How are seedless watermelons produced?

Seedless watermelons are produced by crossing a diploid watermelon (with 22 chromosomes) with a tetraploid watermelon (with 44 chromosomes), resulting in a triploid watermelon (with 33 chromosomes) whose fruit is seedless. These triploid watermelons are sterile hybrids.

Here's a more detailed breakdown:

• The Starting Point: Different Chromosome Numbers: The process begins with two types of watermelons:

  • Diploid Watermelon: A normal watermelon containing two sets of chromosomes (22 in total).
  • Tetraploid Watermelon: A watermelon that has been bred to have four sets of chromosomes (44 in total). This is achieved through the use of a chemical called colchicine.

• The Cross: The male pollen from a diploid watermelon is used to pollinate the female flower of a tetraploid watermelon. This cross-pollination is crucial.

• The Result: Triploid Seeds: The resulting seeds from this cross are triploid, meaning they have three sets of chromosomes (33 in total). These triploid seeds are what are sold to farmers to grow seedless watermelons.

• Growing Seedless Watermelons: Farmers plant these triploid seeds. When the triploid watermelon plant flowers, it is unable to produce viable seeds. This is because the uneven number of chromosomes (33) prevents proper pairing during meiosis (cell division that leads to seed formation).

• Pollination Still Required: Seedless watermelons still need pollination to develop fruit. Therefore, farmers also plant regular diploid watermelons in the field as pollinators. The pollen from the diploid watermelons stimulates fruit development in the seedless watermelons. However, because the seedless watermelon plant is triploid, the resulting fruit develops without mature, black seeds. You might find some small, white, edible "seed coats," which are simply undeveloped seeds.

• Summary in a Table:

In essence, seedless watermelons are a carefully cultivated hybrid that relies on the manipulation of chromosome numbers.