So yesterday was National Watermelon Day. When I think of summer—eating watermelon is one thing that pops into my mind. Eating it on the Fourth of July, fruit salads in the summer, and munching on it during the fall. These days I usually only eat it every so often (and only when I notice that one of the small cafes on campus is carrying it). I’m never sure how it would store frozen, and it always seemed silly trying to find a very small platter of it just for myself, when I wasn’t sure how often that week I’d be eating it.


Watermelons originated (and are still found) in southern and western Africa, and the domestication of the watermelon probably started between 5,000 and 6,000 years ago. As people started to travel in the area (merchant ships and then over land), the watermelon was introduced to areas such as Italy, Greece, and other countries around the Mediterranean Sea, then to China, and then further inland to Europe, and then as sea exploration grew more watermelon was introduced into other areas of the world: the Americas and Australia.

Did you know that there are three main subspecies of watermelon? The wild (which is still harvested today), the semi-wild, and then domesticated; and within the domesticated subspecies there are literately hundreds of different varieties of watermelon. Just within the Americas, we have over 300 different varieties of watermelon that are grown each year3.

The domesticated watermelons are grouped based on their characteristics, which can range from whether or not they have seeds (so seeded vs. seedless), size (petite or mini, and then normal), and then color (which is hard to distinguish in the store; but the colors can range from the normal pinkish-red to an orange or yellow color3).


Thanks to modern molecular genetics and sequencing, scientists have been investigating the nuclear1, and chlorplast2 genomes of the watermelon. It is now known that the watermelon has diploid genome and 11 chromosomes, and is predicted to have a little over 23,000 protein encoding genes1. The use of genomics will now allow for scientists to determine which disease resistant genes have been lost in different watermelon varieties and then figure out the variety to cross them to in order to regain that disease resistant gene.

Re-introduction of disease resistant genes into food crops is essential if we’re going to have enough food to feed a growing world population. Natural crossbreeding and hybridization will work, though it may be faster re-introducing the genes on plasmids and doing it through genetic modification.

So, I will probably do another post on why genetically modified foods aren’t bad—but will end this post with this note: As the population grows, and climate change gets worse we’re going to need crops that can withstand the new climate extremes—and modifying them in the lab/control fields is the way we’re going to have to go.

  1. Guo, et al. 2012 “The draft genome of watermelon (Citrullus lanatus) and resequencing of 20 diverse accessions”. Nature Genetics: 45(1) 51:60
  2. Shi, et al. 2017 “Full Chloroplast Genome Assembly of 11 Diverse Watermelon Accessions”. Frontiers in Genetics: 8(46) 1-4