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Wheat Information
Service
Number 73: 1-4 (1991)
Chracterization
of a disomic wheat-Ae. variabilis addition line resistant to
powdery mildew fungus
P. Spetsov and I. Iliev
Institute for Wheat and Sunflower, General Toshevo, Bulgaria
A disomic addition line (2n=44) has been obtained by crossing T.
aestivum cv. Roussalka with Aegilops variabilis (UUSS,
2n=28)*. It manifested high resistance to powdery mildew in seedling
and adult plant stage, both in greenhouse and field conditions. The
alien pair of chromosomes slightly suppressed the growth of plants in
tillering phase, and necrotic symptom was visually detected, mainly,
in glasshouse.
The added chromosome, not carrying a satellite, did not cause
negative effects on the sporogenesis in plants. As a result, balanced
22-chromosome gametes were formed.
The present paper deals with the characteristics of the newly
obtained disomic addition line.
Materials and Methods
The parents used were Aegilops variabilis (2n=28), collection
number 13.133 (awned type), and T. aestivum var.
erythrospermum, cultivar Roussalka, IWS-Gen. Toshevo's winter
type variety. The cross-combination between the parents was made in
1984, and F1 seeds were irradiated using
60Co,
dose of 10 kR.
BC1 plants with wheat were grown on a infection field and
the resistant progenies were obtained each year by self-pollinating
the derivates. A single plant, having the cytoplasm of common wheat
and isolated in 1988 with high resistance to powdery mildew, was the
ancestor of the disomic addition line (DAL in abbreviation).
First two leaves seedlings grown in a greenhouse were inoculated with
five physiological races of Blumeria graminis (DC) Speer f.
sp. tritici (Erysiphe graminis f. sp.
tritici Em. Marchal) i.e., 59, 59a, 84, 111 and 112
(Iliev 1989). Infection was rated using five progressive grades from
0 to 4: 0, no symptom; 1-2, small areas of mycelium with little or no
conidial formation to scant sporulation; 3, reduced sporulation; 4,
heavy sporulation.
Field assessments were made on plants, grown in the infection plot
that was artificially inoculated by pathogen populations, including
the races of powdery mildew fungus from the glasshouse experiment.
The estimates for adult plant resistance to powdery mildew comprised
leaves and spikes separately, and grouped as follows: VR, high
resistant, no symptom to scant sporulation on the lowest leaves; R,
resistant, mycelium with little conidial formation; and S,
susceptible to the pathogen.
Somatic chromosomes were counted in root-tip cells and meiotic phases
were analysed from PMCs, using the acetocarmine smear method. Some
field observations on plant growth and spike open fertility of the
lines were recorded.
* Genome symbol according to
Kimber and Tsunewaki (1988).
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