V. I. Linkage Maps of Barley (Hordeum vulgare L.) (1)
T. Tsuchiya, Department of Agronomy, Colorado State University, Fort Collins, Colorado 80523. U. S. A.
(1) Supported by USDA-CSU Cooperative Research Grant No. 48-9AHZ-2-265 and CSU Hatch Project.
Since the publication of linkage maps in barley (Tsuchiya, 1983), some new developments have occurred. However, there are still some problems in improving the linkage maps.
Many workers are still using conventional methods of genetic/linkage analysis which does not locate the gene in a particular chromosome arm. On the other hand, with the establishment now of 11 telotrisomic lines covering all seven chromosomes, centromere positions have been located in all seven linkage maps (Figure 1). However, many genes "mapped" by conventional analysis cannot be located or even associated with a chromosome arm. In Table 3 of my previous report (Tsuchiya, 1982) I listed 94 genes which were impossible to locate in the linkage maps in relation to the centromeres. The number of these genes has increased. The revised list will be presented in future issues of BGN.
Fig. 1. Linkage maps of barley, 1984.
Recent progress in linkage mapping in the last year is shown below.
Chromosome 1
The gene f8 (designated as a) for chlorina 8 was associated
with 1L based on telotrisomic analysis. Because of the small number of
F2 plants (56A:3a = 59) the results (37A:3a
= 40 for 2x and 19A:Oa = 19 for 2x + 1 telo portion) led
to the erroneous conclusion that f8 was located in 1L (Tsuchiya,
1972). Additional data from telotrisomic analysis of f8 with 1L
have shown a disomic ratio (55A:9a = 64 in the trisomic portion) indicating
that f8 is on the other arm (1S) (Shahla and Tsuchiya, 1984b). Based on
the available information from conventional linkage analysis, gene f8
was tentatively located in the proximal segment of 1S in the genetic linkage
map. Detailed genetic analysis of f8 is under way with Triplo 1L
and conventional linkage analysis.
Chromosome 4
The linkage map of chromosome 4 needs reinvestigation. Some of the
results from telotrisomic analysis (Tsuchiya and Singh, 1982) may be questionable,
because it was found that telocentric chromosome 4L had at least a terminal
deficiency of a considerable portion of the distal euchromatic segments
(Singh and Tsuchiya, 1982). Attempts are made to recover a complete 4L
in the progenies of the deficient 4L previously used for telotrisomic analysis
(Tsuchiya and Singh, 1982). A linkage map for chromosome 4 is presented
by Haus (1984).
Chromosome 5
The telosomic trisomic for the short arm of chromosome 5 (5S) was obtained
in the progeny of Triplo 5 (Shahla and Tsuchiya, 1984a).
This new telotrisomic for 5S was crossed with a line of Hordeum spontaneum and other varieties which are resistant to many races of powdery mildew of barley. A resistant line of Triplo 5S will be used to determine the definite centromere position in chromosome 5. A detailed linkage map is presented by Jensen (1984) without centromere position located.
Chromosome 6
The centromere position of chromosome 6 was determined tentatively
based on telotrisomic analysis of o with Triplo 6S (Shahla, Shim,
and Tsuchiya, 1983). However, because of close linkage of o with
gs4
and uc2, there is a possibility that more genes will be located
in the short arm of chromosome 6 (6S) when the results of undergoing telotrisomic
analysis are obtained.
Chromosome 7
Telotrisomic analysis with Triplo 7S of the gene nld for narrow
leafed dwarf which was located at distal portion of the short arm (?) of
chromosome 7 and two genes in 7L (f6 and r) showed disomic
ratios, indicating that the gene nld is in the opposite arm (Shahla
and Tsuchiya, 1984c). There is a possibility that the entire linkage map
of chromosome 7 may be reversed. However, the genetic analysis of the gene
ddt which has been located distal to the gene nld in the
linkage map of chromosome 7 is necessary to make final decision on this
matter. The gene ddt was tentatively removed from the linkage map
of chromosome 7 because of the lack of sufficient information for its localization.
The centromere position was placed in the map with no genes in the short
arm (7S) (Fig. 1).
The list of genes in VII.1 (P.100) was slightly improved. An improved list published in this issue shows all available information including literature for each gene. Additional literature was included and some corrections were made in both the list of genes and literature except for some of those reported in "VI. Description of Genetic Stocks in Barley" (p.89-99).
The new linkage maps (Fig. 1) show some of these changes. Additional information on linkage maps is presented in the next sections (p. 84-88).
References:
1. Haus, T. E. 1984. BGN 14:61-62.
2. Jensen, J. 1984.BGN 14:62-65.
3. Shahla, A., J. W. Shim, and T. Tsuchiya. 1983. Association of the gene o for orange lemma with the short arm of chromosome 6 (6S) in barley. BGN 13:83-84.
4. Shahla, A. and T. Tsuchiya. 1984a. Telotrisomic for the short arm of chromosome 5 (5S) in barley. BGN 14:.11-12.
5. Shahla, A. and T. Tsuchiya. 1984b. Telotrisomic analysis of the gene f8 (chlorina) in barley. BGN 14:53-54.
6. Shahla, A. and T. Tsuchiya. 1984c. Telotrisomic analysis in Triplo 7S in barley. BGN 14:52-53.
7. Singh, R. J. and T. Tsuchiya. 1982. Identification and designation of telocentric chromosomes in barley by means of Giemsa-N banding technique. Theor. Appl. Genet. 64:13-14.
8. Tsuchiya, T. 1972. Cytogenetics of the telocentric chromosomes of the long arm of chromosome 1 in barley. Seiken Siho 23:47-62.
9. Tsuchiya. T. 1982. Linkage maps of barley, 1982. BGN 12:100-104.
10. Tsuchiya, T. 1983. Linkage maps of barley, 1983. BGN 13:101-106.
11. Tsuchiya, T. and R. J. Singh. 1982. Chromosome mapping in barley by means of telotrisomic analysis. Theor. Appl. Genet. 61:201-208.
