II. 16 Linkage studies of two mutant genes on chromosomes 1 and 6.
Hayashi, J., R. Takahashi, I. Moriya and T. Nobuoka. The Ohara Institute for Agricultural Biology. Okayama University, Kurashiki, Japan.
a) A glossy-leaf mutant (gl-5) in Kmut 239 on chromosome 1
The mutant Kmut 239 was induced by X-ray irradiation on seed of a two-rowed, covered cultivar, Kirin Choku 1, and kindly provided by Dr. T. Tsuchiya, Colorado State University. The mutant is characterized by lack of waxy bloom on leaf-blades and hence looks glossy, but glossiness of leaves becomes less conspicuous with the advance of growth stage of the plant. Since this character was known to be inherited as simple recessive, a tentative gene symbol (gl-5) was assigned to this mutation.
The linkage of this mutant gene was firstly approached by means of a trisomic method of analysis, using six kinds of trisomics produced from Hordeum spontaneum by Dr. Tsuchiya. The result, shown in Table 1, suggested that the gene (gl-5) was not on chromosomes 2-7, but might be on chromosome 1. Therefore, an ordinary genetic analysis was commenced using a cross between Kmut 239 and Brachytic 119, which was known to have br and n, both on chromosome 1. Interrelationships among three gene pairs, Gl-5/gl-5, Br/br and N/n are as shown in Table 2 and Fig. 1. Further evidence by F3 progeny test will soon be obtained in coming barley season.
Table 1. Linkage analysis of gl-5 by use of trisomics having extra chromosomes 2 - 7.
Figure 1. A map of three genes on chromosome 1.
b) Curly-3 having a new mutant gene (cu-3) on chromosome 6
The genetic material, used in this experiment, is a X-ray induced mutant by Dr. A. Yamashita, National Institute of Agricultural Sciences, from Akashinriki, a cultivar of naked, uzu type. Although it was originally named 'lazy' by him, it seems better to us change its name to curly-3, because its main characteristic is that as in the other curly mutants, every stem-internode curves like a bow in the same direction. All the awns are almost straight, however. The character expression is marked in the normal, long-stemmed forms, but not so conspicuous in the short-stemmed, uzu type plants. A recessive gene controlling this character was tentatively named (cu-3).
Linkage analysis was commenced with a cross between this mutant and "purple" strain, a trisomic type having a chromosome 6 in excess. As shown in Table 3, the curly plants appeared in F2 much less from the expectation of 1 against 3 normal ratio; the observed counts of the normal and curly plants among the 2n and 2n+1 portions of the F2 population fitted well to the expected numbers calculated on the trisomic segregation ratios. This apparently indicates cu-3 being on chromosome 6. Accordingly, a cross was newly made between the mutant and a tester stock having uc-2 and o altogether. The linkage data obtained from the F2 test and a map of three genes on chromosome 6 are given in Table 4 and Fig. 2.
