Hot or Not? Nature vs. Nurture for Hot Pepper Pungency

Across much of the U.S. temperatures are still freezing and there’s still snow on the ground with more to come in the near future. So, today’s post will again feature the spiciness of hot peppers to offer some heat. Of course, here in Louisiana, the high will be an air-conditioner-worthy 74F this afternoon, when just a couple of days before it was a civilization-crippling 28F! Well, southern winters are not the only thing that suffers from a high degree of variability when it comes to heat. Let’s talk about what makes some peppers hot and others not.

A display of hot peppers and a board explaining the Scoville scale at the H-E-B Central Market location in Houston, Texas via Wikipedia, Credit: WhispertoMe

As I mentioned in my previous post, different cultivars of hot peppers can have very different levels of spiciness. They can range from pleasantly mild banana peppers to you’ve-gotta-get-a-video-of-me-eating-this-no-wait-stop-filming-and-take-me-to-the-hospital Smokin’ Ed’s Carolina Reaper peppers. Why? Genetics has a lot to do with it. Pepper breeders and plant scientists have been identifying the genes responsible for spiciness (pungency). Pun1 (Pungency1) is the gene with the most effect on spiciness identified to date. Its gene product adds the tail portion onto vanillylamine, converting it to capsaicin.* Individuals or varieties with mutations in the Pun1 gene have drastically reduced capsaicin levels. I’m not sure that any work has yet been done on the Trinidad Moruga Scorpion or Carolina Reaper peppers, but it’s a safe bet they have a functional Pun1 gene. They may express it in greater amounts than other lesser peppers to explain their insanely high Scoville ratings. But that’s only one gene and pungency is a complex trait. In the super spicy varieties, I’m sure there are multiple factors at work channeling metabolism into a perfect firestorm of capsaicin synthesis. The genome sequence of Capsicum was published this year in Nature (open access!), and scientists hope to find even more clues to pepper pungency among other traits within it.

Genetics, however, is only part of the story. The environment has a significant impact on how spicy the harvested peppers will be. This includes everything from soil composition, fertilization, temperature, and water stress. It turns out that any kind of stress (high temperatures, drought) tends to increase pepper pungency. For hobby gardeners, this means you may want to stress your pepper plants if you’re interested in turning up the heat in your pepper jelly. Just make sure you stress them while the fruit is developing and ripening and do not try to kill the plants right from the beginning.

Variability due to environmental factors can be a problem for commercial pepper growers. For hot peppers that fall in the middle of the Scoville scale and make up the main ingredients of hot sauces and salsas, the environmental factors can swing the measured spiciness of peppers by more than the genetic factors. It may come as a surprise to you, but not everyone is on a quest to pump up the pungency of peppers. Some of us like mild or medium salsas. Growers are usually contracted with chile processors that have particular pungency preferences, and it is in the growers’ interests to meet those demands precisely.

This peck of a problem means that plant scientists have more work to do when it comes to determining how environmental factors affect the spiciness of certain varieties so they can offer recommendations for farmers. However, as with our weather this past week, we are all at the mercy of Nature and there are some conditions that cannot be controlled. This is where plant scientists fall back on the genetic component. By understanding the fundamentals of why the plants are responding to the environment, breeders can develop pepper plants that rely less on environmental factors and more on their genetics for their characteristic pungency.

Worldwide, the hot pepper market is worth ~$14 billion annually and it’s growing. I’m sure hot sauce, hot wings, salsa, chili powder and other pepper products are on your shopping lists this weekend for the Super Bowl, right? While you’re enjoying the game (and/or the commercials) and chowing down on these pepper products, take a moment to acknowledge the hard work that plant scientists, breeders and farmers are doing to make sure you have just the right amount of spice in your life.

Johnna

*Remember when I told you that Capsicum sp. could take you from plain vanilla to superfirehot capsaicin in just a couple of chemical steps? Well, Pun1 performs step 2.

References and Links:

http://www.ncbi.nlm.nih.gov/pubmed/15918882

http://www.nature.com/ng/journal/vaop/ncurrent/pdf/ng.2877.pdf

http://www.extension.org/pages/32603/pepper-heat#.Uu0p47SgS_s

http://www.mdpi.com/1420-3049/18/11/13471

http://www.chilepepperinstitute.org/content/files/environment_produces_significant_effect.pdf

http://hortsci.ashspublications.org/content/46/12/1576.full.pdf

http://hortsci.ashspublications.org/content/43/5/1549.full

http://www.chilepepperinstitute.org/content/files/eval_genotype_environment.pdf

http://www.chilepepperinstitute.org/content/files/pungency_of_chile%281%29.pdf

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