Selectively Breeding Pepper Plants

Have you ever had a pepper plant that was "different" in a way that made it one of your favorites – a pepper plant you'd like to grow year after year? Perhaps, it was an accidental or purposely created hybrid. Or, it was simply a traditional pepper cultivar that happened to have larger fruit, better flavor, or a higher yield.

Now what? You could take cuttings to clone the plant. Cloning would produce an exact genetic copy, though, cloning attempts don't always root successfully – and overwintering the cuttings potentially creates other issues.

It'd be more convenient to take its seeds and attempt to grow it again next year. The problem is that there's no guarantee the resulting pepper plants will share the desired traits of their parent. That's where the process of selective breeding comes in.

What is Selective Breeding?

Selective breeding has been used by humans for thousands of years. It's the process Native Americans used to turn a grass-like plant into modern day corn. These same early civilizations used selective breeding to domesticate small, berry-like wild peppers into the habanero, jalapeno and many of the other popular varieties we now enjoy. The intertwined processes of hybridization, random mutations, natural selection and selective breeding have produced an estimated 50,000 varieties of chile peppers!

Where hybridization and random mutations introduce newness, it's the processes of natural selection and selective breeding that choose which traits endure.

Simply put, selective breeding is a numbers game – take seeds from parent plant(s) with desirable trait(s) and grow a bunch of plants from them. Evaluate the plants and chose the ones that best express the intended traits to self or cross pollinate. Harvest those seeds and repeat the process. Carried out over several to many successive generations, this process can magnify and lock-in the traits desired.

What's Going On Behind the Scenes?

The original "different" plant that produced the desirable traits, was different due to different genetics (assuming it wasn't due to different growing conditions). The difference in genetics was either due to hybridization, a pairing of rare recessive traits, or random genetic mutation(s). This first generation plant is referred to as F1, or the first filial generation. Seeds taken from this first generation plant will be the second filial generation, or F2. Seeds taken from that generation, are referred to as F3 seeds that'll produce F3 plants, and so on.

The earlier generations of these plants hold genetic differences that may, or may not, express themselves in the seeds taken from their pods – even in the event of self-pollination. Early generations are less likely to consistently produce offspring with the desired traits, and are less likely to do so to the fullest extent. This is especially true for F2 hybrid plants, which theoretically, should have the greatest differences among its siblings. Due to the intricacies of genetic science (which we're not going to dive into), the more generations into the process of trait selection, the more likely those traits are to express themselves within the following generation.

Our research suggests once the selection process is successfully carried through to its 7th generation (F7), the seeds from those plants (F8) should reliably produce plants with the desired traits. By this point, the pepper plant should be a nearly homozygous cultivar – meaning its corresponding chromosome pairs should be nearly identical – and reliably produce seeds that "come true" to produce matching offspring plants.

Things to Keep in Mind

As mentioned, selective breeding is a numbers game. The greater the number of offspring plants grown each generation, the better the odds of maximizing the desired traits. We have somewhat limited space for growing peppers, though we've had good results with 6-10 plants per generation. We now target growing 10 plants per generation, while keeping more seeds on-hand in the event additional plants are needed.

It's also important to note the selective breeding process assumes steps are taken to avoid accidental hybridization. The desired plant(s) should be isolated from other pepper plants to ensure either self-pollination or intended cross-pollination occurs.

To maximize trait expression and to produce hardier plants, the top two, or three, plants of a generation should be crossed with each other. This helps to expand the genetic diversity, which provides for a greater genetic base for maximizing desired traits. Along with color, shape, flavor, heat-level and yield, one should also consider including hardiness, disease resistance and germination rates when grading plants for selection.

Additional Resources

• Basic Growing Guide / Quick Growing Tips
• Step-by-Step Growing Guide
• Cloning Pepper Plants
• Hybrid Pepper Plants