Posts Tagged ‘watermelon varieties’

Pleistocene Watermelon (Citrullus lanatus)

August 3, 2019

During July and August I always have watermelon in my refrigerator.  After I run 3.3 miles in 95 degree F heat, nothing quenches my thirst better than a crisp cold slice of watermelon.  Primitive people living in the deserts of North Africa ~5000 years ago discovered the same usefulness of this species, but the story of the watermelon began long before that.

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Wild citron melons in South Africa.  They are a different species than the sweet watermelon we commonly know, but the type specimen (the first described by biologists during the 18th century) of Citrullus lanatus was mistakenly described from a specimen of this species, C. caffer.  Scientists didn’t discover this mistake until a DNA test of the museum specimen was conducted a few years ago.

A recent study of watermelon genetics estimated the citrullus genus (which includes all watermelons) first diverged from the rest of the Cucurbitidae family about 11 million years ago.  This family also includes bottle gourds, squash, and many other plants. There are 6 species of watermelon, and they originally occurred in Africa.  A single species of the 6 spread to India and Australia during pre-history, and man may or may not have been a factor in the distribution of this species.  The sweet watermelon (Citrullus lanatus) diverged from a sister species within this genus about 3 million years ago.  All members of the Citrullus genus are desert vines that survive arid conditions, but thrive and produce heavy yields following occasional downpours.  The abundant seeds are consumed by megafauna such as elephants and rhinos and spread across the landscape in their dung.  Today, elephants often destroy grain crops interplanted with cultivated watermelons when they seek out this delicacy.

The oldest known remains of sweet watermelons were found at a 5,000 year old settlement in Libya.  Harry Paris believes desert people in North Africa began cultivating watermelons as a portable source of water, rather than as a food source, though the seeds are edible and nutritious.  The first watermelons were green-fleshed, watery, and bland or even bitter.  Early farmers selected for sweeter fruit, and the gene for red flesh is paired with an increased sugar content.  Soon ancient mariners started carrying watermelons on their ships as a source of potable water and spread them throughout the warmer parts of the world.  Christopher Columbus brought watermelons to North America in 1493, and the Indians planted them everywhere they would grow.  William Bartram enjoyed a feast of oranges and watermelons when he visited Florida in the fall of 1775.

There are over 1200 varieties of cultivated watermelon.  I’ve successfully grown 2–Georgia Rattlesnake and Florida Black Diamond.  I used to pull out all the stops using fertilizer and special mulching tarp and was able to grow 35 pounders.  This year I bought a cheap $1.50 pack of Congo watermelon seeds and put minimal effort into the project and was justifiably rewarded with zero melons.

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Georgia Rattlesnake.  I successfully grew 35 pounders years ago.

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Black Diamond.  I successfully grew these 1 year too.

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My late grandfather grew Crimson Sweet watermelons.

Among the more interesting varieties of watermelon are the Carolina Cross and the Christmas King.  The Carolina Cross was bred for its prodigious size and holds the record for biggest watermelon ever grown at 351 pounds.  This could be served at baseball games and fairs.  The Christmas King is less sweet than most watermelons but if kept in a cold place will still be edible in late December.  How is that for an extended season?

Most watermelons sold in supermarkets today are seedless–a recent development.  Farmers began growing seedless watermelons during the 1990’s.  To make a seedless watermelon farmers chemically induce a change in the chromosome number in 1 of the parents.  When they backcross the 2 melons with different chromosome numbers it results in a seedless (or sterile) offspring in the same way crossing a horse with a donkey results in a sterile mule.  Modern seedless watermelons are of consistent quality and are just as sweet, crisp, and aromatic as the old time varieties.

Watermelons are mostly sugar water, but they do contain Vitamin C, a type of beta-carotene known as lycopene, and potassium.

The muskmelon (Cucomis melo) is not closely related to the watermelon but shares a common history.  It also was originally cultivated in the North African desert as a portable source of water.  Later, famers over many generations improved the quality of the fruit by selecting the sweeter individuals for seed.  Most people call muskmelons “cantaloupe.”  However, cantaloupe specifically refers to just 1 variety of muskmelon first cultivated in Western France.

References:

Chomicki, G.; and S. Renner

“Watermelon Origins Solved with Molecular Phylogenetics including Linnean Material: another example of Museomics”

New Phytologist Trust October 2014

Paris, Harry

“Origin of the Dessert Watermelon, Citrullus lanatus

Acta Horticulture March 2017