Copyright 1998-2022 Yoshiaki Yoneda
Earlier we described the Japanese morning glory as it appeared in old picture books. This varied morning glory of the Edo era was unique to Japan, and it reached a high level around the world as a horticultural flower. However, the cultivation of the morning glory declined temporarily due to the social unstability from the late Tokugawa period to the Meiji Restoration. However, a great interest in the cultivation arose from the middle period of the Meiji era, and a third cultivation boom occurred in the final stage of the Meiji era. In Europe in 1859, at the same time that Japan was going through the late Tokugawa period, Darwin's On The Origin of Species was published and breeding was progressing from the knowledge of male-female sexuality in plants. Such knowledge was imported to Japan. Therefore, in the third cultivation boom of the Meiji period, artificial crossings were tried in the Japanese morning glory. The first known mention of an artificial crossbreeding method is found in the Complete Works for Cultivation of the Japanese Morning Glory, by H. Uzume (1895). Two years later, A. Yasuda (1897) reported On the Artificial Cross-fertilization between Some Garden Varieties of Japanese Morning Glory. E. Wakana published his Study on Japanese Morning Glory (1902), and argued for crossbreeding method. K. Naganuma commented "About interspecific crossing" in Vol.1 of the Study on Japanese Morning Glory. F. Oka raised Takaramino leaf, which was more complex than the leaves of the morning glory in the Edo era. This leaf is extremely splitted and feels like composing many weeping willow or needle leaves. This Takaramino leaf will be the result of breeding due to a new artificial crossbreeding method.In Explanation of the Japanese Morning Glory (1902), T. Tonami argued that Sei (a fertile polymorphic characteristic) should be distinguished from Suzi (a sterile polymorphic characteristic) when the morning glory is cultivated. If we use the current terminology, each Sei and Suzi characteristic is expressed through a leaf, a stem and a flower by a polymorphic gene. Sei sets seeds in the recessive homozygous state and is therefore maintained easily, while Suzi is sterile in the recessive homozygous state and therefore can be maintained only by the parental stock (heterozygous plants). Explanation of the Japanese Morning Glory describes the criteria for selecting how many parental stock plants to raise, though the idea of segregation ratios is not yet attained. Crossings were explained only in several lines at the end of this book.
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