A chromosome arm from Thinopyrum intermedium × Thinopyrum ponticum hybrid confers increased tillering and yield potential in wheat.

Tiller number is a key component of wheat plant architecture having a direct impact on grain yield. Because of their viability, biotic resistance, and abiotic stress tolerance, wild relative species are a valuable gene source for increasing wheat genetic diversity, including yield potential. Agropyron glael, a perennial hybrid of Thinopyrum intermedium and Th. ponticum, was created in the 1930s. Recent genome analyses identified five evolutionarily distinct subgenomes (J, Jst, Jvs, Jr, and St), making A. glael an important gene source for transferring useful agronomical traits into wheat. During a bread wheat × A. glael crossing program, a genetically stable translocation line, WT153397, was developed. Sequential in situ hybridizations (McGISH) with J-, St-, and D-genomic DNA probes and pSc119.2, Afa family, pTa71, and (GAA)7 DNA repeats, as well as molecular markers specific for the wheat 6D chromosome, revealed the presence of a 6DS.6Jvs Robertsonian translocation in the genetic line. Field trials in low-input and high-input breeding nurseries over four growing seasons demonstrated the Agropyron chromosome arm's high compensating ability for the missing 6DL, as spike morphology and fertility of WT153397 did not differ significantly from those of wheat parents, Mv9kr1 and 'Mv Karizma.' Moreover, the introgressed 6Jvs chromosome arm significantly increased the number of productive tillers, resulting in a significantly higher grain yield potential compared to the parental wheat cultivars. The translocated chromosome could be highly purified by flow cytometric sorting due to the intense fluorescent labeling of (GAA)7 clusters on the Thinopyrum chromosome arm, providing an opportunity to use chromosome genomics to identify Agropyron gene variant(s) responsible for the tillering capacity. The translocation line WT153397 is an important genetic stock for functional genetic studies of tiller formation and useful breeding material for increasing wheat yield potential. The study also discusses the use of the translocation line in wheat breeding. Supplementary information: The online version contains supplementary material available at 10.1007/s11032-024-01439-y.

Chromosome genomics facilitates the marker development and selection of wheat-Aegilops biuncialis addition, substitution and translocation lines.

The annual goatgrass, Aegilops biuncialis is a rich source of genes with considerable agronomic value. This genetic potential can be exploited for wheat improvement through interspecific hybridization to increase stress resistance, grain quality and adaptability. However, the low throughput of cytogenetic selection hampers the development of alien introgressions. Using the sequence of flow-sorted chromosomes of diploid progenitors, the present study enabled the development of chromosome-specific markers. In total, 482 PCR markers were validated on wheat (Mv9kr1) and Ae. biuncialis (MvGB642) crossing partners, and 126 on wheat-Aegilops additions. Thirty-two markers specific for U- or M-chromosomes were used in combination with GISH and FISH for the screening of 44 Mv9kr1 × Ae. biuncialis BC3F3 genotypes. The predominance of chromosomes 4M and 5M, as well as the presence of chromosomal aberrations, may indicate that these chromosomes have a gametocidal effect. A new wheat-Ae. biuncialis disomic 4U addition, 4M(4D) and 5M(5D) substitutions, as well as several introgression lines were selected. Spike morphology and fertility indicated that the Aegilops 4M or 5M compensated well for the loss of 4D and 5D, respectively. The new cytogenetic stocks represent valuable genetic resources for the introgression of key genes alleles into wheat.

Transfer of the ph1b Deletion Chromosome 5B From Chinese Spring Wheat Into a Winter Wheat Line and Induction of Chromosome Rearrangements in Wheat-Aegilops biuncialis Hybrids.

Effective utilization of genetic diversity in wild relatives to improve wheat requires recombination between wheat and alien chromosomes. However, this is suppressed by the Pairing homoeologous gene, Ph1, on the long arm of wheat chromosome 5B. A deletion mutant of the Ph1 locus (ph1b) has been used widely to induce homoeologous recombination in wheat × alien hybrids. However, the original ph1b mutation, developed in Chinese Spring (CS) background has poor agronomic performance. Hence, alien introgression lines are first backcrossed with adapted wheat genotypes and after this step, alien chromosome segments are introduced into breeding lines. In this work, the ph1b mutation was transferred from two CSph1b mutants into winter wheat line Mv9kr1. Homozygous genotypes Mv9kr1 ph1b/ph1b exhibited improved plant and spike morphology compared to Chinese Spring. Flow cytometric chromosome analysis confirmed reduced DNA content of the mutant 5B chromosome in both wheat genotype relative to the wild type chromosome. The ph1b mutation in the Mv9kr1 genotype allowed wheat-alien chromosome pairing in meiosis of Mv9kr1ph1b_K × Aegilops biuncialis F1 hybrids, predominantly with the Mb-genome chromosomes of Aegilops relative to those of the Ub genome. High frequency of wheat-Aegilops chromosome interactions resulted in rearranged chromosomes identified in the new Mv9kr1ph1b × Ae. Biuncialis amphiploids, making these lines valuable sources for alien introgressions. The new Mv9kr1ph1b mutant genotype is a unique resource to support alien introgression breeding of hexaploid wheat.

Identification of New QTLs for Dietary Fiber Content in Aegilops biuncialis.

Grain dietary fiber content is an important health-promoting trait of bread wheat. A dominant dietary fiber component of wheat is the cell wall polysaccharide arabinoxylan and the goatgrass Aegilops biuncialis has high ß-glucan content, which makes it an attractive gene source to develop wheat lines with modified fiber composition. In order to support introgression breeding, this work examined genetic variability in grain ß-glucan, pentosan, and protein content in a collection of Ae. biuncialis. A large variation in grain protein and edible fiber content was revealed, reflecting the origin of Ae. biuncialis accessions from different eco-geographical habitats. Association analysis using DArTseq-derived SNPs identified 34 QTLs associated with ß-glucan, pentosan, water-extractable pentosan, and protein content. Mapping the markers to draft chromosome assemblies of diploid progenitors of Ae. biuncialis underlined the role of genes on chromosomes 1Mb, 4Mb, and 5Mb in the formation of grain ß-glucan content, while other QTLs on chromosome groups 3, 6, and 1 identified genes responsible for total- and water-extractable pentosan content. Functional annotation of the associated marker sequences identified fourteen genes, nine of which were identified in other monocots. The QTLs and genes identified in the present work are attractive targets for chromosome-mediated gene transfer to improve the health-promoting properties of wheat-derived foods.

Molecular Cytogenetic Analysis and Meiotic Pairing Behavior of Progenies Originating from a Hexaploid Triticale (×Triticosecale, Wittmack) and Bread Wheat (Triticum aestivum, L.) Cross.

The chromosomal constitution of 9 dwarf (D) and 8 semidwarf (SD) lines derived by crossing hexaploid Triticale line NA-75 (AABBRR, 2n = 6x = 42) with Triticumaestivum (AABBDD, 2n = 6x = 42) cv. Chinese Spring was investigated using molecular cytogenetic techniques: fluorescence in situ hybridization and genomic in situ hybridization. A wheat-rye translocation (T4DS.7RL), 8 substitution lines, and a ditelosomic addition line (7RSdt) were identified. In the substitution lines, 1, 2, or 4 pairs of wheat chromosomes, belonging to the A, B, or D genome, were replaced by rye chromosomes. Substitutions between chromosomes belonging to different wheat genomes [5B(5A), 1D(1B)] also occurred. The lines were genetically stable, each carrying 42 chromosomes, except the wheat-rye ditelosomic addition line, which carried 21 pairs of wheat chromosomes and 1 pair of rye telocentric chromosomes (7RS). The chromosome pairing behavior of the lines was studied during metaphase I of meiosis. The chromosome pairing level and the number of ring bivalents were different for each line. Besides rod bivalents, univalent and multivalent associations (tri- and quadrivalents) were also detected. The main goal of the experiment was to develop genetically stable wheat/Triticale recombinant lines carrying chromosomes/chromatin fragments originating from the R genome of Triticale line NA-75. Introgression of rye genes into hexaploid wheat can broaden its genetic diversity, and the newly developed lines can be used in wheat breeding programs.

Unlocking the Genetic Diversity and Population Structure of a Wild Gene Source of Wheat, Aegilops biuncialis Vis., and Its Relationship With the Heading Time.

Understanding the genetic diversity of Aegilops biuncialis, a valuable source of agronomical useful genes, may significantly facilitate the introgression breeding of wheat. The genetic diversity and population structure of 86 Ae. biuncialis genotypes were investigated by 32700 DArT markers with the simultaneous application of three statistical methods- neighbor-joining clustering, Principal Coordinate Analysis, and the Bayesian approach to classification. The collection of Ae. biuncialis accessions was divided into five groups that correlated well with their eco-geographic habitat: A (North Africa), B (mainly from Balkans), C (Kosovo and Near East), D (Turkey, Crimea, and Peloponnese), and E (Azerbaijan and the Levant region). The diversity between the Ae. biuncialis accessions for a phenological trait (heading time), which is of decisive importance in the adaptation of plants to different eco-geographical environments, was studied over 3 years. A comparison of the intraspecific variation in the heading time trait by means of analysis of variance and principal component analysis revealed four phenotypic categories showing association with the genetic structure and geographic distribution, except for minor differences. The detailed exploration of genetic and phenologic divergence provides an insight into the adaptation capacity of Ae. biuncialis, identifying promising genotypes that could be utilized for wheat improvement.

Nuclear Disposition of Alien Chromosome Introgressions into Wheat and Rye Using 3D-FISH.

During interphase, the chromosomes of eukaryotes decondense and they occupy distinct regions of the nucleus, called chromosome domains or chromosome territories (CTs). In plants, the Rabl's configuration, with telomeres at one pole of nucleus and centromeres at the other, appears to be common, at least in plants with large genomes. It is unclear whether individual chromosomes of plants adopt defined, genetically determined addresses within the nucleus, as is the case in mammals. In this study, the nuclear disposition of alien rye and barley chromosomes and chromosome arm introgressions into wheat while using 3D-FISH in various somatic tissues was analyzed. All of the introgressed chromosomes showed Rabl's orientation, but their relative positions in the nuclei were less clear. While in most cases pairs of introgressed chromosomes occupied discrete positions, their association (proximity) along their entire lengths was rare, and partial association only marginally more frequent. This arrangement is relatively stable in various tissues and during various stages of the cell cycle. On the other hand, the length of a chromosome arm appears to play a role in its positioning in a nucleus: shorter chromosomes or chromosome arms tend to be located closer to the centre of the nucleus, while longer arms are more often positioned at the nuclear periphery.

Development of a new 7BS.7HL winter wheat-winter barley Robertsonian translocation line conferring increased salt tolerance and (1,3;1,4)-ß-D-glucan content.

Interspecific hybridization between bread wheat (Triticum aestivum, 2n = 42) and related species allows the transfer of agronomic and quality traits, whereby subsequent generations comprise an improved genetic background and can be directly applied in wheat breeding programmes. While wild relatives are frequently used as sources of agronomically favourable traits, cultivated species can also improve wheat quality and stress resistance. A salt-tolerant 'Asakaze'/'Manas' 7H disomic addition line (2n = 44) with elevated ß-glucan content, but with low fertility and an unstable genetic background was developed in an earlier wheat-barley prebreeding programme. The aim of the present study was to take this hybridization programme further and transfer the favourable barley traits into a more stable genetic background. Taking advantage of the breakage-fusion mechanism of univalent chromosomes, the 'Rannaya' winter wheat 7B monosomic line was used as female partner to the 7H addition line male, leading to the development of a compensating wheat/barley Robertsonian translocation line (7BS.7HL centric fusion, 2n = 42) exhibiting higher salt tolerance and elevated grain ß-glucan content. Throughout the crossing programme, comprising the F1-F4 generations, genomic in situ hybridization, fluorescence in situ hybridization and chromosome-specific molecular markers were used to trace and identify the wheat and barley chromatin. Investigations on salt tolerance during germination and on the (1,3;1,4)-ß-D-glucan (mixed-linkage glucan [MLG]) content of the seeds confirmed the salt tolerance and elevated grain MLG content of the translocation line, which can be directly applied in current wheat breeding programmes.

Differing metabolic responses to salt stress in wheat-barley addition lines containing different 7H chromosomal fragments.

Salinity-induced osmotic, ionic and oxidative stress responses were investigated on Asakaze/Manas wheat/barley addition lines 7H, 7HL and 7HS, together with their barley (salt-tolerant) and wheat (relatively salt-sensitive) parents. Growth, photosynthetic activity, chlorophyll degradation, proline, glycine betaine accumulation, sugar metabolism, Na+ and K+ uptake and transport processes and the role of polyamines and antioxidants were studied in young plants grown in hydroponic culture with or without salt treatment. Changes in plant growth and photosynthetic activity of plants demonstrated that the salt tolerance of the addition lines 7H and 7HL was similar to that of barley parent cv. Manas, while the sensitivity of the addition line 7HS was similar to that of the wheat parent cv. Asakaze. The Na accumulation in the roots and shoots did not differ between the addition lines and wheat parent. The activation of various genes related to Na uptake and transport was not correlated with the salt tolerance of the genotypes. These results indicated that the direct regulation of Na transport processes is not the main reason for the salt tolerance of these genotypes. Salt treatment induced a complex metabolic rearrangement in both the roots and shoots of all the genotypes. Elevated proline accumulation in the roots and enhanced sugar metabolism in the shoots were found to be important for salt tolerance in the 7H and 7HL addition lines and in barley cv. Manas. In wheat cv. Asakaze and the 7HS addition line the polyamine metabolism was activated. It seems that osmotic adjustment is a more important process in the improvement of salt tolerance in 7H addition lines than the direct regulation of Na transport processes or antioxidant defence.

Addition of Manas barley chromosome arms to the hexaploid wheat genome.

BACKGROUND: Cultivated barley belongs to the tertiary genepool of hexaploid wheat. Genes of interest can be transferred from barley into wheat through wide hybridization. The application of wheat-barley introgression lines could provide an excellent tool for the transfer of earliness, favourable amino acid composition, biotic stress resistance, abiotic stress tolerance, or good tillering ability into wheat. RESULTS: A set of 10 wheat-barley ditelosomic addition lines (2HS, 2HL, 3HS, 3HL, 4HS, 4HL, 6HS, 6HL, 7HS and 7HL) was developed from the progenies of an Asakaze/Manas wheat-barley hybrid produced in Martonvásár, Hungary. The addition lines were selected from self-fertilized plants of the BC2F2-BC2F4 generations using genomic in situ hybridization (GISH) and were identified by fluorescence in situ hybridization (FISH) with repetitive DNA probes [HvT01, (GAA)7 and centromere-specific (AGGGAG)4 probes]. The cytogenetic identification was confirmed using barley arm-specific SSR and STS markers. The ditelosomic additions were propagated in the phytotron and in the field, and morphological parameters (plant height, tillering, length of the main spike, number of seeds/spike and seeds/plant, and spike characteristics) were described. In addition, the salt stress response of the ditelosomic additions was determined. CONCLUSIONS: The six-rowed winter barley cultivar Manas is much better adapted to Central European environmental conditions than the two-rowed spring barley Betzes previously used in wheat-barley crosses. The production of wheat-barley ditelosomic addition lines has a wide range of applications both for breeding (transfer of useful genes to the recipient species) and for basic research (mapping of barley genes, genetic and evolutionary studies and heterologous expression of barley genes in the wheat background).

McGISH identification and phenotypic description of leaf rust and yellow rust resistant partial amphiploids originating from a wheat × Thinopyrum synthetic hybrid cross.

A Thinopyrum intermedium × Thinopyrum ponticum synthetic hybrid wheatgrass is an excellent source of leaf and stem rust resistance produced by N.V.Tsitsin. Wheat line Mv9kr1 was crossed with this hybrid (Agropyron glael) in Hungary in order to transfer its advantageous agronomic traits into wheat. As the wheat parent was susceptible to leaf rust, the transfer of resistance was easily recognizable in the progenies. Three different partial amphiploid lines with leaf rust resistance were selected from the wheat/Thinopyrum hybrid derivatives by multicolour genomic in situ hybridization. Chromosome counting on the partial amphiploids revealed 58 chromosomes (18 wheatgrass) in line 194, 56 (14 wheatgrass) in line 195 and 54 (12 wheatgrass) in line 196. The wheat chromosomes present in these lines were identified and the wheatgrass chromosomes were characterized by fluorescence in situ hybridization using the repetitive DNA probes Afa-family, pSc119.2 and pTa71. The 3D wheat chromosome was missing from the lines. Molecular marker analysis showed the presence of the Lr24 leaf rust resistance gene in lines 195 and 196. The morphological traits were evaluated in the field during two consecutive seasons in two different locations.

Improvement of the agronomic traits of a wheat-barley centric fusion by introgressing the 3HS.3BL translocation into a modern wheat cultivar.

The 3HS.3BL spontaneous Robertsonian translocation obtained from the progenies of wheat-barley (Chinese Spring × Betzes) hybrids backcrossed with wheat line Mv9kr1 was transferred into the modern Martonvásár wheat cultivar Mv Bodri. The translocation was identified with molecular cytogenetic methods. The inheritance of the translocation was traced using genomic in situ hybridization. Fluorescence in situ hybridization using barley subtelomeric (HvT01) and centromere-specific [(AGGGAG)4] repetitive DNA probes confirmed that the complete barley chromosome arm was involved in the Robertsonian translocation. The wheat-specific repetitive DNA probes identified the presence of the whole wheat genome, except the short arm of the 3B chromosome. Genotypes homozygous for the centric fusion were selected, after which morphological analysis was performed on the plants and the yield components were measured in the field during two consecutive vegetative seasons. The introgression of the 3HS.3BL translocation into the modern wheat cultivar Mv Bodri significantly reduced the plant height due to the incorporation of the dwarfing allele RhtD1b. The presence of the 3HS.3BL translocation in the Mv9kr1 and Mv Bodri wheat background improved tillering and seeds per plant productivity in field experiments carried out in Martonvásár and Keszthely, Hungary.