Analysis of information sources in references of the Wikipedia article "Japanese citrus" in English language version.
During the Edo period, when Kishu mikan were being cultivated, unshu mikan were already being cultivated. However, they were not yet called unshu mikan, but Nakajima mikan. Although mandarins were a luxury, unshu mikan were not the most popular. The unshu mikan is unique in that it is ready to peel and has no seeds. The lack of seeds is good because they are easy to eat, but in the Edo period, the lack of seeds was a factor that made them unpopular. It was believed that eating seedless fruit meant that one could no longer produce offspring, thus ending one's family lineage. When the fruit was named "unshu mikan" in the late Edo period, it was finally recognized. Wenzhou is a mandarin production area in China, and the name "unshu mikan" means "a mandarin comparable to the one produced in Wenzhou". The unshu mikan is often mistaken for a mandarin imported from China, but it is a genuine Japanese mandarin. It was not until the Meiji period that the cultivation of unshu mikan became popular.
Therefore, it is likely that kunenbo was backcrossed to Kishu in the Kagoshima region of Japan several times and Satsuma and Yatsushiro were selected from their offspring.
(After the many years of research, Dr. Tanaka has concluded the place of origin of Satsuma is Nagashima, Kagoshima. Satsuma is a chance seedling of Sōkitsu, Mankitsu, or Tendaisankitsu introduced from Huangyan Zhejiang, China. It appeared in the early Edo period. The place where Satsuma was born by mutation was Nishi-nakajima, Amakusa District, Higo Province (later Nagashima, Kagoshima), and was called Nakajima Mikan or Nagashima Mikan.)
Therefore, it is likely that kunenbo was backcrossed to Kishu in the Kagoshima region of Japan several times and Satsuma and Yatsushiro were selected from their offspring.
(After the many years of research, Dr. Tanaka has concluded the place of origin of Satsuma is Nagashima, Kagoshima. Satsuma is a chance seedling of Sōkitsu, Mankitsu, or Tendaisankitsu introduced from Huangyan Zhejiang, China. It appeared in the early Edo period. The place where Satsuma was born by mutation was Nishi-nakajima, Amakusa District, Higo Province (later Nagashima, Kagoshima), and was called Nakajima Mikan or Nagashima Mikan.)
During the Edo period, when Kishu mikan were being cultivated, unshu mikan were already being cultivated. However, they were not yet called unshu mikan, but Nakajima mikan. Although mandarins were a luxury, unshu mikan were not the most popular. The unshu mikan is unique in that it is ready to peel and has no seeds. The lack of seeds is good because they are easy to eat, but in the Edo period, the lack of seeds was a factor that made them unpopular. It was believed that eating seedless fruit meant that one could no longer produce offspring, thus ending one's family lineage. When the fruit was named "unshu mikan" in the late Edo period, it was finally recognized. Wenzhou is a mandarin production area in China, and the name "unshu mikan" means "a mandarin comparable to the one produced in Wenzhou". The unshu mikan is often mistaken for a mandarin imported from China, but it is a genuine Japanese mandarin. It was not until the Meiji period that the cultivation of unshu mikan became popular.
