| (60) |
In disarticulation of ear, Aegilops
caudata is of umbrella type with ears breaking off only at the
base, |
| (61) |
while Aegilops cylindrica is of
barrel type with ears breaking to pieces with the upper portion of
the rachis adherent to the spikelet. |
| (62) |
If we assume that barrel is dominant over
umbrella, |
| (63) |
the DD-ancestor of Aegilops cylindrica
should be of barrel type. |
| (64) |
On the other hand, Emmer has the wedge
type of disarticulation, which means that the lower portion of each
internode adheres to the spikelet, while Dinkel is of barrel type.
If we assume that barrel is dominant over wedge, |
| (65) |
the DD-ancestor of bread wheat should also
be of barrel type. |
| (66) |
With regard to the character of empty glumes,
Emmer has a narrow glume with a conspicuous apical tooth, while the
glume in Dinkel especially in Triticum Spelta is broad with
truncate apex. Therefore, the hypothetical DD-plant must have a glume
like Dinkel. |
| (67) |
This brings us to disarticulation of ear......,
shape of empty glume,......, chromosome number......of the DD-plant.
|
| (68) |
Let us try to identify it. |
| (69) |
The only diploid species which answers
the morphological requirements of the hypothetical DD-ancestor is
Aegilops squarrosa. |
| (70) |
Namely, disarticulation of ear......barrel
type. |
| (71) |
Shape of empty glume......truncate. |
| (72) |
Chromosome number .......14.
But, has Aegilops squarrosa the D-genome? To prove this was
more difiicult than it would seem, since all attempts to cross Aegilops
squarrosa with cylindrica and bread wheat failed. Finally
this proof has been beyond doubt established. |
| (73) |
Thus, an ancestor of bread wheat was found.
Now, we will see how bread wheat could have been synthesized from
Aegilops squarrosa and a tetraploid wheat. |
| (74) |
A hybrid between wild Emmer, Triticum
dicoccoides, and Aegilops squarrosa has 21 somatic chromosomes
and is sterile. |
| (75) |
As a result of meiosis in such a hybrid
usually sterile gametes are formed. But sometimes gametes with the
somatic chromosome number of 21 are formed. From the union of two
such gametes 42-chromosome hexaploid plants were synthesized. |
| (76) |
Morphology of the synthesized wheat on
the left side is very similar to that to Triticum Spelta. A
hybrid between the artificial product and Triticum Spelta showed
normal chromosome pairing at first metaphase. This proved definitely
that the synthesized plants belong to the collective species vulgare. |
| (77) |
By similar means, several hexaploid wheats
were synthesized. Of all of them, one, synthesized from cultivated
Triticum persicum and Aegilops squarrosa, resembles
most our bread wheat. |