifying alleles of the reduced height genes frequently used in breeding programs. Three CAPS have been developed to identify the Rht-B1b, Rht-D1b, Rht-B1p alleles, as well as two dCAPS for Rht-B1b, Rht-B1e. STS-markers for the insertioncontaining alleles Rht-B1c, Rht-B1h and Rht-B1i-1 have been selected from publications. The proposed markers were tested during the genotyping of 11 bread wheat accessions from the VIR collection with the abovementioned mutant alleles and the wild-type Rht-B1a and Rht-D1a. The presence of nonsense mutations was also conf irmed by the results of allele-specif ic PCR. This marker system, along with the existing ones, can be used to identify dwarf ing alleles of the Rht-B1 and Rht-D1 genes in bread wheat for genetic screening of accessions from ex situ collections and/or for marker-assisted selection

WINTER HARDINESS OF BREAD WHEAT FROM THE VIR COLLECTION IN ENVIRONMENTS OF THE NORTHWESTERN AND CENTRAL BLACK SOIL REGIONS OF RUSSIA

Background. Winter wheat resistance to adverse winter­ing conditions is one of the most important adaptive charac­teristics. To obtain high yields, modern wheat cultivars should have various protective reactions. For their success­ful combination in one genotype, the availability of appro­priate initial material is of great importance. In Russia, the accessions from the VIR collection are traditionally used as initial material for wheat breeding. The aims of the present study were (1) to evaluate winter hardiness in accessions from the VIR collection in a field test, and (2) to use the ob­tained data and those on the geographical origin of acces­sions for making up the target sub-collection and perform­ing its eco-geographical studies.Materials and methods. The initial sample for field screening contained 431 acces­sions of common winter wheat from different regions of Russia and the former USSR, and 484 accessions from 18 foreign countries. Winter hardiness of these accessions was tested in the environmental conditions of the North­western region (Pushkin, 59°41′N 30°20′E, 2006/2007, 2007/2008 and 2013/2014) and of the Central Black Soil re­gion (Yekaterinino, 52°59′N 40°50′E, Tambov Province, 2007/2008 and 2008/2009). The degree of winter hardi­ness was determined in accordance with the technique de­veloped at VIR.Results and conclusions. In 2006/2007, in Pushkin, a high and a very high degree of winter hardiness was displayed by 114 accessions with the origin from Rus­sia and the former USSR as well as by 12 accessions from foreign countries. Based on the obtained data and taking into account the diversity of the geographical origin of ac­cessions, the target sub-collection was formed, whose ac­cessions were subjected to eco-geographical two-year field studies (Pushkin, 59°41′N 30°20′E, 2007/2008, 2013/2014, and Yekaterinino, 52°59′N 40°50′N, Tambov Province, 2007/2008, 2008/2009). The Friedman’s variance analysis has shown that variation on winter hardiness in 158 acces­sions from the target sub-collection was determined by the environmental conditions of wheat cultivation (χ2э = 256.7; df = 4; χ2W=0.05 = 9.5) and by genetic differences between ac­cessions (χ2э = 239.3; df = 157; χ2W=0.05 = 187.2) at that effect of the prior was stronger than that of the latter. By using the cluster analysis (k-means algorithm), the target sub-collec­tion structure has been revealed. Twelve accessions that overwintered well at both geographical locations during all the years of testing were identified

Resistance of synthetic hexaploid wheat to the leaf rust pathogen

Background. One of the promising sources for enrichment of the common wheat (Triticum aestivum L.) gene pool with new alleles is synthetic hexaploid wheat (SHW), or allopolyploids from crossing tetraploid wheats (2n = 4x = 28, BBAA) with accessions of Aegilops tauschii Coss. (2n = 2x = 14, DD), and subsequent doubling of the chromosome number in the hybrids. Objectives of the study were to evaluate the SHW accessions from the VIR collection for resistance to Puccinia triticina Erikss. populations collected in Russia; genotype the accessions; and summarize information from the published sources concerning the resistance of the studied accessions to other harmful diseases and pests.Materials and methods. Resistance of 36 SHW accessions from the VIR collection to the populations of P. triticina was assessed in the laboratory and in the field, under artificial infection pressure, using the techniques developed by the Institute of Plant Protection. A phytopathological test and PCR markers were used to identify the Lr genes.Results and conclusion. The SHW accessions were characterized according to their resistance to the Russian populations of the wheat leaf rust pathogen. The sources of resistance in the phase of emergence and in adult plants were identified. The phytopathological test isolated three accessions with Lr23; the PCR marker of Lr21=Lr40 was found in 11 accessions, Lr39=Lr41 in 19, and Lr22a in 3. At the same time, k-65496, k-65515 and k-65517 had si multaneously Lr21=Lr40 and Lr39=Lr41, while k-65497, k-65503 and k-65508 had Lr22a and Lr39=Lr41. The analysis of published data showed that many of the studied SHW accessions were also resistant to other harmful diseases and insect pests, so they are of interest for further studying and possible use in domestic breeding

Resistance of old winter bread wheat landraces to tan spot

Background. The most effective and environmentally safe way to combat wheat diseases is to produce cultivars resistant to their pathogens. For this purpose, old landraces are often used as genetically diverse sources of traits important for breeding. In the process of wheat breeding for resistance to tan spot caused by the fungus Pyrenophora tritici-repentis (Died.) Drechs. (abbr. Ptr), selection is carried out against the dominant allele of Tsn1, the gene of sensitivity to the toxin Ptr ToxA, which induces necrosis and represents the main pathogenicity factor of Ptr controlled by the ToxA gene. The aim of the study was to characterize a set of bread wheat (Triticum aestivum L.) accessions from the VIR collection for resistance to various Ptr populations, genotype these accessions using Xfcp623 – a DNA marker of the Tsn1 gene, and identify sources of tan spot resistance.Materials and methods. Sixty-seven accessions of winter bread wheat landraces were studied. Seedling resistance to two Ptr populations was assessed using a 5-point scale adopted at VIZR. The allelic state of Tsn1 was identified by PCR.Results. Dominant alleles of Tsn1 were found for 55% of the studied accessions. Seventeen accessions were resistant or moderately resistant to two Ptr populations and an isolate from Krasnodar Territory previously used for their characterization. Nine of them had the tsn1tsn1 genotype, and 8 had Tsn1Tsn1. The accessions mainly belonged to three agroecological groups proposed by N. I. Vavilov: “steppe winter bread wheat (Banatka wheats)”, “North European forest awnless bread wheats (Sandomirka wheats)”, and “Caucasian mountain winter bread wheat”.Conclusion. The identified 17 accessions resistant to Ptr are potential breeding sources of resistance. In the studied set of accessions, no significant relationship was found between the allelic state of the Tsn1 gene in the accession and its response to the infection with pathogen populations, including isolates with the ToxA gene

Genetic diversity and breeding value of synthetic hexaploid wheat introduced into the VIR collection

For the  successful  development of wheat  breeding in Russia, a genetically  diverse  and  well-characterized starting material, mainly stored  at the VIR collection, is needed. To replenish  the collection, 36 lines (accessions) of synthetic hexaploid  wheat  (SHWs) developed at CIMMYT by crossing Triticum durum with Aegilops tauschii were studied.  Our research  was aimed at studying  the SHWs using a complex of morphological and economically  valuable traits in the environments of European Russia’s northwestern part (E30°, N59°), evaluating the reaction  of the SHWs to a photoperiod  and determining their genetic heterogeneity and similarities by gliadins as biochemical  markers. The results showed that the variability of different traits for SHWs fits into the framework of the genus  Triticum, and so SHWs can be classified as poorly domesticated forms. Their distinctive feature, valuable for wheat  breeding, is a large weight  of a thousand grains (up to 60.6 g). This trait was characterized by a low degree of variability and a low correlation  with other  traits. The reaction  of wheat  plants to the length  of the day is crucial for their transition  from vegetative to reproductive development. The SHWs studied differed from common wheat and one another by responses to the short day and by the length  of the ‘emergence-heading’ phase  if they grew under  the conditions of a long day. The delay in the development of plants with a short photoperiod ranged from 5.4 to 53.8 days. On a long day, the duration of the ‘emergence-heading’ phase  varied from 39.5 to 53.9 days. A possible genetic basis for the differences  identified is discussed.  To assess the diversity of SHWs, we also used  gliadin proteins as informative  biochemical  markers. It was revealed  that 21 SHWs were homogeneous, and the rest, heterogeneous. Forty-four different biotypes were found for the SHWs studied,  from which 36 were unique.  Relationships between biotypes have been  demonstrated using cluster analysis. It should be noted that 13 SHWs were unstable. In each of them, some plants differed from the others  in terms of a complex of morphological characters, reaction to a photoperiod, and gliadin patterns. It is possible that the instability of accessions  is the result of genome rearrangement in SHWs. SHW accessions  and the forms isolated from them are considered as sources of new genetic variability to improve common wheat

Source material for breeding winter bread wheat for grain quality in the north of the Middle Volga Region

Background. Development of cultivars with high stable yields and high grain quality is the main trend in wheat breeding. The aim of this study was to characterize a set of winter bread wheat accessions from the VIR collection and the working collection of Kazan Scientific Center in terms of their yield, protein content in grain (P, %), and swelling of flour in acetic acid (S, ml), and select the best accessions for the combination of these characters for use in a crossbreeding program.Materials and methods. Twenty-three winter bread wheat accessions were studied for the abovementioned characters in the north of the Middle Volga Region using conventional techniques. The study lasted three years (2016–2019).Results and conclusion. The yield of the accessions varied across the years of studies; however, none of them surpassed the reference cv. ‘Kazanskaya 560’. The values of protein content in grain were medium or high. The following accessions had high and stable levels of protein content in grain (15.1–16.1%): ‘TAW 42971/80’ (k-58363, Germany); ‘Lutescens 471 N8’ (Kazakhstan); ‘Rita’ (k-58057), ‘Scotty’ (k-59322) and ‘Nelson’ (all from the U.S.); ‘Moskovskaya 39’ (k-65160, Russia); ‘Bilotserkivchanka’ (k-64330) and ‘Barkan’ (k-64495) (both from Ukraine). Flour swelling power in acetic acid did not fall below 50 ml, attesting to the formation of high-quality grain. This was also confirmed by the protein quality index determined by the S : P ratio, which ranged from 3.6 to 4.7. Sources with high-quality protein were selected from the tested accessions for use in breeding: ‘CDC Clair’ (k-64168, Canada), ‘Lutescens 471 Н8’ (Kazakhstan), ‘Moskovskaya 39’ (Russia), ‘Barkan’ (Ukraine), and ‘Favorytka’ (k-64337, Ukraine)

Source material for breeding winter bread wheat in the north of the Middle Volga region

Background. Bread wheat (Triticum aestivum L.), due to significant progress in breeding, has high potential of biological productivity, but its implementation is quite low. To change the situation for the better, it is necessary to increase the resistance of developed cultivars to unfavorable abiotic and biotic factors in the regions of its cultivation. To solve this problem, source material is required. The purpose of this research was to evaluate a set of winter wheat accessions from the VIR collection, and first of all, the newly introduced accessions, and the accessions from the working collection of Kazan Scientific Center of the Russian Academy of Sciences for variability of agronomic traits and stability under the conditions of the north of the Middle Volga region, and to identify sources promising for inclusion in the crossing programs.Materials and methods. A three-year field study of 166 winter bread wheat accessions was carried out. All accessions were assessed for their overwintering and plant and ear productivity traits using the methods developed by VIR and the State Variety Trials. The best accessions, or sources, were selected by comparing them with the reference cv. ‘Kazan 560’, taking into account the quantitative values of such indicators as “general adaptability” (ОАСi ), variance of “specific adaptability” (σ2САСi ) and “relative stability” (Sgi) for each accession according to A. V. Kilchevsky and L. V. Khotyleva.Results and conclusion. Descriptions of winter bread wheat accessions are presented in the context of their agronomic traits. Groups and subgroups of accessions with different trait variability levels were identified. Some accessions with stable levels of trait manifestation exceeded the reference in ear productivity. All of them are promising for wheat breeding programs. It is shown that the group of accessions “weakly changing” over the years of study differs from the group of “moderately/strongly changing” accessions in values of correlations between traits and the number of significant correlations