The genetic differences between the board-leaf teas from India and small-leaf teas from China have been revealed by three New York City high school students under the guidance of scientific experts.
Using tabletop DNA technologies they also found several herbal brews and a few brands of tea contain ingredients unlisted on the manufacturers' package.
Catherine Gamble, 18, Rohan Kirpekar, 18, and Grace Young, 15, of Trinity School in Manhattan, were guided by DNA "barcoding" experts at The Rockefeller University, an ethno-botanist at Tufts University and a molecular botany expert at The New York Botanical Garden.
The young scientists discovered that the tea plant includes a genetic difference between broad-leaf assamica variety tea exported from India and small-leaf sinensis variety tea exported from China, the two largest tea-producing countries by far.
"We were excited to make a genetic discovery, particularly in an important crop plant like tea that scientists have scrutinized in detail," said Young.
"This finding will help track commercial shipments and aid research on the geographic origin and diversity of wild and cultivated tea plant resources," Selena Ahmed of Tufts University stated.
The students also helped construct a "Klee diagram," a clever new way to visually represent the genetic relationship between species.
Like a heat map, where hot is shown in red and cold in blue, their Klee diagram depicts the genetic relationships among and within the families of plants consumed as teas, using a color scale from red (a close genetic relationship) to blue (distant).
Based on the DNA of 39 plants tested, the image is the world's first family portrait of tea and herbal tea plants.
The finding was published in the Nature journal Scientific Reports.