A new DNA analysis of more than 400 types of lettuce reveals the humble beginnings of the food as a wild plant that was grown by ancient Egyptians after the vegetable we know today.
Researchers at Wageningen University & Research and the Chinese BGI found that modern lettuce varieties are largely similar to their weed-like predecessors, which were grown only for their seed oil about 6,000 years ago.
The ancient Romans and Greeks then brought the plants from the Caucasus to Europe, where they were grown and made into leafy vegetables on plates.
The DNA story continues to America, where softer, smooth butter lettuce was transformed into tougher, crispy iceberg lettuce.
Although the study reveals the lettuce’s interesting history, the team could help reveal certain genes that are resistant to droughts and certain diseases, and enable farmers to grow better crops.
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The researchers found that modern lettuce varieties mostly resemble their weed-like predecessors, which were grown just for their seed oil around 6,000 years ago. Many of the Egyptian murals with lettuce feature Min (pictured), the god of fertility, who is said to be consuming the plant for sexual stamina
According to the study published in Nature, there are 2,500 different types of lettuce, 1,500 varieties are grown by farmers and there are around 1,000 wild lettuce plants that appear on the roadside and in nature reserves.
The new analysis was performed to determine the DNA order for all 2,500 types, including an analysis of the genetic variants and the differences and similarities between these variants.
However, the team makes a few hundred at a time, starting with the first 445 types of lettuce.
“It turns out that modern varieties of cultivated lettuce are largely similar to their wild predecessor Lactuca serriola from the Caucasus, and the first cultivated salads must have been grown for seeds and used for oil,” scientists said in a statement.
From Egypt, the Romans brought lettuce seeds to Europe where they were bred for consumption, and as the plant traveled it also switched to different varieties, including butterhead. However, it was turned into crispy iceberg when seeds were brought to America by Christopher Columbus
The new analysis was performed to determine the DNA order for all 2,500 types, including an analysis of the genetic variants and the differences and similarities between these variants
Ancient Egyptian wall paintings show the cultivation in lettuce, some date from the year 2700 BC. However, show a very different plant than what we can easily find in the supermarket.
The ancient lettuce is drawn as an upright plant attached to a long stem, along with a leaf protruding from a central base – far from the heads seen today.
Many of the Egyptian murals with lettuce feature Min, the god of fertility, who is said to consume the plant for sexual stamina.
The lettuce grown by the ancient Egyptians was called Lactuca serriola and has an upright plant attached to a long stem, along with a leaf that protrudes from a central base. A modern version of the weed that grew around 6,000 years ago is shown
And the people of that time harvested oil from the wild seeds for medicine, cooking and mummification.
Over time, the weeds were bred to produce leaves that are less bitter to eat.
When the Romans came to Egypt they first saw lettuce and brought seeds back to Europe, where they grew them to make them more tangible.
The study not only found its ancient roots, but also found out how the youngest iceberg lettuce differed in the genetic material of the wild Lactuca virosa from the “old” lettuce, which has long been suspected based on the genealogical data of these lettuce varieties.
Analysis of the relationship between DNA information and the characteristics of the cultivated lettuce shows that rigorous selection was made for characteristics desirable for production and consumption, the “domestication characteristics” such as the absence of spines and thorns, resulting in reduced diversity in led to the regions of DNA in which the genes for these traits are located, ”the researchers said.
It also seems possible to determine the position of multiple genes in DNA by analyzing the relationship between DNA variation and traits through so-called Genome Wide Association Studies (GWAS).
The study not only found its ancient roots, but also found how the youngest iceberg lettuce differed from the “old” lettuce in the genetic material of the wild Lactuca virosa, a fact long suspected based on the genealogical data of these lettuce varieties
According to Rob van Treuren and Theo van Hintum, the two co-authors of the publication in Wageningen, the study shows how much information can be gathered from DNA information in a genebank collection.
“Determining the DNA order of the material in our collections and others allows science to trace previously hidden characteristics in thousands of varieties and wild populations of lettuce and other crops,” the researchers said in a statement.
“We have thus received the key to a huge treasure chest. For example, imagine that research shows that certain genes are important for resistance to drought or a certain disease.
“Then you could look in the DNA data for genetic resources whose genes look very similar, and with those resources you could grow plants much faster and more effectively than previously possible. That is downright revolutionary. ‘