The use of chloroplast markers for the traceability of certified sustainably produced cacao (Theobroma cacao) in the chocolate industry

Allainguillaume, Jo�l; wetten, Andy

Abstract

Recently the chocolate industry has changed to a higher demand for sustainably certified cacao (Rainforest Alliance, UTZ, and FairTrade) and closer attention is being paid to how this sustainably produced cocoa can be traced. Companies like Mars, Hershey and Ferrero have stated that by 2020, all their cocoa will be certified sustainable. There is therefore a need for methodologies to be developed enabling the characterisation and geographical tracking of certified cocoa products. Research on chloroplast ultra-barcoding in cacao has revealed a level of DNA polymorphism sufficient to reliably identify lineages below the species level such as subspecies or varieties (Kane et al. 2012). This level of variation, in conjunction with the high copy number of the chloroplast genome, offers possibilities to develop reliable DNA assays which being, less susceptible to industrial DNA degradation than single locus nuclear markers, are suitable for the characterisation of sustainably produced chocolate products. DNA was extracted from 159 representative trees of major cacao cultivars present in the International Cocoa Quarantine Centre in Reading (UK). All accessions were screened with four chloroplast simple sequence repeat (cpSSR) markers also known as microsatellites, to assess the chloroplast haplotype diversity of Theobroma cacao. These loci were designed from polymorphic sites identified by Kane et al. (2012) to allow for multiplex PCR amplification. Fluorescently labelled products were screened using capillary analysis and all markers scored using GeneMarker. Eleven cpSSR alleles were identified across the four loci revealing six unique cacao chloroplast haplotypes. All markers were screened on DNA extracted from a range of commercially available chocolate products. The capillary profiles generated were normalised to determine the proportion of each specific cpSSR alleles per locus identified in each chocolate sample. Principal Component Analysis (PCA) of all samples for the proportion of all alleles gave contrasting results with distinct clustering observed for chocolate produced from beans harvested by small cooperatives in Peru, Ecuador, Venezuela, Trinidad and Madagascar but no differentiation was observed for chocolate derived from West African plantations reflecting the lack of allelic diversity found in cultivars in West Africa. These results indicate that this sensitive and relatively low cost barcoding approach has potential to support cocoa certification programmes for the Fine cocoa/premium cocoa market but is not likely to be appropriate for the identification of bulk cocoa production.

• Presentation Conference Type: Conference Paper (Published)
• Conference Name: International Symposium on Cocoa Research (ISCR), Lima, Peru, 13-17 November 2017
• Start Date: Nov 13, 2017
• End Date: Nov 17, 2017
• Acceptance Date: Jun 1, 2017
• Publication Date: 2018
• Deposit Date: Sep 29, 2021
• Publisher: CAB International
• Book Title: International Cocoa Symposium 2017 Proceedings
• Public URL: https://uwe-repository.worktribe.com/output/7442613
• Publisher URL: https://www.icco.org/icco-documentation/international-cocoa-symposium-2017/international-cocoa-symposium-2017-proceedings/#toggle-id-5