Seedless watermelon seeds

In my last column, I discussed how a seedless watermelon seed is produced.

But seedless watermelons won’t be successfully grown without taking a few extra measures to insure that the system works.

First of all, the triploid embryo is poorly developed inside the seed. This makes them less likely to germinate, without taking special care. Moisture control and temperature must be observed carefully, or else poor germination will occur. And even when they do germinate, they are usually weak plants.

Once you finally get a good plant started, it will eventually outgrow the weak stage and take off in the field like any other watermelon plant. However, to produce melons, special care must be taken to insure good pollination.

Since triploid watermelon plants are sterile, that means that their own pollen will not fertilize the flower. To produce a fruit, you must use pollen from a normal diploid watermelon. That means that a diploid pollenator watermelon plant must be grown in the field in close proximity to the triploid melon. This introduces another element of concern … the grower must select a diploid watermelon cultivar which is easily differentiated from the seedless watermelon, so that they are not mixed together when shipping.

Occasionally, you will find a fully-developed seed in a triploid watermelon. Obviously, something didn’t go according to plan. It seems that very rarely, fertile gametes are produced by the triploid plant. One estimate puts this occurrence at less than 0.1%, which is why hard seeds are rare. More likely you will see seed traces, which are pale, undeveloped seeds. The likelihood of seeing seed traces is much higher, and will vary depending on the genetic tendency of the cultivar to produce seed traces, and the growing conditions.

Because seedless watermelons are hybrid plants, there is a lot of hand labor needed to make the crosses. In addition, the tetraploid parent doesn’t produce as many female flowers compared to diploid plants. These and other factors combine to make triploid seed very expensive.

So in a nutshell, that’s how a seedless watermelon is developed. It’s not too complicated, but does involve a little understanding of genetics. Explaining the genetics usually isn’t too hard, unless it’s in a foreign language. Once I was giving a tour of a watermelon field in Mississippi County to a group of East Europeans. Through an interpreter, they asked how did you get a seedless watermelon if there was no seed? So I gave a quick version of what you have just read. The interpreter looked at me, as if to say, "Huh?".

Well, the interpreter took off into some explanation, none of which I understood, although every once in a while I heard something that sounded like "chromosome." I later asked Anthony Ohmes, our Mississippi County Agronomy Specialist, how much of that did he think made it through the interpreter to them. "Probably not much," was his quick reply.