GrainGenes

The position of 39 translocation breakpoints on chromosome 5H (7) were mapped on linkage group 7 of the Igri/Franka map. This was done by PCR of STS derivatives from mapped RFLP probes with template DNA obtained from microdissected translocated chromosomes (Korzun and Künzel, 1995). In the same report they indicate that the Gatersleben collection of stocks with chromosome 5H (7) translocation breakpoints includes a total of 304; 137 have been assigned to the long arm and 68 to the short arm (11 located in the satellite). In terms of zones of differential recombination rates along the length of chromosome 5H (7), there is a zone of suppressed recombination between the centromere and the NOR. In distal regions, areas of low recombination rates are interspersed between regions of high recombination. Translocation breakpoints also tend to be clustered in distal regions of the chromosome.

An RFLP map consisting of a total length of 1817 cM and 133 markers was constructed on an F₂ population derived from a hybrid between H. vulgare and H. spontaneum (Sherman et al., 1995). The map of chromosome 5H (7) consisted of two linkage groups. When common intervals were compared between this map and others it was shown that they were on average 2.75 + 1.75 times greater than the Steptoe x Morex map. On chromosome 5H (7) common distances were 3-9 times greater than on the Steptoe x Morex map. The expected synteny between rice and barley chromosomes was observed for five chromosomes. The expected synteny between chromosomes 6H and 5H (7) of barley with 2 and 9 of rice was not observed.

Several post harvest dormancy loci on barley chromosome 5H (7), 7H (1) and 4H have previously been detected by QTL analysis (Ullrich et al., 1993). In subsequent studies it was shown that the locus on the long arm of chromosome 5H (7) (SD1) had a major effect on seed dormancy and was at least partly epistatic to the dormancy locus located near the telomere of the long arm of that chromosome (Han et al., 1996).

An update on the three RFLP maps produced by the North American Barley Genome Mapping Program (Steptoe x Morex, Harrington x TR360 and Harrington x Morex) show that the numbers of markers on chromosome 5H (7) are 78, 46 and 17 respectively (Kleinhofs, 1995). The details of other barley maps can be seen on the internet.

The H/T population from trials at 17 locations over 2 years was analyzed for QTLs for seven agronmic traits (Tinker et al., 1996). One region near the end of the short arm of chromosome 5H (7) affected 6 of the 7 traits scored. These traits were yield, maturity, height, lodging, kernel weight and test weight.

Using trisomic analysis it was found that chromosome 5H (7) had a major effect on the de-epoxydase gene that catalyzes the synthesis of xanthophyll, one of the pigments involved in the light reaction of photosynthesis (Murai et al., 1996).

Multi ovary mutants were isolated in M₂ generation following neutron treatments. Using a rice agamous-like gene as a probe, two genomic DNA clones were isolated from barley. One of these

(JS/8B) mapped to the distal portion short arm of barley chromosome 5H (7) (Soule et al., 1995).

A screening of a total of 84 marker loci across 8 cultivars with mildew resistance and their progenies, detected genes for resistance on 5 chromosomes including chromosome 5H (7). On the latter a second locus with minor effects was found that has not been previously reported (Saghai-Maroof et al., 1994).

The rpg4 locus giving resistance to race QCC of barley stem rust was tagged with 3 RAPD markers and 2 RFLP markers. The latter assign the resistance locus to chromosome 5H (7) (long arm) (Borovkova et al., 1995).

QTLs for lodging resistance and steam breakage were located on chromosome 5 H (chromosome 7) (Backes et al. 1995).

Combinations of multiple recessive marker stocks for chromosome 5H (7) include 2 genetic male steriles, 3 dwarfs and a cs (corn stalk) gene (Wolfe et al., 1995).

References:

Backes, G., A. Graner, B. Foroughi-Wehr, G. Fischbeck, G. Wenzel and A. Jahoor. 1995. Localization of quantitative trait loci (QTL) for agronomic important characters by the use of a RFLP map in barley (Hordeum vulgare L.). Theor. Appl. Genet. 90: 294-302.

Borovkova, I.G., B.J. Steffenson, Y. Jin, J.B. Rasmussen, A. Kilian, A. Kleinhofs, B.G. Rossnagel and K.N. Kao. 1995. Identification of molecular markers linked to the stem rust resistance gene rpg4 in barley. Phytopathology 85: 181-185.

Han, F., S.E. Ullrich, J.A. Clancy, V. Jitkov, A. Kilian and I. Romagosa. 1996. Verification of barley seed dormancy loci via linked molecular markers. Theor. Appl. Genet. 92: 87-91.

Kleinhofs, A. 1995. NABGMP mapping update. BGN 25: 62-70.

Korzun, L. and G. Künzel. 1995. Integration of translocation breakpoints of barley chromosomes 3 and 7 into the Igri/Franka derived RFLP maps. BGN 25: 13-16.

Murai, J., J. Fujigaki, A. Wadano and T. Taira. 1996. Probable location of de-epoxydase gene catalyzing xanthophyll cycle on the seventh chromosome based on trisomic barley (Hordeum spontaneum). V International Oat Conference and VII International Barley Genetics Symposium proceedings. pp. 357-359.

Saghai-Maroof, M.A., Q. Zhang and R.M. Biyashev. 1994. Molecular marker analyses of powdery mildew resistance in barley. Theor. Appl. Genet. 88: 733-740.

Sherman, J.D., A.L. Fenwick, D.M., Namuth, N.L.V. Lapitan. 1995. A barley RFLP map: alignment of three barley maps and comparisons to Gramineae species. Theor. Appl. Genet. 91: 681-690.

Soule, J., I. Skodova, D. Kudrna, A. Kilian and A. Kleinhofs. 1995. Molecular and genetic characterization of barley flower development mutants. BGN 25: 76-80.

Tinker, N.A., D. Mather, B.G. Rossnagel, K.J. Kasha, A. Kleinhofs, P.M. Hayes, D.E. Falk, T. Ferguson, L.P. Shugar, W.G. Legge, R.B. Irvine, T.M. Choo, K.G. Briggs, S.E. Ullrich, J.D. Franckowiack, T.K. Blake, R.J. Graf, S.M. Dofing, M.A. Saghai Maroof, G.J. Scoles, D. Hoffman, L.S. Dahleen, A. Kilian, F. Chen, R.M. Biyashev, D.A. Kudrna and B.J. Steffenson. 1996. Regions of the genome that affect agronomic performance in two-row barley. Crop Sci. 36: 1053-1062.

Wolfe, R.I., P.M. Hayes and L. Shugar. 1995. Multiple dominant and recessive genetic marker stock development. BGN 25: 57-58