Saturday, December 3, 2016

Genetic Diversity of Theobroma cacaon

Cocoa or cacao (Theobroma cacao) is native to the South American rainforest, but it is thought to have been domesticated in southern Mexico and the northern Central American region. The hypothesized centre of genetic diversity is located in the upper Amazonian region. It is also well known that the Peruvian Amazon harbours a large number of diverse cocoa populations. 

During the past several decades, several expeditions have been made and a substantial amount of germplasm, from both wild populations and cultivated accessions, has been collected from this region. Today, a fraction of these accessions are maintained as ex-situ collections in various countries.

The first organized cocoa germplasm collecting expedition in the Peruvian Amazon started in 1937–1938. And the collecting sites included Rio Nanay, Rio Morona, Rio Marañón and their tributaries. This led to the establishment of the germplasm collection in Iquitos, Peru known as the ‘Pound Collection’, named after the collector F. J. Pound. Many commercial clones, now called ‘International clones’, have their origin in this collection.

Organic cacao native in Peru

Pound's expeditions were aimed at searching for genotypes resistant to witches' broom disease, caused by the fungus Crinipellis perniciosa, and this germplasm has therefore been widely used in breeding programmes as a source of resistance to witches' broom disease.

The hypothesis that the Peruvian Amazon hosts a high level of genetic diversity, and the diversity has a spatial structure in the native habitat of cocoa. The introduction of breeding progenies in the rehabilitation programme is changing the cocoa germplasm spectrum in this region. Identifying the patterns of distribution of intraspecific genetic variation can provide data concerning the temporal and special dynamics of this economically important crop, which has not been previously studied in depth at the population level. The spatial structure of cocoa diversity recorded here highlights the need for additional collecting and conservation measures for natural and semi-natural cocoa populations in the Peruvian Amazon. Read more Genetic Diversity and Structure of Managed and Semi-natural Populations of Cocoa (Theobroma cacao) in the Huallaga and Ucayali Valleys of Peru

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