The Surprisingly Simple Parentage of Seedless Watermelon

One of summer’s sweetest treats are fresh, ripe watermelons. Whether eating it cut up or right off the rind, this juicy red fruit is a refreshing break from summer’s heat. The fruit comes in a variety of sizes, and also in seeded and seedless options.

But have you ever stopped to think about that – how do we get seedless watermelons?

Think about it. With a seeded watermelon, those big black seeds inside the fruit could be cleaned and planted to produce a new crop. But the little white “seeds” in a seedless watermelon are immature and cannot be planted to produce a new crop. So, how is it done?

The National Watermelon Promotion Board explains:

Chromosomes are the building blocks that give characteristics, or traits, to living things including plants and watermelons. Watermelon breeders discovered that crossing a diploid plant (bearing the standard two sets of chromosomes) with a tetraploid plant (having four sets of chromosomes) results in a fruit that produces a triploid seed. (Yes, it has three sets of chromosomes). This triploid seed is the seed that produces seedless watermelons!

In other words, a seedless watermelon is a sterile hybrid which is created by crossing male pollen for a watermelon, containing 22 chromosomes per cell, with a female watermelon flower with 44 chromosomes per cell. When this seeded fruit matures, the small, white seed coats inside contain 33 chromosomes, rendering it sterile and incapable of producing seeds. This is similar to the mule, produced by crossing a horse with a donkey.

That’s all it is, good old fashioned breeding. By understanding the genetic material in the watermelon, we are able to breed the plants to give us the seedless version.

Many people have mistakenly thought that these watermelon are produced with genetic engineering, making the seedless watermelon a “GMO.” Nope. This type of breeding is not considered one of those methods classified as genetic engineering and, therefore, the fruit does not fall into that category. In fact, the seedless watermelon has been around for some 50 years, while GMOs only debuted about 20 years ago.

Now, you can enjoy that summer treat and show off some scientific knowledge with your friends.