How a New Variety of Strawberry Plants is Developed

new strawberry varietiesHave you ever wondered how a new variety of strawberry plants is developed?  The big, luscious strawberries that we all know and love haven’t always existed.  In fact, they are a relatively new phenomenon.  The original wild-type strawberry species produced (and still produce) tasty strawberries.  But, those strawberry plants cranked out tiny (relatively speaking) fruits.  When the first Garden Strawberry was successfully bred (see the Strawberry Plant page for more of the development history of today’s strawberry plants), the path was paved for the creation of the strawberry cultivars we grow today.

While the most successful breeding programs are funded by the state, individuals or non-governmental groups can endeavor to breed better strawberry plants as well.  This post describes some of the thoughts and targets that should guide any strawberry plant breeding program.

Genetically Modified Strawberries Need Not Apply

With the tinkering going on in the genomes of quite a few organisms these days, it may be a comfort to know that genetic engineering of strawberry plants is uncommon.  All of the most commonly purchased and planted strawberry varieties have been developed using traditional crossbreeding methods.  This means that the average plant breeder can strive to develop an improved cultivar himself in the same way the “big boys” do it (assuming you have the time, patience, and facilities needed).

What Are the Goals When Developing a New Variety of Strawberry Plants?

The primary goal of a breeding program is to develop a cultivar that is especially suited to a particular growing environment in ways that make it have superior traits when compared to existing strawberry varieties.  New strawberry varieties should improve production efficiency and/or produce strawberries that possess more beneficial traits or better expression of beneficial traits.  The major challenge is to develop strawberry plants that exhibit new and improved traits without diminishing or losing any of the previously established beneficial traits.

Additionally, new strawberry cultivars should be developed in an effort to solve environmental drawbacks for any given location.  Because of this, different cultivars will likely be developed in different states that are ideally suited for the state or area in which it was developed.  For example, a new cultivar that does splendidly in Maine may do terribly in Florida, and vice versa.

So, this is the process of developing a new strawberry variety:

Step 1: Determine the Traits You Want in the New Strawberry Variety

The desired traits will likely forever be in a state of flux.  New strawberry varieties will be sought whenever changes in climate, weather patterns, and especially commercial demands and cultivation or agricultural practices change.  And, with new, improved cultivars being developed, the standard for acceptance of a new strawberry variety will also continually ratchet upward.

It is almost a given that improvement in certain traits would be desired.  If improvement in yield, strawberry size, ease of harvest, and the pattern of production can be achieved, this is desired.  Other improvements can also be sought for strawberries destined for the marketplace.  The appearance of the strawberries, the color of the berries, the durability, shelf-life, and shipping quality of the new strawberry variety, and flavor improvements are areas that can be targeted for new cultivars.

Breeding new strawberry plants that have resistance or tolerance against the common pests and diseases endemic to the target location is also very important.  What good is a wonderful new strawberry variety if the plant gets killed off prior to harvest?  The cull rate, level of uniformity of berry size, and the structure and size of the mature strawberry plants are all factors that can be targeted for improvement in a new strawberry variety.

Can change with the commercial market, will usually get increased standards as new strawberry plants are successfully bred.  May also have to change with new improved or changing cultivation and agricultural practices.  Target traits for any new cultivar include: improved production attributes (yield, production pattern, fruit size, ease of harvest), superior quality for both fresh and processing markets (fruit appearance, color, shipping quality, shelf life, and flavor), and resistance or tolerance to important pests and pathogens. factors that affect harvest efficiency (cull rate, consistency of fruit size, plant size and architecture) have gained importance.  Therefore, further improvements in productivity must not be obtained at the expense of added production costs.

Step 2: Choose the New Strawberry Variety’s Parents

Once the traits that are to be targeted for improvement are identified, the parent plants must be selected.  Here, established plants are usually selected based on their different strengths with the hope that the crossbreeding will pass on the beneficial traits from each, thus producing a new strawberry variety with improved overall traits and performance (with none of the negative characteristics of the parent plants).

Step 3: Repeatedly Breed the Parent Strawberry Plants

Once you have chosen your parent strawberry plants, crossbreed them.  Again.  And again.  And again.  The big operations and breeding programs will start the next phase only after performing 100 to 150 controlled crossbreeds between selected parent cultivars.  Unless a backyard gardener has lots of time and space on his hands, he will have to settle for fewer crosses (and fewer opportunities to select a “winner” later).

Step 4: Grow Strawberry Seedlings from the Fruit of the Crossbred Plants

Once the genetic information is collected and stored within the seed, collect seeds, plant them, and grow seedlings (see the Strawberry Seeds page for help here).  Here also, do what you can by planting as many as you possibly can.  The big operations will start off with seedling populations well into the thousands (8,000 to 14,000, total).

Initial evaluations are performed on the basis of seedling performance, with primary populations of 7,000-12,000 seedlings established at both South Coast and Davis, and a supplemental population of 1-2,000 at Watsonville. Approximately 200-300 items are retained from each primary seedling population,

Step 5: Evaluate the Seedlings and Select the Best

The professional or state-sponsored breeding programs will only keep two to three hundred seedlings out of all those thousands.  The strongest, most vigorous seedlings are selected and the others are culled.  The small-time or home breeder should keep a higher percent of total seedlings.  Usually selecting the top 5% is adequate.

Step 6: Test the New Varieties of Strawberry Plants

Now that the best seedlings have been selected, they need to be further tested.  The seedlings should be planted in an area and in a way that simulates how and where they will be cultivated if it turns out they do have improved traits.  The runner production should also be evaluated (for help, visit the Growing Strawberries page).

Additionally, if possible, the new strawberry varieties should be tested to determine their resistance or susceptibility to common pathogens and pests that commonly affect strawberry plants.  This determination should be made for each retained and planted seedling strawberry plant group once they have been established.  They should be tested for resistance/susceptibility to two-spotted spider mites, Anthracnose crown rot, and Verticillium wilt at a minimum.

Step 7: Selection of the Specific Strawberry Plants that Perform Best

It is time to pick the winning new strawberry variety!  If the genetic manifestation of the targeted qualities is present without introduction of negative qualities, it is a winner.  If, after multiple years of trials and observation, the new variety holds up and proves to be superior, it is time to release it.  If it was created in the home garden, the developer gets naming rights, so be creative!

A Few Closing Words on New Strawberry Varieties

It is not easy to create successful new strawberry cultivars.  But, the benefits that come when success is found make it worth the effort.  Plus, the home gardener will learn much throughout the process.  In addition, remember that the entire process will take patience.  The large breeders and development programs can complete the entire process and introduce a new strawberry variety in as little as 5 to 6 years.  It is more likely to take a home gardener 10 or so years to adequately evaluate and record and prove that there is improvement.

But, remember, it can’t hurt to experiment.  And, you never know…you might hit the jackpot on your first try and create a new strawberry variety that sweeps the fruit world by storm.  Happy crossbreeding!

If you would like information on the many strawberry varieties that have already been developed, be sure to visit the Strawberry Varieties page.


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