Integration of deletion breakpoints of chromosome 7H (1) into the Igri/Franka-derived RFLP map

Translocation (T) breakpoints have been successfully used as physical landmarks in constructing cytologically integrated molecular linkage maps of high resolution for all barley chromosomes (Künzel et al. 2000). Recent progress in generating, isolating and defining deletion and wheat/barley translocation chromosomes added to common wheat (Shi and Endo 1997, 1999; Schubert et al. 1998) resulted in a number of lines suitable for deletion (D)-mapping in barley (T. R. Endo, unpublished). The combination of D-mapping with T-mapping would refine the cytogenetic maps of barley. As the first step for this purpose, we determined the positions of 19 D-breakpoints of chromosome 7H (1) relative to STS-markers on the corresponding Igri/Franka linkage map.

Out of 93 RFLP clones localized in chromosome 7H (1) on the Igri/Franka genetic map, 64 RFLP markers had been previously converted into locus-specific STS markers (Künzel et al. 2000). Primer sets of these STS markers were tested for PCR fragment polymorphism between barley (cv. Betzes) and wheat (cv. Chinese Spring), and were checked simultaneously for the arm specifity of their PCR products using wheat-barley telosome addition lines.

A total of 26 markers differentiated between barley and wheat (Table 1). These 26 markers, which were used for D-mapping, cover 158.1 cM of the entire 200.1 cM-length of the linkage map 7H (1). The map positions of the 19 D-breakpoints are shown in Table 2, together with the previously determined positions of 31 T-breakpoints. This result shows that the distribution patterns of both the D- and T-breakpoints are similar, with a tendency to cluster in certain regions of the map. Since precise measurements of the deleted barley chromosome segments are not yet available, their sizes were only roughly estimated, based on the physical positions of neighbouring T-breakpoints which were used for the physical mapping by Künzel et al. (2000).

Künzel, G., L. Korzun, and A. Meister. 2000. Cytologically integrated physical restriction fragment length polymorphism maps for the barley genome based on translocation breakpoints. Genetics 154: 397-412.

Schubert, I., F. Shi, J. Fuchs, and T. R. Endo. 1998. An efficient screening for terminal deletions and translocations of barley chromosomes added to common wheat. Plant J. 14: 489-495.

Shi, F. and T. R. Endo. 1997. Production of wheat-barley disomic addition lines possessing an Aegilops cylindrica gametocidal chromosome. Genes Genet. Syst. 72: 243-248.

Shi, F. and T. R. Endo. 1999. Genetic induction of structural changes in barley chromosomes added to common wheat by a gametocidal chromosome derived from Aegilops cylindrica. Genes Genet. Syst. 74: 49-54.

Table 1 STS primers from RFLP probes of the Igri x Franka map which amplify different PCR products for barley and wheat

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Table 1 continued