Coordinator's Report: Chromosome 5

Jens Jensen
Agricultural Research Department
Risø National Laboratory, DK-4000
Roskilde, Denmark

The two isoenzyme loci Pgd2 (Phosphogluconate dehydrogenase) on chromosome 5 and Aco2 (Aconitate hydratase) are apparently linked with a recombination frequency of 42 ± 4 percent (Brown 1983). the Aco2 locus is therefore probably located on chromosome 5.

In Table 1 are given the new reported recombination frequencies which are applicable for map estimation and the corresponding map estimates. The loci designated m1-a_ma, Hrd A2, Hrd B2, and Hrd F3 in the table are considered to be identical with loci M1-a, Hor1, Hor2, and HrdF, respectively. The map of chromosome 5 is shown in Figure 1 and is estimated based on all available data by the procedure of Jensen and Jørgensen (1975a, 1975b) with modification applied to the data of Table 1 (Jensen 1987). The new data have caused several changes on the linkage map. A new locus, M1-ra (powdery mildew resistance), has been included in the map. The distance between Hor1 and Hor2 has increased significantly, and the distance between M1-at and Pa4 has decreased very much. Further, the locus M1-p (powdery mildew resistance) has been removed from the map since it is not localized on chromosome 5 (see last year's report).

References:

Biyashev, R. M., Netsvetayev, V. P. and Sozinov, A. A. 1986. Genetic control of some qualitative morphological and bio- chemical characters and location of three genetic factors in chromosomes 1 and 5 of Hordeum vulgare L. Genetika: 296-303 (in Russian).

Brown, A. H. D. 1983: Barley. In Isozymes in Plant Genetics and Breeding. Part B, p. 57-77. Elsevier Science Publ. B.V., Amsterdam, 1983.

Doll, H. and Jensen, H. P. 1986. Localization of powdery mildew resistance gene M1-ra on barley chromosome 5. Hereditas 105:61-65.

Jensen, J. 1987. Linkage map of barley chromosome 5. In Barley Genetics V. Proc. Int. Barley Genet. Symp., Okayama, Japan, October 6-11, 1986 (in press).,

Table 1. New reported recombination frequencies used for estimating the chromosome 5 map.

Jensen, J. and Jørgensen, J. H. 1975a. The barley chromosome 5 linkage map. 1. Literature survey and map estimation procedure. Hereditas 80:5-16.

Jensen, J. and Jørgensen, J. H. 1975b. The barley chromosome 5 linkage map. II. Extension of the map with four loci. Hereditas 80: 17-26.

Fig. I. The barley chromosome 5 linkage map with the best fit to all avail- able linkage data. The map positions are given in centimorgans (cM). The order and positions of Some M1- loci and of closely linked loci may not be indefinite. The position of the centromore is probably slightly above that of locus fs2.

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