Cytomolecular identification of individual wheat-wheat chromosome arm associations in wheat-rye hybrids

Chromosome pairing in the meiotic metaphase I of wheatrye hybrids has been characterized by sequential genomic and fluorescent in situ hybridization allowing not only the discrimination of wheat and rye chromosomes, but also the identification of the individual wheat and rye chromosome arms involved in the chromosome associations. The majority of associations (93.8%) were observed between the wheat chromosomes. The largest number of wheat-wheat chromosome associations (53%) was detected between the A and D genomes, while the frequency of B-D and A-B associations was significantly lower (32 and 8%, respectively). Among the A-D chromosome associations, pairing between the 3AL and 3DL arms was observed with the highest frequency, while the most frequent of all the chromosome associations (0.113/ cell) was found to be the 3DS-3BS. Differences in the pairing frequency of the individual chromosome arms of wheat-rye hybrids have been discussed in relation to the homoeologous relationships between the constituent genomes of hexaploid wheat

Increased micronutrient content (Zn, Mn) in the 3Mb(4B) wheat- Aegilops biuncialis substitution and 3Mb.4BS translocation identified by GISH and FISH

3Mb Triticum aestivum L. (Mv9kr1)-Aegilops biuncialis Vis. (MvGB642) addition lines were crossed with the Chinese Spring ph1b mutant genotype (CSph1b) to produce 3Mb-wheat chromosome rearrangements. In the F3 generation, 3Mb(4B) substitution lines and 3M b.4BS centric fusions were identified with in situ hybridization using repetitive and genomic DNA probes, and with SSR markers. Grain micronutrient analysis showed that the investigated Ae. biuncialis accession MvGB382 and the parental line MvGB642 are suitable gene sources for improving the grain micronutrient content of wheat, as they have higher K, Zn, Fe, and Mn contents. The results suggested that the Ae. biuncialis chromosome 3M b carries genes determining the grain micronutrient content, as the 3Mb.4BS centric fusion had significantly higher Zn and Mn contents compared with the recipient wheat cultivar. As yield-related traits, such as the number of tillers, the length of main spike, and spikelets per main spike, were similar in the 3Mb.4BS centric fusion and the parental wheat genotype, it can be concluded that this line could be used in pre-breeding programs aimed at enriching elite wheat cultivars with essential micronutrients. | Des lignées d'addition 3Mb Triticum aestivum L. (Mv9kr1) – Aegilops biuncialis Vis. (MvGB642) ont été croisées avec le mutant Chinese Spring ph1b (CSph1b) afin de produire des réarrangements chromosomiques 3Mb–blé. Au sein de la génération F3, des lignées de substitution 3Mb(4B) et des fusions centriques 3Mb.4BS ont été identifiées par hybridation in situ au moyen de sondes d'ADN répété ou génomique ainsi qu'avec des marqueurs SSR. Une analyse de la composition du grain en matière de micronutriments a montré que l'accession étudiée de l'Ae. biuncialis (MvGB382) et la lignée parentale MvGB642 constituent des sources valables pour améliorer le contenu en micronutriments chez le blé, du fait qu'elles ont une teneur accrue en K, Zn, Fe et Mn. Ces résultats suggèrent que le chromosome 3Mb de l'Ae. biuncialis porte des gènes contribuant a` déterminer le contenu en micronutriments puisque la fusion centrique 3Mb.4BS présentait un contenu en Zn et en Mn significativement supérieur a` la variété de blé réceptrice. Puisque les composantes de rendement comme le nombre de talles, la longueur de la tige principale et le nombre d'épillets par épi étaient semblables chez la fusion centrique 3Mb.4BS et chez le génotype de blé parental, les auteurs en concluent que cette lignée pourrait s'avérer utile dans des programmes de pré-sélection visant a` accroître la teneur en micronutriments essentiels chez les cultivars élites de blé. [Traduit par la Rédaction

Development and genetic mapping of sequence-tagged microsatellites (STMs) in bread wheat (Triticum aestivum L.)

The density of SSRs on the published genetic map of bread wheat (Triticum aestivum L.) has steadily increased over the last few years. This has improved the efficiency of marker-assisted breeding and certain types of genetic research by providing more choice in the quality of SSRs and a greater chance of finding polymorphic markers in any cross for a chromosomal region of interest. Increased SSR density on the published wheat genetic map will further enhance breeding and research efforts. Here, sequence-tagged microsatellite profiling (STMP) is demonstrated as a rapid technique for the economical development of anonymous genomic SSRs to increase marker density on the wheat genetic map. A total of 684 polymorphic sequence-tagged microsatellites (STMs) were developed, and 380 were genetically mapped in three mapping populations, with 296 being mapped in the International Triticeae Mapping Initiative W7984 × Opata85 recombinant inbred cross. Across the three populations, a total of 479 STM loci were mapped. Several technological advantages of STMs over conventional SSRs were also observed. These include reduced marker deployment costs for fluorescent-based SSR analysis, and increased genotyping throughput by more efficient electrophoretic separation of STMs and a high amenability to multiplex PCR.M. J. Hayden, P. Stephenson, A. M. Logojan, D. Khatkar, C. Rogers, J. Elsden, R. M. D. Koebner, J. W. Snape and P. J. Shar