Utilization of a Wheat660K SNP array-derived high-density genetic map for high-resolution mapping of a major QTL for kernel number.

In crop plants, a high-density genetic linkage map is essential for both genetic and genomic researches. The complexity and the large size of wheat genome have hampered the acquisition of a high-resolution genetic map. In this study, we report a high-density genetic map based on an individual mapping population using the Affymetrix Wheat660K single-nucleotide polymorphism (SNP) array as a probe in hexaploid wheat.

A SNP-Based Molecular Barcode for Characterization of Common Wheat.

Wheat is grown as a staple crop worldwide. It is important to develop an effective genotyping tool for this cereal grain both to identify germplasm diversity and to protect the rights of breeders. Single-nucleotide polymorphism (SNP) genotyping provides a means for developing a practical, rapid, inexpensive and high-throughput assay.

Regulation of leaf senescence and crop genetic improvement.

Leaf senescence can impact crop production by either changing photosynthesis duration, or by modifying the nutrient remobilization efficiency and harvest index. The doubling of the grain yield in major cereals in the last 50 years was primarily achieved through the extension of photosynthesis duration and the increase in crop biomass partitioning, two things that are intrinsically coupled with leaf senescence. In this review, we consider the functionality of a leaf as a function of leaf age, and divide a leaf's life into three phases: the functionality increasing phase at the early growth stage, the full functionality phase, and the senescence and functionality decreasing phase.

TaCKX6-D1, the ortholog of rice OsCKX2, is associated with grain weight in hexaploid wheat.

The cytokinin oxidase/dehydrogenase (CKX) gene plays a principal role in controlling cytokinin levels and has been shown to be a major quantitative trait locus (QTL) affecting grain number in rice. However, the function and evaluation of the haplotypes of the wheat CKX gene have yet to be illustrated. In this study, TaCKX6-D1, a wheat ortholog of rice OsCKX2, was cloned and its haplotype variants were determined to be significantly associated with the 1000-grain weight on the basis of linkage mapping, association analysis and gene expression analysis.

The characterization and geographical distribution of the genes responsible for vernalization requirement in Chinese bread wheat.

The frequency and distribution of the major vernalization requirement genes and their effects on growth habits were studied. Of the 551 bread wheat genotypes tested, seven allelic combinations of the three Vrn-1 genes were found to be responsible for the spring habit, three for the facultative habit and one for the winter habit. The three Vrn-1 genes behaved additively with the dominant allele of Vrn-A1 exerting the strongest effect.

[SSR mapping of stripe rust resistance gene from Ae. tauschii].

A dominant wheat stripe rust resistance gene, temporarily designated as YrY201, was identified in an accession Y201 of Aegilops tauschii. By bulk segregation analysis, three microsatellite markers Xgwm273b, Xgwm37 and Wmc14 were found to be linked to YrY201 with genetic distance of 11.5, 5.

Evolutionary and functional study of the CDPK gene family in wheat (Triticum aestivum L.).

Calcium-dependent protein kinases (CDPKs) are crucial sensors of calcium concentration changes in plant cells under diverse endogenous and environmental stimuli. We identified 20 CDPK genes from bread wheat and performed a comprehensive study on their structural, functional and evolutionary characteristics. Full-length cDNA sequences of 14 CDPKs were obtained using various approaches.

[Comparison of methods to construct a full-length cDNA library].

The use of full-length cDNA libraries is an effective tool to obtain complete gene information in a high-efficiency, high-throughput manner, especially in organisms with huge genomes that are not amenable to whole genome sequencing. In this review, we outlined several methods of full-length cDNA library construction and compared their advantages and disadvantages based on their respective principles. Drawing on our own experience, we described the Cap-trapper method in detail, with an emphasis on its application in wheat full-length cDNA library construction as well as the determination of the ratio of full-length cDNA in a library.

[Construction of a full-length cDNA library of Aegilops speltoides Tausch with optimized cap-trapper method].

To discover new genes in a throughput manner,the cap-trapper method published previously was optimized for raising the efficiency in the construction of full-length cDNA library. Using the optimized protocol,we successfully constructed a full-length cDNA library of Aegilops speltoides,which contained 3.0 x 10(6) clones and more than 99% of plaques were recombinant phages.

Homoeologous cloning of omega-secalin gene family in a wheat 1BL/1RS translocation.

Wheat 1BL/1RS translocations are widely planted in China as well as in most of the wheat producing area in the world for their good qualities of disease resistance and high yield. 1BL/1RS translocations are however poor in bread making, partially caused by a family of small monomeric proteins, omega-secalins, which are encoded by genes on 1RS. Based on published sequence of a rye omega-secalin gene we designed a pair of primers to cover the whole mature protein coding sequence.

Microsatellite diversity within Oryza sativa with emphasis on indica-japonica divergence.

The molecular evolution of cultivated rice Oryza sativa L. has long been a subject of rice evolutionists. To investigate genetic diversity within and differentiation between the indica and japonica subspecies, 22 accessions of indica and 35 of japonica rice were examined by five microsatellite loci from each chromosome totalling 60 loci.

[Isolation, characterization and expression analysis of male sterility gene homology sequence in wheat].

One 134 bp fragment was amplified in anthers of male sterile and fertile wheat using one pair of degenerated primer designed based on the conserved domain of MS2 gene in Arabidopsis thaliana and Oryza sativa, and one 1604 bp male sterility gene homology sequence was extended by in silico cloning based on the 134 bp fragment. The amino acids encoded by the male sterility gene homology sequence include a 200 amino acid conserved domain of male sterility, and this sequence expressed only in wheat male fertile anthers; no expression in male sterile anthers, roots and leaves. This research demonstrated that the cloned male sterile homology sequence is specific to wheat anther development.

[Microsatellite marker development and applications in wheat genetics and breeding].

Microsatellites are simple, tandemly repeated one to six nucleotide sequence motifs. They are very useful as genetic markers because they are co-dominant, detect high levels of allelic diversity, and are easily assayed by the polymerase chain reaction ( PCR ). In wheat, SSR markers have been applied to genetic mapping,detection of genetic diversity, identification of varieties and genotypes,gene tagging, QTL analysis, and marker-assisted selection.

[Research on the preparation of bacterial artificial chromosome (BAC) vector DNA].

Bacterial artificial chromosome (BAC) library plays a pivotal role in genomics studies. A crucial step in BAC library construction is preparation of BAC vector DNA. Preparation of highly purified vector DNA is affected by a series of factors including digestion of restriction enzyme and dephosphorylation of linearized vector DNA.

[cDNA libraries construction and screening in gene expression profiling of disease resistance in wheat].

A wheat line, Bai Nong 3217/Mardler BC5F4 with resistance to powdery mildew, was used to construct a conventional cDNA library and a suppression subtractive hybridization (SSH) cDNA library from wheat leaves inoculated by Erysiphe graminis DC. Three hundred and eighty-seven non-redundant ESTs from the conventional cDNA library and 760 ESTs from the SSH cDNA library were obtained, and the ESTs similarity analysis using BLASTn and BLASTx were conducted by comparing these ESTs with sequences in GenBank. The results showed that the redundancy of some kinds of genes such as photosynthesis related genes and ribosome related genes was higher in the conventional cDNA library but the varieties and quantities of disease resistance genes were less than those in the SSH cDNA library.

[ESTs analysis of resistance to powdery mildew in wheat at primary infected stage].

A wheat line, Bai Nong 3217 x Mardler BC5F4 with resistance to powdery mildew was used in the study. A suppression subtractive hybridization cDNA library was constructed from wheat leaves challenged by Erysiphe graminis DC at primary stage. Seven hundred and sixty ESTs were acquired, and the ESTs similarity analysis based on BLASTx software was finished by comparing sequences in nr database of GenBank.