BGN 12: Primary trisomic analysis of Zbc for zebra Colorado gene BARLEY GENETICS NEWSLETTER, VOL. 12, II. RESEARCH NOTES
First and Tsuchiya, pp. 78-79

II. 28. Primary trisomic analysis of Zbc for zebra Colorado gene. (1)

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

(1) Supported in part by USDA/SEA Research Grant 12-14-5001-265 and USDA/SEA Competitive Research Grant 5901-0410-9-0334-0 to T. Tsuchiya.

An attempt was made to associate the incompletely dominant mutant gene Zbc for zebra (Colorado) with primary trisomic analysis. Trisomic plants for chromosome 4 (Triplo 4) of the variety Shin Ebisu 16 (Tsuchiya, 1967) were pollinated with homozygotes of Zbc stock. Mutants were of original Utah T41 stock. The inheritance of this gene was found to be incompletely dominant (Tsuchiya, 1981). However, for the sake of convenience, it was treated as a recessive. Homozygous plants (Zbc Zbc) have yellow bands on the first leaf and patches of yellow on subsequent leaves. Heterozygotes show a general pale yellow-green color.

F2 segregation was observed in a diploid control from selfed diploid F1 hybrids and in populations from selfed trisomic F1 hybrids. Normal green plants and heterozygotes were classified as normal. A disomic ratio (32:9 = 41; X2 for 3:1, 0.203) was observed in the diploid control.

F2 populations from trisomic F1 plants were separated into two groups: diploid and primary trisomic after chromosome counts, and the segregation ratio was calculated in each group.

If the Zbc gene were located on chromosome 4 (critical combination), no trisomic plants carrying the gene in the homozygous condition would be expected with chromosome segregation. However, 11 out of 38 trisomic F2 plants were homozygous for the mutant gene. Disomic (3:1) ratios were obtained in both the trisomic and disomic sections (Table 1).

Table 1. F2 data from the cross between Triplo 4 and Zbc (Utah T41) in barley.

These data indicate that this zebra (Colorado) gene is not located on chromosome 4. Tsuchiya and Baldivia (1981) have shown that Zbc in Utah T41 was not associated with chromosome 6 by primary trisomic analysis. Further studies are underway to associate this gene with remaining five primary trisomic types.


Tsuchiya, T. 1967. The establishment of a trisomic series in a two-rowed cultivated variety of barley. Can. J. Genet. Cytol. 9:667-682.

Tsuchiya, T. and Ruth Baldivia. 1981. Primary trisomic analysis of an incompletely dominant zebra mutant, Zbc in barley. BGN 11:63.

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