Abstract
The cacao tree (Theobroma cacao L.) is native to the Amazon basin and widely cultivated in the tropics to produce seeds, the valuable raw material for the chocolate industry. Conservation of cacao genetic resources and their availability for breeding and production programs are vital for securing cacao supply. However, relatively little is still known about the phylogeographic structure of natural cacao populations. We studied the geographic distribution of cpDNA variation in different populations representing natural cacao stands, cacao farms in Ecuador, and breeding populations. We used six earlier published cacao chloroplast microsatellite markers to genotype 233 cacao samples. In total, 23 chloroplast haplotypes were identified. The highest variation of haplotypes was observed in western Amazonia including geographically restricted haplotypes. Two observed haplotypes were widespread across the Amazon basin suggesting long distance seed dispersal from west to east in Amazonia. Most cacao genetic groups identified earlier using nuclear SSRs are associated with specific chloroplast haplotypes. A single haplotype was common in selections representing cacao plantations in west Ecuador and reference Trinitario accessions. Our results can be used to determine the chloroplast diversity of accessions and in combination with phenotypic assessments can help to select geographically distinctive varieties for cacao breeding programs.
Highlights
Cacao trees (Theobroma cacao L.) are native to the Amazon basin, and their valuable seeds are the raw material for the chocolate industry [1,2]
We suggest that the four wild provenances associated with haplotype H10 in western Amazonia of Peru and Ecuador could be screened for agronomic traits to test their use in breeding programs, potentially adding useful traits to Nacional cultivars
Populations with at least two common haplotypes may have been dispersed by humans from this center of cacao genetic diversity to new suitable habitats following a west to east route of migration in the Amazon basin
Summary
Cacao trees (Theobroma cacao L.) are native to the Amazon basin, and their valuable seeds are the raw material for the chocolate industry [1,2]. Western Amazonia is considered to be a putative center of origin of cacao based on high phenotypic [1,12,13] and genetic [2,14,15] diversity. This part of the Amazon is a region of high biodiversity [16,17,18,19,20] that in the past served as a forest refugium favoring accumulation of high tree diversity [21,22]. At least 29 crop species and 38 utilizable palms with probable origin in western Amazonia highlight the importance of the plant genetic resources observed in this part of the Amazon [23,28]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
