When and where the domestication of the wild bitter tasting, white-fleshed watermelon happened has long been a mystery, but ancient DNA has cracked the case. Back in the 19th-century watermelon leaves were found draped on an ancient Egyptian mummy from 3,500 years ago. These leaves were sent to be preserved in the herbarium at Kew Gardens in London, where they have been carefully preserved, and undisturbed since 1876.
When a botanist from the University of Munich heard about these leaves she wondered if they contained DNA that might illuminate what the ancient melons were like. From a very small sample donated by Kew Gardens, a DNA sample was extracted, which was sequenced at the University of Oxford.
Fortunately, the partial DNA sequence contained two genes of interest. One of the gene codes for the production of cucurbitans, which cause the bitter taste of wild watermelons. This gene was disabled in the ancient watermelon DNA, meaning they would have been sweet to taste. The other gene controls the conversion of lycopene, which is a red pigment, into another chemical. In the ancient watermelon DNA, this gene was also disabled, which would have allowed these ancient fruits to accumulate lycopene and have red flesh.
While the partial DNA sequence did not shed any light on the size or shape of the ancient fruit, it is clear that it has been at least 3,500 years since humans first started enjoying the delicious fruit.
Source: New Scientist
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