If one does a Google search for tea +genetic +DNA the results suggest
that quite a lot of research has been done on the DNA of tea, and that
is only seeing the English, while I rather think that the main bulk of
studies will have been published in Japanese, as well as Chinese and
Korean. Some interesting stuff there, including the discovery that
wild tea in Korea has 2 clearly defined origins, one Chinese (ancient)
and one Japanese (recent).

Br Anthony