Søren just made a post on this topic, and it occurred to me I don’t ever remember anyone blogging about this very useful concept.
Grex is the Latin (and probably more correct) name, but some people may know it by it’s English name of Genepool Mix. The basic idea is to cross pollinate a number of plants, such that you get a mixture of genes that express themselves differently on different plants. A common example of a grex that some of us may have grown in our own gardens is 5-color Rainbow Swiss Chard. This is a grex made of different kinds of swiss chard, and so with one set of seeds you can grow many different colors. This is different from seed mixtures that are also sometimes sold, and are made by simply taking seeds from different kinds of plants and putting them in one package. A grex actually contains a mixture of genes, and probably no two seeds in any given package would have exactly the same genetic makeup.
A grex is commonly used in two ways. The first is in the case of the Rainbow Swiss Chard, and is for the purpose of creating a plant variety with a mixture of plants. The second is as a breeding tool.
Creating your own variety that is a grex is actually very difficult to do correctly. With such a large combination of genes, many can express themselves in undesirable ways, perhaps creating off flavors or appearances. When you create a genetically stable plant variety, you only need to concern yourself with one set of genes that express themselves the same way each time. With a grex you have dominate and recessive genes and gene combinations to concern yourself with. There is a reason there are not many grexes available for planting in your own garden, and those that do exist are not usually commercially developed.
As a breeding tool, sometimes grexes are very useful. If for example you want to create your own tomato by cross pollinating two other tomatoes, this will certainly work, especially if you have an idea of what you want in the resulting tomato and have parent tomatoes with corresponding traits. If you don’t have a clear idea in your head what kind of tomato you want in the end, or you have more than two parent tomatoes that have traits you want to try to get, a grex can be a better alternative.
But actually, as in the case of a tomato, there are disadvantages to grexes as well. Tomatoes need many years (sometimes as many as 10) of successive replanting to become genetically stable, and this time is likely to be much longer when working with a grex. It is better to use grexes as a breeding tool with plants that become genetically stable sooner.
When I visited Lieven a few months ago, he was busy with two grexes, lettuce and kale.
The grex that Søren is working on is a particularly interesting one. Melons are an unusually difficult plant to grow and breed in northern latitudes. Even if you do manage to get a ripe melon, you frequently don’t get one ripe enough to produce seeds. Trying to develop a variety suited to your own garden can be a very difficult undertaking. The answer to this problem? A grex, consisting of as many northern climate melons that could be found, grown initially in a more southern location! With a bit of luck, Søren will be able to create his own melon variety by selectively saving seeds from those melons that do well in his garden.
Søren got these seeds from the Seed Ambassadors when they were travelling around Europe. The Seed Ambassadors also traveled to Belgium, where I met them and I got some of these melon seeds too. If I have the space, I hope to grow them next year too. What a great gift from gardeners in more southern latitudes to ones further north!
Hi.
Talked with a lady, who have been breeding her own seeds for 20+ years. She has followed her own head, and done interesting things. For practical reasons she let white and red cabbage cross, in that way she has made her own white/pink/red cabbage grex. But to keep it a good grex, she has developed a practice of selection, to keep the colours in balance. There will develop a lot of pink cabbage, but if parents are selected for deep red or pure green, she gets more white and red, and less pink. She can do the selection before transplant, and still have a lot of material to select also for health and size. She do the same thing with yellow and red onions. I think a balanced grex allways goes with a balanced selection. Making a new grex include finding the right selection criterions.
I hesitate to include tomatoes into the grex family. Tomatoes (like lettuce and bean) are strong inbreeders. You will start with a cross, but end with one or more varieties in a mix. The varieties will repeat themselfes in each generation. I would rather call it a landrace, or should we make a new word “gardenrace”. In a grex I would expect genetic recombination in each generation.
For sure if you are trying to create a ‘stable’ grex, as a variety to grow yourself and/or share with others, this would have to be with outbreeding plants. Otherwise you would have to keep cross-pollinating the plants by hand, and that wouldn’t be very practical!