The rpg4 locus conferring resistance to stem rust race QCC is located in the sub-telomeric region of barley chromosome 7M. The two closest distal RFLP markers, ABG391 & R273 are located at 1.6 and 0.8cM respectively from the gene while on the pronominal side the RFLP markers ABG496 and MWG740 are located about 9.6 and 6.9 cM from the gene. The gene was also tagged with AFLP markers which have since been cloned and used as RFLP or PCR-based markers (Druka et al. 1998)

QTL analysis with RFLP of the Barley yellow mosaic virus resistance locus ym3 in the Japanese cultivar I Shukushinazu proved to be located on barley chromosome 7 (5H) and not on chromosome 2 as previously reported (Saito et al. 1998). It was linked to markers ABG705 and CDO749 by 11.7cM and 5.4cM respectively (Saeki et al. 1997).

A high density BGH AFLP map was used to map a number of loci for resistance to barley leaf rust (Qi et al. 1998). Three loci Rphq1, Rphq2 and Rphq3 were found to be resistant at the seedling stage to isolate 1.2.1 of barley leaf rust plus another locus resistant to isolate 24 but not to 1.2.1 were all located on barley chromosome 7 (5H).

A study was initiated to map the dehydrin genes of barley and determine whether any cosegregated with the winterhardiness QTL previously mapped on chromosome 5H (Pan et. al. 1994). A total of 11 dehydrin genes were identified in the cultivar Dicktoo with three of these dhn1, dhn2 and dhn9, mapping to chromosome 5H. Efforts are underway to determine if any of these cosegregate with the winterhardiness QTL. (Choi et. al. 1998).

Ullrich et. al. (1998) showed that there is at least one Beta amylase QTL on every barley chromosome.

QTLs for Fursarium Head Blight resistance in barley are beginning to be reported. Resistance from the Zhedar-1 parent was mapped to QTLs on chromosomes 1(7H) 2(2H) and 7(5H). (Meafin et. al. 1998). The latter locus accounted for 20% of the phenotypic variability. That locus is marked by clones Xabg712 and Xcdo504.

QTLs for freezing tolerance in a population derived from a hybrid between cultivars Arda and Opale were mapped to chromosomes 2, 3 and 7 (Tuberosa et. al. 1997). It was concluded that both parents contributed equal numbers of QTLs for freezing tolerance.

It has been shown that barley chromosome region 7L shared synteny with rice chromosome 3L (Han et. al. 1998). With the exception of minor translocation and inversion events the genetic distances in the syntenic regions were comparable.

References:

Choi, D-W, B. Zhu, and T.J. Close. 1998. Chromosome assignments and expression characteristics of 11 barley dehydrin genes. Poster P190 in Plant and Animal Genome VI. Mapping and Tagging; Wheat, Barley, Rye, Oat. p. 125, San Diego, CA.

Druka, A., F. Han, A. Kilian, D. Kudrna, B. Steffenson, and A. Kleinhofs. 1998. Saturation mapping of the barley stem rust resistance gene rpg4 region. Poster P183 in Plant and Animal Genome VI. Mapping and Tagging; Wheat, Barley, Rye, Oat, p. 123. San Diego, CA.

Han, F., A. Kleinhofs, S.E. Ullrich, A. Kilian, M. Yano, and T. Sasaki. 1998. Synteny with rice: Analysis of barley malting quality QTLs and rpg4 chromosome regions. Genome 41:373-380.

Meafin, A., L.S. Dahleen, B.J. Steffenson, R.D. Horsley, P.B. Schwarz, and J.D. Franckowiak. 1998. Mapping genes conferring resistance to Fusarium Head Blight in barley. In Current Research on Fusarium Head Blight of Small Grains. North Dakota University.

Qi, X., G. Jiang, W. Chen, R.E. Niks, P. Stam, and P. Lindhout, 1998. Isolate-specific QTLs for partial resistance to Puccinia hordei in barley. Poster P185 in Plant and Animal Genome VI. Mapping and Tagging; Wheat, Barley, Rye, Oat. p. 124. San Diego, CA.

Pan, A., P.M. Hayes, F. Chen, T. H. H. Chen, T. Blake, S. Wright, I. Karsai, and Z. Bodo. 1994. Genetic analysis of the components of winterhardiness in barley (Hordeum vulgare L.). Theor. Appl. Genet. 89:900-910.

Saeki, K., C. Miyazaki, N. Hirota, A. Saito, K. Ito, and T. Konishi, 1997. RLFP mapping of a Ba YMV resistance gene ym3 in barley, BGN 28:61-63.

Saito, A., K. Saeki, N. Hirota, K. Ito, C. Miyazaki, and T. Konishi, 1998. QTL mapping of barley yellow mosaic virus (BaYMV) resistance gene in cv. I shukushirazu on chromosome 7(5H) in barley. Poster P187 in Plant and Animal Genome VI. Mapping and Tagging; Wheat, Barley, Rye, Oat. p124. San Diego, CA.

Tuberosa, R., M.C. Sanguineti, E. Noli, E. Casarini, G. Galiba, and J. Sutka, 1997. Mapping QTLs for tolerance to freezing temperatures in barley. Abstract p68 in Application of marker-aided selection in cereal breeding programs. Eucarpia Cereal Section meeting. Tulln Austria Sept. 22-23, 1997. Ed. H. Buerstmayr and P. Ruckenbauer.

Ullrich, S.E., F. Han, and J.A. Clancy, 1998. Comparative mapping of Beta-amylase activity loci among three barley crosses. Poster 191 in Plant and Animal Genome VI. Mapping and Tagging; Wheat, Barley, Rye, Oat. p125. San Diego, CA.