Researchers say all Japan’s somei-yoshino trees originated in a Tokyo park

The Yomiuri Shimbun

12:25 JST, March 29, 2022

A research team says all somei-yoshino cherry trees in Japan likely originated from four trees in a corner of Ueno Park in Taito Ward, Tokyo.

The team, led by Kazusa DNA Research Institute in Kisarazu, Chiba Prefecture, presented the find at a Japanese Society of Breeding conference in March.

The species does not reproduce through seed propagation, but rather via grafting and cuttings. As such, every somei-yoshino tree in Japan is likely a clone with the same genome, except for slight variations. This also explain why the flowers of such trees bloom and fall at the same time if in similar climatic conditions.

The circumstances behind the genesis of the species are not known. Some experts believe it was a result of natural hybridization of wild species, while others posit it came about through crossbreeding by a gardener in Somei-mura (present-day Toshima Ward, Tokyo) during the Edo period (1603-1867).

The location of the original tree is also unknown, but in 2015, Chiba University researchers analyzed the genes of somei-yoshino trees in Ueno Park and reported that one of the four trees in a corner near the center of the park was a possible candidate.

Kenta Shirasawa, a senior researcher at the institute who specializes in plant genetics and breeding, worked with his team to analyze 46 trees in 19 prefectures across Japan — from Aomori to Miyazaki — including the four in Ueno Park. Genomes were compared by examining subtle variances.

Based on these variances, the 46 trees were divided into six groups — each of the Ueno Park trees fell within a different group. It is unlikely that the four trees were planted side by side in Ueno Park by chance, leading researchers to presume that the differently grouped trees all originated from the Ueno quartet and spread throughout the country.

Ikuo Nakamura, a professor of plant genetics at Chiba University who reported the original tree candidates in 2015 and was not part of the current team, said: “The detailed genome analysis reinforces some of our reported findings. It would be even more interesting if we could identify the original trees by discerning their age.”