Our learning in tea plants is taking it’s next steps with Professor Goa’s studies, published this month, from the South China Agricultural University, Guangzhou, with Camellia sinensis variety assamica cultivar Yunkang 10.
Tea plants have two varieties the first originally found in China around the Ichow hills in Sichuan (Camellia sinensis variety sinensis), found around BC 2736, and the second discovered in India around the hills of Sivagasar, Assam (Camellia sinensis variety assamica) in 1823. Although they originally grew in the same continent they were found in different countries and so are very likely to have different genetic profiles. Tea plants are now grown in over 30 countries around the world and have been cultivated specifically for each areas mainly hybrids within the varieties with a small number of combined the varieties as well. Early studies with both varieties (11 C.s. var sinensis and 24 C.s. var assamica) by Dr Powell’s group (Scottish Crop Research Insititute) showed that Camellia sinensis is a very distinct species the two varieties were also distinct groups. The Tea Research Foundation of Kenya found that the C.S var assamica clones are also very distinct from each other. More recently studies at the UPASI Tea Research Foundation (South India) has shown that there is biochemical differentiation not only between the two varieties but also within the C.S var assamica clones. They also identified 30 potential target genes for further investigation for the development of the plants. Studies at the Institute of Himalayan Bioresource Technology (Himachal Predesh) with genetic markers have provided more understanding of the distinctive differences between the two tea plant varieties. Cheng Hoa’s group has studied the genes for enzymes in C.S. var sinensis cv Longjing 43 and cv Zhonghuang2 related to compounds identified with the quality of plants. There have been many recent improvements in DNA analysis of the genome including Nir Friedman and Aviv Regev’s team co-ordinated from MIT and Harvard University (Cambridge Massechusetts) who developed the trinity genome sequencing technique in 2011. These new techniques are increasing our capabilities to analyse the genomes of tea plants. The C.s. var sinensis cultivar Longjing 43 has been sequenced by Professor Wan Xiao-Chiu’s team at the Anhui Agricutlural Univeristy (Hefei). Their following studies of 18 tea plants and their wild relatives which showed that the Camellia sinensis plants are very different from their plant relatives and also that the C.s var sinensis and var assamica are also distinct groups based on their genetic profiles. More studies at the Fujian Academy of Agricultural Sciences, by Rang Wang’s team, has also build more genetic understanding of 66 cultivars of tea plant.
The recently published studies by Professor Li-Zhi Gao’s (South China Agricultural University, Guangzhou) large team across a number of institutes is building on the tea genome knowledge in particular with a genome sequence of C.s. var assamica cultivar Yunkang 10. The tea plant varieties have and unusually large genome (size of the combination of genes) and has had two rounds of development. The tomato, potato, coffee and pepper plant genomes are smaller. The two rounds of development have potentially supported the development in the plants of tea flavour compounds such as polyphenols and terpenoids and an expansion of enhanced disease resistance. The development of caffeine production appears to be similar in tea and cocoa plants and different to the coffee plant. The high contents of genes for making catechins and caffeine in tea plants is thought to support the development of the tea flavours we like. The wild relatives of the tea plant also potentially offer a source for developing new hybrid plants which can continue to grow in changing agronomic and climatic conditions as well as giving us new tea qualities to enjoy. The studies also identified the ways tea plants make the the important mixtures for the tea we like including polyphenols, theanine and caffeine in the leaves and other parts of the plant. Another group led by Monique Simmonds at the Royal Botanical Gardens, Kew have recently published a study of the abundance of 30 compounds which influence taste in 21 cultivars of C.s. v sinensis. This shows that a modelling technique (linear discriminate analysis) can accurately distinguis the cultivars with the levels of 12 of these compounds including theobromine, gallocatechin, epicatechin gallate and chlorogenic acid. Also a few of the compounds give a good indication of the harvest time.
It will be really interesting to see how the differences between the green tea (C.s. v sinensis) and the black tea plant (C.s. v assamica) and the subspecies (C.s. v assamica ssp Lasiocalyx) develops. The research is continuing in a number of countries including India and China to explore the developments which we can make with the tea plants and their hybrids. The important aspect is that the work uses good methodology which is validated and supports the interesting evidence and conclusions which can be developed.
This understanding of tea is following the great work pioneered by the human genome project, giving us techniques to understand tea qualities and good cultivation qualities for a great future in tea.
Dr. Andrew Scott, Chairman ISO/TC 34/SC – 8 Food Products – Tea Committee, Member of the World Green Tea Association (Japan)
Dr. Scott is a biochemist with research experience in drug metabolism (doctoral studies at the University of Surrey supported by Glaxo) and food biochemistry (at the Chorleywood and Campden Food Research Association). He joined The Tetley Group, now a subsidiary of Tata Global Beverages and was the company’s Director, Science & Technology, bringing innovative new tea products to Tetley markets across the globe (1991-2010).
He joined Nestec Ltd as Global Tea Scientist and supported tea science research in Nestlé’s global tea businesses (2011-2016). He has been a member of the BSI AW8 Tea Committee since 1991 and was appointed appointed Chair of ISO/TC 34, Food products, SC 8, Tea, in 2004. The committee has been working on new standards to measure substances characteristic of tea, and more recently, published the new green tea standard, upgraded black tea standard, the white tea technical bulletin and will publish the L-theanine method of analysis this year.
He also worked with the Food and Agriculture Organization Intergovernmental Group on Tea since 2005 on pesticide regulations for tea in North America, EU, Australia and India and the global use of ISO Tea standards in the international trade of tea.
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