BIOLOXÍA E XEOLOXÍA 4º ESO. 2023/24

So, how are seedless watermelons grown? 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 – simple cross-breeding. And to be clear on the subject, this is not genetic modification. Cross-breeding is two parents and their offspring.

Importantly and interestingly, seedless watermelon still need to be pollinated by their seeded parent, so oftentimes growers will plant seeded and seedless in their field. However, the seeded commercial harvest and retail sales only add up to about 8%, meaning seedless watermelon makes up for 92% of all watermelon sales. Seedless watermelon is hugely popular in the United States and it is here to stay.