Genetic identity and origin of ‘Piura Porcelana’ – a fine-flavored traditional variety of cacao (Theobroma cacao) from the Peruvian Amazon

Authors: AREVALO, ENRIQUE - Tropical Crop Institute (ICT); ZHOU, LIN - Nanjing Agricultural University; Meinhardt, Lyndel; MOTILAL, LAMBERT - Cocoa Research Unit - Trinidad; Mischke, Barbara; Zhang, Dapeng

Submitted to: Tree Genetics and Genomes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/2/2019
Publication Date: 1/16/2019
Citation: Arevalo, E., Zhou, L., Meinhardt, L.W., Motilal, L., Mischke, B.S., Zhang, D. 2019. Genetic identity and origin of ‘Piura Porcelana’ – a fine-flavored traditional variety of cacao (Theobroma cacao) from the Peruvian Amazon. Tree Genetics and Genomes. 15:11.

Interpretive Summary: Cacao (Theobroma cacao L.) is a tropical rainforest tree that is the source of cocoa powder and butter used in the confectionary industry. While the origin of cacao is the Amazon region of South America, to date nearly all of the evidence for domestication of this crop is found in Central America. There are several traditional varieties of the crop in Central and South America that appear to have some form of domestication prior to the arrival of Europeans. Despite their long history very little is known about the geographical origin of these varieties. Using Single Nucleic Polymorphism (SNP) markers, we compared the genetic identity of one of the traditional varieties ‘Piura Porcelana’ with reference cacao germplasm and wild cacao collected in northern Peru. The results suggest that this traditional variety is derived from wild cacao in the Santiago and Morona river systems in northern Peru and results from an independent domestication event in the Amazon. The ‘Piura Porcelana’ is part of the larger Morona-Santiago cacao population of Ecuador and Peru and this is new evidence supporting the hypothesis of cacao domestication by indigenous peoples in South America. These results will be used by scientists and extension specialists to study and preserve these traditional cacao varieties, which will ultimately ensure these cacaos are available to chocolate consumers.

Technical Abstract: Cacao (Theobroma cacao L.) is tropical rainforest tree that is indigenous to the Amazon region of South America. The drainage systems of the Upper Amazon are where the largest diversity of cacao populations is found. Although it’s generally accepted that cacao was first cultivated in Mesoamerica, it has been hypothesized that domestication also took place in South America, the center of origin. ‘Piura Porcelana’ is a traditional cacao variety from northern Peru that is cultivated for the gourmet chocolate market. The demand for fine-flavored cacao used in high-end chocolates and the corresponding premium prices paid for distinct cacao flavors provide economic incentives for the use and conservation of these traditional varieties. Using Single Nucleic Polymorphism (SNP) markers, we compared the genetic identity of ‘Piura Porcelana’ cacao with ten known cacao germplasm groups existing in the ex situ cacao genebanks, along with the living wild population from the Santiago and Morona river valleys in northern Peru. The results showed that ‘Piura Porcelana’ shares general population membership with the ‘Nacional’ cacao from Ecuador. However, ‘Piura Porcelana’ substantially differed from Nacional (Fst = 0.132) suggesting its unique varietal status. The high genetic similarity between ‘Piura Porcelana’ and the wild cacao from Morona-Santiago Rivers suggested that the wild progenitors of ‘Piura Porcelana’ were from these river valleys and this traditional variety is the result of independent domestication in northern Peru. These results provide new evidence of cacao domestication in the Amazon and will contribute to the sustainable use and conservation of these cacao genetic resources.