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Vegetable Seed Saving Handbook


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Breed Your Own Varieties

Create Your Own Varieties!

As a home gardener, you can easily develop new varieties adapted to your tastes and local climate, or to low-care gardening techniques. Often, all that's needed is a sharp eye and an idea of what to look for. Productive, low-care food plants are especially important in these days of changing values, declining resources and chemical-dependent hybrid food plants.

How to Select a New Strain from an Existing Variety

According to Breed Your Own Vegetable Varieties , the easiest way to create new plant varieties is by simple 'selection.' Selection means allowing only plants that show desirable traits to produce seeds. If any plants don't show the traits you are looking for, you prevent them from pollinating the plants you have selected. It's possible to see changes in your variety the very next season!

Good candidates for selection might show better-than-average productivity under your gardening conditions, or high drought tolerance, or particularly good taste for instance. After a few seasons of saving seeds from only plants with the desired traits, a new strain can be created that is markedly different from the original variety.

Be careful not to go overboard when deciding which plants will be kept from reproducing, however—a healthy degree of genetic variability is essential to the vigor of any breeding population. If you become too selective and reduce the total number of parent plants to too-low a number, your variety will soon weaken from loss of genetic variability.

A good idea for maintaining some genetic diversity when selecting new varieties is to plant some seeds of the original variety in with your newly-selected seeds each season—especially after a season or two of aggressively developing the new traits. This will slow the process of creating your new variety over the short term, but will ensure that your seeds maintain their vigor over the long term because of having a sufficiently broad range of genetic characteristics.

An interesting example of ensuring continued vigor in a new variety by occasionally reintroducing some of its original ancestral genetic variability is the traditional Mexican practice of allowing an occasional teosinte plant (corn's wild ancestor) to grow among the corn plants in their fields. The campesinos know that the wild teosinte will add genetic variability, adaptability and vigor to their domesticated seed stocks.

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Advantages and Disadvantages of Selection

The selection process has complementary advantages and disadvantages. Careful consideration should be given to balancing these influences so as not to cause damage to a variety's genetic health and diversity.

Selection By Itself Lowers Genetic Diversity

Selection used by itself always results in the loss of genetic material. Without taking steps to counteract this loss, a selected variety's gene pool will be smaller and less diverse than the gene pool of the original variety (a gene pool is the sum total of all the genetic traits contained in the entire population—no one plant will contain all the genes available to the variety as a whole).

This genetic narrowing may include genes that are useful elsewhere, or under different growing conditions, or even under your own conditions but in a different year. The group of plants within your newly selected variety will not have the genetic ability to respond successfully to as wide a range of situations as the variety that was started with—even though the new variety may be better adapted to your situation during a particular growing season.

The reason the new variety's gene pool will be smaller is that the new variety was formed by subtracting traits from the original variety (by keeping particular plants from reproducing). The practice of planting a few of the original variety's seeds with your new selection is one way to help counteract this trend toward genetic loss.

Ways To Keep Your Selection Genetically Diverse

The above point (i.e., selection narrows the original genetic base) is important to keep in mind when choosing a starting variety from which to make selections. Don't start with a variety already overly-refined by earlier selections. Previous selection means that characteristics will already have been lost that might be useful under your conditions.

Start With a Diverse Variety

If you can find an older, more variable variety to start with, you'll have a broader range of potentially-useful characteristics to select from. Greater initial variation gives you a better chance of finding the adaptations you are looking for, while still ending up with as genetically diverse a population as possible.

Mix Some of Your Favorite Varieties For a Wider Genetic Base

Another way to keep your new selection from becoming too genetically-narrow is to grow two or more varieties together for a couple years, and then start selecting your new strain from the resulting mix.

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Advantages of Selection

The main advantage of selection is that plants from your newly selected variety will more consistently exhibit the traits you prize... good taste, prettier foliage or flowers, better adaptation to your growing conditions or climate, etc. By selecting the individual plants in a variety that perform well for you and discarding those less adapted, you can create a more useful variety from a less useful one.

Selection vs. Preservation

It is important to remember that selection must be secondary to preservation of the original genetic material. If you are growing a variety for preservation specifically, do not select out plants that perform poorly for you. If you do, you may discard genetic material valuable to someone else under different conditions.

When a variety is preserved intact, selections can always be made later. Once selections have been made, however, the genetic material discarded is lost permanently unless somebody, somewhere is preserving the original variety. Though completely avoiding loss of some genetic material as a result of local growing conditions is virtually impossible, for preservation purposes an attempt is at least made to save all the original traits.

If you want, you can practice both selection and preservation simply by treating the two batches of seed (preserved and selected) as separate varieties (see Avoiding Unconscious Selection and Avoiding Cross-Pollination).

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How to Make Breeding Selections

To select for local adaptation or other traits, grow your starting variety as usual. It's best to start with a large planting, to increase your chances of finding enough individual plants with the traits you are looking for. The plants may even be planted a little too closely and pruned to allow planting more plants in a smaller-than-usual area. The primary short-term goal is to identify and save seeds from as many plants as possible with the hoped-for characteristics.

Actual selection can begin to take place as soon as the plants show desired or unwanted traits. Allow individual plants to flower and produce seed only if they share the trait or traits you're looking for. Or, several groups with distinct traits can be selected and bred into several new varieties. When selecting for more than one distinct group of traits, of course, best results will come from keeping the newly-selected groups isolated in subsequent plantings, to allow them to stabilize into new varieties without cross-pollinating each other.

Be sure to remove unwanted plants before they have had a chance to shed pollen, or they will contribute unwanted genes to your preferred group of plants. The more plants with the desired traits that you allow to breed and produce seed for succeeding generations, however, the wider (and hence more stable) will be the genetic base of your new variety.

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Finding Selection Material

The best plant varieties to start with show a high degree of variation between individual plants. Some seed companies (see Plant Breeding Resources) sell 'breeding' varieties which are ideal for the purpose of selecting new strains because of their genetic variability.

An example of a highly-variable variety would be an old 'Indian corn' that has multi-colored kernels ranging through reds, blues, yellows, white and black. Older traditional and heirloom plants often contain more variation than newer varieties, and wild plants show even greater variation between individuals. Nature is fluid and ever-changing, so unique traits can be found in any plant population, waiting to be preserved as new varieties.

'Land races' are another good source for the genetic variability that lends itself to selection. Land races, which come from a plant's geographical place of origin, are an intermediate step between wild and domesticated plants. They have never been inbred into distinct, uniform varieties, and often still interbreed with nearby wild ancestors. This infusion of wild genes invigorates the domesticated plants and widens their genetic base.

Forcing Selection for Low-Care Plants

One possible type of selection is aimed at adapting a variety to require less care under your own specific local growing conditions. This process can be accelerated by purposely stressing a planting until some percentage of the most-susceptible plants die or fail to produce seeds. The remaining plants are then better-adapted to the stressing conditions. Repeating this process for several generations can produce a variety significantly better adapted to your climate, soil and gardening habits than the starting variety.

An example of purposeful stressing would be to force for drought-resistance by letting the most drought-intolerant young plants die of water stress before the survivors are allowed to grow to maturity and produce seeds. Similar selections can be made for low fertility, season-extension (i.e., frost-tolerance), etc.

Be sure when stressing plants for selection purposes, however, to allow the plants time to recover from the stresses and regain some vigor before flowering starts, in order to insure good, healthy seed crops.

Keep in mind that seeds produced by plants which have been stressed (purposefully or otherwise) are not likely to live as long in storage as seeds produced by more robust plants. When stressing plants to produce adapted seeds, replant the stressed seeds more often than you would plant normal, healthy seeds of that variety.

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Hybridizing and Stabilization

While cross-pollination is to be strictly avoided when growing a variety for preservation, crossing is not an absolute 'taboo.' Just as traditional Mexican farmers have learned to naturally hybridize their corn plants with teosinte to increase vigor, home gardeners can hybridize their own favorite plants to increase the vigor and diversity of their seed stocks. By allowing varieties to 'hybridize' or cross-pollinate, new populations with more diverse gene pools are produced. The hybridized, highly-variable varieties that result can then be regrown for several generations in order to select from and stabilize them into new open-pollinated varieties that breed true-to-type.

Again, however, don't practice hybridization with rare heirloom varieties in need of preservation! Use only varieties with plentiful sources, or first create a good quantity of seed grown specifically for preservation purposes and then experiment with just a small quantity of those seeds.

How to Create Open-Pollinated Plants from Hybrids

New open-pollinated plants can be created by crossing, or 'hybridizing,' two or more varieties and then simply regrowing the resulting cross normally, until it is stabilized into a new open-pollinated variety. Hybrid plants can be created by a variety of means, from very simple to quite complex.

On a very simple level, one or more favorite varieties of plants which will cross-pollinate (peppers, for example) can be grown together and allowed to naturally cross. During the first generations a mixed group of characteristics will be produced. The mixed plants can then either be allowed to continue mixing and stabilize naturally, or they can be separated into groups that share particular traits found in the initial crossings.

Another simple way to work with hybrids for selection and stabilization is simply to plant your favorite commercial hybrid variety(ies) and allow them to produce seeds. Then collect and replant the seeds over several generations, selecting for desired traits or allowing the plants to blend naturally. In this way you can stabilize new, open-pollinated varieties with unique combinations of traits, and no longer have to rely on the original hybrid variety.

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Creating and Stabilizing 'F2' Hybrids

On a more technical level, 'F1' (conventional 'hybrid') plants can be produced by hand-pollinating a female of one variety with a male of another variety (or even two plants from different, but closely related, species). The female is then allowed to produce seeds while being kept from crossing with any other plants. This controlled method produces very specific, reproducible hybrid crosses (this is how commercial hybrids are produced). Varying levels of care and difficulty are involved, each beyond the scope of this handbook.

F1 hybrids are usually produced from two distinctly different, open-pollinated parent varieties. While the resulting first-generation hybrid offspring (the 'F1' generation) are outwardly uniform, each F1 plant actually contains great genetic diversity.

When these F1 offspring mature and produce seeds, very diverse 'packages' of genes are mixed to create the second (F2) generation. Unlike the apparently-uniform F1 generation, the F2 generation will show a wide range of different physical characteristics.

F2 hybrid seeds are not 'stabilized' into varieties, however, and so do not reliably reproduce true-to-type offspring. Stabilization is achieved by replanting for several generations and selecting (if desired) for desirable traits as described above. Remember to segregate plant groups chosen to form new varieties, to allow them to breed only with each other. In this way the new, selected-for traits stabilize and will be reproduced consistently by subsequent generations.

You've created a new variety adapted to your own, local gardening conditions and cooking tastes!

Learn More

To learn more about breeding new vegetable or flower varieties right in your own garden, read Carol Deppe's excellent book Breed Your Own Vegetable Varieties: The Gardener's & Farmer's Guide to Plant Breeding & Seed Saving .


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Reprinted from Vegetable Seed Savers Handbook, Jack Rowe 1998, howtosaveseeds.com