Where Do Seedless Watermelons Come From?

When a run-of-the-mill watermelon and a souped-up frankenmelon love each other very much, they come together and make a baby seedless wundermelon.

Seedless watermelons are a lot like mules – sterile hybrids formed by crossing genetically incompatible parents. Normal, seeded watermelons are diploid (have 2 sets of chromosomes) just like us, with one set from mom and one from dad. When the two combine, their seeds grow into a plant that looks like a combination of its parents. Just like us.

But sometimes farmers treat some of their watermelons with colchicine, a chemical that allows chromosomes to duplicate but prevents them from splitting into two cells.

This creates a tetraploid – a super-squash with four complete sets of chromosomes. The fruit isn’t genetically modified; cells contain the same DNA as standard melons – just twice as many.

Next, the farmer introduces this new tetraploid watermelon to a regular melon. If they hit it off, they’ll produce a triploid melon with 3 sets of chromosomes. This offspring will grow up to be a normal looking vine that produces flowers and fruit. But when it tries to reproduce, the chromosomes can’t divide properly. This means that real seeds never develop.

Those Little White Things

But wait a second - what are those soft white shells in the supposedly seedless melon that look like the tiny, underdeveloped seeds? These are the ovules (also called “pips”), the part of the plant that would become the seed in a normal watermelon. It’s really just soft coating – you can’t actually plant them.

For the past 50 years, this melon has saved millions of adults from losing face in no-holds-barred seed–spitting contests. Let’s face it: the nine-year-olds always win. So next time you’re savoring seedless watermelon, show some gratitude for the miracle of science responsible for its existence.

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July 16, 2012 - 5:02pm
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