The seeds of the cacao tree are the key ingredients in the production of cocoa and chocolate. Over 90 per cent of the world’s cocoa is produced by smallholder farmers, many of whom rely on the cacao tree for their livelihood. However, some farmers lose up to 80 per cent of their crops to disease each year. The researchers claim that their findings will significantly reduce the number of cacao crops which are killed in this way.
“Beyond the major effort to properly categorise and understand cacao’s proper genetic history, this new classification of cacao genotypes and the localisation of their geographic origins will facilitate the collection of new germplasm with resistance to the devastating cacao diseases,” said Dr. Juan Carlos Motamayor, lead scientist with the cocoa genetics division of Mars, Inc.
“The new findings… should considerably help to speed up the genetic improvement of this species and the selection of new cultivars capable of withstanding the diseases that threaten the existence of our beloved chocolate,” Dr. Motamayor went on to say.
The study, published in the online science journal PLoS ONE, was led by scientists from confectionery giant Mars, Incorporated, the US Department of Agriculture – Agricultural Research Service (USDA-ARS) and major cocoa institutions CIRAD-France, CEPLAC-Brazil and INIAP-Ecuador.
The cacao tree has traditionally been classified into three groups: Criollo, Forastero and Trinitario. Beans from the Forastero group account for around 80 per cent of the world’s chocolate production. Only around 10 per cent is produced from Criollo, which is the rarest and most expensive. Trinitario, a hybrid of the other groups, makes up the remainder of production.
The report states that previous collections of cacao germplasm have “not contributed to cacao improvement because its relationship to cultivated selections was poorly understood”. For the purposes of the report, 1,241 individual trees covering a wide geographical area were genotyped with 106 microsatellite markers.
The results led the scientists to produce a list of ten genetic clusters, which they have labelled Marañon, Curaray, Iquitos, Nanay, Contamana, Amelonado, Purús, Nacional and Guiana. They hope that germplasm curators and geneticists will apply this new classification scheme to their management and exploitation of cacao.
Moreover, the scientists propose the establishment of new mating schemes between the groups to create new, stronger genetic models of cacao and minimise loss.
The export of cacao beans is the primary source of income for several West African countries such as the Côte d’Ivoire and Ghana. Other producers include Colombia, Mexico and Sierra Leone.
Source: PLoS One
3(10): e3311. doi:10.1371/journal.pone.0003311
“Geographic and Genetic Population Differentiation of the Amazonian Chocolate Tree (Theobroma cacao L)”
J. C. Motamayor, P. Lachenaud, J. Wallace da Silva e Mota, R. Loor, D. N. Kuhn, J. Steven Brown, R. J. Schnell