Genetic improvement in bread wheat (Triticum aestivum L., AABBDD, 2n=6x=42) for various economically important characters has remained a challenge for breeders. The present study investigated diversity of the high molecular weight (HMW) as well as low molecular weight (LMW) glutenin subunits in 84 wheat genotypes including Pakistani land races, cultivars and Aegilops tauschii derived primary synthetic hexaploid wheats (SHWs). For HMW-GS, 15 x-type and 9 y-type subunits were observed in all three groups. Nei's diversity index was highest for Glu-D t 1 locus in synthetics hexaploid wheats and revealed that the D genome from Ae. tauschii carried maximum diversity for HMW-GS. Of the 33 different combinations, the highest combinations observed in SHWs were 'null, 6+8, 2.1+10.5' followed by 'null, 6+8, 1.5+10' and '2*, 6+8, 2+12', while, the Pakistani cultivars and land races harbored 'null, 20, 12+2' and '1, 7+8, 2+12' alleles. For LMW-GS, six alleles were found at Glu-A3 locus and nine were found at Glu-B3 locus. Predominant alleles were Glu-A3c, Glu-A3d and Glu-A3b, which were observed in 41 (50.61%), 19 (23.45%) and 12 (14.81%) genotypes, respectively. At Glu-B3 locus, at the most prevalent alleles were Glu-B3h (18.51%), and Glu-B3i (17. 28%). High number of HMW-GS (Glu-D t 1 locus) and LMW-GS combinations reported here highlights the potential use of SHWs for transferring allelic variation from this synthetic stock to bread wheat for broadening genetic base of quality traits. Furthermore, Ae. tauschii derived primary SHWs also encoded both x and y-type alleles and offers possibility of these SHWs for the introduction of novel glutenin variability into elite bread wheat cultivars for different end use products.
[前沿资讯] Multi-parent populations in crops: a toolbox integrating genomics and genetic mapping with breeding 进入全文
[前沿资讯] Genome-wide mapping and allelic fingerprinting provide insights into the genetics of resistance to wheat stripe rust in India, Kenya and Mexico 进入全文
Stripe or yellow rust (YR) caused by Puccinia striiformis Westend. f. sp. tritici Erikss. is a persistent biotic-stress threatening global wheat production. To broaden our understanding of the shared genetic basis of YR resistance across multi-site and multi-year evaluations, we performed a large genome-wide association study using 43,706 YR observations on 23,346 wheat lines from the International Maize and Wheat Improvement Center evaluated between 2013 and 2019 at sites in India, Kenya and Mexico, against predominant races prevalent in the countries. We identified 114 repeatable markers tagging 20 quantitative trait loci (QTL) associated with YR on ten chromosomes including 1D, 2A, 2B, 2D, 3A, 4A, 4D, 5A, 5B and 6B, among which four QTL, QYr.cim-2DL.2, QYr.cim-2AS.1, QYr.cim-2BS.2 and QYr.cim-2BS.3 were significant in more than ten datasets. Furthermore, we report YR-associated allelic fingerprints for the largest panel of wheat breeding lines (52,067 lines) till date, creating substantial opportunities for YR favorable allele enrichment using molecular markers. Overall, the markers and fingerprints reported in this study provide excellent insights into the genetic architecture of YR resistance in different geographical regions, time-periods and wheat germplasm and are a huge resource to the global wheat breeding community for accelerating YR resistance breeding efforts.
[学术文献] Development and characterization of an EMS-mutagenized wheat population and identification of salt-tolerant wheat lines 进入全文
Triticum aestivum (wheat) is one of the world’s oldest crops and has been used for >8000 years as a food crop in North Africa, West Asia and Europe. Today, wheat is one of the most important sources of grain for humans, and is cultivated on greater areas of land than any other crop. As the human population increases and soil salinity becomes more prevalent, there is increased pressure on wheat breeders to develop salt-tolerant varieties in order to meet growing demands for yield and grain quality. Here we developed a mutant wheat population using the moderately salt-tolerant Bangladeshi variety BARI Gom-25, with the primary goal of further increasing salt tolerance.After titrating the optimal ethyl methanesulfonate (EMS) concentration, ca 30,000 seeds were treated with 1% EMS, and 1676 lines, all originating from single seeds, survived through the first four generations. Most mutagenized lines showed a similar phenotype to BARI Gom-25, although visual differences such as dwarfing, giant plants, early and late flowering and altered leaf morphology were seen in some lines. By developing an assay for salt tolerance, and by screening the mutagenized population, we identified 70 lines exhibiting increased salt tolerance. The selected lines typically showed a 70% germination rate on filter paper soaked in 200 mM NaCl, compared to 0–30% for BARI Gom-25. From two of the salt-tolerant OlsAro lines (OA42 and OA70), genomic DNA was sequenced to 15x times coverage. A comparative analysis against the BARI Gom-25 genomic sequence identified a total of 683,201 (OA42), and 768,954 (OA70) SNPs distributed throughout the three sub-genomes (A, B and D). The mutation frequency was determined to be approximately one per 20,000 bp. All the 70 selected salt-tolerant lines were tested for root growth in the laboratory, and under saline field conditions in Bangladesh. The results showed that all the lines selected for tolerance showed a better salt tolerance phenotype than both BARI Gom-25 and other local wheat varieties tested.
[学术文献] Characterization of the Q.Ymym region on wheat chromosome 2D associated with wheat yellow mosaic virus resistance 进入全文
Yellow mosaic disease, caused by wheat yellow mosaic virus (WYMV), is one of the most serious diseases of winter wheat in Japan and China. A single major QTL for WYMV resistance in the Japanese wheat variety 'Yumechikara', designated Q.Ymym, has been mapped on a 43.6 cM linkage block between the two markers Xcfd233 and Xgwm349 on chromosome 2D. We were able to obtain two recombinants within the block, which facilitated reducing the size of the linkage block. The pseudomolecule sequence of 'Chinese Spring' (CS) indicated that the original Q.Ymym region of 43.6 cM corresponded to 68.5 Mb and the narrowed Q.Ymym region represents a size of 27.3 Mb. The sequence features of the Q.Ymym region were unique in comparison with CS sequences, which may have led to the low recombination rate within the block. The Q.Ymym haplotype block was detected in other WYMV‐resistant varieties but not in the susceptible varieties used in this study. The unique sequence structure of the Q.Ymym region allowed the development of co‐dominant markers for use in marker‐assisted selection.
[学术文献] Identification of Fusarium graminearum-responsive miRNAs and their targets in wheat by sRNA sequencing and degradome analysis 进入全文
Fusarium head blight (FHB), a prevalent disease of bread wheat (Triticum aestivum L.) caused by Fusarium graminearum, leads to considerable losses of yield and quality in wheat production. MicroRNAs (miRNAs) are important regulators of plant defense responses. Here, to better understand the F. graminearum-responsive miRNAs, we constructed sRNA libraries for wheat cultivar Sumai 3 challenged with F. graminearum and sterile water, respectively. As a result, a total of 203 known miRNAs from 46 families and 68 novel miRNAs were identified. Among them, 18 known and six novel miRNAs were found to be differentially expressed between the F. graminearum-infected samples and the controls and thus were considered to be responsive to F. graminearum. The expression patterns of eight miRNAs were further validated by stem-loop qRT-PCR. Meanwhile, target genes were validated by degradome sequencing. Integrative analysis of the differentially expressed miRNAs and their targets revealed complex miRNA-mediated regulatory networks involved in the response of wheat to F. graminearum infection. Our findings are expected to facilitate a better understanding of the miRNA regulation in wheat-F. graminearum interaction.