A number of molecular markers have been mapped to barley chromosome 5 in a cross between H.vulgare cv 'Captain' × a H.spontaneum line (Wang et al. 1992). The order of the genes on barley chromosome 5 agree with the order of those on rye chromosome 1. The North American Barley Genome Mapping Project (NABGMP) reported a comprehensive linkage map of barley chromosome 5 obtained by using molecular markers on chromosome doubled haploid lines from the cross 'Steptoe × Morex' (Kleinhofs et al. 1993). From the NABGMP (Hayes et al. 1993) there have also been a report of localization of quantitative trait loci (QTL) in the 'Steptoe × Morex' cross. Two QTL was found on chromosome 5, one for plant height and one for the malting related traits. diastatic power, alpha amylase and malt extract.
The information in above mentioned papers was not detailed enough so that the reported loci could be incorporated in the current map of chromosome 5. However, Kleinhofs et al. (1993) provided description of the used markers and their segregation on an electronic bulletin board (BBS). Based on the information on the BBS it is possible to calculate the linkage information needed to incorporate the markers into the linkage maps. Extraction of the relevant information and calculating the recombination frequencies requires a great deal of work. Therfore, most if not all barley linkage map coordinators have utilized only the data that are published in the scientific literature journals.
Five recombination frequencies (see table 1) were reported by Schuller et al. (1992) between locus Mla (barley powdery mildew resistance) and the two hordein loci Horl and Hor2 and the three RFLP loci MWG1H036, MWG1H060 and MWG1H068 Since the authors also described the order of these loci the data are utilized in the present update of the linkage map.
Valuable information for the coordinators to compile may occur in Barley Genetics Newsletter Vol. 22. Unfortunately, I have not yet seen it, and its information has to be reported in BGN Vol. 23.
Based on the information in Table I and former issues of BGN and using the procedure by Jensen (1987), the linkage map of barley chromosome 5 was estimated. A drawing of the map is shown in Figure 1. The new linkage data has only resulted in minor adjustments of the mappositions of the loci, but 5 new loci are, the three RFLP and the two Ndh loci, were included in the map. The map comprises now 42 loci.
Guerin,J.R., R.C. Lance, A.H.D. Brown, and D.C. Abbott. 1993: Mapping of malt endopeptidase, NADH diaphorase and esterase loci on barley chromosome 3L. - Plant Breeding (submitted)
Hayes, P.M., B. H. Liu, S.J. Knapp, F.Q. Chen, B. Jones, T. Blake, J.D. Franckowiak, D. Rasmusson, M. Sorrells, S.E. Ullrich, D. Wesenberg, and A. Kleinhofs. 1993: Quantitative trait locus effects and environmental interaction in a sample of North American barley germplasm. - Theoretical and Applied Genetics 87:392-401.
Jensen, J. 1987: Linkage map of barley chromosome 4. - In: Barley Genetics V. Okayama, Japan: 189- 199.
Kleinhofs, A., A. Kilian, M.A. S. Maroof, R.M. Biyashev, P. Hayes, F.Q. Chen, N. Lapitan, A. Fenwick, T.K Blake, V. Kanazin, E. Ananiev, L. Dahleen, D. Kudrna, J. Bollinger, S.J. Knapp, B. Liu, M. Sorrells, M. Heun, J.D. Franckowiak, D. Hoffman, R. Skadsen, and B.J Steffenson 1993: A molecular, isozyme and morphological map of the barley (Hordeum vulgare) genome. - Theoretical and Applied Genetics 86: 705 -712.
Schuller,C., G. Backes, G. Fischbeck, and A. Jahoor. 1992: RFLP markers to identify the alleles on the Mla locus conferring powdery mildew resistance in barley. - Theoretical and Applied Genetics 84:330-338.
Wang, M.L., M,D. Atkinson, C,N. Chinoy, K.M. Devos, and M.D. Gale.1992: Comparative RFLP-based genetic maps of barley chromosome 5 (11-1) and rye chromosome IR. - Theoretical and Applied Genetics 84:339-344.