It’s in the genes: humans traded peppers along global trade routes

The pepper genus contains a variety of capsicums that are large and sweet, as well as hot peppers commonly called chilis. These familiar fruits brighten up fresh produce markets and are used in culinary dishes all over the world. Peppers are native to southern North America and northern South America but have a global distribution today.

Because of the culinary and trade importance of peppers, their genomic information is stored in many gene banks with the aim of preserving genetic diversity for future breeding purposes. This genomic information was used in a recent study to trace the historical distribution of the most economically important pepper species (Capsicum annuum) along the trade routes of the world. 

“We conducted a huge genomic scan of over ten thousand pepper (Capsicum spp.) samples from worldwide gene banks and used the data to investigate the history of this iconic staple,” said Dr. Pasquale Tripodi, researcher at the Italian research institute CREA and co-first author of the study.

Collaboration with the gene banks produced genomic information for peppers from 130 countries on five continents. The data were analysed using a method called ReMIXTURE, which was specially developed to assess the genetic similarity between the pepper variants from different regions. 

“The results reflect a vision of pepper as a highly desirable and tradable cultural commodity, spreading rapidly throughout the globe along major maritime and terrestrial trade routes,” explained Dr. Mark Timothy Rabanus-Wallace from IPK Leibniz Institute, who co-led the study and who developed the ReMIXTURE method.

“A large factor in pepper’s initial appeal was certainly its pungency, especially in non-tropical Europe where hot spices were rare and imported black pepper could fetch good prices.” 

There was considerable overlap in the kinds of peppers collected from the different regions. For example, Eurasian peppers were similar to those found in neighboring regions, indicating their spread along trade routes such as the Silk Road. In addition, European and African peppers were similar to varieties found in the Americas, revealing the impact of transatlantic trade between these continents.  

The data also showed that in South America, Mesoamerica, Eastern Europe and Africa, there is a high occurrence of region-unique peppers, giving evidence for selective breeding of the crop in these regions.

This is supported by the finding that certain characteristics, such as pungency, were not distributed uniformly across the globe. Human culture has clearly influenced the spread of peppers with desirable traits.

The research team used the data to check for duplicate accessions between gene banks. They found 1,618 duplications within and between gene banks, which indicates considerable overlap of samples and waste of valuable scientific time. 

“This significant level of duplication should motivate the development of genetic pre-screening protocols to be used in genebanks for documenting the potential duplicate samples upon first acquisition,” concluded Dr. Nils Stein, who is the head of the research group Genomics of Genetic Resources at the IPK Leibniz Institute. 

The results of the study are published in Proceedings of the National Academy of Sciences.

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By Alison Bosman, Earth.com Staff Writer