Summer is in full swing in North America, and watermelons are on the menu. You might be wondering about some of the specialty watermelons you see at the grocery store — seedless watermelons, mini watermelons, yellow-fleshed, even cube-shaped. How did these fruits come to be? How did they come to be SQUARE?!! Could it be genetic engineering?

In a word, no. We're happy to report that there are no commercially available watermelons on the market at this time, and all the above-mentioned varieties are the product of traditional selection and breeding and innovative cultivation practices (which we'll explore below).

How to make a GMO

Genetically modified organisms are living organisms, such as plants or animals, that have been subjected to biotechnology to alter their fundamental characteristics. Biotechnology can use synthetic genetic sequences to change the organism's genetic material, or force the combination of very unrelated organisms that would not normally reproduce in nature. You can find out more in our article, What Is a GMO?

How to make a seedless watermelon

Seedless watermelons invite the most speculation among shoppers who prefer to avoid GMOs. However, several kinds of seedless fruits are the product of non-GMO techniques, such as mutation breeding. 

All living things have chromosomes inside the nucleus of their cells, including the crops we eat. Chromosomes are how genetic information is stored and passed on to future generations through reproduction. Different organisms have different numbers of chromosomes and different numbers of copies of those chromosomes. For example, humans usually are diploid creatures, with two copies of 23 chromosomes, for a total of 46. 

Typically, watermelons are also diploids, but seedless watermelons are triploid, with three copies of their chromosomes. Seedless watermelons are created by crossing a common diploid watermelon (two copies of the chromosomes) with a tetraploid watermelon (which has four copies of the chromosomes). Each parent plant passes on half its genetic information, so the progeny ends up with three pairs of chromosomes, making it unable to produce viable seeds.

More novel melons: Mini, cube-shaped, multi-colored

Mini, or personal-sized watermelons, are created through selective breeding and have been available commercially since 2003. For example, one researcher described her company's work selecting the smallest, sweetest and earliest-ripening fruits to create a line of mini watermelons for shoppers concerned about food waste or excess food packaging.

Watermelons have also appeared in grocery stores in unconventional shapes, such as cubes, pyramids and even hearts. These, too, are non-GMO. They are grown by placing a translucent mold around a young fruit so it grows into the intended shape. The square watermelon might appeal to shoppers looking to maximize fridge space, while the heart-shaped melon could make an interesting Valentine's Day gift. You'll have to save up for it, though — oddly-shaped melons can fetch hundreds of dollars. 

Red-fleshed watermelons are the most common variety, but the fruit also comes in yellow, orange, pink, or even white. The range of colors comes about through naturally occurring variation in how much lycopene, an antioxidant that causes the flesh to be more red, is present. Differently-hued watermelons might have a slightly different taste than their red-fleshed counterparts, but they offer similar nutritional benefits and can be used interchangeably in recipes. 

A mini, cube-shaped or yellow watermelon might also be seedless if the tetraploid mutation is bred into the novel strain — but, they're still not GMOs. That means you can enjoy all of summer's sweetness with confidence.

At the Non-GMO Project, we're committed to helping you make informed choices about the food you eat. By understanding the difference between traditional breeding and genetic modification, shoppers can navigate the grocery store with confidence. Stay cool and savor the sweet taste of summer, without GMOs. 

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