Where Your Watermelon Came From

About four,300 years in the past, somebody drew a melon on the wall of a tomb in Egypt. It’s large, fats, inexperienced and generously striped: Everything you’d anticipate a watermelon to be. It’s subsequent to grapes and different fruits, suggesting it was eaten again then as we eat watermelon now, uncooked and for its candy style.

This element of a portray within the tomb of Khnumhotep in Saqqara was a puzzle. While scientists believed that watermelon’s wild ancestors got here from the African continent, nobody knew of a wild watermelon wherever close to the Nile Valley. Where did this melon come from?

One concept held that the West African egusi melon, grown for its seeds, is perhaps a descendant of watermelon’s most up-to-date wild ancestor, suggesting watermelon’s origins have been on that aspect of the continent. But a paper printed Monday in Proceedings of the National Academies of Sciences finds that the small, spherical Kordofan melon, native to the Kordofan area of Sudan, is way more intently genetically associated to our trendy watermelon.

The discover means that watermelon is East African, and the Kordofan melon’s genetics might be ripe pickings for breeders hoping to enhance future watermelon varieties. Because Kordofan isn’t removed from Egypt, it might additionally counsel an origin for the mysterious ovoid inexperienced fruit painted on that tomb wall.

A Kordofan melon.Credit…Shan WuA four,450-year-old Egyptian papyrus depicting a watermelon-like object, suggesting that the candy fruit, presumably derived from Kordofan melons, was consumed in historical Egypt’s Nile Valley.Credit…Lise Mannich

The discovery required digging into forgotten corners of African botany, mentioned Guillaume Chomicki, a botanist on the University of Sheffield in England and an writer of the brand new paper.

The Kordofan melon, which is about six inches extensive, white on the within and a pale, gently striated inexperienced on the skin, has lengthy been grown by farmers in what’s now Sudan. In the late 1800s, a German botanist wrote that it is perhaps a progenitor of the trendy watermelon. Later, Soviet scientists questioned the identical factor.

Most members of the watermelon’s genus, Citrullus, have bitter flesh. But the Kordofan melon is nice. That instructed it or one in every of its ancestors might be the supply of the trendy watermelon.

To see the place it fell within the watermelon household tree, the researchers behind the present paper sequenced the genomes of seven Citrullus species. They discovered that the Kordofan melon had way more overlap with the trendy selection than with the West African egusi or some other melons, suggesting that they’re extra intently associated.

“We are really confident in saying this is the closest relative,” Dr. Chomicki mentioned.

The Kordofan melon and the trendy watermelon almost certainly arose from a long-ago wild melon, the outcomes counsel. Farmers would have realized this melon was sweeter than others and bred it into new, tasty varieties.

Researchers nonetheless don’t know, nonetheless, who took this wild melon ancestor and turned it into what’s on the tomb wall in Saqqara, or set it on the trail to what we eat immediately. Dr. Chomicki and his colleagues are planning to sequence the genomes of melon seeds present in African archaeological websites to attempt to decide the place and when people coaxed early watermelons right into a extra edible kind.

The wild kinfolk of domesticated crops might be sources of contemporary, fascinating genes for breeders. A brand new coloration, a hardy resistance to drought or a brand new strategy to struggle off blight are the sorts of treasures wild crops can convey to the gene pool of domesticated varieties.

Even varieties which can be nearer to the supply, because the Kordofan melon could also be, may also help. The new research discovered that it has completely different types of genes associated to illness resistance than the usual watermelon.

It’s not clear if there are nonetheless any wild variations of the Kordofan melon or its kinfolk rising in Sudan, Dr. Chomicki mentioned. In the 1800s, the German botanist wrote, there have been patches of the melons rising wild. But this area, which is close to Darfur, is now tough for researchers to achieve entry to due to violence.

Many wild kinfolk of crop crops are going through extinction all over the world, a results of human disturbance and local weather change. When they go, they take alternatives to enhance home varieties with them.

Dr. Chomicki has by no means tasted the Kordofan melon — for his or her evaluation, the workforce members needed to depend on samples collected by others. The tales of its candy taste, the telltale signal that it might have had a narrative to inform about trendy watermelon, are nonetheless secondhand.

“But I still have some seeds,” he mentioned, “so I will plant them and see.”