II. 12. Zebra striped leaves: Problems in gene and stock designation and proposed new symbols for zoned or zebra mutants in barley. (1)
T. Tsuchiya, Department of Agronomy, Colorado State University, Fort Collins, Colorado 80523, U.S.A.
(1) Supported by USDA-CSU Cooperative Research Grant 58-9AHZ-2-265 and CSU Hatch project.
A mutant which showed transverse yellow band was first reported by Immer and Henderson (1943) as zoned leaf with gene symbol zd. This gene showed close linkage with k, gl, and lg9. The symbol zd was later changed to z by Robertson, Wiebe and Shands (1947, 1955).
Robertson (1964) used another symbol zc for "zoned leaf" or "zoned (Colorado)" without showing previous symbols or explanations for these "changes".
Robertson, Wiebe, Shands and Hagberg (1965) used symbol zd for "Zebra striped leaves" (zd) in "Description of Character" (p. 34). However, in Tables 1 (p. 35) and 5 (p. 38) in the same paper the symbol zbc was introduced, zc as previous symbol based on the report of Woodward (1957). Reviewing the linkage maps, it is obvious that z (Robertson et al. 1947, 1955), zc (Robertson 1964) and zbc (Robertson el al., 1965) are all the same gene and located between lg4 and lg3 in linkage group (chromosome ) 4. In the linkage maps of Robertson (1971) zbc was also used. These results indicated that z, zc, zd and zbc are all the same gene. Similarly Smith (1951) and Nilan (1964) located the gene z and zc between lg4 and lg3, respectively.
Smith (1951) used symbol z and cited Immer and Henderson (1943), but did not give previous symbol (zd) used by Immer and Henderson (1943). Nilan (1964) used zc for "zoned leaf (Colorado)" as the symbol and listed z and zd as previous symbols.
Combining all this information, it seems to be reasonable to consider that the presently utilized symbol zbc for the mutant "zebra striped leaf" is the same gene as the previously used symbols, zd, z, and zc. All these genes (actually the same gene) are located between 1g4 and 1g3 in the linkage group (chromosome) 4.
If we accept the above conclusion, then two problems arise: One is the genetic stocks representing these (or this) gene(s). There are many stocks with the same symbol as shown by many publications. Inheritance studies and allelism tests showed that there are at least two different genetic stocks; one is a simple recessive mutant (CSU B8-9 and some Utah stocks) similar to the stock described by Immer and Henderson (1943). The other is an incompletely dominant stock which shows extremely different characteristics from CSU B8-9 and Utah stocks which are allelic to CSU B8-9. The incompletely dominant mutant gene is in the stock Utah T41 and University of Alberta Accession 43 (Tsuchiya, 1975) and was given a new symbol zbc2 (Tsuchiya, 1983).
The second problem is the map location of the gene zbc (z, zc, and zd). As obvious from all previous publications and linkage maps these genes (or the gene) are located between 1g4 and 1g3 in chromosome (linkage group) 4. Repeated trisomic analysis failed to show association of either recessive zbc in CSU B8-9 or incompletely dominant zbc2 in the stock Utah T41 with cTiromosome 4 (Furst, 1983).
Since the incompletely dominant gene zbc2 was associated with chromosome 5 (Furst, 1983; Shahla and Tsuchiya, 1984)and the gene zbc was not associated with chromosome 5, it is obvious that zbc is different from zbc2 confirming previous conclusion (Tsuchiya, 1983).
The recessive gene zbc showed no association with chromosome 1, 3, 4, 5, 6 and 7, suggesting its location in chromosome 2.
Now then, a question arose. How do we explain all the data of genetic/linkage analysis by many barley geneticists working on the gene(s) for zebra striped leaf? Some eight workers have shown linkage between various marker genes in group 4 with zd, z, zc or zbc . All data from trisomic analysis by Tsuchiya and his associates showed no association of gene(s) for zebra striped leaf with chromosome 4 (Furst, 1983).
There is a possibility that the extra chromosome 4 in the primary trisomic (Triplo 4) has deficiency in the very locus where zbc, (z, zc, zd) is located. With several multiple marker stocks in chromosome 4, conventional linkage analysis is now underway to study these problems.
Regardless of problems discussed here, the present symbol with subscript c (zbc, zbc2) are meaningless. Also there is a symbol zb for zebra stripe mutant located in chromosome 3 (Tsuchiya and Singh, 1974). It is, therefore, appropriate to assign new symbols for these two genes for zoned or zebra striped mutants as follows:
References:
Furst, E. 1983. M.S. Thesis, Colorado State University
Immer, F.R. and M.T. Henderson. 1983. Genetics 28:419-440.
Nilan, R.A. 1964. The cytology and genetics of barley. 1951-1962. Washington State Univ. Press, 278 pp.
Robertson, D.W. 1964. Barley Genetics I:159-180.
Robertson, D. W. 1971. Barley Genetics II:220-242.
Robertson, D.W., G.A. Wiebe and R.G. Shands. 1947. J. Amer. Soc. Agron. 39:464-473.
Robertson, D.W., G.A. Wiebe and R.G. Shands. 1955. Agron. J. 47:418-425. Robertson, D.W., G.A. Wiebe and R.G. Shands. 1965.Crop Sci. 5:33-43.
Shahla, A. and T. Tsuchiya. 1984. BGN 14:
Smith, L. 1951.Bot. Rev. 17:1-51, 133-202, 285-355.
Tsuchiya, T. 1975. BGN 5:67-67.
Tsuchiya, T. 1983. BGN 13:84.
Tsuchiya, T, and R.J. Singh. 1974. BGN 4:96-97.
