**Cytological investigation of winter two-rowed barley cv. Castor, the
first Bulgarian cultivar of high cold resistance**

J. Stoinova^1^, K. Tsvetkov^2^ and S. Tsvetkov^2^

^1^D. Kostov Institute of Genetics, Bulgarian Academy of Sciences, 1113
Sofia

^2^Dobrudja Agricultural Institute, 9520 General Toshevo

**Absract**

The cytological investigation comprises diakinesis, metaphase I,
anaphase I and telophase II. In diakinesis 14.3% of the cells examined
contain 6 closed bivalents and 1 open bivalent. The latter forms a rod
bivalent in metaphase I. In anaphase there are laggard chromosomes in
5.8% of the cells while 7.0% of the cells contain anaphase bridges.
There are not disturbances in telophase II and the meiotic stability is
a prerequisite for high yield of about 800-850 kg/dca (a field trial).

**Key words**: barley, meiosis, open bivalent, anaphase bridge

Two-rowed barley cultivars occupying arable area in Bulgaria, belong to
the winter-spring cereals which are highly productive and of low cold
resistance. In severe winters with poor snow most barley plants die
resulting in large economical loses. In 1993-2003 Prof. S. Tsvetkov
working at the Dobrudja Agricultural Institute released the first
Bulgarian two-rowed barley cultivar Castor possessing exclusively high
cold resistance along with good productivity. The cytological analysis
of the cultivar and the relationship between meiosis and grain yield
were the subject of this study.

The standard aceto-carmine method was used to examine 35 cells for
diakinesis, 145 cells for metaphase I, 170 cells for anaphase I and 200
tetrads for telophase II. Table 1 provides data indicating that in
diakinesis over 85% of the cells contain 7 closed bivalents while 14.3%
of the cells contain one open bivalent, associated with nucleolus. The
phenomenon has been observed in other investigations (Stoinova, 1994;
Stoinova and Tsvetkov, 2004).

The data concerning metaphase I indicate that almost 80% of the cells
contain 7 closed bivalents/cell. The open bivalent in diakinesis forms a
rod bivalent at metaphase I in 17.3% of the cells (Fig. 1a). Five closed
and 2 rod bivalents were scored in four cells, while in one cell four
closed and 3 rod bivalents were scored. Neither univalents nor
multivalent associations were observed.

There were laggard chromosomes and bridges in anaphase cells (Fig. 1b
and 1c). The laggards form genetically inactive micronuclei at telophase
II only in single tetrads. At that phase cell partitions are properly
situated, except for one preparation where 2 triads were observed. The
presence of anaphase bridges was more interesting as their emergence is
associated with paracentric inversion in heterozygous state. Synapsis
between inverted and non-inverted chromosomes is accompanied by loop
formation in pachytene. In the case of crossing over in that inversion
loop anaphase bridges and fragments may be formed.

Anaphase bridges may result from gamma irradiation with 5 to 50 kR of
barley chromosomes, the bridge frequency increasing with irradiation
dose (Chandra and Makde, 1982). The barley ring chromosomes may also
lead to anaphase bridges in about 10% of the assayed cells (Singh and
Tsuchiya, 1981). Bridge configurations have been found in tumor cells as
well (Hoffelder, et al., 2004).

Disturbances at anaphase I in plant cells depend on environmental
temperature. In two bean cultivars the disturbances have been found to
vary from 34.5% to 58% at 22-26° C and decrease to 22-31% at 15-19° C
(Konstantinov, 1971). Sakata et al. (2000) have shown that in barley the
early stage until meiosis of PMCs is the most sensitive to high
temperature stress. The stress may cause emergence of abnormal and
irregularly shaped pollen grains at the heading stage. In cultivar
Castor the disturbances at anaphase I are most probably due to high
temperature during spike fixation, since chromosome reconstruction of
inversion type proceed with very low frequency under normal environment,
in the absence of chemical or physical mutagens and no ring chromosomes
have been observed. The lack of disturbances at final meiosis phase is a
prerequisite for normal pollen production and pollination as well as for
high grain yield (up to 800-850 kg/dca a field trial).

The data from this cytological investigation suggest that meiosis in
cultivar Castor proceeds without formation of univalents and multivalent
associations at metaphase I with low percentage of laggard chromosomes
and anaphase bridges while micronuclei may be present only in a single
tetrads.

Table 1. Analysis of meiosis in barley Castor

<table style="width:100%;">
<colgroup>
<col style="width: 5%" />
<col style="width: 7%" />
<col style="width: 5%" />
<col style="width: 7%" />
<col style="width: 7%" />
<col style="width: 7%" />
<col style="width: 5%" />
<col style="width: 7%" />
<col style="width: 7%" />
<col style="width: 7%" />
<col style="width: 7%" />
<col style="width: 7%" />
<col style="width: 7%" />
<col style="width: 5%" />
</colgroup>
<tbody>
<tr class="odd">
<td colspan="4">Diakinesis</td>
<td colspan="4">Metaphase I</td>
<td colspan="6">Anaphase I</td>
</tr>
<tr class="even">
<td colspan="2"><p>Cells with</p>
<p>7closed bivalents</p></td>
<td colspan="2"><p>Cells with</p>
<p>6 closed +</p>
<p>1 open bivalent</p></td>
<td colspan="2"><p>Cells with</p>
<p>7 closed bivalents</p></td>
<td colspan="2"><p>Cells with</p>
<p>6 closed + 1 rod bivalent</p></td>
<td colspan="2">Normal cells</td>
<td colspan="2"><p>Cells with</p>
<p>laggard chromo-</p>
<p>somes</p></td>
<td colspan="2"><p>Cells with bridge configur-</p>
<p>ation</p></td>
</tr>
<tr class="odd">
<td>n</td>
<td>%</td>
<td>n</td>
<td>%</td>
<td>n</td>
<td>%</td>
<td>n</td>
<td>%</td>
<td>n</td>
<td>%</td>
<td>n</td>
<td>%</td>
<td>n</td>
<td>%</td>
</tr>
<tr class="even">
<td>30</td>
<td>85.7</td>
<td>5</td>
<td>14.3</td>
<td>119</td>
<td>82.7</td>
<td>26</td>
<td>17.3</td>
<td>148</td>
<td>87.2</td>
<td>10</td>
<td>5.8</td>
<td>12</td>
<td>7.0</td>
</tr>
</tbody>
</table>

![](media/image1.jpeg){width="4.444444444444445in"
height="4.177777777777778in"}

Fig. 1a. Metaphase I with rod bivalent

![](media/image2.jpeg){width="4.364583333333333in"
height="3.5729166666666665in"}

Fig.1b. Anaphase I with laggard chromosome

![](media/image3.jpeg){width="3.9770833333333333in"
height="4.347222222222222in"}

Fig.1c. Anaphase I with bridge configuration

**References:**

Chandra, A. and Makde, K. H. 1982. The rupture of radiation including
bridges in barley. BGN 12: 11-13.

Hoffelder, D. R., Luo, L., Burke, N .A., Watkins, S. C., Gollin, S. M.
and Sanders, W. S. 2004. Resolution of anaphase bridges in cancer cells.
Chromosoma 112:389-397.

Konstantinov, A. V. 1971. Meiosis. Minsk, 18-19.

Sakata, T., Takahashi, H., Nishiyama, I. and Higashitani, A. 2000.
Effects of high temperature on the development of pollen mother cells
and microspores in barley, *Hordeum vulgare* L. J of Plant Res.
113:395-402.

Singh, R. J. and Tsuchiya. 1981. Ring chromosomes in barley (*Hordeum
vulgare* L.). Chromosoma 82:133-141.

Stoinova, J. 1994. Characteristics of meiosis in some winter barley
varieties. Cytologia 59:423-426.

Stoinova J. and Tsvetkov, S. 2004. Meiosis and productivity
relationships in Bulgarian winter barley lines. BGN 34:5-9.