Since the appointment of a coordinator for the earliness genes at the 4th International Barley Genetics Symposium at Edinburgh, Scotland, in 1981, no report has been written.
In this issue of BGN a short report will be given over the early maturity mutants, which are included in the large Swedish mutation collection. These mutants were designated as praematurum with the symhol mat (Gustafsson et al., 1969). Subsequently, this name and its symbol were used for the Swedish early maturity mutants.
Over the years about 1100 different induced early mutants have been isolated and examined. Various Swedish high-yielding varieties have been used for the induction of these mutants (Gustafsson et al., 1960). The mutants have been grouped into three categories according to their heading time, with a variation between one and ten days:
The distribution of the mutants localized to the 9 mat loci is as follows:
| Locus mat | -a | -b | -c | -d | -e | -f | -g | -h | -i | Total |
| Frequency | 62 | 49 | 31 | 2 | 9 | 7 | 4 | 2 | 6 | 172 |
Special characteristic differences among some of the loci deserve to be mentioned. The mat-a locus has a special property, narnely a profound change of photo- and thermo-period reaction. It is denoted as "photoperiod insensitive" (or short-day tolerant, heading and forrning ample amounts of seed under short-day conditions (Gustafsson and Lundqvist, 1976; Gustafsson et al., 1982). Mutants of the loci mat-c and mat-e are characterized by delayed heading, and thus less pronounced short-day neutrality. The mutants of all the other 6 loci are long-day adapted like their parent varieties.
Concerning relationship to earlier known earliness genes, allelism tests have been carried out only in a limited scale. It could be established that eak located on chromosome 5 (Jensen, 1981) is allelic to the Swedish mat-a gene (Favret and Frecha, 1967; Takahashi and Yasuda, 1971; Yasuda, 1977; Sogaard and von Wettstein-Knowles, 1987).
All the 1100 Swedish mutants are incorporated in the Nordic Gene Bank and the collection is open for use to every barley research worker and breeder. Requests of early mutant seed stocks can be sent to the coordinator for earliness genes.
References:
Favret, E. A., and J. H. Frecha. 1967. Allelism test of genes for earliness. Barley Newsl. 10:121.
Gustafsson, Å., and U. Lundqvist. 1976. Controlled environment and short-day tolerance in barley mutants. In: Induced Mutations in Cross-breeding. Proceedings of an Advisory Group. Vienna, 1975, IAEA, Vienna, P. 45-53.
Gustafsson, Å., A. Hagberg, and U. Lundqvist. 1960. The induction of early mutants in Bonus barley. Hereditas 46:675-699.
Gustafsson, Å., A. Hagberg, U. Lundqvist, and G. Persson. 1969. A proposed system of symbols for the collection of barley mutants at Svalöv. Hereditas 62:409-414.
Gustafsson, Å., I. Dormling, and U. Lundqvist. 1982. Gene, genotype and barley climatology. Biol. Zentralblatt 101:763-782.
Jensen, J. 1981. Coordinator's report: Chromosome 5. BGN 11:87-88.
Lundqvist, U. 1991. Swedish mutation research in barley with plant breeding aspects. A historical review. In: Plant Mutation Breeding for Crop Improvement. Proc. Int. Symp. Vienna, 1990, IAEA. Vienna. p, 135-148.
Søgaard, B., and P. von Wettstein-Knowles. 1987. Barley: genes and chromosomes. Carlsberg Res. Commun. 52:123-196.
Takahashi, R., and S. Yasuda. 1971. Genetics of earliness and growth habit in barley. Barley Genetics II, Proc. Second Int. Barley Genetics Symp., Pullman, 1969. (Ed. R. A. Nilan). Washington State University Press, Pullman, p. 388-408.
Yasuda, S. 1977. Linkage of the barley earliness gene eak and its pleiotropic effects under different growth conditions. Ber. d. Ohara Inst. f. landw. Biol., Okayama Univ. 17: 15-28.