Directed change in seed dormancy period of Moskovka Spring Wheat

V. E. PISAREV and M. D. ZHILKINA

Institute of Non-Chernozem Zone Agriculture, Moscow, U.S.S.R.

The Moskovka spring wheat variety (T. aestivum var. graecum) has been so far standardised for production in 18 regions and autonomous republics of the non-chernozem zone, i.e. in an area stretching from the Baltic to the Ural Mountains.

The Moskovka wheat is high-yielding, smut-resisting,of very high baking quality, and resists lodging. However, together with good qualities, Moskovka has shown an undesirable characteristic - short post-harvest dormancy. Given a rainy and warm autumn the variety will start germinating in the field condition.

In working to change the heredity of Moskova variety the period of grain forming form milky through gold to complete ripeness was used.

In one case grain after-ripening in sheaves was subjected to low temperature(about 0 Centigrade) and, in another case, physiologically ripe seed was heated by immersion in hot water (55 Centigrade) for 30 minutes. In that time the seed swelled, absorbing over 25 per cent water to its weight,and the caryopsis began coming out of dormancy in conditions unusual for a germinating seed. The result in both cases was the same, viz. a shift in the heredity of the processed seed toward a longer post-harvest dormancy. However, on examination, the grain that was subjected to low temperature showed a tendency to developing a pale-pink colouring.

200 of such grains were selected and sown in vegetation pots. Cropping was done individually, plant by plant. Out of the 176 plants 72 yielded the typical white grain of var. graecum, while 102 plants yielded red grain, e. i. they were of var. erythrospermum Germination of grain gave the following results: after twelve days 80 percent of the whitec-oloured grain germinated and only 4 per cent of the red-coloured variety.

Anatomical examination of red-coloured grain revealed that as distinct from the parent Moskovka seed it has a wellpronounced layer of inner integument of golden-yellow colour. This golden layer can be clearly seen between the colourless layer of inner integument and the inner epidermis of the nucellus. The absence of such a pigment layer in grain skin is a distinctive feature of the white-grain Moskovka.

This emergence of a solid pigment layer is seen as the main cause of a longer dormancy period in the red-grain variety. So long as atmosphere oxygen cannot penetrate this layer seed germination is retarded.

To achieve a quantity transformation of white-grain Moskovka into a new, red-grain, variety the technique of "prewinter sowing" was used. This technique envolves sowing seed a few days prior to ground freezing, which for Moscow region falls on the first ten days of December. Seed is required in this case just to start germinating, which process is then stopped by the complete freezing of the ground. This technique is a usual practice at Soviet breeding stations to combat smut (Ustilago tritici Jensen).

Subsequently the red-grain plants thus obtained were used as the foundation stock to establish a new variety, Krasnozernaya (Red-grain). The following table gives the data on the retarded germination of the new variety obtained in the course of five years.


It should be noted that the new variety has retained the high baking quality of the parent variety and in a number of non-chernozem regions has considerably surpassed it in yields.

Morphologically the new variety, Krasnozernaya has no difference.

This transformation of a white-grain variety into a red-grain variety is seen as a process of mutation caused by temperature shock.