The Mechanism of the Origination of Auto-allopolyploidy and Aneuploidy in Higher Plants Based on the Cases of Iris and Triticeae.

Cytomixis is a natural process of chromatin exchange among cells. In Iris confusa and I. japonica, the synchronized cytomixis takes place between PMC\u27s during a stage just before meiosis. This process produces euploid and aneuploid offspring. The chromosome number of a fertile diploid plant is 30 (2n). Most accessions of I. confusa and I. japonica are sterile aneuploids. The chromosome numbers are varied, ranging 2n = 28 to 60. In Triticeae cytomixis plays an important role in spontaneous chromosome doubling or redoubling, resulting in the origin of auto-allopolyploidy and aneuploidy. We have obtained amphidiploid plants by spontaneous chromosome doubling. These plants indicate indirectly that cytomixis takes place in the macrosporocytes, giving rise to high level auto-allopolyploid Triticeae species

Origin of worldwide cultivated barley revealed by NAM-1 gene and grain protein content

The origin, evolution and distribution of cultivated barley provides powerful insights into the historic origin and early spread of agrarian culture. Here, population-based genetic diversity and phylogenetic analyses were performed to determine the evolution and origin of barley and how domestication and subsequent introgression have affected the genetic diversity and changes in cultivated barley on a worldwide scale. A set of worldwide cultivated and wild barleys from Asia and Tibet of China were analyzed using the sequences for NAM-1 gene and gene-associated traits-GPC (grain protein content). Our results showed Tibetan wild barley distinctly diverged from Near Eastern barley, and confirmed that Tibet is one of the origin and domestication centers for cultivated barley, and in turn supported a polyphyletic origin of domesticated barley. Comparison of haplotype composition among geographic regions revealed gene flow between Eastern and Western barley populations, suggesting that the Silk Road might have played a crucial role in the spread of genes. The GPC in the 118 cultivated and 93 wild barley accessions ranged from 6.73% to 12.35% with a mean of 9.43%. Overall, wild barley had higher averaged GPC (10.44%) than cultivated barley. Two unique haplotypes (Hap2 and Hap7) caused by a base mutations (at position 544) in the coding region of the NAM-1 gene might have a significant impact on the GPC. SNPs and haplotypes of NAM-1 associated with GPC in barley could provide a useful method for screening GPC in barley germplasm. The Tibetan wild accessions with lower GPC could be useful for malt barley breedin

The Study on N Genome of Leymus Species

Leymus Hochst. is a perennial genus of Triticeae. All species in Leymus have the genomes NX. The genome N is from the genus Psathyrostachys. Two Psathyrostachys species, diploid P. huashanica Keng ex Kuo and P. juncea (Fische.) Nevski (2n= 14), were hybridized with allotetraploid, Leymus secalinus (Georgi.) Tzvelev and L. multicaulis (Kar. & Kir.) Tzvelev. Meiotic behavior of the synthetic hybrids was studied. The chromosome pairings indicated that one L. secalinus genome and one L. multicaulis genome were closely homologous with both P. huashanica and P. juncea genomes. The data of genomic analysis in the hybrids of P. huashanica crossed with L. secalinus and L. multicaulis are so similar to those in the hybrids of P. juncea crossed with L. secalinus and L. multicaulis, there is no significant difference between them. Both P. huashanica and P. juncea are possible donors of the N genome of L. secalinus and L. multicaulis

Inheritance and identification of molecular markers associated with a novel dwarfing gene in barley

Background Dwarfing genes have widely been used in barley breeding program. More than 30 types of dwarfs or semidwarfs have been reported, but a few has been exploited in barley breeding because pleiotropic effects of dwarfing genes cause some undesired traits. The plant architecture of newly discovered dwarfing germplasm "Huaai 11" consisted of desirable agronomic traits such as shortened stature and early maturity. Genetic factor controlling the plant height in dwarf line Huaai 11 was investigated. Results The Huaai 11 was crossed with tall varieties Monker, Mpyt, Zhenongda 3, Zaoshu 3, Advance, Huadamai 1, Huadamai 6, Hyproly and Ris01508. All the F1 plants displayed tall trait. Both tall and dwarf plants appeared in all the F2 populations with a 3:1 segregation ratio, suggesting that dwarfism of Huaai 11 is controlled by a single recessive gene, btwd1. Allelism test indicated that this dwarfing gene in the Huaai 11 is nonallelic with the gene br, uzu, sdw1 and denso. Using a double haploid population derived from a cross of Huadamai 6 and Huaai 11 and SSR markers the novel dwarfing gene was mapped onto the long arm of chromosome 7H, and closely linked to Bmac031 and Bmac167 with genetic distance of 2.2 cM. Conclusion Huaai 11 is a new source of dwarf for broadening the genetic base of dwarfism. This dwarf source was controlled by a recessive dwarfing gene btwd1, was mapped onto the long arm of chromosome 7H

Phylogenetic analysis of two single-copy nuclear genes revealed origin and complex relationships of polyploid species of Hordeum in Triticeae (Poaceae)

Accepted versionTwo single-copy nuclear genes, the second largest subunit of RNA polymerase II (RPB2) and thioredoxin-like gene (HTL), were used to explore the phylogeny and origin of polyploid species in Hordeum. Our results were partly in accord with previous studies, but disclosed additional complexity. Both RPB2 and HTL trees confirmed the presence of Xa genome in H. capense and H. secalinum, and that H. depressum originated from H. californicum together with other American diploids, either H. intercedens or H. pusillum. American diploids solely contributed to the origin of H. depressum. The Asian diploids, either iH. bogdanii or H. brevisubulatum, contributed to the formation of American polyploids except H. depressum. RPB2 and HTL sequences showed that H. roshevitzii did not contribute to the origin of American tetraploids. Our data showed a close relationship between the hexaploids H. procerum and H. parodii and the tetraploids H. brachyantherum, H. fuegianum, H. guatemalense, H. jubatum, and H. tetraploidum. The involvement of the diploid H. pusillum and the tetraploid H. jubatum in the formation of H. arizonicum was also indicated in the HTL phylogeny. Our results suggested a possible gene introgression of W- and P-genome species into the tetraploid H. jubatum and the hexaploid H. procerum

Genetic Divergence in Domesticated and Non-Domesticated Gene Regions of Barley Chromosomes

Publisher's version/PDFLittle is known about the genetic divergence in the chromosomal regions with domesticated and non-domesticated genes. The objective of our study is to examine the effect of natural selection on shaping genetic diversity of chromosome region with domesticated and non-domesticated genes in barley using 110 SSR markers. Comparison of the genetic diversity loss between wild and cultivated barley for each chromosome showed that chromosome 5H had the highest divergence of 35.29%, followed by 3H, 7H, 4H, 2H, 6H. Diversity ratio was calculated as (diversity of wild type – diversity of cultivated type)/diversity of wild type×100%. It was found that diversity ratios of the domesticated regions on 5H, 1H and 7H were higher than those of non-domesticated regions. Diversity ratio of the domesticated region on 2H and 4H is similar to that of non-domesticated region. However, diversity ratio of the domesticated region on 3H is lower than that of non-domesticated region. Averaged diversity among six chromosomes in domesticated region was 33.73% difference between wild and cultivated barley, and was 27.56% difference in the non-domesticated region. The outcome of this study advances our understanding of the evolution of crop chromosomes

Tibet as a potential domestication center of cultivated barley of China

Publisher's version/PDFThe importance of wild barley from Qinghai-Tibet Plateau in the origin and domestication of cultivated barley has long been underestimated. Population-based phylogenetic analyses were performed to study the origin and genetic diversity of Chinese domesticated barley, and address the possibility that the Tibetan region in China was an independent center of barley domestication. Wild barley (Hordeum vulgare ssp. spontaneum) populations from Southwest Asia, Central Asia, and Tibet along with domesticated barley from China were analyzed using two nuclear genes. Our results showed that Tibetan wild barley distinctly diverged from Southwest Asian (Near East) wild barley, that Central Asian wild barley is related to Southwest Asian wild barley, and that Chinese domesticated barley shares the same haplotypes with Tibetan wild barley. Phylogenetic analysis showed a close relationship between Chinese domesticated barley and the Tibetan wild barley, suggesting that Tibetan wild barley was the ancestor of Chinese domesticated barley. Our results favor the polyphyletic origin for cultivated barley

Cloning and Characterization of TaTGW-7A Gene Associated with Grain Weight in Wheat via SLAF-seq-BSA

Thousand-grain weight (TGW) of wheat (Triticum aestivum L.) contributes significantly to grain yield. In the present study, a candidate gene associated with TGW was identified through specific-locus amplified fragment sequencing (SLAF-seq) of DNA bulks of recombinant inbred lines (RIL) derived from the cross between Jing 411 and Hongmangchun 21. The gene was located on chromosome 7A, designated as TaTGW-7A with a complete genome sequence and an open reading frame (ORF). A single nucleotide polymorphism (SNP) was present in the first exon between two alleles at TaTGW-7A locus, resulting in a Val to Ala substitution, corresponding to a change from higher to lower TGW. Cleaved amplified polymorphic sequence (CAPS) (TGW7A) and InDel (TG9) markers were developed to discriminate the two alleles TaTGW-7Aa and TaTGW-7Ab for higher and lower TGW, respectively. A major QTL co-segregating with TaTGW-7A explained 21.7–27.1% of phenotypic variance for TGW in the RIL population across five environments. The association of TaTGW-7A with TGW was further validated in a natural population and Chinese mini-core collections. Quantitative real-time PCR revealed higher transcript levels of TaTGW-7Aa than those of TaTGW-7Ab during grain development. High frequencies of the superior allele TaTGW-7Aa for higher TGW in Chinese mini-core collections (65.0%) and 501 wheat varieties (86.0%) indicated a strong and positive selection of this allele in wheat breeding. The molecular markers TGW7A and TG9 can be used for improvement of TGW in breeding programs

Origin and Reticulate Evolutionary Process of Wheatgrass Elymus trachycaulus (Triticeae: Poaceae)

Publisher's version/PDFTo study origin and evolutionary dynamics of tetraploid Elymus trachycaulus that has been cytologically defined as containing StH genomes, thirteen accessions of E. trachycaulus were analyzed using two low-copy nuclear gene Pepc (phosphoenolpyruvate carboxylase) and Rpb2 (the second largest subunit of RNA polymerase II), and one chloroplast region trnL–trnF (spacer between the tRNA Leu (UAA) gene and the tRNA-Phe (GAA) gene). Our chloroplast data indicated that Pseudoroegneria (St genome) was the maternal donor of E. trachycaulus. Rpb2 data indicated that the St genome in E. trachycaulus was originated from either P. strigosa, P. stipifolia, P. spicata or P. geniculate. The Hordeum (H genome)-like sequences of E. trachycaulus are polyphyletic in the Pepc tree, suggesting that the H genome in E. trachycaulus was contributed by multiple sources, whether due to multiple origins or introgression resulting from subsequent hybridization. Failure to recovering St copy of Pepc sequence in most accessions of E. trachycaulus might be caused by genome convergent evolution in allopolyploids. Multiple copies of H-like Pepc sequence from each accession with relative large deletions and insertions might be caused by either instability of Pepc sequence in H- genome or incomplete concerted evolution. Our results highlighted complex evolutionary history of E. trachycaulus.This project was supported in part by an internal grant from Anhui Agricultural University, a discovery grant (RGPIN-2014-05249) from the Natural Sciences and Engineering Research Council of Canada, and a Senate Research Grant at Saint Mary’s University, Canada. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Identification of QTL underlying physiological and morphological traits of flag leaf in barley

Publisher's Version/PDFBackground: Physiological and morphological traits of flag leaf play important roles in determining crop grain yield and biomass. In order to understand genetic basis controlling physiological and morphological traits of flag leaf, a double haploid (DH) population derived from the cross of Huaai 11 × Huadamai 6 was used to detect quantitative trait locus (QTL) underlying 7 physiological and 3 morphological traits at the pre-filling stage in year 2012 and 2013. Results: Total of 38 QTLs distributed on chromosome 1H, 2H, 3H, 4H, 6H and 7H were detected, and explained 6.53% - 31.29% phenotypic variation. The QTLs flanked by marker Bmag829 and GBM1218 on chromosome 2H were associated with net photosynthetic rate (Pn), stomatal conductance (Gs), flag leaf area (LA), flag leaf length (FLL), flag leaf width (FLW), relative chlorophyll content (SPD) and leaf nitrogen concentration (LNC). Conclusion: Two QTL cluster regions associated with physiological and morphological traits, one each on the chromosome 2H and 7H, were observed. The two markers (Bmag829 and GBM1218) may be useful for marker assisted selection (MAS) in barley breeding.This project was supported in part by the National Natural Science Foundation of China (31301310 and 31228017) and the earmarked fund for China Agriculture Research System (CARS-5)