| (16) |
In 1913, Schulz has divided the wheat
species into three groups on the basis of morphological characters.
His Einkorn or monococcum group comprises the wild growing
Triticum aegilopoides and the cultivated Triticum monococcum.
|
| (17) |
In the Emmer group we find the wild growing
Triticum dicoccoides and several cultivated types, for instance,
Triticum dicoccum, durum, turgidum and polonicum. |
| (18) |
In the Dinkel or vulgare group we
find the cultivated husked Triticum Spelta and naked types,
Triticum compactum and vulgare. |
| (19) |
Let us arrange those wheats in a table.
In this table the Dinkel group is the only one without a wild type.
This classification into three groups is in full agreement with Sakamura's
arrangement, based upon the chromosome numbers, 7, 14 and 21. |
| (20) |
To-day the most widely cultivated wheat
is the bread wheat whose botanical name is Triticum vulgare.
Next to it, the macaroni wheat of the Emmer group, Triticum durum,
is grown extensively, |
| (21) |
while Einkorn is scarcely cultivated. |
| (21') |
But in ancient times Einkorn represented
the wheat crop in Egypt and elsewhere. Also Emmer was in use of old
times. It is supposed that the origin of bread wheat is the most recent.
|
| (22) |
In the Einkorn and Emmer groups wild types
are found which are considered to be the ancestors of the cultivated
forms, while the wild type of bread wheat was not yet discovered.
What kind of wild growing wheat was the bread wheat's precursor? Did
it already die out or was it not yet found? To solve this question,
we must consider the karyological situation. |
| (23) |
The chromosome numbers of the three wheat
groups show a polyploid relationship with 7 as basic number. Accordingly,
Einkorn wheats are diploid, Emmer wheats tetraploid and Dinkel or
vulgare wheats hexaploid.
If the polyploid species were derived from the doubling of 7 chromosomesets,
they would be autopolyploids. However, Emmer could not be obtained
by experimental doubling of Einkorn chromosomes. Emmer, therefore,
cannot be autotetraploid. Similarly, Dinkel can not be autohexaploid.
If a tetraploid has 2 different kinds of chromosome-sets, for instance,
A and B, it is, after Kihara's terminology, an allotetraploid. Such
plant forms must be derived from hybridization between 2 different
species. In order to decide whether a similar relationship exists
between Emmer and Dinkel, |
| (24) |
Kihara began, in 1918 in Sapporo, to study
pentaploid hybrids between two groups. (25) |
| (26) |
In 1927 this study was transferred to Kyoto
University. |