Five new duplications of segments in chromosomes 5 and 6 in barley.

Teresa Sodkiewiczš, Wojciech Sodkiewiczš and Arne Hagberg˛.
šInstitute of Plant Genetics, Polish Academy of Sciences, str. Strzeszynska 34, PI-60-479 Poznan, Poland.
˛Department of Plant Breeding Research, The University of Agricultural Sciences, S-268 31 Svalöv, Sweden

The comprehensive research work on barley at Svalöv yielded among many induced mutations also a large collection of translocation lines, described in a series of papers as Hagberg, A. et al. 1978. Part of this collection of T-lines was the basic material for production of duplications of chromosome segments. Most suitable for cytological studies are the translocations involving the chromosomes carrying satellites as cytological markers. Thus, the first duplication in barley was described by Hagberg in 1962 and was selected from a cross: T6-7a x T6-7d. Later on several duplication lines have been selected - in all 52 D-lines from T6-7 x T6-7 - with duplicated chromosome segments covering most of the chromosomes 6 and 7 (Hagberg, A. et al. 1987, and 1991; Hagberg, G. et al. 1983; Hagberg, P. et al. 1974, 1978. This is a good example proving the use of translocations for "chromosome engineering" in barley.

The aim of this work was to create lines with duplicated segments of chromosomes 5 and 6 in barley. Chromosome 5 is very interesting because it carries several genes for disease resistance and also genes for composition of "storage protein" important for the nutritional value of the grains. The genes and the linkage map of chromosome 5 is described in detail by the coordinator of Chromosome 5 J. Jensen, Risø, Denmark (see also Kjaer et al., 1991).

For production of duplications the method suggested by Burnham and Hagberg (1956) was used. The investigations on chromosome morphology in translocated T5-6 lines by Hagberg, G. et al. (1975) was used for selection of 10 lines with break points in the long arms of chromosome 5 and 6. All of these 10 reciprocal translocations (T5L-6L) were produced by ionizing radiation and received from the collection at Svalöv.

The 10 lines were crossed diallelicly. Observations were made in the F1-generation regarding chromosome configuration in metaphase I of meiosis and the pollen fertility in each combination. Thus, a preliminary indication was obtained of the relative location of the break points. In the F2-generation the plants were examined cytologically in root mitosis to find whether it was possible to select plants homozygous for a duplication of the chromosome segments between the break points of the two translocations crossed. This also gives an important information as to the relative break positions for the two translocation lines.

The chromosome morphology of the T5-6v showed the most striking deviation from the normal karyotype of the 10 T-lines in the present investigation, with the long arm of chromosome 5 being considerably longer than normal. Thus, it was possible to select homozygous duplications in the crosses T5-6v x T5-6b, T5-6v x T5-6k and T5-6v x T5-6o. The cross T5-6v x T5-6p gave a homozygous duplication that was sterile and thus could be kept only in heterozygous condition.

In addition it was possible to select plants homozygous for duplication from the F2-generation of the cross T5-6k x T5-6o. This is giving the information regarding the detailed relative location of these translocation break points. Figure 1 is suggesting the relative location of the translocation break points in the long arms of chromosomes 5 and 6 for the translocations involved in this study that have yielded duplications: T5-6b, T5-6k, T5-6o, T5-6p and T5-6v.

The new duplications are named following the nomenclature used in the collection of duplications included in the Nordic Gene Bank (NGB) (Hagberg, A. and P. Hagberg, 1994) : D5-6, 204 - 208 or briefly D204-D208:

D204 is selected from T5-6v x T5-6p
D205 is selected from T5-6v x T5-6o
D206 is selected from T5-6v x T5-6k
D207 is selected from T5-6v x T5-6b
D208 is selected from T5-6k x T5-6o

The influence on the plant morphology of the new duplications presented in this paper is one of the main goals to investigate. The results of this part of the investigation will be published elsewhere. The material of D-lines D204 - 208 is kept at the institute in Poznan, Poland.

References:

Burnham, C. R. and A. Hagberg. 1956. Cytogenetic notes on chromosomal interchanges in barley. Hereditas 42: 467-482.

Hagberg, A. 1962. Production of duplications in barley. Hereditas 48: 243-246.

Hagberg, A. and P. Hagberg. 1991. Coordinator's Report.- Chromosome duplications.- Stock list of lines to be included in the Nordic Gene Bank (NGB). BGN 21: 130-136.

Hagberg, A., L. Lehmann and P. Hagberg. 1978. Segmental interchanges in barley. II. Translocation involving chromosomes 6 and 7. Z. Pflanzenzüchtung 81: 89-110.

Hagberg, A. and G. Hagberg. 1987. Some vigorous and productive duplications in Barley. In: Barley Genetics V. Proc. of the 5th Int. Barley Genet. Symp., Okayama.: pp 423-426.

Hagberg, G., A. Hagberg and T. Sodkiewicz. 1983. Duplication of chromosome segments in barley chromosomes 6 and 7. BGN 13: 32-35.

Hagberg, G., L. Lehmann and P. Hagberg. 1975. Segmental interchanges in barley. I. Translocations involving chromosomes 5 and 6. Hereditas 80: 73-82.

Kjaer, B., V. Haahr and J. Jensen. 1991. Associations between 23 Quantitative traits and 10 Genetic Markers in a Barley Cross. Plant Breed. 106: 261-274.


Fig. 1. Proposed relative positions of translocation breakpoints on the long arm of chromosomes 5 and 6, respectively.