This 2020 Chinese paper reviewed this century’s research into tea:
“Tea plants contain rich and unique characteristic secondary metabolites, such as catechins, theanine, and caffeine, which are essential to the formation of tea quality. It is not only the three major types of secondary metabolites but also the volatile terpenoids, saponins, polysaccharides, and other phenolic conjugates that contribute to the beneficial health effects and the enjoyable flavors of various teas.
The contents of these secondary metabolites vary greatly among different varieties and Camellia species. They also differ significantly in several morphological traits (e.g., leaf size) and stress resistance characteristics (e.g., cold tolerance), showing a divergent genetic makeup. The genome sequence of a single individual of a tea plant variety cannot represent the entire gene pool.
Modern transgenic breeding technology has provided us a new solution for the molecular design of breeding strategies. Although great progress has been made in the last two decades, the genomics and molecular biology of tea plants are still not fully understood. Compared to other crops such as rice, there is a long way to go.”
https://www.nature.com/articles/s41438-019-0225-4 “Tea plant genomics: achievements, challenges and perspectives”