|MOTILAR, LAMBERT - Cocoa Research Unit - Trinidad|
Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 1/15/2016
Publication Date: 2/22/2016
Citation: Zhang, D., Motilar, L. 2016. Origin, dispersal and current global distribution of cacao genetic diversity. In: Bailey, B. A., Meinhardt, L.W., editors, Cacao Diseases: A history of old enemies and new encounters. Switzerland: Springer. 3-31.
Technical Abstract: Cacao (Theobroma cacao L.) is cultivated globally as the unique source of cocoa butter and powder for the confectionery industries. In spite of its economical importance, cocoa was and continues to be dominantly produced in low-input and low-output systems. Production constraints, including depletion of soil fertility on cocoa farms, increasing damage due to diseases and pests, as well as raising labor cost, limit cacao sustainability. The future of the world cocoa economy depends significantly on sustainable use of a broad genetic base for breeding of improved varieties with disease and pest resistance, desirable quality traits, and the ability to adapt to changing environments. Cacao is very different from any other major field crops because of the availability of large amount of wild germplasm, which are widely distributed in the Amazon and are co-evolving with the pathogens. Moreover, these wild populations can be readily crossed with cultivated varieties without reproductive barriers. So far only a small set of wild germplasm, mostly from the “Pound Collection”, has been used in breeding. Contribution from this small set of clones has made tremendous impact in cacao disease resistance and adaptability. However, breeding efforts in the past 70 years has been reshuffling this small fraction of genetic diversity, with little addition of new germplasm. The on-farm genetic diversity in Southeast Asia and West Africa is low and cannot meet the challenge of mounting pressure of disease and pests. Breeding programs should take full advantage of the available wild populations to broaden the genetic base of resistance and increase the on-farm genetic diversity in the future, in order to cope with the mounting pressure of diseases and pests.