Junmei Wang

A New QTL for Plant Height in Barley (Hordeum vulgare L.) Showing No Negative Effects on Grain Yield

Introduction Reducing plant height has played an important role in improving crop yields. The success of a breeding program relies on the source of dwarfing genes. For a dwarfing or semi-dwarfing gene to be successfully used in a breeding program, the gene should have minimal negative effects on yield and perform consistently in different environments. Methods In this study, 182 doubled haploid lines, generated from a cross between TX9425 and Naso Nijo, were grown in six different environments to identify quantitative trait loci (QTL) controlling plant height and investigate QTL × environments interaction. Results A QTL for plant was identified on 7H. This QTL showed no significant effects on other agronomic traits and yield components and consistently expressed in the six environments. A sufficient allelic effect makes it possible for this QTL to be successfully used in breeding programs.

A Single Locus Is Responsible for Salinity Tolerance in a Chinese Landrace Barley (Hordeum vulgare L.)

Introduction Salinity and waterlogging are two major abiotic stresses severely limiting barley production. The lack of a reliable screening method makes it very hard to improve the tolerance through breeding programs. Methods This work used 188 DH lines from a cross between a Chinese landrace variety, TX9425 (waterlogging and salinity tolerant), and a Japanese malting barley, Naso Nijo (waterlogging and salinity sensitive), to identify QTLs associated with the tolerance. Results Four QTLs were found for waterlogging tolerance. The salinity tolerance was evaluated with both a hydroponic system and in potting mixture. In the trial with potting mixture, only one major QTL was identified to associate with salinity tolerance. This QTL explained nearly 50% of the phenotypic variation, which makes it possible for further fine mapping and cloning of the gene. This QTL was also identified in the hydroponic experiment for different salt-related traits. The position of this QTL was located at a similar position to one of the major QTLs for waterlogging tolerance, indicating the possibility of similar mechanisms controlling both waterlogging and salinity tolerance. Conclusion The markers associated with the QTL provided a unique opportunity in breeding programs for selection of salinity and waterlogging tolerance.

Assessment of genetic diversity by simple sequence repeat markers among forty elite varieties in the germplasm for malting barley breeding

The genetic diversity and relationship among 40 elite barley varieties were analyzed based on simple sequence repeat (SSR) genotyping data. The amplified fragments from SSR primers were highly polymorphic in the barley accessions investigated. A total of 85 alleles were detected at 35 SSR loci, and allelic variations existed at 29 SSR loci. The allele number per locus ranged from 1 to 5 with an average of 2.4 alleles per locus detected from the 40 barley accessions. A cluster analysis based on the genetic similarity coefficients was conducted and the 40 varieties were classified into two groups. Seven malting barley varieties from China fell into the same subgroup. It was found that the genetic diversity within the Chinese malting barley varieties was narrower than that in other barley germplasm sources, suggesting the importance and feasibility of introducing elite genotypes from different origins for malting barley breeding in China.

Molecular characterization and functional analysis of barley semi-dwarf mutant Riso no. 9265.

Backgroundsdw1/denso is one of the most important and useful semi-dwarf genes in barley breeding. At least four sdw1/denso alleles have been reported and HvGA20ox2 is considered as the candidate gene. Up to date, results of studies have not univocally proven the genetic relationship between sdw1/denso and HvGA20ox2.ResultsIn the present study, a complete deletion of Morex_contig_40861 including both HvGA20ox2 and Mloc_56463 genes was identified at the sdw1 locus from a semi-dwarf mutant Riso no. 9265. Expression of the genes encoding gibberellin biosynthesis (HvGA20ox1 and HvGA3ox2) were increased in the mutant compared to the wild type Bomi, while the expression of GA catabolic gene HvGA2ox3 was decreased. Over-expression of HvGA20ox2 could rescue the semi-dwarf phenotype and increase GAs concentration.ConclusionsWe confirmed that a GA biosynthetic enzyme HvGA20ox2, acted as GA 20-oxidase, is the functional gene for the sdw1/denso semi-dwarfism. Lose of HvGA20ox2 is partially compensated by HvGA20ox1 and further feedback is regulated by gibberellin. We also deduced that the sdw1/denso allele itself affects later heading owing to its reduced endogenous GAs concentration.

Identification of Suitable Reference Genes for Barley Gene Expression Under Abiotic Stresses and Hormonal Treatments

Barley (Hordeum vulgare L.) is an important cereal crop and also can be considered as a model plant for the Triticeae family. Quantitative real-time PCR (qRT-PCR) has emerged as a more practical technique to study barley gene expression, and the data normalization with reference genes is essential for accurate and reliable results. In this study, 17 candidate reference genes were evaluated from two distinct plant tissues (roots and leaves) at the barley seedling stage under different abiotic stresses (osmotic, salt, and heat) and hormonal treatments (gibberellin A3 (GA3) and methyl jasmonate (JA)). Our qRT-PCR data were analyzed with three commonly used software packages: geNorm, NormFider, and BestKeeper. In combination with the analysis of these three packages, four to five candidate genes were selected as suitable reference genes in each experimental set. These results confirmed that expression stability of reference genes depends on the experimental conditions. This study is the systematic analysis for the selection of superior reference genes for qRT-PCR in barley under different abiotic and hormonal treatments and will benefit further studies on gene expression in barley and other species of Triticeae family.

A study of genetic diversity of colored barley (Hordeum vulgare L.) using SSR markers

Colored barley is used for the development of barley-containing functional food because of the special nutrients present in its grains. Meanwhile, grain color, which is also one of the primary traits selected in crop domestication, can be used as an important indicator of crop evolution and domestication. In this study, 35 SSR marker pairs were used to analyze the genetic diversity of 277 germplasm accessions representing yellow, purple, blue, and black barley. The analysis revealed that rich genetic variation was mainly caused by the genetic diversity of individuals. Differently colored barley populations could be further divided into subpopulations. As per PCoA, AMOVA, and structure analysis, a complex evolutionary relationship existed among the four colored barley populations. This phenomenon may have been the result of long-term multidirectional selection by humans on the basis of barley use. Studies on colored barley provide useful data for future breeding and utilization of these materials.

Pathotypes and Genetic Diversity of Blumeria graminis f. sp. hordei in the Winter Barley Regions in China

Barley powdery mildew caused by Blumeria graminis f. sp. hordei (Bgh) is one of the most destructive foliar diseases of barley in the winter barley region of China. The evaluation and assessment of the virulence and diversity of Bgh populations help to determine effective sources of resistance to the pathogen. 515 isolates were collected from seven populations of Bgh on cultivated barley in seven geographically distant locations in 2006. Their virulence was determined by inoculation onto 26 differential host lines. All of the isolates belonged to 58 pathotypes and 13 of which included 81% of these isolates. The most abundant pathotype was pathotype 0047 (18.3%), the second most abundant was pathotype 0045 (11.8%) and the third most abundant was pathotype 0057 (7.8%). Most of virulent genes investigated in this study showed similar frequencies in the seven different areas. These indicate that the seven locations may be in a uniform epidemiological region and barley cultivars in these areas may have similar genetic background. Diversities within these populations and distances between these populations measured by KOIND package were different. Correlations were not found between the genetic distance and the geographical distances between different locations. This suggested that long distance spread and local epidemics existed in the major winter barley growing regions in China.

Characterization and mapping of a Prbs gene controlling spike development in Hordeum vulgare L.

The barley mutant, poly-row-and-branched spike (prbs) showed altered inflorescence morphology: complete conversion of the rudimentary lateral spikelets in two-rowed barley into fully developed fertile spikelets similar to the six-rowed phenotype, and additional spikelets in the middle of spike. Moreover, branched spikes emerged in progeny from a cross between the mutant and a six-rowed barley cultivar. Morphological observation of the development of immature spikes of the mutant and descendants with branched spikes showed that the Prbs gene is involved in spikelet development in the triple-mound stage. In mutant prbs, new meristems initiated at the flanks of lateral spikelets and middle spikelet meristems were converted to branch meristems, developing branched spikes. These observations suggested that the Prbs gene plays a crucial role in spikelet initiation and identity maintenance. The Prbs gene may be an important modifier in inflorescence differentiation from a panicle into a spike. The branched spikes emerging in hybrids from a cross between the mutant and six-rowed barley cultivar were not conferred by the gene vrs1 or Int-c, which decide spike morphology in six-rowed barley. These results imply that although six-row genes vrs1 and Int-c and prbs have similar effects on lateral spikelet development, they have different functions in branched spikes. The Prbs gene was mapped to chromosome 3H between SSR marker Bmag0023 and marker Cbic60 at a genetic distance of 3.3 and 5.4 centimorgans (cM), respectively.

Toward Identification of Black Lemma and Pericarp Gene Blp1 in Barley Combining Bulked Segregant Analysis and Specific-Locus Amplified Fragment Sequencing

Black barley is caused by phytomelanin synthesized in lemma and/or pericarp and the trait is controlled by one dominant gene Blp1. The gene is mapped on chromosome 1H by molecular markers, but it is yet to be isolated. Specific-locus amplified fragment sequencing (SLAF-seq) is an effective method for large-scale de novo single nucleotide polymorphism (SNP) discovery and genotyping. In the present study, SLAF-seq with bulked segregant analysis (BSA) was employed to obtain sufficient markers to fine mapping Blp1 gene in an F2 population derived from Hatiexi No.1 × Zhe5819. Based on SNP screening criteria, a total of 77,542 polymorphic SNPs met the requirements for association analysis. Combining two association analysis methods, the overlapped region with a size of 32.41 Mb on chromosome 1H was obtained as the candidate region of Blp1 gene. According to SLAF-seq data, markers were developed in the target region and were used for mapping the Blp1 gene. Linkage analysis showed that Blp1 co-segregated with HZSNP34 and HZSNP36, and was delimited by two markers (HZSNP35 and HZSNP39) spanning 8.1 cM in 172 homozygous yellow grain F2 plants of Hatiexi No.1 × Zhe5819. More polymorphic markers were screened in the reduced target region and were used to genotype the population. As a result, Blp1 was delimited within a 1.66 Mb on chromosome 1H by the upstream marker HZSNP63 and the downstream marker HZSNP59. Our results demonstrated the utility of SLAF-seq-BSA approach to identify the candidate region and discover polymorphic markers at the specific targeted genomic region.

Establishment of a highly efficient regeneration method from the scraped broken embryo of mature barley seed

Hua, W., Zhu, J., Shang, Y., Wang, J., Jia, Q., Lin, F. and Yang, J. 2013. Establishment of a highly efficient regeneration method from the scraped broken embryo of mature barley seed. Can. J. Plant Sci. 93: 1029-1035. An efficient and reproducible plant regeneration system for mature barley would represent a significant innovation for barley tissue culture and genetic transformations to optimize barley crop traits. To address this need, we used scraped broken embryos (SBEs) from dried barley seeds to establish a highly efficient regeneration system. Mature SBEs cultured in an induction medium with 2 mg L-1 2,4-D offered the best callus formation (92.99% induction efficiency) and no germination. Furthermore, calli arising from SBEs had the highest regeneration frequency (69.72%) in FHG medium with 1 mg L-1 6-benzylaminopurine. We then compared three different cultivars: Golden Promise, Zaoshu3, and Zhepi8 for callogenesis and regeneration using an established protocol. Zhepi8 had the greatest callus induction (92.78%) and regeneration (68.24%). Our innovative methods for mature barley plant reproduction will contribute to improvements in genetic barley transformation as an alternate regeneration system.