BGN 10: Linkage maps of barley, 1980 BARLEY GENETICS NEWSLETTER, VOL. 10, V. CURRENT LINKAGE MAPS OF BARLEY
Tsuchiya, pp. 95-98

V. 1. Linkage maps of barley, 1980*

T. Tsuchiya. Department of Agronomy, Colorado State University, Fort Collins, Colorado 80523, U.S.A.

* Supported partly by Research Grant No. 12-14-5001-265 from USDA/SEA.

Results from the linkage analysis, conventional and translocation analysis, have been published in recent volumes of Barley Genetics Newsletters and some scientific journals. However, it has been rather difficult for this author to locate many of those genes in the chromosome maps. Main causes of the difficulties are:

1. Limited amount of information is based on the three point test, especially with the back cross method with multiple recessive. Therefore, the information may not be very reliable.

2. Some experiments have been carried out in the field where some homozygous mutants could not survive. The data from this work may also not be very reliable.

3. Genetic markers which were well studied and rather precisely located have not been included in the linkage analysis. Therefore, it is extremely difficult to locate those genes adequately in the chromosome maps.

4. At present five of seven chromosomes have centromere located in the chromosome map in relation to several marker genes based on the results from telotrisomic analysis. Some 50 genes have been associated in 10 arms of five chromosomes, 1 to 5. Under these circumstances, it is almost impossible to locate some new mutant genes adequately in the chromosome map, because it is extremely difficult to figure out with which arm these genes are associated. Without arm location it is almost impossible to locate genes in the chromosome maps of those five chromosomes.

The following are several aspects recognized in each chromosome:

Chromosome 1: There is a conflicting result on the arm location of ac2 in this chromosome (Søgaard, 1977b; Tsuchiya, 1972). The order of three closely linked genes, br, gs3 and fc was established as br-5.386-f 2.107-gs3 by three point test (Shahla, 1980). However, the telotrisomic analysis could not give a definite relationship between centromere and these genes, (Shahla, 1980). The symbol (Rs) for red stem should be changed. However, this will be maintained until the whole system will be changed in the near future.

Chromosome 2: The symbol (Re 2) for the second gene for Purple lemma and pericarp is also maintained as is the case of Rs. The gene yst3 for yellow streak 3 was found not to be located either 2L or 2S (Tsuchiya and Hang, 1979), and eliminated from the map (Table 1).

Chromosome 3: The symbol rnt for reduced number of tiller was changed to lnt for lower number of tillers which was originally suggested by the researcher (Nonaka, personal communication).

Chromosome 4: The gene i for deficiens has failed to show trisomic ratio in the telotrisomic analysis with Triplo 4S (Tsuchiya and Hang, 1979). However, it will remain at the same locus until more information is obtained.

Chromosome 5: A detailed map was presented by Jensen (1980). However, there is some uncertainty for several genes in relation to the established good markers. Thus the map has a rather limited number of genes located. Other genes are listed in Table 1.

Chromosome 6: A necrotic leaf spot gene (nec) was reported to be located on chromosome 6 (Kasha, 1980). Häuser and Fischbeck (1979) also reported another necrotic gene on chromosome 6. However, these authors did not show any results of allelism testing with necrotic genes on chromosome 6 reported by Jensen (1971). Therefore, it is difficult to even give a symbol. I suggest J. Jensen, K. Kasha and G. Fischbeck communicate with each other and solve the problem of this confusion. Based on the report by Kasha (1980), alb,,q was eliminated from the map and placed in Table 1. Centromere location in the linkage map is still not known.

Chromosome 7: No information on the definite centromere location is available yet. Many genes associated with this chromosome have not been located in the map without question.

Because of those problems discussed above the linkage maps have not been improved very much this year. More information is needed from the detailed linkage analysis with the use of multiple genetic marker stocks including well known gene markers for further improvement of linkage maps in barley.

Figure 1 shows linkage maps with some revisions. Table 1 presents the list of genes associated with each chromosome or chromosome arm.

Figure 1. Linkage maps of barley, 1980.

Table 1. List of genes associated but not located definitely with respective chromosome/chromosome arm in barley, 1980.

References:

1. Jensen, J. 1971. Mapping of 10 mutant genes for necrotic spotting in barley by means of translocation. Barley Genetics II (Proceed. IInd Intern. Barley Genet. Symp.):213-219.

2. Jensen, J. 1980. Coordinator's report: Chromosome 5. BGN 10:88-90.

3. Kasha, K.J. 1980. Coordinator's report: Chromosome 6. BGN 10:

4. Seip. L. and T. Tsuchiya. 1979. Trisomic analysis of a mutant gene ovl for ovaryless or male in barley. BGN 9:89-90.

5. Shahla, A. 1980. Physical localization of genes in the short arm of chromosome 1 (1S) in barley. Ph.D. Thesis. Colorado State Univ., Fort Collins, Colorado, U.S.A. 91pp.

6. Søgaard, B. 1977a. The localization of eceriferum loci in barley. IV. Three point tests of genes on chromosome 7 in barley. Carlsberg Res. Commun. 42:35-43.

7. Søgaard, B. 1977b. Ibid. V. Three point tests of genes on chromosome 1 and 3 in barley. Carlsberg Res. Commun. 42:67-75.

8. Tsuchiya, T. 1972. Cytogenetics of telotrisomics in barley. BGN 2:93-98.

9. Tsuchiya, T. and A. Hang. 1979. Telotrisomic analysis of yst3 and i in barley. BGN 9:106-108.

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