A Database for Triticeae and Avena
II. 7. Microspore derived chromosome number and structural variants
of barley (Hordeum vulgare L.).
Wolfgang Friedt and Bärbel Foroughi-Wehr, Department of Plant Genetics,
Gesellschaft für Strahlen- und Umweltforschung mbH München, D-8059
In previous investigations it was demonstrated that a great variation
of chromosome number may occur in somatic cells of microspore derived plants
in various species (D'Amato 1977). In root tips of regenerated barley plants
haploid, diploid, tetraploid as well as aneuploid cells were observed (Mix
et al. 1978). The present study deals with the nature of chromosomal variation
in the germ cells (PMCs) of microspore derived barley plants.
Diploid and tetraploid barley stocks were used as donors for anther
culture. As a diploid donor the cultivar 'Dissa' was grown. This variety
proved to respond best to the culture methods applied. As tetraploid donors
the cv. 'Haisa II' and a selected strain out of crosses of 'Haisa II' to
other tetraploid stocks were used. This material was originally chosen
in order to detect obscure chromosome mutations in the tetraploids. The
culture methods and staining techniques applied were described earlier
(Foroughi-Wehr et al. 1976; Friedt 1979).
A. Anther culture of diploid donor plants
Anther derived progenies show large variation in fertility. Not only
in the first (A1) but also in successive generations, completely sterile
A detailed cytogenetic study of a random sample of 280 out of 2000 plants
obtained through anther culture of barley cv. 'Dissa' revealed that the
chromosome numbers in germ cells do not vary as much as in somatic cells.
Only haploid, diploid and tetraploid but no aneuploid complements have
been found in PMCs so far and their frequencies have been estimated as
approximately 20%, 70% and 10%, respectively (Table l).
Table l. Progeny of anther culture of barley cv.
'Dissa' in the Al-generation*
The diploid progenies usually show complete seed set, whereas the tetraploid
individuals exhibit a large variation in fertility ranging from 0 to almost
100%. The haploid progenies are usually sterile. However, some spikes were
found with one single seed. This can be explained by premeiotic fusion
or endoreduplication of haploid cells and/or by meiotic C-metaphase formation
leading to di-haploid gametes (Fig. 1A).
Figure 1. PMCs from haploid (A), diploid (B, C,
D) and tetraploid (E, F) individuals.
A. PMC with 14 univalents produced by premeiotic fusion or endoreduplication
as an explanation for occurrence of single seeds in spikes of haploid individuals.
B. PMC in MI with seven bivalent-rings (7 II).
C. Heterozygous reciprocal translocation obtained through anther culture
of tetraploid barley. PMC in MI with five bivalent-rings (5 II) and a ring
of four chromosomes (1 IV).
D. Two PMCs in AI with normal chromosome-separation (left) and chromatid
bridge-formation (right), respectively.
E. PMC in MI with 6 II and 4 IV.
F. PMC in AI with irregular separation of chromosomes (15:13) explaining
the production of a trisomic plant via anther culture of tetraploid barley.
In other cases plants with more than 20 fully sterile ears spontaneously
produced one completely fertile spike. In addition, one plant with diploid
and tetraploid ears was also found. This may be explained with the presence
of diploid and tetraploid cells in the somatic tissue of the Plants. A
number of regenerated individuals showed extreme variation in phenotypic
characters such as chlorophyll defects, stunted growth and leaf irregularities.
All of the diploid plants studied except one were cytologically normal.
The latter proved to be heterozygous for a reciprocal translocation.
B. Anther culture of tetraploid donor plants
Out of 23000 cultured anthers isolated from tetraploid stocks of barley
32 white and 19 green plants were regenerated. Most of the latter were
phenotypically similar to normal diploid barley. However, in meiotic first
anaphase of two diploid individuals chromatid-bridge formation was observed
(Fig. 1D). One of the two plants showed in addition varying chromosome
numbers in the PMCs. Another plant was trisomic (2n=2x+1=15) for chromosome
6 or 7 (nucleolar chromosomes; Friedt et al. 1977), three were heterozygous
for reciprocal translocations (Fig. 1C), four individuals were tetraploid
(2n=4x=28; Fig. E, F), and the other plants showed normal meiotic chromosome
behavior (Fig. 1B). The progenies of successive generations will be investigated
for variation in quantitative characters. Additionally, backcrosses to
the original diploid barley cv. 'Haisa II' (already carried out) will reveal
further possible hidden homozygous chromosome mutations.
The present study shows that only about 20% of anther derived barley
plants are haploid. However, together with the approximately 70% diploids
which are produced via spontaneous diploidization 90% of the anther progeny
can be used immediately in barley breeding programs. The remaining 10%
which are obviously exclusively tetraploids can be useful in breeding programs
for tetraploid barley as well as for genetic studies.
Because of the occurrence of chromosome mutations in diploid progenies
derived from anther culture of tetraploid plants it can be assumed that
also in the spontaneous diploid progenies from anther culture of diploid
donor plants hidden chromosome-as well as gene-mutations may be present.
Such obscure mutations would be disadvantageous in breeding programs. To
find out the nature and rate of such mutations, the anther progeny have
been backcrossed to their original diploid donor variety. The first backcross
generation is going to be investigated cytogenetically.
We wish to thank Dr. Gisela Gosch-Wackerle for very helpful advice.
D'Amato, F. 1977. Cytogenetics of differentiation in tissue and cell
cultures. In J. Reinert and Y.P.S. Bajaj (Ed.), Applied and fundamental
aspects of plant cells, tissue and organ culture, 343-356. Springer-Verlag,
Foroughi-Wehr, B., G. Mix, H. Gaul and H. M. Wilson. 1976. Plant production
from cultured anthers of Hordeum vulgare L. Z. Pflanzenzüchtg.
Friedt, W. 1979. Untersuchungen an autotetraploiden Gersten unter besonderer
Berücksichtigung der Diploidisierung II. Z. Pflanzenzüchtg. 82:311-339.
Friedt, W., B. Foroughi-Wehr, G. Mix and H. M. Wilson. 1977. Anther
culture of autotetraploid Hordeum vulgare and the production of
trisomic individuals. BGN 7:29-33.
Mix, G., H. M. Wilson and B. Foroughi-Wehr. 1978. The cytological status
of plants of Hordeum vulgare L. regenerated from microspore callus.
Z. Pflanzenzüchtg. 80:89-99.
BGN 10 toc
BGN Main Index