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EN
SSRs derived from EST were molecular markers belonging to the transcribed region of the genome. Therefore, any polymorphism detected using EST-SSRs might reflect the better relationship among species or varieties. Using wheat EST-SSR markers, 60 durum wheat (Triticum durum L.) accessions from seven countries were investigated. Twenty-five primer pairs could amplify successfully in the 60 durum wheat accessions, of which trinucleotide repeats were the dominant type, and revealed 26 loci on all seven wheat homologous chromosome groups. A total of 87 eSSR alleles were detected, and the number of alleles detected by a single pair of primers ranged from 1 to 11, with an average of 3.3 alleles per locus. Higher numbers of alleles and PIC were identified on the B genome than those on the A genome.
EN
SSRs derived from EST were molecular markers belonging to the transcribed region of the genome. Therefore, any polymorphism detected using EST-SSRs might reflect the better relationship among species or varieties. Using wheat EST-SSR markers, 60 durum wheat (Triticum durum L.) accessions from seven countries were investigated. Twenty-five primer pairs could amplify successfully in the 60 durum wheat accessions, of which tri-nucleotide repeats were the dominant type, and revealed 26 loci on all seven wheat homologous chromosome groups. A total of 87 eSSR alleles were detected, and the number of alleles detected by a single pair of primers ranged from 1 to 11, with an average of 3.3 alleles per locus. Higher numbers of alleles and PIC were identified on the B genome than those on the A genome.
EN
Tibetan semi-wild wheat (Triticum aestivum ssp. tibetanum Shao) is one of the Chinese endemic hexaploid wheat genetic resources, distributed only in the Qinghai-Xizang Plateau of China. It has special characters, such as a hulled glume and spike disarticulation. However, seed dormancy, another important character for wheat resistance to pre-harvest sprouting, was rarely reported. Seed dormancy of more than 10 Tibetan semi-wild wheat accessions was evaluated, and their germinations were 0% or near 0% with both treatments of threshed seeds and intact spikes at hard dough stage. Tibetan semi-wild wheat accession Q1028 was investigated for its seed dormant characters by testing the seed germination percentages of intact spikes, seeds with bract powder, normal seeds, seeds with pierced coat, and sectioned embryos. It was observed that embryo dormancy of Q1028 accounted for its seed dormancy. Using threshed seeds and intact spikes at hard dough stage, the inheritance of seed dormancy was carried out using the F1, F2, F3 and F2BC1 populations of the cross between Q1028 and a wheat line 88?1643, susceptible to preharvest sprouting. The germinations of seeds and intact spikes in F1 plants were 1.0% and 0.9%, respectively. It indicated that seed dormancy of Q1028 was inherited as a dominant trait. From the genetic analysis of the F2, F3 and F2BC1 populations it was found that the strong seed dormancy of Q1028 was controlled by two dominant genes.
EN
Cytological and agronomic characteristics of a F2 population from Triticum aestivum L. ? T. durum Desf. hybrids were analyzed plant by plant. Means of morphologic traits in the F2 population were similar to those of the low-value parent. On average, F2 hybrids had 36.54 chromosomes per plant, indicating that each gamete lost 2.73 chromosomes at meiosis of the F1 generation. More than half of plants had 36?39 chromosomes, so male gametes with 19?21 chromosomes seemed to be superior to the others. The distribution frequency of chromosomes in this study differed from that in a previous report, where a different tetraploid wheat was used. This shows that a different breeding strategy may need to be taken when exploiting a different tetraploid wheat. According to our results, some plants with 42 chromosomes, having all the wheat A, B and D chromosomes, would appear in the F3 population, which provides a chance to obtain stable bread wheat lines from the self-pollinated progenies. Alternatively, the desirable individuals of the F2 population were backcrossed to bread wheat, which is very useful and efficient for the improvement of bread wheat by exploiting desirable genes in durum wheat.
EN
Three low-molecular-weight glutenin subunit (LMW-GS) genes, designated LMW-Td1, LMW-Td2 and LMW-Td3, were isolated from wild emmer wheat (Triticum dicoccoides), which is the tetraploid progenitor of common wheat (T. aestivum). The complete nucleotide sequence lengths of LMW-Td1, LMW-Td2 and LMW-Td3 are 858, 900 and 1062 bp, respectively. LMW-Td1 and LMW-Td3 can encode proteins with 284 and 352 amino acid residues, respectively, whereas LMW-Td2 is a putative pseudogene due to the presence of 3 inframe stop codons in its C-terminal domain. The deduced protein sequences of the 3 genes share the same typical polypeptide structures with known LMW-GS genes containing 8 cysteines in the mature protein domains. LMW-Td1 was clearly distinguished from all known LMW-GS genes, and considered as a novel LMW-GS gene. Two hydrophobic motifs (i.e. PIIIL and PVIIL) were observed in the repetitive domain of LMW-Td3. Sequence comparison indicates that sequences of the 3 LMW-GS genes from this study are strongly similar to known LMW-GS genes. Our phylogenetic analysis suggests that LMW-Td1 and LMW-Td2 are homologous with genes on chromosome 1A, and LMW-Td3 is closely related to genes on chromosome 1B.
EN
Genetic differences between 20 Chinese wheat (Triticum aestivum L.) landraces highly resistant to Fusarium head blight (FHB) and 4 wheat lines highly susceptible to FHB were evaluated by means of microsatellite markers, in order to select suitable parents for gene mapping studies. Thirty-nine out of 40 microsatellite markers (97.5%) were polymorphic among the 24 wheat genotypes. A total of 276 alleles were detected at the 40 microsatellite loci. The number of alleles per locus ranged from 1 to 16, with an average of 6.9 alleles. Among these microsatellite loci, the largest polymorphism information content (PIC) value was 0.914 (GWM484), while the lowest PIC value was 0 (GWM24). The mean genetic similarity index among the 24 genotypes was 0.419, ranging from 0.103 to 0.673. Clustering analysis indicated that the highly susceptible synthetic wheat line RSP was less genetically related to and more divergent from the Chinese highly resistant landraces. These results were useful in the identification of suitable parents for the development of mapping populations for tagging the FHB resistance genes among these Chinese wheat landraces.
EN
Extensive genetic variations of low-molecular-weight glutenin subunits (LMW-GS) and their coding genes were found in the wild diploid A- and D-genome donors of common wheat. In this study, we reported the isolation and characterization of 8 novel LMW-GS genes from Ae.longissima Schweinf. & Muschl., a species of the section Sitopsis of the genus Aegilops, which is closely related to the B genome of common wheat. Based on the N-terminal domain sequences, the 8 genes were divided into 3 groups. A consensus alignment of the extremely conserved domains with known gene groups and the subsequent cluster analysis showed that 2 out of the 3 groups of LMW-GS genes were closely related to those from the B genome, and the remaining was related to those from A and D genomes of wheat and Ae. tauschii. Using 3 sets of gene-group-specific primers, PCRs in diploid, tetraploid and hexaploid wheats and Ae. tauschii failed to obtain the expected products, indicating that the 3 groups of LMW-GS genes obtained in this study were new members of LMW-GS multi-gene families. These results suggested that the Sitopsis species of the genus Aegilops with novel gene variations could be used as valuable gene resources of LMW-GS. The 3 sets of group-specific primers could be utilized as molecular markers to investigate the introgression of novel alien LMW-GS genes from Ae. longissima into wheat.
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