Identification of Teas Cultivated in Eastern, Southeastern and Southern Asia Based on Nucleotide Sequence Comparison of Ribulose 1,5-bisphosphate Carboxylase Large-subunit of Chloroplast DNA and 18S Ribosomal RNA of Nuclear DNA

抄録

Nucleotide sequences of the ribulose 1,5-bisphosphate carboxylase large-subunit (rbcL) in chloroplast (cp) DNA and 18S ribosomal RNA encoded in nuclear DNA (nuclear-encoded 18S-rRNA) were determined to clarify genetic diversity among cultivated teas. The nucleotide sequence alignment of rbcL in cpDNA enabled the taxonomic distinction of the section Thea. On the basis of these data, the rbcL nucleotide sequences of 195 cultivated teas in the Asian region were classified. The cultivated teas are separated into five groups: CSs type (var. sinensis), CSa type (var. assamica), type CSaa (like var. assamica), CIt type of C. irrawadiensis, and CTa type of C. taliensis. All the cultivated teas from the East Asia (China, Korea, and Japan) region were of the CSs type, whereas the cultivated teas from Bangladesh, Laos, Sri Lanka and Thailand were CSa type. The cultivated teas from India were separated into CSs and CSa types. The rbcL nucleotide sequences of the teas currently cultivated in Yunnan, China were CSa and CIt types, and the teas of Vietnam were CSa, CSs and CIt types. On the other hand, the teas cultivated in Myanmar included all types of CSs, CSa, CSaa, CIt and CTa. In addition, differences in nucleotide sequences were observed at three positions in 870 nuclear-encoded 18S-rRNA nucleotide sequences. The different nucleotide sequences of nuclear-encoded 18S-rRNA distinguished C. sinensis (var. sinensis and var. assamica) from wild tea species. Similarly, almost all cultivars tested were divided into the Cs type of C. sinensis (var. sinensis and var. assamica) and Cw type of wild tea species by alignment of nuclear-encoded 18S-rRNA nucleotide sequences, with an interspecific hybrid between C. sinensis and C. taliensis identified in a region of Myanmar. Analysis of genetic relationships indicated that many teas cultivated in the Myanmar region differ from the tea groups of East and South Asia. Our data indicated that the endemically cultivated teas in parts of Myanmar are conservationally important as new sources of desirable teas for future breeding programs and improvement of tea products.