Flow karyotyping and chromosome sorting in bread wheat ( Triticum aestivum L.)

Previously, we reported on the development of procedures for chromosome analysis and sorting using flow cytometry (flow cytogenetics) in bread wheat. That study indicated the possibility of sorting large quantities of intact chromosomes, and their suitability for analysis at the molecular level. However, due to the lack of sufficient differences in size between individual chromosomes, only chromosome 3B could be sorted into a high-purity fraction. The present study aimed to identify wheat stocks that could be used to sort other chromosomes. An analysis of 58 varieties and landraces demonstrated a remarkable reproducibility and sensitivity of flow cytometry for the detection of numerical and structural chromosome changes. Changes in flow karyotype, diagnostic for the presence of the 1BL.1RS translocation, have been found and lines from which translocation chromosomes 5BL.7BL and 4AL.4AS-5BL could be sorted have been identified. Furthermore, wheat lines have been identified which can be used for sorting chromosomes 4B, 4D, 5D and 6D. The ability to sort any single arm of the hexaploid wheat karyotype, either in the form of a ditelosome or a isochromosome, has also been demonstrated. Thus, although originally considered recalcitrant, wheat seems to be suitable for the development of flow cytogenetics and the technology can be applied to the physical mapping of DNA sequences, the targeted isolation of molecular makers and the construction of chromosome- and arm-specific DNA libraries. These approaches should facilitate the analysis of the complex genome of hexaploid bread wheat.