Guwahati: A quiet revolution is brewing in the world of tea. For the first time, scientists have cracked the genetic code of India’s Assam tea (Camellia sinensis var. assamica), unlocking mysteries buried deep in its DNA. This landmark discovery, achieved by decoding the chromosome-scale genome of the Assam tea variety TV1, can potentially reshape tea cultivation globally.
In a landmark discovery, a team of scientists from different institutions in India have decoded the first chromosome-scale genome sequence of India’s Assam tea variety TV 1(C. sinensis var assamica), marking a major advancement in our understanding of tea genetics. Unlike previous studies, which focused primarily on the Chinese type of tea (Camellia sinensis var. sinensis), this breakthrough is the first in-depth chromosome-level study on Indian Assam-type tea of popular cultivar TV-1, a subspecies integral to the tea industry in India, Sri Lanka, and African tea-producing nations.
With Assam tea prized for its strong flavour and high caffeine content, the research provides an unparalleled look at how its genome has adapted and diversified, focusing on domestication traits and caffeine biosynthesis pathways.
The study, published in a renowned journal Industrial Crops and Products, Elsevier Publication, provides insights into how Assam tea evolved, developed its distinctive traits, and synthesized caffeine, revealing the genetic adaptations that differentiate it from China tea (C sinensis var. sinensis).
This breakthrough holds significant implications for the global tea industry, potentially aiding tea breeders develop climate-resilient, high-yielding, and high-quality varieties.
The multi-institutional collaborative study was funded by National Tea Research Foundation, Tea Board India and led by Dr Tapan Kumar Mondal, Principal Scientist Indian Council of Agricultural Research-National Institute for Plant Biotechnology (NIPB), New Delhi; TRA – Tocklai Tea Research Institute (TTRI) Jorhat, UPASI Tea Research Foundation, TRI, Valparai and Darjeeling Tea Research and Development Centre, Tea Board, Kolkata West Bengal.
This partnership reflects a concerted effort to advance research in tea cultivation and production, underscoring a commitment to enhancing the tea industry through scientific innovation.
The genus Camellia includes more than 300 species but only two of them viz. China tea i.e. C. sinensis and Assam tea i.e. C. sinensis var assamica are cultivated as large-scale plantation crops to produce tea the world over primarily due to caffeine and other secondary metabolites. While the China-type plants are small bushes having smaller leaf sizes and multiple branches, the Assam-type plants are big trees with large leaves but limited branches.
The Chinese type is predominantly found in temperate zones in high hills such as in China whereas the Assam type is predominant in plain or lower altitudes such as in India and Sri Lanka.
Later, the Assam type was introduced to African tea-producing countries, preferably growing in lower altitudes with tropical climates for commercial cultivation.
Dr Sangeeta Borchetia, Scientist and Principal Investigator from Tea Research Association informed that the study was the first in-depth look at the Assam-type tea genome of clone TV1 which was released by Tocklai in 1949. Cultivar TV 1, an yAssam-type (C. assamica) Indian tea was used for decoding its genome due to its commercial importance as well as breeding value in the Indian tea industry.
Young leaves were collected from Tocklai Tea Research Institute, Jorhat, for DNA extraction.
The Evolutionary Split: Assam vs. China Tea
Assam tea is prized for its strong flavor and high caffeine content, distinguishing it from the milder-flavored China tea. By analyzing 150 tea genotypes worldwide, the research team led by Dr Tapan Kumar Mondal, Principal Scientist, NIPB, New Delhi identified that Assam and China tea diverged approximately 5.5 million years ago, each adapting to its specific growing conditions—Assam tea in tropical lowlands and China tea in mountainous regions.
Gene fusion: The analysis revealed over 500 genes in Assam tea that have been shaped by domestication, including genes linked to caffeine production, leaf size, and branching patterns. These traits help explain Assam tea’s robust flavour and its adaptability to warm climates.
The team also found unique gene fusion events in Assam tea, adding to the understanding of tea’s complex evolutionary mechanisms. Over 500 domestication-related genes were identified, including those influencing caffeine production, leaf size, and branching patterns. These adaptations explain Assam tea’s bold flavour and resilience to warm climates.
Unlocking New Breeding Potential
The results of this study are now accessible through the Tea India Genome e-Resource (TIGeR) database, a new online resource for researchers and breeders globally. This database provides valuable genetic information to guide precision breeding efforts, helping tea producers develop varieties resilient to climate change and pest challenges while maintaining desired taste and yield characteristics.
The study reveals Assam tea’s unique journey through evolution and how it developed its strong taste and high caffeine. This new genetic information will be a big help to tea farmers and scientists, who can use it to grow better tea plants that meet global demands.
“The availability of a high-quality chromosome-level Assam type reference genome would aid in understanding the evolution and domestication history between the China and Assam types.
Genomic information of this cultivar will be useful for Sri Lanka, Pakistan, and African countries such as Malawi and Kenya, where the tea industry has been developed from the seeds of Assam type of tea,” the study says.
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