Since the appointment of the coordinators for the ear morphology genes at the 4th International Barley Genetics Symposium at Edinburgh, Scotland, in 1981, not many reports have been written. In this issue of BGN, a short report will be given over one of the Swedish ear morphology gene groups: the 'Calcaroides' mutants (Gustafsson, 1947; Nybom, 1954).

The awn is an elongation of the lemma that characterizes normally in the barley plant. For a long time the dominant 'Hooded' (K) mutants have been known among barley varieties. With this mutant, an additional flower is formed as a branch from the lemma, a situation rarely found in nature. These extra florets are often malformed, but can be fertile and form seeds. This gene 'Hooded' (K) is localized in chromosome 4 (Smith, 1951, Nilan, 1964).

Over the years during the Swedish mutation research 22 different 'Calcaroides' mutants were induced by different mutagens. In contrast to the similar 'Hooded' mutant type, the calcaroides mutants develop characteristic appendages corresponding to transformed lemmas. The awns show a hood-like modification, but without floret primordia and consequently without seed (Bossinger et al., 1992a, 1992b).

Based on phenotypical differences, the calcaroides mutants can be grouped into three categories:

1. the whole spike has the hood-like modification,
2. the upper half of the spike has the hood-like modification, and
3. only the tip of the spike has the hood-like modification.

Intensive studies have been conducted to define their genetic relationships. Today, 4 different cal loci among 20 localized mutants are established; 2 mutants could not yet be localized definitely.

Three of the four gene loci are recessive, the fourth, Cal-c, with 1 allele is dominant. The loci have not yet been localized to a specific chromosome. Analysis of the dominant mutant Cal-cl5 crossed to the dominant 'hood' (K) gene indicated non-allelism. Both F₁ and F₂ generations have been studied.

There seems to be no special phenotypical differences among the loci. The three catogeries as described above are represented for both cal-a and cal-d. The mutants of locus cal-b have two different phenotypes. The dominant Cal-c gene gives the whole spike phenotype.

All the Swedish calcaroides mutants have been incorporated in the Nordic Gene Bank, and the mutant group is open for use by barley research workers and geneticists. Requests for calacaroides mutant seed stocks can be sent to the coordinator for ear morphology genes.

References:

Bossinger, G., W. Rohde, U. Lundqvist, and F. Salamini. 1992a. Genetics of barley development: Mutant phenotypes and molecular aspects. pp. 231-263. In P.R. Shewry (ed.) Barley: Genetics, Biochemistry, Molecular Biology and Biotechnology. CAB International, Wallingford, Oxon, UK.

Bossinger, G., U. Lundqvist, W. Rohde, and F. Salamini. 1992b. Genetics of plant development in barley. p. 989-1022. In L. Munck, K. Kirkegaard, and B. Jensen (eds.) Barley Genetics VI, Vol. II. Proc. Sixth Int. Barley Genet. Symp. Helsingborg 1991, Munnksgaard International Publishers Ltd., Copenhagen.

Gustafsson, Å. 1947. Mutations in agricultural plants. Hereditas 33:1-100.

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.

Nilan, R.A. 1964. The cytology and genetics of barley, 1951-1962. Washington State University Press, Pullman.

Nybom, N. 1954. Mutation types in barley. Acta Agriculturae Scandinavica IV:3:430-456.

Persson, G. 1969. An attempt to find suitable genetic markers for dense ear loci in barley I. Hereditas 62:25-96.

Smith, L. 1951. Cytology and genetics of barley. Botanical Review 17:1-355.

Sogaard, B., and P. von Wettstein-Knowles. 1987. Barley: genes and chromosomes. Carlsberg Research Communications 52:123-196.