II. 17. Duplication of chromosome segments in barley chromosomes 6 and 7.
Gunborg Hagberg, Arne Hagberg and Theresa Sodkiewicz*, Swedish University of Agricultural Sciences, Department of Crop Genetics and Breeding, S-26800 Svalov, Sweden.
* Permanent addbess: Polish Academy of Science, Institute of Genetics, Poznan, Poland.
In genetic studies as mapping chromosomes, studing dose effects, or identifying DNA-structure etc., directed production of duplications might be of considerable interest. The production of duplication of chromosome segments can be achieved by crossing certain reciprocal translocations with suitable relative position of break points. In such cross combinations the plants with duplicated choromosome segments segregate in the F2-generation. One out of nine plants are homozygous for the duplication. Five such duplications are reported earlier (Hagberg 1962 and Hagberg & Hagberg 1978).
Translocations involving the chromosome 6 and 7 are studied in detail by Hagberg et al. (1978) A total number of 38 reciprocal translocations involving 6 and 7 are included in these studies. Thirty-three of these are used in the present investigations mainly based on T-lines induced in Bonus barley. Using available information regarding the relative position of the 33 break points we suggest the chromosome maps shown in Figure 1 for the distribution of the actual break points. This information is composed of results from analyses of mitosis and meiosis of the translocations back crossed to the original barley variety Bonus. The observations are also including pollen fertility studies. Diallelic crosses between the T6-7 translocation lines are studied in the Fl generation regarding chromosome configuration in metaphase I of meiosis and the pollen fertility in each combination. This is giving a preliminary indication of the break point positions in relation to each other.
Following this information those combinations which have similar break point positions but with some indication of dissimilarity that can be recognized cytologically, are studied in the F2 generation. In some of the F2 combinations duplications are obtained, in others they are not. This is depending on the relative break positions (cf. Gopinath and Burnham, 1956) and the result: duplication or not, which means viable gamete or lethal, is a valid additional information about break position included in the maps in Figure 1.
All the possible combinations in the diallelic series are not yet analysed but so far 30 duplication lines are obtained. Eighteen combinations are giving no duplications so far.
The following combinations T6-7 x T6-7 are giving duplications:
break points in short arm of 6 and short arm of 7:
ae x k, ae x l, ae x X ae x w, ae x aa, ae x ab, an x l, an x X, an
x aa, an x ab, l x X, l x aa, l x ab, l x ap, X x ab, X x ap, aa x ab
break points in long arm of 6 and short arm or centromere of 7:
al x e, al x i
break points in short arm of 6 and long arm or centromere of 7:
d x a, d x m, d x v, d x af, d x ag, d x ah, d x ai, p x ak
break points in long arm of 6 and long arm of 7:
b x ad, z x ad, ad x ao
The following 18 combinations have not given any duplications because
of unfavorable relative break point positions:
a x i, a x m, d x f, d x i, d x y, d x ac, d x al, e x i, h x ad, k
x 1, k x X, k x aa, k x an, l x w, m x af, w x X, w x aa, w x ab
Many more combinations are being analysed and the total information from these studies will be published elsewhere. The duplicated segments will be used genetically and used in dose effect studies and investigated biochemically.
References:
Gopinath, D. M. and C. R. Burnham. 1956. A cytogenetic study in maize of deficiency - duplication produced by crossing interchanges involving the same chromosomes. Genetics 41:382-395.
Hagberg, A. 1962. Production of duplications in barley breeding. Hereditas 48:243-246.
Hagberg, A., L. Lehmann and P. Hagberg. 1978. Segmental Interchanges in Barley II. Translocations Involving Chromosomes 6 and 7. Z. Pflanzenzuchtung 81:89-110.
Hagberg, P. and A. Hagberg. 1978. Segmental Interchanges in Barley III. Translocations Involving Chromosomes 6 and 7 Used in Production of Duplications. Z. Pflanzenzuchtung 81:111-117.
