| Their dispersion in the remote ages would have taken place slowly from man to man
through communications between remote villages. The dispersion was so slow that it was
not until the 7th century that the first samples of wheat grains reached Japan from China.
It may be presumed that there were already cultivations of wheats in the Tang era in
China. Among many improved modern cultivated varieties of wheat, "Norin 10", a Japanese dwarf wheat variety, has become well known for its dwarfness as the breeding material for Mexican semidwarfs. Its pedigree is as follows, after INAZUKA (1971): Norin 10 was obtained from an artificial cross of Turkey red as mother and Fultz-Daruma as father. According to the old records, Fultz and Turkey red were introduced from the U.S.A., Fultz around 1892 and Turkey red later. Fultz-Daruma was a line from a cross of Daruma as female and Glassy Fultz as male. Daruma is believed to have been a representative variety of the Kanto district, known as Shiro-Daruma, while Glassy-Fultz is believed to have been a glassy derivative from Fultz with mealy grain." It is our further subject to trace back the origin and routes of Daruma in the near future. It seems very probable that the short culm varieties developed in the East and the tall culm varieties in the West. Peripheral Diversity Cultivated plants must have dispersed from the places of their origins to neighboring places, along with the spread of human culture, overcoming various barriers, geographical and ecological, one after another, until they come to a barrier of extremity, such as a high mountain range, a desert, the seas, or other. During the course of the dispersion, diversity occurred to yield modified forms adaptable to the diverse geographical and ecological conditions encountered. Mutations and introgressive hybridizations took place, resulting in the accumulation of diversity as the spread of the species continued. It is worth notice here that SCHIEMANN (1939) stated that "Nach unseren experimentellen Erfahrungen wirken aber extreme Aussenbedingungen mutationsausloesend. So wird as Nebeneinander normaler und extremer Bedingungen, wie es sich besonders haeufig in Gebirgsgegenden findet, leicht zur Ausbildung einer Mannifaltigkeit fuehren." Ultimately a barrier would be reached and not traversed. At the barrier of extremity we should find the greatest diversity. I have proposed to call this "peripheral diversity" in my previous paper (Yamashita, 1978). This may be compared to our daily observations; as waste papers, fallen leaves, sand and other trash are blown about by the wind, it trends to accumulate, in all its diversity, at walls (barrier) and in corners. It is here where the accumulation of diversity of those elements is seen. Old cultivars may be either eliminated by natural as well as human selection, or replaced by better new cultivars, to meet the demand of increasing human population. This is why the change to new recommended varieties takes place so rapidly in the central densely populated areas, resulting in the loss of valuable gene resources. This is being called genetic erosion. Therefore, the diversity remains accentuated in the peripheral areas. If the above theory is accepted, some of the questions, if not all, raised in the Vavilovian concept, mentioned before, may be answered. The centers of some of the crops listed comprehensively by VAVILOV (1951) could be the centers of the peripheral diversities of the present theory of the far past distribution of ancient crops, spread over a period since the stage of the development of human culture in the middle Stone Age (SCHIEMANN, 1939). They could not be the centers of the formation of cultivated plants of VAVILOV (1951). |
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