Transferring diversity of goat grass to farmers’ fields through the development of synthetic hexaploid wheat

Abstract Genetic variation in wheat is needed to address global food security challenges, particularly as climates change. Crop wild relatives are unique reservoirs of useful alleles for crop improvement and are important components of genebank collections. We analyzed how the derivatives of ‘goat grass’ (Aegilops tauschii) have been used to widen the genetic base for wheat breeding and surveyed wheat breeders to elicit adoption estimates. Synthetic hexaploid wheat (SHW) is derived by crossing goat grass with durum wheat, serving as a bridge to transfer desirable traits into modern varieties of bread wheat. Our data show that wheat scientists used 629 unique accessions from 15 countries for pre-breeding, producing 1577 primary SHWs. These derivatives represented 21% of the germplasm distributed by the genebank of the International Maize and Wheat Improvement Center between 2000 and 2018. Over the period, more than 10,000 samples of SHW were sent to 110 institutions in 40 countries, with rising numbers of synthetic hexaploid-derived lines (SHDL) included in international nurseries. Lines were screened for major diseases of wheat. At least 86 varieties have been selected from SHDL and released in 20 countries. Survey estimates indicate the highest scale of adoption in southwest China and India, with 34% and 7% of reported wheat area, respectively. These varieties demonstrate resistance to pests and pathogens, high yield potential, good quality attributes, and suitability for biofortified wheat.

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CIMMYT's use of synthetic hexaploid wheat in breeding for adaptation to rainfed environments globally.

Australian Journal of Agricultural Research ◽

10.1071/ar07223 ◽

2008 ◽

Vol 59 (5) ◽

pp. 461 ◽

Cited By ~ 30

Author(s):

J. Lage ◽

R. M. Trethowan

Keyword(s):

Hexaploid Wheat ◽

Wheat Breeding ◽

Trial Data ◽

Emmer Wheat ◽

Yield Potential ◽

Synthetic Hexaploid Wheat ◽

Interspecific Hybridisation ◽

Coefficient Of Parentage ◽

Yield Trial ◽

Synthetic Hexaploid

The International Maize and Wheat Improvement Center (CIMMYT) has had significant impact on wheat production in rainfed regions of the developing world. During the last decade, yield potential has increased in drought-prone areas partly due to the use of synthetic hexaploid wheat (SHW), produced through interspecific hybridisation of Triticum turgidum spp. and Aegilops tauschii, followed by chromosome doubling. The objectives of this study were to document the use of SHW in wheat breeding at CIMMYT and quantify its potential effect on global wheat adaptation. The first SHW-derived lines targetted at rainfed conditions appeared in the 5th Semi-Arid Wheat Yield Trial (SAWYT) representing 8% of the lines, increasing to 46% by the 15th SAWYT. During the same period the average coefficient of parentage of SHW in all synthetically derived crosses decreased from 75 to 19%. Average yield rank of genotypes across locations and years was used as a performance indicator of the SHW-derived lines in SAWYT 5–12. In the 5th SAWYT the average rank of the SHW-derived lines was 30 (out of 50) increasing to 25 by the 12th SAWYT. SAWYT 11 was the first trial to include SHW-derived lines bred exclusively for rainfed environments, using directed selection for drought tolerance. International trial data from SAWYT 11 and 12 showed that the SHW-derived line Vorobey was a top-performing line. Vorobey performed well across all environments compared with the best locally adapted check cultivar at each location; trial means ranged from 1 to 8 t/ha. To further exploit genetic diversity for adaptation to drought, SHW has been produced using emmer wheat (T. turgidum L. subsp. dicoccon) as the tetraploid parent. Yield trial data from Mexico show that SHW derivatives based on emmer wheat improved yield performance under drought compared with their drought-tolerant recurrent parents. The use of SHW in wheat breeding for rainfed environments at CIMMYT has increased significantly over the past 10–15 years and the performance and effect of the derived lines have improved with time.

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Ozone Tolerance Found in Aegilops Tauschii and Primary Synthetic Hexaploid Wheat

Plants ◽

10.3390/plants8070195 ◽

2019 ◽

Vol 8 (7) ◽

pp. 195 ◽

Cited By ~ 2

Author(s):

Brewster ◽

Hayes ◽

Fenner

Keyword(s):

Hexaploid Wheat ◽

Aegilops Tauschii ◽

Grain Weight ◽

Synthetic Hexaploid Wheat ◽

Shoot Biomass ◽

Seed Head ◽

Modern Wheat ◽

Synthetic Hexaploid ◽

1000 Grain Weight ◽

Ozone Levels

Modern wheat cultivars are increasingly sensitive to ground level ozone, with 7–10% mean yield reductions in the northern hemisphere. In this study, three of the genome donors of bread wheat, Triticum urartu (AA), T. dicoccoides (AABB), and Aegilops tauschii (DD) along with a modern wheat cultivar (T. aestivum ‘Skyfall’), a 1970s cultivar (T. aestivum ‘Maris Dove’), and a line of primary Synthetic Hexaploid Wheat were grown in 6 L pots of sandy loam soil in solardomes (Bangor, North Wales) and exposed to low (30 ppb), medium (55 ppb), and high (110 ppb) levels of ozone over 3 months. Measurements were made at harvest of shoot biomass and grain yield. Ae. tauschii appeared ozone tolerant with no significant effects of ozone on shoot biomass, seed head biomass, or 1000 grain + husk weight even under high ozone levels. In comparison, T. urartu had a significant reduction in 1000 grain + husk weight, especially under high ozone (−26%). The older cultivar, ‘Maris Dove’, had a significant reduction in seed head biomass (−9%) and 1000 grain weight (−11%) but was less sensitive than the more recent cultivar ‘Skyfall’, which had a highly significant reduction in its seed head biomass (−21%) and 1000 grain weight (−27%) under high ozone. Notably, the line of primary Synthetic Hexaploid Wheat was ozone tolerant, with no effect on total seed head biomass (−1%) and only a 5% reduction in 1000 grain weight under high ozone levels. The potential use of synthetic wheat in breeding ozone tolerant wheat is discussed.

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Empirical verification of heterogeneous DNA fragments generated from wheat genome-specific SSR primers

Canadian Journal of Plant Science ◽

10.4141/cjps08041 ◽

2008 ◽

Vol 88 (6) ◽

pp. 1065-1071 ◽

Cited By ~ 6

Author(s):

Qijiao Chen ◽

Lianquan Zhang ◽

Zhongwei Yuan ◽

Zehong Yan ◽

Youliang Zheng ◽

...

Keyword(s):

Common Wheat ◽

Hexaploid Wheat ◽

Chinese Spring ◽

Triticum Turgidum ◽

Sequence Data ◽

Aegilops Tauschii ◽

Single Locus ◽

Synthetic Hexaploid Wheat ◽

D Genome ◽

Synthetic Hexaploid

Due to the high polymorphisms between synthetic hexaploid wheat (SHW) and common wheat, SHW has been widely used in genetic studies. The transferability of simple sequence repeats (SSR) among common wheat and its donor species, Triticum turgidum and Aegilops tauschii, and their SHW suggested the possibility that some SSRs, specific for a single locus in common wheat, might appear in two or more loci in SHWs. This is an important genetic issue when using synthetic hexaploid wheat population and SSR for mapping. However, it is largely ignored and never empirically well verified. The present study addressed this issue by using the well-studied SSR marker Xgwm261 as an example. The Xgwm261 produced a 192 bp fragment specific to chromosome 2D in common wheat Chinese Spring, but generated a 176 bp fragment in the D genome of Ae. tauschii AS60. Chromosomal location and DNA sequence data revealed that the176 bp fragment also donated by 2B chromosome of durum wheat Langdon. These results indicated that although a single 176 bp fragment was appeared in synthetic hexaploid wheat Syn-SAU-5 between Langdon and AS60, the fragment contained two different loci, one from chromosome 2D of AS60 and the other from 2B of Langdon which were confirmed by the segregating analysis of SSR Xgwm261 in 185 plants from a F2 population between Syn-SAU-5 and Chinese Spring. If Xgwm261 in Syn-SAU-5 was considered as a single locus in genetic analysis, distorted segregation or incorrect conclusions would be yielded. A proposed strategy to avoid this problem is to include SHW’s parental T. turgidum and Ae. tauschii in SSR analysis as control for polymorphism detection. Key words: Synthetic hexaploid wheat, microsatellite, segregation distortion, Xgwm261, transferability

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Detection of splicing variants in the leaf and spike transcripts of wild diploid wheat Aegilops tauschii and transmission of the splicing patterns to synthetic hexaploid wheat

Plant Gene ◽

10.1016/j.plgene.2016.11.002 ◽

2017 ◽

Vol 9 ◽

pp. 6-12

Author(s):

Julio C.M. Iehisa ◽

Moeko Okada ◽

Kazuhiro Sato ◽

Shigeo Takumi

Keyword(s):

Hexaploid Wheat ◽

Aegilops Tauschii ◽

Diploid Wheat ◽

Synthetic Hexaploid Wheat ◽

Splicing Variants ◽

Synthetic Hexaploid ◽

Splicing Patterns

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Frequent numerical and structural chromosome changes in early generations of synthetic hexaploid wheat

Genome ◽

10.1139/gen-2021-0074 ◽

2021 ◽

Author(s):

Siyu Zhang ◽

Pei Du ◽

Xueying Lu ◽

Jiaxin Fang ◽

Jiaqi Wang ◽

...

Keyword(s):

Hexaploid Wheat ◽

Aegilops Tauschii ◽

Tetraploid Wheat ◽

Snp Markers ◽

Synthetic Hexaploid Wheat ◽

Chromosome Variation ◽

Metaphase Chromosomes ◽

Wheat Evolution ◽

Significant Difference ◽

Synthetic Hexaploid

Modern hexaploid wheat (Triticum aestivum L.; AABBDD) evolved from a hybrid of tetraploid wheat (closely related to Triticum turgidum L. ssp. durum (Desf.) Husn., AABB) and goatgrass (Aegilops tauschii Coss., DD). Variations in chromosome structure and ploidy played important roles in wheat evolution. How these variations occurred and their role in expanding the genetic diversity in modern wheat is mostly unknown. Synthetic hexaploid wheat (SHW) can be used to investigate chromosome variation that occurs during the early generations of existence. SHW lines derived by crossing durum wheat ‘Langdon’ with twelve Ae. tauschii accessions were analyzed using oligonucelotide probe multiplex fluorescence in situ hybridization (FISH) to metaphase chromosomes and SNP markers. Cluster analysis based on SNP markers categorized them into three groups. Among 702 plants from the S8 and S9 generations, 415 (59.12%) carried chromosome variations involving all 21 chromosomes but with different frequencies for each chromosome and sub-genome. Total chromosome variation frequencies varied between lines, but there was no significant difference among the three groups. The non-random chromosome variations in SHW lines detected in this research may be an indication that similar variations occurred in the early stages of wheat polyploidization and played important roles in wheat evolution.

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Allopolyploidization Enhances Genetic Recombination of the Ancestral Diploid Genome in the Evolution of Wheat

10.21203/rs.3.rs-80690/v1 ◽

2020 ◽

Author(s):

Hongshen Wan ◽

Jun Li ◽

Shengwei Ma ◽

Fan Yang ◽

Liang Chai ◽

...

Keyword(s):

Hexaploid Wheat ◽

Genetic Recombination ◽

Recombination Frequency ◽

Aegilops Tauschii ◽

Synthetic Hexaploid Wheat ◽

Evolutionary Potential ◽

D Genome ◽

Diploid Genome ◽

Synthetic Hexaploid ◽

The Impact

Abstract Background: Genetic recombination produces different allelic combinations potentially, providing new variations to the selection pools for domestication. Allopolyploidization increases evolutionary potential of the hexaploid common wheat by taking its advantages of heterosis and gene redundancy. May there be any relationship between allopolyploidization and genetic recombination? To study the impact of allopolyploidization on genetic recombination in different ancestral genomes of wheat, we generated synthetic hexaploid wheat by crossed tetraploid Triticum turgidum with diploid Aegilops tauschii to simulate its evolutionary hexaploidization process. Results: Using Wheat Breeder’s Genotyping Array, the genotypes of F2 individuals were investigated in both tetraploid (A1A1B1B1 x A2A2B2B2) and their synthetic hexaploid wheat derived populations (A1A1B1B1DD x A2A2B2B2DD). And the genotypes of the diploid population (D1D1 x D2D2) and their synthetic hexaploid wheat derived population (AABBD1D1 x AABBD2D2) were obtained with DArT-Seq™ technology. Based on genotypes of F2 populations, the genetic recombination frequency of homologous chromosome were consequently calculated in ancestral tetraploid AABB (4x), diploid DD (2x) and their synthetic hexaploid AABBDD (6x) plants, respectively. The recombination frequency of the ancestral diploid genome DD from Aegilops tauschii was found enhanced significantly more than 2 folds after their hexaploidization, while no significant changes was found in their ancestral tetraploid genome AABB via hexaploidization.Conclusions: Allopolyploidization enhancing genetic recombination of the ancestral diploid genome is found to increase the evolutionary potential of wheat, which is beneficial for wheat to conquer their narrow origination of D genome, quickly spread and make it a major crop of the world.

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