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Background & Techniques
The books available from the library give detailed information on seed saving and plant breeding techniques, including specific guidelines on a plant-by-plant basis (see also the websites on the links page) so I won’t reinvent the wheel here. But I thought it might be useful to offer the following brief primer to get the ball rolling.
There are various characteristics we might want to select & breed for in our vegetables such as large size, small size, taste, early maturing, late maturing, long harvest season, pest & disease resistance, drought tolerance, damp tolerance, colour. A lot of this work has already been done by our forebears and the professional breeders of today, but their concerns are not necessarily the same as ours. If we want plants which have exactly the characteristics we’re looking for and which perform optimally for us here in Frome, then we’d better breed them ourselves! Alternatively, if we come across plants in our gardens that seem to exhibit useful or interesting traits of some kind then why not save the seeds? In either case, we’ll be helping to maintain and improve the genetic diversity of our food base, which is best not left to the professionals alone (see my rant for further details).
Seed-saving is the first step in a local plant-breeding programme. By choosing to save seed from the plants we like best, we’re already embarking on a selective breeding programme which can form the basis for new and improved varieties (unless the plant’s desirable characteristics have nothing to do with its genetic inheritance – it pays to be scientific in our breeding efforts!)
But it’s not quite that simple. If the plants we’re saving from were a hybrid (a cross between two different varieties) then their seeds probably won’t produce many plants with characteristics like the parent plant – hybrids are usually identified on seed packets as ‘F1’. Even if the plant is not a hybrid (a so-called open pollinated variety), its seeds may still not produce plants like the parent plant. It probably will if it’s an inbreeder (a plant that pollinates itself) – typical inbreeders are lettuce, tomatoes and beans. But if it’s an outbreeder (a plant pollinated by other plants) then the seed will transmit the characteristics of both parent plants and so to control the variety we need to select for the characteristics of both parents (not always easy when pollination occurs by the wind or by small insects). Typical outbreeders are brassicas, cucurbits and spinach. The distinction isn’t hard and fast, though – there’s a continuum between inbreeding and outbreeding.
There are various further issues to contend with if we want to breed new plant varieties in which the seeds produce uniform, quality plants that are true to type. These include inbreeding depression, gene linkage, codominance, variable expressivity and polyploidy and they affect the kind of plant-breeding approach we have to take (see glossary). Their names alone might sound enough to put you off trying to breed plants, but it’s worth remembering that our ancestors worked out how to breed plant varieties successfully long before anyone even knew what gene linkage or codominance was.
I imagine that our forebears just saved seeds from plants they liked the look of, and watched to see what happened when they sowed them. Not a bad way to proceed. Doing things this way you might quickly get the traits you want, or you might only get them after a lot of trial and error, or you might never get them at all, depending on the underlying characteristics of the plant. But by arming ourselves with a bit of modern genetic knowledge, we can save ourselves a lot of time.
We can save ourselves time too by conducting careful trials, including controls. If Tomato Plant A avoids blight when all the others in the row succumb, is it because it’s genetically endowed with a resistant trait that we can work with as breeders, or did it just get lucky? We can help each other by figuring out some good trial designs to isolate true genetic traits. In fact, by working and learning together I’m confident that we can make Frome a flourishing epicentre of vegetable biodiversity!
Chris Smaje |
