II. 19. Two new dwarfism genes on barley chromosome 1*.
* May be chromosome 3 (Editor, T. Tsuchiya)
I. Szarejko and M. Maluszynski (1) Department of Genetics, Silesian University, Katowice, Jagiellonska 28, Poland.
(1) Present address: Joint FAO/IAEA Division, A-1400 Vienna, P.O. Box 100, Austria.
Dwarf mutant 862 PK of spring barley variety Plena was received after mutagenic treatment by N-nitroso-N-methylurea (MNH). It is about 45% shorter in comparison to the parent variety. This mutant produces a very dense rosette with narrow, light-green erect leaves. Also in the flowering stage the whole plant is much more light coloured than a plant of the parent variety. Its maturity is distinctly delayed.
Semidwarf mutant 267 MK was selected from the stock Mg 4170 also after mutagenic treatment by MNH. This mutant is only about 15% shorter than the parent variety. Its phenotype is very characteristic, the thin culms with narrow, short, dark-green, erect leaves (particularly narrow and short flag leaves) have a larger number of internodes with the first internode being shorter in comparison to the parent variety. Also two other characters distinguish this mutant from the Mg 4170 stock. These are the bracteatum mutation in the collar region, consisting of an elongated basal rachis internode, the lack of normal collar and forming the large glume-like bract in its place (Briggs, 1978) and also the mutation in s locus, which is responsible for reduction of the length of rachilla hair.
Crosses of mutants with parent varieties indicated that their dwarf
or semidwarf character is controlled each by a single recessive gene (Table
1). The following symbols for these genes are proposed:
dw-1 - light green dwarf (862 PK)
sdw-b - bracteatum semidwarf (267 MK)
Table. 1. Results from crosses of 862 PK (dw-1) and 267 MK (sdw-b) with their parent varieties.
Investigation on the localization of mutant genes was carried out by crossing with a set of 10 translocation lines (T1-3b, T1-7f, T3-7c, T3-7d, T4-7b, T4-5e, T2-5a, T6-7ae, T6-7i), which were received from Svalof. Linkage was observed in all crosses of dw-1 gene with tester lines involving chromosome 3 which indicates localization on this chromosome. The gene sdw-b was linked only with the chromosome translocation break point T3-7c (Table 2).
Table 2. Results from crosses of dw-1 and sdw-b mutants with translocation lines, showing linkage.
The F2 progeny of crossing the two mutants with each other indicated linkage between dw-1 and sdw-b genes which means that the latter is located on chromosome 3 as well (Table 3). This result was confirmed by independent segregation in F2 progeny of the sdw-b mutant, which has also mutation of rachilla hair, allelic to gene s from chromosome 7, with high, normal long rachilla hair forms.
Both mutants were then crossed with the following markers for more precise localization of investigated genes: uz (semibrachytic) and ari-a (short awns) from chromosome 3 and in addition, for sdw-b mutant with marker r (smooth awns) from chromosome 7. Gene dw-1 as well as sdw-b are located, rather on the long arm of chromosome 3 because they inherit independently from ari-a locus on the short arm of chromosome 3. The dw-1 gene is linked with uz locus from long arm of this chromosome and is located in a distance of 20.5% of crossing-over from it.
The localization of ari-a and uz genes in adequate arms of chromosome 3 was determined unequivocally by use of the telotrisomic stocks (Tsuchiya and Singh, 1982; Singh et al., 1982). The sdw-b gene is located probably distal to dw-1 gene because it segregated independently with uz gene as well as with translocation break points T1-3b and T3-7d from chromosome 3.
References:
Briggs, D.E. 1978. Barley. Ed. Chapman and Hall Ltd., New York.
Immer, F.R. 1930. Genetics 15:81-98.
Singh, R.J., A. Shahla and T. Tsuchiya. 1982. BGN 12:42-44.
Tsuchiya, T. and R.J. Singh. 1982. Theor. Appl. Genet. 61:201-208.
