A close linkage between Hs for hairy sheath and sh, a gene for spring growth habit was found in 1951 by Takahashi and Yamamoto, and two years later one more gene, yh for yellow head was added to this small linkage block. The gene arrangement was Hs - sh - yh, the distances of Hs - sh, sh - yh and Hs - yh being 5.1%, 210% and 8.5%, respectively (Takahashi, Hayashi and Yasuda 1957). After nine more years, we determined by means of trisomic analysis that the small linkage block was on chromosome 4 (Takahashi and Hayashi 1966). However, because of the large distance from these three genes to several marker genes known to be on chromosome 4, we could not determine the exact locations of these genes on this chromosome for a long time.

In 1977 Jørgensen found that five genes are arranged on chromosome 4 in the order of f₉, K, M1_g, br₂ and m1-o as shown in Figure 1, and further that m1-o was also linked with yh for yellow head with 28.6% recombination, although he stated that the data were inconclusive regarding the order of the three loci, br₂, m1-o and yh. Nielsen et al. (1983) indicated a close linkage between yh and Bmyl, a gene controllling beta amylase, and suggested from their results that these two loci were located distantly in the chromosome arm not carrying f₉ and K. Encouraged by these findings, we resumed our work to locate the two genes Hs and yh on chromosome 4. Two experiments were performed for this. The first one aimed to establish the linkages of m1-o with Hs and yh, using a cross between a strain with m1-o and Kimugi having Hs and yh together. Table 1 shows the F₂ and F₃ segregation data obtained in this experiment. The result clearly indicated linkages of these three genes. The recombination value between m1-o and yh was 25.53%, a value close to that obtained by Jørgensen (1977), and those of Hs with m1-o and yh were 22.53% and 8.67%, respectively. Thus, the three loci were found to be arranged in the order of m1-o, Hs and yh, as seen in Figure 1.

In the second experiment, interrelationships of Hs and yh with f₉ for chlorina seedling was gl₃ for glossy leaf were studied using a cross involving these four parts of genes. The result of the F₂ segregation in the cross, which is shown in Table 2, clearly indicates that both Hs and yh inherited independently of f₉ and gl₃, and f₉ and gl₃ were very loosely linked with 42.9% recombination. On the other hand, the recombination value between Hs and yh was found to be 10.3% which was almost similar to that found in the first experiment. In Figure 2 is shown a map of chromosome 4 including the genes f₉, gl₃, m1-o, Hs, together with those gene loci indicated by Jørgensen (1977).

References:

Jørgensen, J. Helms. 1977. Location of the ml-o locus on barley chromosome 4. "Induced mutations against plant diseases" IAEA-SM-214/3.

Nielsen, G., Hanna Johansen, Jens Jensen and J. Hejgaard. 1983. Localisation on barley chromosome 4 of genes coding for beta- amylase (Bmy1) and protein Z (Paz1). Barley Genetics Newsletter 13:55-56.

Takahashi, R. and J. Hayashi (Yamamoto). 1951. Physiology and genetics of ear emergency in barley and wheat I. Inheritance and linkage of a gene for "photo-sensitivity" in barley. (in Japanese) Nogaku Kenkyu 40:13-24.

Takahashi, R., J. Hayashi and S. Yasuda. 1957. Four genes in linkage, which are inherited independently of the markers in the known seven linkage groups in barley. (in Japanese) Nogaku Kenkyu 45:49-58.

Takahashi, R. and J. Hayashi. 1966. Inheritance and linkage studies in barley II. Assignment of several new mutant genes to their respective linkage groups by trisomic method of analysis. Ber. Ohara Inst. landw. Biol., Okayama Univ. 13:185-198.