Integration of 70 translocation breakpoints into the Igri/Franka-derived RFLP maps for 2H and 6H

Larissa Korzun and G. Künzel

Institute of Plant Genetics and Crop Plant Research
D-06466 Gatersleben, Germany

PCR-assisted mapping of RFLP-detecting DNA probes via their sequence-tagged sites on microisolated translocation chromosomes of barley progressed to a technique of high efficiency in relating genetic to physical distances (Künzel and Korzun 1996). By this method, a large number of translocation breakpoints (TB's) has exactly been localized between the linearly ordered markers of the Igri/Franka RFLP maps corresponding to chromosomes 1H, 3H and 5H (Sorokin et al. 1995, Korzun and Künzel 1996). Here, we report the results for two further chromosomes, 2H and 6H, with 33 and 37 TB's integrated into the respective linkage maps.

With respect to chromosome 2H translocations involving one SAT-chromosome, e.g., T2-6 or T2-7, were preferentially used to ensure that at least one of the two interchanged chromosomes (the satellited one) could be individually microisolated for PCR. In the map of 2H, the centromere was localized to the 123.2 cM position between two cosegregating markers, MWG557 and MWG2058, which are physically separated by at least 40% of the chromosome length. Similarly in 6H, the centromere was allocated to an interval of 0.7 cM between MWG2264 and ABG20 that also relates to about 40% of the chromosome length. Other clusters of cosegregating markers could be resolved at least partially by inserted TB's, e.g., at the 103.9 and 138.6 cM positions in the map of 2H (Click here for Table 1) or at the 93.4, 99.0 and 105.3 cM positions in the map of 6H (Click here for Table 2). As previously shown for chromosomes 1H, 3H and 5H, many TB's are clustered within the large median chromosome regions characterized by low recombination rates. The TB's found outside these regions show a tendency to be clustered at specific regions of the genetic maps. A peculiarity common to both SAT-chromosomes (5H and 6H) in relation to the Igri/Franka-maps is, that the short arms are split by the NOR's into the satellites showing high recombination and proximal regions of suppressed recombination that contain no markers.

Including this report, a total of 179 TB's have exactly been inserted into five linkage maps: 1H (38), 2H (33), 3H (32), 5H (39) and 6H (37). Images of cytogenetically integrated genetic maps showing the position of TB's relative to the RFLP loci are available on the GrainGenes database WWW so far for chromosomes 1H, 3H, 5H and 6H.

Acknowledgement

This research was supported by the BMBF (Grant No. 0311002).

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