Seedless watermelons are created by cross-breeding a diploid watermelon (normal watermelon with two sets of chromosomes) with a tetraploid watermelon (a watermelon with four sets of chromosomes). This results in a triploid watermelon (a watermelon with three sets of chromosomes) that produces seedless fruit.
Here's a more detailed explanation of the process:
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Creating Tetraploid Watermelons: First, breeders create tetraploid watermelons. This is typically done by treating diploid watermelon seedlings with a chemical called colchicine. Colchicine interferes with cell division, resulting in cells that have double the number of chromosomes.
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Cross-Pollination: The tetraploid watermelon is then cross-pollinated with a diploid watermelon. This means the pollen from a diploid watermelon is used to fertilize the female flowers of a tetraploid watermelon.
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Triploid Seeds: The resulting seeds from this cross are triploid (having three sets of chromosomes). These are the seeds you buy to grow seedless watermelons.
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Growing Seedless Watermelons: When you plant these triploid seeds, they grow into vines that produce seedless watermelons. These watermelons are seedless because the uneven number of chromosomes (three) prevents the plant from properly developing mature seeds through meiosis.
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Pollination is Still Required: Although the watermelons are seedless, the female flowers still need to be pollinated to stimulate fruit development. Therefore, seedless watermelon farmers typically plant diploid watermelons alongside the seedless varieties to provide the necessary pollen. Bees or other pollinators transfer the pollen from the diploid watermelons to the seedless watermelon flowers.
In summary, seedless watermelons are the product of cross-breeding watermelons with different numbers of chromosomes, creating a "mule" of the watermelon world that can produce the desired fruit but not viable seeds. Seed companies sell the seeds of these triploid varieties, which farmers then plant, ensuring pollination by also planting diploid watermelons.
