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F1 Hybrid. What is it?

Often the most expensive seed varieties in the catalogues are labelled as F1 hybrids. This article explains what F1 hybrids are and assesses their advantages and disadvantages

We often see F1 hybrid seeds in catalogues and, nearly as often, we wonder what exactly they are. Even more intriguing is the question: 'Is an F2 better than an F1?'

The simplest way to define an F1 hybrid is to take an example. Let us say a plant breeder observes a particularly good habit in a plant, but with poor flower colour, and in another plant of the same type he sees good colour but poor habit. The best plant of each type is then taken and self-pollinated (in isolation) each year and, each year, the seed is re-sown. Eventually, every time the seed is sown the same identical plants will appear. When they do, this is known as a 'pure line'.

If the breeder now takes the pure line of each of the two plants he originally selected and cross pollinates the two by hand the result is known as an F1 hybrid. Plants are grown from seed produced and the result of this cross pollination should have a good habit and good colour.

This is the simplest form of hybridisation; there are complications, of course. A completely pure line can sometimes take seven or eight years to achieve. Sometimes, a pure line is made up of several previous crossings to begin to build in desirable features and grown on until it is true before use in hybridisation.

To summarise, an F1 hybrid is the result of crossing two pure lines to achieve the desired result. This seems a lot of trouble to go to but there are definite advantages. Scientific and accurate breeding programmes have made it possible not only to bring out the outstanding qualities of the parent plants, but in most cases, these qualities have been enhanced and new desirable characteristics added to the resultant hybrid plants. In addition to qualities like good vigour, true-ness to type, heavy yields and high uniformity which hybrid plants enjoy, other characteristics such as earliness, disease resistance and good holding ability have been incorporated into most F1 hybrids. Uniform plant habit and maturity, coupled with uniformity in shape or size have made hybrid vegetables extremely suitable for mechanical harvesting.

We can't expect to get all these advantages for nothing. Because creating F1 hybrids involves many years of preparation to create pure lines and these pure lines have to be constantly maintained so that the F1 seed can be harvested each year, the seed is more expensive. The problem is compounded because to ensure that no self pollination takes place, all the hybridising of the two pure lines sometimes has to be done by hand. So you often have to pay more for your seed or get fewer in a packet. Seed is often collected by hand too to ensure that each plant is as productive as possible.

It is not only the gardeners who benefit, there are advantages for the plant breeders too. With ordinary varieties anyone can grow them and collect the seed which can then be re-sown in the garden or, on a larger scale, sold. So a plant breeder who puts a lot of work into creating a variety which is not an Fl hybrid can soon find someone else selling it and getting a share of the financial reward. But seed collected from an Fl hybrid will not produce plants the same as those from which it is collected. Only by crossing the pure lines can the variety be made - and only the original breeder has the necessary pure lines.

So it works both ways. The gardener gets better, though more expensive, varieties and the plant breeder gets a reasonable return on the investment.

Source of article
Growing From Seed - Winter 1989-90 Vol. 4 Number 1
© The Seed Raising Journal from Thompson & Morgan

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