Thursday, February 21, 2013
The watermelon, or Citrullus lanatus, belongs to a family of climbing vines that include cucumbers and gourds. And like all fruits, they naturally have seeds. The seedless versions are not genetically modified, as some might assume, but are hybrids that have been grown in the United States since the middle of the 20th century. Breeders match the pollen from a diploid plant, one that contains 22 chromosomes per cell, and the flower of a tetraploid plant, which contains 44 chromosomes per cell. The result is a triploid with 33 chromosomes that is incapable of producing seeds. (The tiny white ones you sometimes find are seed coats, where a seed did not mature.) Breeders call it the mule of the watermelon world.
From a Washington Post article, Watermelons: What happened to the seeds?