Synergizing breeding strategies via combining speed breeding, phenotypic selection, and marker-assisted backcrossing for the introgression of Glu-B1i in wheat

Wheat is a major food crop that plays a crucial role in the human diet. Various breeding technologies have been developed and refined to meet the increasing global wheat demand. Several studies have suggested breeding strategies that combine generation acceleration systems and molecular breeding methods to maximize breeding efficiency. However, real-world examples demonstrating the effective utilization of these strategies in breeding programs are lacking. In this study, we designed and demonstrated a synergized breeding strategy (SBS) that combines rapid and efficient breeding techniques, including speed breeding, speed vernalization, phenotypic selection, backcrossing, and marker-assisted selection. These breeding techniques were tailored to the specific characteristics of the breeding materials and objectives. Using the SBS approach, from artificial crossing to the initial observed yield trial under field conditions only took 3.5 years, resulting in a 53% reduction in the time required to develop a BC2 near-isogenic line (NIL) and achieving a higher recurrent genome recovery of 91.5% compared to traditional field conditions. We developed a new wheat NIL derived from cv. Jokyoung, a leading cultivar in Korea. Milyang56 exhibited improved protein content, sodium dodecyl sulfate-sedimentation value, and loaf volume compared to Jokyoung, which were attributed to introgression of the Glu-B1i allele from the donor parent, cv. Garnet. SBS represents a flexible breeding model that can be applied by breeders for developing breeding materials and mapping populations, as well as analyzing the environmental effects of specific genes or loci and for trait stacking.

Identification of new nucleotide sequences of the Glu-B1-1 gene encoding x-type glutenins in bread wheat

Studies of the genetic base and polymorphism of bread wheat cultivars aimed at identifying alleles of genes associated with high baking and other economically valuable traits seem to be relevant, since bread wheat, along with all representatives of the Triticeae tribe, has a huge genetic potential for creating cultivars with high technological and rheological properties of grain flour. The aim of this study was sequencing and analysis of the nucleotide sequences of the Glu-B1-1 gene, and analysis of the predicted amino acid sequences of its protein product in three cultivars of bread wheat. Thus, in the course of genotyping cultivars and lines of bread wheat for the Glu-B1-1 gene, in the cultivars 'Avesta', 'Leningradka krupnozernaya' and line C-75094, previously undescribed changes in the size of amplifiable regions of the Glu-B1-1 gene for high-molecular weight glutenins were found. Comparative analysis of the nucleotide sequences of these genes with known sequences showed the presence of two deletions in 'Avesta' and C-75094 and the presence of seven single-nucleotide substitutions in 'Leningradka krupnozernaya'. Alignment of the predicted Glu-B1 amino acid sequences of the studied accessions and the standard cultivar carrying the Glu-B1-a allele showed that deletions in the amino acid sequences of 'Avesta' and C-75094 accessions are localized in the central domain of the protein and affect the amount of tri-, hexa-, and nonapeptides, and in 'Leningradka krupnozernaya', a decrease in GQQ and PGQGQQ by one unit was revealed. In addition, substitutions of five amino acids were found in 'Leningradka krupnozernaya'. Thus, we have found previously undescribed deletions and substitutions in the nucleotide sequences of the Glu-B1-1 gene for high-molecular-weight glutenins, which lead to changes in amino acid sequences in functionally important regions, namely, in the central domains of protein molecules. The identified mutations can be used for genotyping bread wheat cultivars.

Molecular Characterization and Marker Development of the HMW-GS Gene from Thinopyrum elongatum for Improving Wheat Quality

The quality of wheat primarily depends on its storage protein quality, especially in regards to gluten content and high-molecular-weight glutenin subunits (HMW-GS). The number of HMW-GS alleles is limited in bread wheat (Triticum aestivum L.), whereas it is abundant in wheat relatives. Therefore, HMW-GS alleles from wheat relatives could provide a potential for improving quality in wheat breeding. Thinopyrum elongatum (EE) is one of the relatives of wheat. The E genome is closely related to the ABD genome in wheat; therefore, Th. elongatum is often used as an excellent exogenous gene donor for wheat genetic improvement. In this study, the high-molecular glutenin subunit gene was cloned and sequenced from Th. elongatum. A specific molecular marker for identifying the Glu-1Ey subunit gene was developed and applied to detected wheat-Th. elongatum alien introgression lines. Quality analysis indicated that the substitution and addition lines containing Th. elongatum alleles significantly (p < 0.05) increased grain protein content by 3.76% to 5.11%, wet-gluten content by 6.55% to 8.73%, flour 8-MW by 0.25% to 6.35%, and bread volume value by 33.77 mL to 246.50 mL, in comparing it with Chinese Spring. The GMP content and lactic acid SRC showed significant positive correlations with flour processing quality and might be used as indicators for wheat quality. The results were expected to provide a novel route for improving processing quality in wheat quality breeding.

Genetic polymorphism of high-molecular-weight glutenin subunit loci in bread wheat varieties in the Pre-Ural steppe zone

High-molecular-weight glutenins play an important role in providing high baking qualities of bread wheat grain. However, breeding bread wheat for this trait is very laborious and, therefore, the genotyping of variety samples according to the allelic composition of high-molecular-weight glutenin genes is of great interest. The aim of the study was to determine the composition of high-molecular-weight glutenin subunits based on the identification of the allelic composition of the Glu-1 genes, as well as to identify the frequency of the Glu-1 alleles in bread wheat cultivars that are in breeding work under the conditions of the Pre-Ural steppe zone (PSZ). We analyzed 26 winter and 22 spring bread wheat varieties from the PSZ and 27 winter and 20 spring varieties from the VIR collection. Genotyping at the Glu-A1 locus showed that the Ax1 subunits are most common in winter varieties, while the predominance of the Ax2* subunits was typical of spring varieties and lines. In the Glu-B1 locus, the predominance of alleles associated with the production of the Bx7 and By9 subunits was revealed for both winter and spring varieties. In the case of the Glu-D1 gene, for all the wheat groups studied, the composition of the Dx5+Dy10 subunits was the most common: in 92.3 % of winter and 68.2 % of spring PSZ accessions and in 80 % of winter and 55 % of spring VIR accessions. The analysis of genotypes showed the presence of 13 different allelic combinations of the Glu-A1, Glu-B1, Glu-D1 genes in the PSZ varieties, and 19 combinations in the VIR varieties. The b b/al/с d allelic combination (Ax2* Вх7+Ву8/8*/9 Dx5+Dy10) turned out to be the most common for the PSZ spring varieties and lines, while for the PSZ winter accessions it was a с d (Ax1 Вх7+By9 Dx5+Dy10); the b с a and b с d genotypes (Ax2* Вх7+Ву9 Dx2+Dy12 and Ax2* Вх7+Ву9 Dx5+Dy10, respectively) occur with equal frequency among the VIR spring accessions; in the group of VIR winter varieties, the combination of the a b/ al d alleles (Ax1 Вх7+Ву8/8* Dx5+Dy10) prevails. The most preferred combination of alleles for baking qualities was found in the spring variety 'Ekaterina' and winter varieties 'Tarasovskaya 97', 'Volzhskaya S3', as well as in lines k-58164, L43510, L43709, L-67, L-83, which are recommended for further breeding programs to improve and preserve baking qualities in the conditions of the Pre-Ural steppe zone.

Effect of high molecular weight glutenin subunits on wheat quality properties, across a wide range of climates and environments in Iran

High molecular weight glutenin subunits (HMW-GSs) at the Glu-1 loci play an important role in the variation of dough strength, elasticity, and end-use quality of bread wheat. Multilocation trials in a wide range of climatic conditions and crop management practices help explain the role of HMW-GSs in the rheological properties of dough. In the current study, allelic variation of HMWs and quality scores were determined in 28 bread wheat cultivars across a wide range of climates and locations in Iran. Twelve HMW-GSs subunits (3 at Glu-A1, 7 at Glu-B1 and 2 at Glu D-1) in 16 unique combinations were identified in the studied cultivars. In the most rheological properties associated with good bread-making quality, the compositions of 1/17 + 18/5 + 10, 1/13 + 16/5 + 10 and 2*/7 + 9/5 + 10 (all with a quality score of 10) had significantly higher values than the other allelic compositions. While, the lowest values were observed in 1/21 + 19/2 + 12 (quality score of 6). The degree of dough softening was significantly greater in 1/21 + 19/2 + 12 than other allelic combinations. At Glu-A1, Glu-B1 and Glu-D1, 2*, 17 + 18 and 5 + 10 had significantly greater qualitative and rheological properties than the other subunits, which are related to the good quality of wheat flour. While null at Glu-A1, subunits 21 + 19 at Glu-B1 and 2 + 12 at Glu-D1 were associated with weak baking quality. Moreover, the highest dough softening values at Glu-A1, Glu-B1 and Glu-D1 were observed in null, 21 + 19 and 2 + 12 subunits, respectively. A negative and significant correlation (P < 0.05) was observed between the degree of dough softening and other qualitative and rheological properties related to good bread-making performance. The results of this study demonstrated the role of HMW-GSs in determining the end-use quality of bread wheat across a wide range of climates and environments.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-023-01324-6.

Premature Termination Codon of 1Dy12 Gene Improves Cookie Quality in Ningmai9 Wheat

The area between middle and lower reaches of the Yangtze River is the largest region for soft wheat production in China. In soft wheat breeding, the lack of germplasm with desirable quality for end-use products is a barrier. Ningmai9 is the main variety of soft wheat planted in this area. To create germplasm with better quality and yield potential than Ningmai9, mutants of HMW-GSs in Ningmai9 induced by ethylmethanesulfonate (EMS) were obtained. SDS-PAGE showed that two mutants, md10 and md11, were HMW-GS 1Dy deletions. DNA sequencing confirmed that one mutation was caused by a C/T substitution, resulting in the change of CAA encoding glutamine into the termination codon TAA, and another mutation was due to a G/A substitution in the central repetitive domain of the coding region, causing TGG encoding tryptophan to become the termination codon TGA. The premature termination codon of the 1Dy12 gene affected the expression of 1Dy12 and kept the mRNA at a lower transcription level during the kernel development stage in comparison with the wild type. HMW-GS 1Dy12 deletion mutants decreased the content of HMW-GSs and glutenin macropolymers, mixograph envelope peak time and TIMEX width, water solvent retention capacity (WSRC), and lactic acid solvent retention capacity (LASRC). In the HMW-GS 1Dy12 deletion lines, the sugar-snap cookie diameter was 8.70-8.74 cm, which was significantly larger than that in the wild type of 8.0 cm. There were no significant differences in spike number, kernel number, thousand kernel weight, and yield between the deletion lines and wild type. Overall, the study indicated that the knockout of the HMW-GS gene induced by EMS is an effective way to improve wheat quality, and deletion mutants of HMW-GS 1Dy12 decrease gluten strength and increase sugar snap cookie diameter without yield penalty in Ningmai9 wheat.

Rapid and Easy High-Molecular-Weight Glutenin Subunit Identification System by Lab-on-a-Chip in Wheat (Triticum aestivum L.)

Lab-on-a-chip technology is an emerging and convenient system to easily and quickly separate proteins of high molecular weight. The current study established a high-molecular-weight glutenin subunit (HMW-GS) identification system using Lab-on-a-chip for three, six, and three of the allelic variations at the Glu-A1, Glu-B1, and Glu-D1 loci, respectively, which are commonly used in wheat breeding programs. The molecular weight of 1Ax1 and 1Ax2* encoded by Glu-A1 locus were of 200 kDa and 192 kDa and positioned below 1Dx subunits. The HMW-GS encoded by Glu-B1 locus were electrophoresed in the following order below 1Ax1 and 1Ax2*: 1Bx13 ≥ 1Bx7 = 1Bx7^OE > 1Bx17 > 1By16 > 1By8 = 1By18 > 1By9. 1Dx2 and Dx5 showed around 4-kDa difference in their molecular weights, with 1Dy10 and 1Dy12 having 11-kDa difference, and were clearly differentiated on Lab-on-a-chip. Additionally, some of the HMW-GS, including 1By8, 1By18, and 1Dy10, having different theoretical molecular weights showed similar electrophoretic mobility patterns on Lab-on-a-chip. The relative protein amount of 1Bx7^OE was two-fold higher than that of 1Bx7 or 1Dx5 and, therefore, translated a significant increase in the protein amount in 1Bx7^OE. Similarly, the relative protein amounts of 8 & 10 and 10 & 18 were higher than each subunit taken alone. Therefore, this study suggests the established HMW-GS identification system using Lab-on-a-chip as a reliable approach for evaluating HMW-GS for wheat breeding programs.

Effects of 1Dy12 subunit silencing on seed storage protein accumulation and flour-processing quality in a common wheat somatic variation line

Dissecting the functions of high molecular weight glutenin subunits (HMW-GSs) is helpful for improving wheat quality via breeding. In this study, we used a wheat mutant AS273 in which HMW-GS 1Dy12 was silenced to investigate the silencing mechanism of 1Dy12 and its effects on gluten accumulation and flour-processing quality. Results suggested that the expression of 1Dy12 in AS273 was decreased by one fifth during grain development; a stop codon produced by a base mutation (C/T) led to truncated translation; the absence of 1Dy12 stimulated the accumulation of low molecular weight glutenin subunits (LMW-GSs), gliadins, and glutenin macropolymers, and was resulted in larger protein bodies; AS273 had an inferior flour-processing performance. Based on the outputs achieved in this study it is concluded that 1Dy12 makes important contributions to bread, sponge cake and biscuit-processing quality.

Cloning and characterization of special HMW glutenin subunit genes from Aegilops longissima L. and their potential for wheat quality improvement

Identification and cloning of new glutenin genes from wheat-related species can provide candidate gene resources for quality improvement of wheat. In this study, ten special high-molecular-weight glutenin subunits (HMW-GS), including five x-type (1S^l2x, 1S^l16x, 1S^l17x, 1S^l23x, and 1S^l25x) and five y-type (1S^l2y, 1S^l6y₁, 1S^l16y, 1S^l17y, and 1S^l23y) from Aegilops longissima L. (S^lS^l, 2n = 2x = 14) were identified, and their complete encoding genes were cloned by allelic-specific polymerase chain reaction (AS-PCR). The deduced amino acid (aa) residues of the x-type subunit genes ranged from 821 aa (2469 bp) to 941 aa (2829 bp), while those of the y-type subunit genes varied from 749 aa (2250 bp) to 771 aa (2361 bp). These special HMW-GS had a longer central repetitive domain with more glutamine repeats and glutamine residues compared to the previously characterized HMW-GS in common wheat, which provided a structural basis for superior gluten quality formation. The authenticity of the four cloned genes were verified by matrix-assisted laser desorption ionization time-of-flight/time-of-flight mass spectrometry (MALDI-TOF/TOF-MS). Abundant single-nucleotide polymorphism (SNP) and insertion/deletion (InDel) variations among these genes were identified, which would benefit for developing specific molecular markers used for wheat gluten quality improvement. Phylogenetic analysis revealed that the 1S^l-encoded HMW-GS had close relationships with those from bread wheat, which were divergent from Triticum species at 2.10-10.00 million years ago. Our results indicate that the 1S^l genome contains superior candidate glutenin genes that have potential application values for the improvement of wheat bread making quality.