V.1. New linkage maps of barley.

T. Tsuchiya, Department of Agronomy, Colorado State University, Fort Collins, Colorado 80521, U.S.A.

Since the publication of the linkage maps of barley in BGN 2(163-167), some new information has been obtained. Also, some suggestions and comments have been obtained from Dr. A. Kleinhofs of Washington State University, U.S.A., and Dr. R. Takahashi of Ohara Institute for Agricultural Biology, Okayama University, Japan. It is possible to change, not correct, the location of those genes in the maps. However, in view of the incompleteness of our linkage data, it seems to be reasonable not to change the present map position until reliable data are obtained by critical, conventional linkage analysis in a coupling phase cross or by telotrisomic analysis using multiple recessive marker stocks. The main changes in the new maps are as follows:
1. Centromere positions in the linkage maps are based on the available information obtained by telotrisomic analysis.
2. Some genes have been eliminated based on the results of allelism testing (gl 4 in chromosome 6 and a_c 3 in chromosome 3).
3. The arm location of some genes has been changed based on the available results from telotrisomic analysis.
4. Several genes are added from recent publications.

Chromosome 1
F2 and F3 data from crosses between gs 3 Br F_c  x Gs 3 br f_c  indicated that distance of gs 3-f_cshould be closer than that of gs 3-br (Tsuchiya, et al., unpublished). Fedak, et al. (1972) reported that the order of those three genes is f_c - gs 3 - br with br at the distal position. Critical analysis is necessary to verify this by means of telotrisomic analysis using a triple recessive stock.

No report was obtained from the coordinator.

Chromosome 2
Telotrisomic analysis showed that tr, gp (=gp 2), li, gs 5 and ms 2 are located on the long arm, and f, lg, e, and probably sk for subjacent hood are on the short arm (Tsuchiya and Singh, 1973). Since e is on the short arm and gs 5 is on the long arm, the gene order in relation to the centromere should be changed to lg-f-e-centromere-gs 5. Preliminary data indicated that gp-li is closer than gp-tr and tr-li. Critical analysis is necessary to verify the data.

The map prepared by coordinator (G. W. R. Walker) is different from the one prepared by T. Tsuchiya.

Chromosome 3
Critical telotrisomic analysis was conducted with several genes. The results suggest that the centromere position is located between al and yst 2, and the telocentric chromosome of the stock being used is the long arm of chromosome 3. Another finding of telotrisomic analysis is that wst, cu 2 and uz should be moved from the distal end of the short arm to somewhere, probably the distal part of the long arm of this chromosome (Tsuchiya and Singh, 1973). Analysis is now underway for some genes such as als, a_n, and x_s. The gene a_c was found to be allelic to a_c 3 as far as the stocks maintained in the Stock Center in Fort Collins (Tsuchiya, unpub.) are concerned. Therefore, a_c 3 has been removed from the present map. A new gene, rnt, for reduced number of tillers was added to this group (Nonaka, 1973). It is difficult, however, to map this gene because of the conflict regarding the location of uz gene (see below).

Another finding in the linkage map of chromosome 3 is the relative distance among three genes uz, wst, and al. As reported in a brief note in this issue of BGN (Tsuchiya and Jensen, 1973), no double recessive homozygote was obtained in about 2,000 F2 plants from the cross between uz and wst. These two genes must be very close to each other on this chromosome. Also, there is no doubt that wst is allelic to wst 3 (Tsuchiya, 1972a; Tsuchiya and Jensen, 1973) and wst 3 is completely linked with uz (Takahashi and Moriya, 1969).

There are some conflicts between the results obtained from conventional linkage analysis and telotrisomic analysis, particularly the location of uz, wst and al. Further detailed analysis is necessary to furnish conclusive data for them.

In a recent letter, Takahashi stated that his statement regarding the segregation of several double recessive (uz-wst) plants in about 600 F2 plants from crosses between uz and wst (Takahashi, 1972) was incorrect.

These results suggest that there may be no need to explain the complete linkage between uz and wst 3 by a paracentric inversion as suggested by Tsuchiya (1972a), even though there is a paracentric inversion in the wst 3 stock.

Chromosome 4
Light green gene lg 2 was restored in the map. Two more genes, ari-c, cer-j (glossy sheath) were located on the map. The third gene mapped on chromosome 4 (Søgaard, 1973) (cer-zg) was not located in the map because of lack of allelism testing with gl and gl 3 already mapped in chromosome 4.

Since telotrisomic analysis is not completed yet for the K locus, it is not possible to locate the centromere position definitely on the map. Since f 9 was located in the telocentric chromosome and lg 4, br 2, gl (and gl 2), and yh were located on the other arm of this chromosome (Tsuchiya and Singh, 1973), it is reasonable to assume that the telocentric chromosome is the short arm of chromosome 4. However, because of the morphological resemblance of this telotrisomic to the primary trisomic for chromosome 4, it is assumed that the telocentric chromosome could be the long arm and the linkage map should be reversed. Critical data is necessary to confirm this assumption. For more detail, refer to the coordinator's report by T. E. Haus in this issue (p. 84-85).

Chromosome 5
Reversion of the long and the short arm of chromosome 5 is now official (Tsuchiya, 1972b). A recent paper by Fedak, et al. (1972) has shown that two more genes, sp,,b for Parkland Spot and rvl for revoluted leaves, have been located on the long arm of chromosome 5.

No report was obtained from the coordinator.

Chromosome 6
Allelism tests have shown that gl 4, which was believed to be located on this chromosome, is allelic to gl 3 in chromosome 4 (Tsuchiya, 1973). Since more marker genes were used in the linkage analysis of gl 3 than for gl 4, it seems to be reasonable to conclude that gl 3 (=gl 4) is located in chromosome 4. No further data on linkage for this chromosome has been obtained.

No coordinator's report was received.

Chromosome 7
Almost no improvement in the linkage map of this chromosome has been made. Takahashi (personal communication) suggested that va 3 should be dropped because of lack of enough information to locate the gene in the map (Walker, et al., 1963).

No report was obtained from the coordinator.

Critical study of the literature on linkage analysis in barley and our own experience with allelism testing and trisomic analysis, particularly telotrisomic analysis, leads the present writer to feel that there is a great deal of work to be done in barley linkage studies in order to improve our present linkage maps. More good genes should be accurately located on each chromosome arm. Many multiple recessive marker stocks should be developed for each arm or at least each chromosome. Conventional and/or telotrisomic analysis of linkages should be made using the multiple marker stocks to be established.

With the purpose of helping each coordinator to attempt to develop multiple marker stocks, useful marker genes so far associated with each chromosome are listed below. The symbols in parentheses are suggested arm location.

Chromosome 1
sb for subnodal bract (1S)
f 4 for chlorina seedling (1L)
f 5 for chlorina seedling (1S)
ert-a, ert-d, and ert-m for erectoides
ari-d for short awn

Chromosome 2
gs 6 for glossy sheath and sheath (2S)
sk for subjacent hood (2S)

Chromosome 3
br_x for brachytic (stock is not available at the Stock Center in Fort Collins)
ari-a for short awn
ert-c and ert-ii for erectoides

Chromosome 4
int-c for intermedium
ert-i for erectoides
yh for yellow head
Hs for hairy sheath

Chromosome 5
int-a for intermedium
ms for male sterile
ert-b for erectoides

Chromosome 6
clh for curly leaf dwarf
f 6 for chlorina seedling

Chromosome 7
ert-g, ert-n for erectoides
ari-e for short awn
lax-a for lax spike
va and va 3 for variegated (white stripe)

Fig. 1. Chromosome maps of barley.

References:

Fedak, G., T. Tsuchiya and S. B. Helgason. 1972. Use of monotelotrisomics for linkage mapping in barley. Can. J. Genet. Cytol. 14:949-957.

Nonaka, S. 1973. A new type of cultivar, Mitake, with very few in number, but thick and stiff culms. BGN 3:45-47.

Takahashi, R. 1972. Information of linkage and mapping of genes on chromosome 3. BGN 2:127-131.

Takahashi, R. and I. Moriya. 1969. Inheritance and linkage studies in barley. Ber. Ohara Inst. landw. Biol. 15:35-46.

Tsuchiya, T. 1972a. A case of paracentric inversion affecting genetic behavior of a white streak gene. BGN 2:104-105.

Tsuchiya, T. 1972b. Revision of linkage map of chromosome 5 in barley by means of telotrisomic analysis. J. Hered. 63:373-375.

Tsuchiya, T. 1973. Allelic relationships between two glossy seedling genes, gl 3 and gl 4 in barley. BGN 3:66-67.

Tsuchiya, T. and Debra A. Jensen. 1973. Further results on the allelic relationship between wst and wst 3. BGN 3:69-70.

Tsuchiya, T. and R. J. Singh. 1973. Further information on telotrisomic analysis in barley. BGN 3:75-78.

Walker, G. W. R. et al. 1963. Recent barley mutants and their linkage, II. Genetic data for further mutants. Can. J. Genet. Cytol. 5:200-219.

BGN 3 toc
BGN Main Index