In Sweden, since many years, the interest for ear morphology genes has concentrated on the intermedium (int) genes and the six-row or hexastichon (hex-v) gene. These mutants affect the development of the lateral florets, with genic interactions leading to synergistic enhancements depending on the specific constellation of alleles and loci. In all, 12 such different gene loci have been studied in more detail. Four of them have been localized to four of the seven barley chromosomes.
The Japanese researchers at Okayama University (Fukuyama, Takahashi, and Hayashi) has been studying several induced so-called "six-row" mutants concerning genetics and linkage. They assigned the gene symbols v1 - v5. In 1987, Professor T. Konishi provided me with seeds of the different sixrow lines. They were crossed with the Swedish int and hex genes. Two alleles of int-a, -c, -d, and -e and one allele of int-f and hex-v were used for crossing (Table 1).
Table 1 can be summarized as follows: both v1 lines are allelic to hex-v, v3 to int-a, v4 to int-e, and v5 to int-c; v2 is not allelic to any of the 5 most common int loci or the hex-v locus. More studies will be conducted with the other six int loci. It is known that the Int-d locus shows a tendency to be more or less dominant to the two-row normal state. Unpublished data show that Int-d is linked to locus hex-v, thus it is located to chromosome 2.
All combinations listed in Table 1 were studied also in the F2 generation, where it was possible to verify very clearly the F1 statements. The exact segregation ratios will be published in a later issue of BGN.
References:
Fukuyama, T., J. Hayashi, and R. Takahashi. 1975. Genetic and linkage studies of the five types of induced "six-row" mutants. BGN 5:12-13.
Fukuyama, T., R. Takahashi, and J. Hayashi. 1982. Genetic studies on the induced six-row mutants in barley. Ber. Ohara Inst. landwirtsch. Biol. Okayama Univ. 18:99-113.
Gustafsson, A., and U. Lundqvist. 1980. Hexastichon and intermedium mutants in barley. Hereditas 92:229-236.
Lundqvist, U, and U. Lundqvist. 1988. Induced intermedium mutants in barley: origin, morpholoqy and inheritance. Hereditas 108:13-26.