‘Somerset’ is a popular hardy seedless grape for home gardens. Photo: Gurney’s
Question: I’m not much of a gardener, but I’ve been growing ‘Somerset’ red grapes with great success for a few years now and I’m really quite proud of my results. I have just one plant and I harvested two bushels of grapes this year. They’re seedless and that always intrigues me. If they’re seedless, how do they reproduce? And where do they come from?
Answer: The first answer is quite simple: they don’t reproduce, not by seed at any rate. But you can take a cutting of any grape vine and produce an identical plant that way. Or you can graft it onto another grape plant. So, once a seedless grape has been developed, from then on in, you just keep multiplying it by cuttings or grafting.
The same goes for fertile grapes, the ones that do produce seed: you don’t start new ones from seed unless you’re experimenting or hybridizing. Instead, nurseries keep a good variety going by starting identical plants from cuttings or grafts.
That also applies to most other fruits: apples, oranges, raspberries, pears, cherries, etc. Rarely are they grown from seed. Instead, plant nurseries “clone” the best varieties through cuttings or by grafting.
And, of course, seedless grapes, with no seeds you have to unobtrusively dispose of when eating in public, are the ideal table grape and now make up the bulk of the table grape market worldwide. And raisins are produced by drying seedless grapes. Wine grapes, on the other hand, actually need the seeds: with certain varieties especially, the seeds rich in tanins help give the wine its desired flavor.
But Where Do Seedless Grapes Come From?
Now, as to where seedless grapes come from (and there are in fact dozens of varieties!), that’s more complicated.
Every now and then, Mother Nature makes a mistake and produces, from seed, a plant that can’t carry out full seed production. Seeds do start to form, but then abort, yet the fruit continues to mature, giving you a seedless grape. If you cut a seedless grape open, you’ll find tiny specks inside: those are aborted embryos. The tiny black specks inside bananas—another seedless fruit!—are likewise aborted embryos.
Seedless grapes are believed to date back to Roman times. The green seedless grape we know today as ‘Thompson’s Seedless’ (it has had many different names over the eons, including ‘Lady deCoverly’) seems to have been one of the original seedless varieties and is likely the parent, directly or indirectly, of most of the seedless grapes of today.
Hybridizers can actually cross seedless grapes together (the flowers are fertile) to produce new seedless varieties. As the fertilized fruit starts to grow, however, they must perform an “embryo rescue”: removing the still living seed embryo before it can abort. They can then grow it on in tissue culture (i.e. in a laboratory) until it is large enough to sprout and produce a new grape plant. So, you could say seedless grapes are test tube babies!
But you only have to do that to create new seedless varieties. If you have a seedless grape whose traits please you, like ‘Somerset’, just start new ones through cuttings or grafting!
Hi i Just read your work regarding seedless grape breeding by embryo rescue. can you just explain me which nutrient medium you used and what are growth conditions required for it?
Sorry, I only reported about this. I didn’t do it myself. You’d need to look for a hybridizer who does this sort of thing.
Most people who do not enjoy gardening do not realize how common cloning is, or that we do not do much of it in the nursery industry. Some of the citrus and rhododendrons cultivars that I used to grow have been getting cloned for centuries.
Many of the old redwoods that were grown (for landscape purposes) prior to the development of cultivars were grown from seed. Their genetic variability is very obvious.
Inquiring minds wanted to know, and you answered. 🙂