II.32 Linkage analysis of barley mutants.
R. Takahashi, J. Hayashi, T. Konishi and I. Moriya. The Ohara Institute for Agricultural Biology, Okayama University, Kurashiki, Japan.
1. Linkages of five dwarf mutants.
a) Node-less or single elongated-internode dwarf (R101).
The origin, characteristics and linkage of the gene (sid, formerly nls) for the node-less or a single internode dwarf in a mutant strain R101 was already reported in BGN No. 3, p. 65. In order to locate the gene on chromosome 4, a three point test was made using a cross between R101 and K - gl3 - B1 tester. The F2 data obtained and a map of the three genes are given below:
The gene (sid) was shown to be independent of n, v, uz, b, o and s.
b) Semi-dwarf mutant with slightly winding peduncles (G754).
The mutant, G754, was induced from a cultivar, Kogen-mugi, by irradiation with 60Co. The seed was received from Dr. M. Toda, Nagano Agric. Experiment Station. It is ca. 15 cm shorter than the original variety, and has characteristic winding at the upper part of peduncles. Its head is compact (due to l), awn short (lk2) and kernel naked (n). Only one cross with a cultivar, Natsudaikon-mugi, was sufficient to locate this mutant gene (wnd). As seen in the following table and a map of four genes, the gene for the semi-dwarf is located on chromosome 1, although the observed number of the dwarfs in F2 was slightly more than the expected number from 3:1 segregation ratio.
c) Curly dwarf with compact head (OUM 120)*
*OUM is the Okayama University Mutants accession number. They are all those induced by EMS treatment by T. Konishi at the Ohara Institute for Agricultural Biology, Okayama University, Kurashiki, Japan.
This mutant was induced by EMS treatment of a uzu type cultivar, Akashinriki, by T. Konishi. Most of the leaves are short, more or less twisted and often longitudinally creased. Stem internodes are more or less curved alternately at each node. Stems are short (ca. 40 cm), head is compact, awn is short, and kernels are short and round. Two crosses were used for a linkage study: Cross A = OUM 120 x Col-orange, Cross B = OUM 120 x Nigrinudum. The F2 linkage data, shown below, indicate the gene (cud) is in chromosome 7. Also, the gene (cud) was known to be independently inherited of the following markers: n, v, uz, K, B, and o, on chromosome 1, 2, 3, 4, 5, and 6, respectively.
d) Lazy-like dwarf (OUM 5).
This mutant was also induced by EMS treatment of Akashinriki. This shows so-called "lazy" or extremely procumbent growth before its boot stage. Late maturity and high responsiveness to GA3 are the characters to be noted also. Although its stems and leaves are generally short, they are markedly elongated by GA3 application. These characters are conditioned simultaneously by a single recessive gene (lzd, formerly designated tentatively dw4 by Konishi 1972) on chromosome 3. Locating the gene was done using a cross, OUM 5 x Russian 82. The F2 and F3 linkage data and a linkage map are given below:
e) Slender type dwarf (OUM148).
This EMS-induced mutant may be called slender type dwarf, as it has short and slender stems. Its spikes are lax with slender caryopses. The linkage was studied using a cross, OUM 148 x Russian 83. As shown in the following table and map, the gene (sld, formerly dw1 by Konishi 1972) is located on chromosome 3, rather close to uz.
2. Chlorina Mutants.
a) Chlorina mutant, T. 95.
A chlorina mutant T. 95, was received from the late R. W. Woodward, Utah Agricultural Experiment Station, Logan, Utah. This mutant always develops conspicuous chlorina leaves throughout all stages independently of light or temperature, although plants of this mutant type are often killed by low temperature during winter months. Five crosses were used to detect linkage of the gene for chlorina character in T. 95, but only the F2 data suggesting linkage, which were obtained in three crosses, are shown in the following table. As is apparent in the table, the gene tentatively named (f10) is located close to lg4, and 9.22% and 17% apart from K and gl3, respectively. A map of genes on chromosome 4 was set up from these and some other sources of data, and is shown in the following:
Since two chlorina genes, f9 and lg4, are also known to be on chromosome 4, located rather close to K (Takahashi et al. 1972, Immer and Henderson 1943 and Robertson et al. 1947), a test for allelism was made between (f1O) and these two genes. Ten plants each of the F1's of the crosses with f9 (Kmut 174) and lg4 which was received from Dr. Tsuchiya, Colorado State Univ. were used. The results have indicated that (f1O) is different from f9 and lg4. It is mentioned here that lg4 is much lighter in seedling color than f9 and (f1O), and definitely distinguished from the latter (as seen in the above table).
b) Allelism test between two chlorina genes, f2 and lg5 on chromosome 3.
In 1957 we received from Dr. T. E. Haus, Colorado State University, seed of lg5 (C. I. 6151, USDA 152). Afterwards, Dr. Tsuchiya provided us the seed of f2 (BGS 0117) as a marker stock of chromosome 3, of which he described the linkage relation in BGN No. 1, pp. 64-65. Because of the similarity in appearance, an allelic test was made using F1 and F2 plants derived from a cross between lg5 and f2. The result clearly indicated that these two are the same gene. As shown by Highkin and his coworker (1950, 1962), these two stocks proved to be entirely devoid of chlorophyll b.
