Consumer & Logistics > Watermelons

How Do We Get “Seedless” Watermelon” Seed?

We asked Bob Gillette, seed salesman from Abbott & Cobb, Inc., “How do we get ‘seedless watermelon’ seed?” He sent us the following reply:

“You asked me to explain how we get Seedless Watermelon Seed. I will tell you as much as I know and I hope the explanation will be about 90% accurate.

1. First I should explain the principle of where these seeds come from. Making a Seedless Watermelon seed uses the same principle as breeding a Mule. A Mule is a cross between a horse and a donkey. The horse is the mother and the Donkey is the father. When they breed, the result is a Mule. A Mule is sterile which means it cannot reproduce.
2. Much the same principle applies to plants. All species of plants make seed to reproduce. Each specie reproduces itself by different methods. In Watermelons the melon is the host by which seeds are formed to cause reproduction.
3. To create Seedless Watermelon seed is to start with a mother variety that will not pass on dominant traits to the offspring. The variety most used is the Charleston Grey variety as it is neutral and produces the most seed per melon. The seed of this variety is soaked in an acid, which makes it think it is a Tetraploid rather than a Diploid. The acid is really adding chromosomes to its genetics causing it to become a Tetraploid.
4. The treated seed (tetraploid) is grown in a field along with a pollinator, which is another Diploid. This pollinator will add the desired characteristics of the seedless melon to the Tetraploid.
5. Each watermelon plant will have both male and female flowers on each branch. The male flowers have to be removed from the Tetraploid so as to make sure the females are pollinated with the desired pollinator.
6. How one can distinguish between a male flower and a female flower is the female flower will have a baby melon the size of a pea on it. The farm worker removes the male by hand so the female will pollinate with the desired pollinator.
7. Pollen is take from the pollinator and rubbed onto the female flower of the Tetrapolid. To make this job easier, only four branches are allowed to grow on the Tetraploid. To distinguish between the pollinated flowers and the non pollinated flowers a bread tie is twisted behind the pollinated flower. The plants are pollinated every day until there are no more female flowers.
8. When the melons are mature, only the melons that have the brad tie on their stem are picked. They are put into bins and fed into a melon crusher to extract the seed. The extracted seed is then washed and dried.
9. After drying, the seed is shipped to the seed company for sizing, germination, disease testing and packaging.”

We found additional definitions and explanation on the Internet:

“ploid” –the number of single sets of chromosomes in a cell

“diploid” –2 sets of chromosomes

“tetraploid” –having twice the normal number of chromosomes

“polyploidy” – can be induced in cell culture by some chemicals (e.g. colchicines, which causes chromosome doubling)

An average plant has 2 sets of chromosomes. To enhance certain qualities in some species, scientists have bred Tetraploids (four sets of chromosomes).
The flowers on Tetraploids are generally bigger than on other varieties of the same species, but there are fewer of them and the plant generally grows slower than the types with 2 sets of chromosomes.