II. 21. Primary trisomic analysis of three mutant genes in barley. (1)
Elizabeth Furst and T. Tsuchiya, Department of Agronomy, Colorado State University, Fort Collins, Colorado 80523, U.S.A.
(1) Supported by USDA/SEA Competitive Research Grant No. 5901-0410-9-0334-0 and 82-CRCR-1-1020 to T. Tsuchiya and CSU Hatch Project.
Primary trisomic analysis is being used to associate the gene for spiral and two genes for zebra (Colorado) with the appropriate chromosomes.
The gene for spiral character, produced by radiation (Tsuchiya, unpublished) shows simple recessive inheritance and is easily identified at different growth stages from early seedling stage. Seedling roots are curly, while the roots of normal plants are straight (Tsuchiya, 1974a). The young plant has droopy leaves with wrinkles at various parts of leaf blades and does not grow straight; plants are bent at the nodes and sometimes in internodes. At heading, awns are severely waved, and the neck is crooked. Some heads even show a twist. The upper portion of the top internode has a spiral nature with which the mutant name "spiral neck" or "spiral" was adopted.
Two different stocks for "zebra Colorado" were studied because they have often been confused in past linkage studies. The gene symbol ''zbc'' had been shown on the map of chromosome 4 until this confusion was realized (Tsuchiya, 1976).
One of these stocks has been maintained as CSU B8-9 and carries a gene for "zebra Colorado" (zbc) that shows simple recessive inheritance. Homozygous recessive plants are uniformly pale yellow-green in color. This gene was located in chromosome 4 by Immer and Henderson (1943), but it was later found that the result was incorrect, at least with the stock in the Genetic Stock Center at Colorado State University (Tsuchiya, 1974b).
The other stock, designated as Utah T41, carries a gene for zebra Colorado that shows incompletely dominant inheritance. Homozygous mutants have yellow bands on the first leaf, and patches of yellow on later leaves. Heterozygotes are a general pale green color, intermediate between green and bright yellow.
Each of the seven primary trisomic types of the variety S.E. 16 were pollinated with pollen from homozygous mutants. The trisomic F1 plants derived from these crosses were allowed to self-pollinate to produce F2 seed. The F2 population was then separated into two groups; trisomic and disomic by chromosome counts, and each section was observed for segregation of the mutant gene.
A summary of the results obtained so far is shown in Table 1. These results indicate that gene for Spiral mutant was not associated with any of chromosomes 4, 5, 6 and 7. The gene zbc in CSU stock B8-9 and zebra gene in Utah T41 were not associated with chromosomes 4, 6 and 7.
Table 1. Summary of primary trisomic analysis for the spiral gene and two genes for zbc.
However, zebra gene in Utah T41 showed trisomic ratio in chromosome 5 with no homozygous mutant in a total of 31 trisomics studied in three F2 population. It is therefore concluded that the incompletely dominant zebra gene in Utah T41 and Univ. Alberta Acc. 43 is associated with chromosome 5.
References:
Immer, F. R. and M. T. Henderson. 1943. Linkage studies in barley. Genetics 28:419-440.
Seip, Lindy and T. Tsuchiya. 1978. Trisomic analysis of lg4 and zbc. BGN 8:86-89.
Tsuchiya, T. 1974a. Root character of curly mutants in barley. BGN 4:88-90.
Tsuchiya, T. 1974b. Report from Genetic Stock Center at Fort Collins, Colorado. BGN 4:107-110.
Tsuchiya, T. 1976. Linkage information as of April 1976. BGN 6:110-113.
Tsuchiya, T. and Ruth Baldivia. 1981. Primary trisomic analysis of an incompletely dominant zebra mutant, zbc, in barley. BGN 11:63-64.
