| Synthesis and Origin of Hexaploid Wheats In 1944, Kihara found that Aegilops squarrosa carries the D genome of the hexaploid wheats. In the same year McFadden and Sears drew the similar conclusion from the synthesis of hexaploid amphidiploids of the hybrid between T. dicoccoides spontaneo-villosum and Ae. squarrosa by the use of the colchicine method. While, in 1946, Kihara and Lilienfeld produced also the amphidiploid of T. dicoccoides spontaneo-nigrum x Ae. squarrosa through the union of unreduced gametes. In these amphidiploids the seed fertility were fairly good. And the F1 hybrids from the cross between the amphidiploid and hexaploid wheat (Dinkel wheat) had good fertility. In 1948, Kihara and his collaborators obtained the amphidiploids of various combinations, among which two combinations are worth while to describe; they are hybrids between two varieties of T. persicum and Ae. squarrosa No. 2. These two hybrids produced abundant normal pollen grains (up to 85%) and were fairly fertile. The tetraploid T. persicum is a species which has very distinct vulgare characters. As to morphology, the F1, T. persicum x Aegilops squarrosa, was identical with a hexaploid species, which was given to us as "T. persicum rubiginosum" by a Russian colleague. However, the ear in the F1 is fragile and the type of disarticulation is that of Ae. squarrosa, viz. barreltype. Then, where did our cultivated 6x wheats originate? If the progenitors of cultivated 6x wheats were wild plants, the two parent species must have been wild. The place where they grew together must be the place of origin. From the knowledge available to us at present, Armenia and the western part of Iran are the region where the hybridization had a chance to take place. However, there is no descisive evidence that wild hexaploid wheats such as our amphidiploids grew there. If the cultivated 4x wheats, as T. dicoccum, T. durum, T. persicum, etc. contributed one of the parents, the hexaploid probably arose under cultivation. Then the place of origin could have been the whole area where Ae. squarrosa grew wild. The Asiatic hexaploid species, such as T. Macha and others, which were recently described, may have originated in this way. The geographical distribution of these species is restricted to the regions where Ae. squarrosa grows wild most probably in Transcaucasia. Collections of the Kyoto University Scientific Expedition to the Karakoram and Hindukush, 1955 In the summer of 1955, the Kyoto University, Kyoto, Japan, organized the Scientific Expedition to the Karakoram and Hindukush. Kihara was the leader and eleven specialists in their respective fields, botany, anthropology and geology, two cameramen and a reporter joined the party. Aegilops squarrosa, one of the ancestors of our common wheat, was found around Quetta, Pakistan, in the beginning of the expedition by Kihara and Yamashita, which is probably the south-easternmost limit of the distribution of this genus. This species was found mostly in association with cultivated wheat everywhere, while in the northern district of Afghanistan, a large natural population of this species was found. The tour from Quetta,through Afghanistan, to Azerbaijan, Iran, was made from late May to early August. Along a distance of over 5,000 km Aegilops squarrosa var. typica was seen widely distributed, and its specimens were collected in over 100 different localities. Aegilops squarrosa var. strangulata was, however, found only in a restricted area in Gorgan, Iran. Number of strains and habitats collected of Triticum and Aegilops are given in the Tabs. 1 and 2. (A change was made in the arrangement of materials from that given in the tables reported in WIS No. 2.) |
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