Ancient discovery could help us develop more disease resistant watermelons

  • Scientists have identified the closest relative and potential progenitor of the watermelon as the Kordofan melon
  • The discovery shows that watermelons lost key disease-resistant genes during the domestication process, which could be why they are susceptible to viruses
  • Genetic analyses of the Kordofan melon could help us to breed more disease-resistant watermelon and reduce use of pesticides

An ancient melon which is the closest relative and potential ancestor of the watermelon, has been discovered by scientists.

A team of scientists led by Dr Guillaume Chomicki, from the University of Sheffield, has discovered the potential progenitor of the domestic watermelon, the Kordofan melon, using DNA sequencing technologies and analyses with historical data and Ancient Egyptian iconography.

The discovery could explain why watermelons are so susceptible to disease as their analysis shows how key disease-resistant genes were lost as the melon was domesticated, and also help us to breed more disease-resistant watermelons in the future.

The findings show that the melon originates from North Eastern Africa, in the region of Kordofan in Sudan, settling decades old debate and giving us more insight into how the watermelon was domesticated.

Dr Guillaume Chomicki, from the University of Sheffield’s Department of Animal and Plant Sciences, said: “The watermelon is one of the most important tropical fruits, with over 200 million tons produced every year, but it is also very susceptible to disease.

“There are specific watermelon diseases, such as the Watermelon mosaic virus and they are also very sensitive to fungal infections. In conventional agriculture, they are frequently treated with fungicides, and insecticides to limit virus transfer.

“Our analysis clearly shows that the Kordofan melon has more disease resistant genes, and different versions of those too. This means that the genome of the Kordofan melon has the potential to help us breed disease-resistant watermelons and allow non-GM gene editing. Achieving this would be reducing substantially pesticide use in watermelon farming.”

The new research, published in the journal PNAS, also found that the wild progenitor of the watermelon was already non-bitter and farmers brought these naturally sweet forms into cultivation, this contrasts dramatically with other crop species in the same family such as cucumber or squash, in which the loss of bitterness is the result of domestication.

The genomic work, together with new interpretations of ancient Egyptian iconography by Dr Chomicki and colleagues shows that Egyptians were cultivating sweet watermelons at least 4,200 years ago.

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