A QTL for resistance to spot blotch at the adult plant stage caused by Cochliobolus sativus was reported to be located in the interval ABG500A to ABG494 on barley chromosome 5 by Steffenson et al. (1996). According to Figure 1, it is in the interval position +24.1 to -3.7 cM. It is therefore apparently located in the centromeric region and may not be on the plus arm as suggested by the authors.

Colinearity of RFLP markers in the Hor1, Mla, Hor2 region of barley chromosome 5 with common markers in homoeologous chromosomes in diploid and hexaploid oat and maize was reported by Yu et al. (1996). Corresponding to the hordein loci in barley they found prolamin coding loci in oats in homoeologous chromosome positions. Further, corresponding the barley powdery mildew resistance locus Mla on chromosome 5, different disease resistance loci in homoeologous chromosome positions in oats and maize were found.

Gene or genes for leaf chlorosis and leaf rolling which apparently is responsible for resistance to the Russian wheat aphid were found associated with the sequence-tagged-site (STS) PCR markers B-hordein and D14 on the short arm of chromosome 5 (Niepto-Lopez and Blake 1994).

The HemA genes encoding glutamyl-tRNA reductase were assigned to barley chromosome 5 and to the homoeologous chromosomes 1A, 1B, and 1D of common wheat, and rye (Bougri et al. (1996).

Eight AFLP marker were mapped in relation to previously mapped markers in the cross 'Proctor'x'Nudinka' (Becker et al. 1995). The map and all the marker scorings can be found in GrainGenes on the Internet.

The gene B (black kernel) from chromosome 5 was found expressed in wheat-barley hybrids. Expression was proportional to number of the B alleles (Taketa and Takeda 1996).

The hordein region on chromosome 5 was found to affect diastatic power in both the 'Steptoe'x'Morex' and the 'Harrington'x'TR306' crosses (Mather and Hayes 1996).

A 58 cM long linkage map with 6 molecular markers on barley chromosome 5 in doubled haploid lines from the cross 'Arda'x'Opale' was reported by Noli et al. (1996).

The inheritance of aleurone response to gibberellic acid was found controlled by a gene designated rga (Aksenovich 1996). The gene was found linked with 9.2+/-0.2 and 17.9+/-0.2% recombination to loci trd and B, respectively. Aksenovich conclude that locus rga are identical to locus ea-k.

An integration of the four separate barley genetic maps from 'Proctor'x'Nudinka', 'Igri'x'Franka', 'Steptoe'x'Morex', and 'Harrington'x'TR306' was reported by Qi et al. (1996). A consensus linkage map of the barley genome was reported by Langridge et al. (1995). The map is based on the doubled haploid populations 'Proctor'x'Nudinka', 'Igri'x'Franka', 'Steptoe'x 'Morex', 'Clipper'x'Sahara 3771', 'Haruna Nijo'x'Galleon' and 'Chebec' x 'Harrington' and an F₂ population from the cross 'Shannon'x'Proctor'. Data of the haploid populations can be found on GrainGenes on the Internet.

In the former issues of BGN there have been given a linkage map of barley chromosome 5 based on the procedure for estimating linkage maps by Jensen (1987) and based on mainly classical markers and on two-point tests available in published journal. Since most research workers now have access to the Internet I will consider freely available data on the Internet as officially published unless the opposite is explicitly stated. My policy of considering all published linkage data for barley chromosome 5 should therefore also include those available on the Internet. For multi-point tests conducted by the use of molecular markers are usually listed as raw segregation data. To estimate the linkage map is it necessary to have estimates of pair-wise recombination frequencies and their standard deviations, therefore, such calculations has to be done first by me. Further, it is often difficult with the molecular markers to be sure that markers with the same name in different materials are identical (located in the same position). Markers with different names may also be identical. An example of the last situation may occur in the linkage maps shown in Figure 1 where cMWG733 from the cross 'Steptoe'x'Morex' map in position -33.8+/-3.43 cM and MWG733A from the cross 'Harrington'x'TR306' map in -34.2+/-3.02 cM. However, as the mapping populations both are from the north American mapping project the two markers are probably different.

The map of barley chromosome 5 mentioned above and shown in Figure 1 is based on the linkage information reported in the former issues of BGN and in the mapping populations 'Igri'x'Franka', 'Steptoe'x'Morex', and 'Harrington'x'TR306'. The map was presented as a poster at the VII International Barley Genetics Symposium in Saskatoon, Saskatchewan, Canada (Jensen 1996). The map has 102 markers and is 147 cM long. Ten "classical" markers, present on the map in BGN Vol. 25 which have only few linkage data, are omitted: Mlat, HrdC, HrdD, HrdE, MWG1H036, MWG1H060, MWG1H068, Lys4, cer-zi and cud2. The map estimation procedure omit linkage data which do not fit into the map. The results of this was that each of the above mentioned loci had only a recombination estimate to one other locus. They could therefore not be ordered in relation to other loci on the map and was consequently omitted from the map.

The omission of these loci is probably the reason for that the map in Figure 1 is 19 cM shorter than the linkage map of barley chromosome 5 in BGN Vol. 25.

The position of the centromere is between position +23.8 and +14.0 cM using the same assumption and calculations as in BGN Vol. 25.

References:

Aksenovich, A.V. 1996. Studying inheritance of variations in response of barley aleurone to gibberellic acid. Genetika 32: 1243-1247 (referred from Current Contents: Life Sciences week no. 9651).

Becker, J., P. Vos, M. Kuiper, F. Salamini and M. Heun. 1995. Combined mapping of AFLP and RFLP markers in barley. Molecular & General Genetics 249: 65-73.

Bougri, O.V., V.N. Korzun and B. Grimm. 1996. Chromosomal assignment of the genes encoding glutamyl-tRNA reductase in barley, wheat, and rye and their organization in the barley genome. Hereditas 124: 1-6.

Jensen, J. 1987. Linkage map of barley chromosome 4: In: Barley Genetics V. Proc. Fifth Int. Barley Genet. Symp., Okayama, Japan. Sanyo Press Co., pp. 189-199.

Jensen, J. 1996. The barley chromosome 5 linkage maps. In Proc. V. International Oat Conference & VII International Barley Genetics Symposium. University Extension Press, University of Saskatchewan, Vol. 1 pp. 333-334.

Langridge, P., A. Karakousis, N. Collins, J. Kretschmer and S. Manning. 1995. A consensus linkage map of barley. Molecular Breeding 1: 389-395.

Mather, D.E. and P.M. Hayes. 1996. Comparison of grain and malt quality QTL in barley mapping populations. In Proc. V. International Oat Conference & VII International Barley Genetics Symposium. University Extension Press, University of Saskatchewan, Vol. 1 pp. 350-352.

Nieto-Lopez, R.M. and T.K. Blake. 1994. Russian wheat aphid resistance in barley: Inheritance and linked molecular markers. Crop Science 34: 655-659.

Noli, E., M.C. Sanguineti, R. Tuberosa, S. Salvi, and E. Schiliro. 1996. Linkage analysis and distribution of RAPD markers in barley. In Proc. V. International Oat Conference & VII International Barley Genetics Symposium. University Extension Press, University of Saskatchewan, Vol. 1 pp. 366-368.

Qi, X.Q., P. Stam and P. Lindhout. 1996. Comparison and integration of four barley genetic maps. Genome 39: 379-394.

Steffenson, B.J., P.M. Hayes and A. Kleinhofs. 1996. Genetics of seedling and adult plant resistance to net blotch (Pyrenophora teres f. teres) and spot blotch (Cochliobolus sativus) in barley. Theoretical and Applied Genetics 92: 552-558.

Taketa, S. and K. Takeda. 1996. Expression of barley marker genes in wheat-barley hybrids. In Proc. V. International Oat Conference & VII International Barley Genetics Symposium. University Extension Press, University of Saskatchewan, Vol. 2 pp. 586-588.

Yu, G.X., A.L. Bush and R.P. Wise. 1996. Comparative mapping of homoeologous group 1 regions and genes for resistance to obligate biotrophs in Avena, Hordeum, and Zea mays. Genome 39: 155-164.