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Variability and selection for morphological bean traits in wild cocoa trees (Theobroma cacao L.) from French Guiana

Lachenaud P., Oliver G.. 2005. Genetic Resources and Crop Evolution, 52 : p. 225-231.

Under the conditions prevailing at Paracou-Combi (French Guiana), 96 local wild cocoa trees belonging to ten populations from the Camopi and Tanpok rivers, and already pre-selected for other agronomic criteria, were characterized for their average fresh bean weight, an important selection criterion. Other traits, such as the average length and width of a bean, along with the percentage of flat beans, were also studied. The variability found for average fresh bean weight was substantial, with a coefficient of variation of 10.5% and extremes of 2.20 and 3.82 g. The average of 2.97 g (i.e. 1.04 g for a fermented dried cocoa bean) was higher than the control, the Upper Amazon Forastero clone NA 32. The main five populations were not statistically different for the three morphological bean descriptors (average weight, average length and width), but they were for the percentage of flat beans, which was relatively high on average (6.9, on fresh beans). An analysis of variance of the basic data (i.e. per pod on 3250 pods) showed a highly significant tree effect, enabling ortets selection. Given the high heritability of the average bean weight, these ortets could be used as clones, or as parents in crosses with other genetic groups. A list of trees with small beans, hence which ought theoretically to be avoided in breeding programmes, is provided. (Résumé d'auteur)

Mots-clés : germplasm; clone; poids; dimension; variation génétique; fève de cacao; caractéristique du peuplement; caractère agronomique; plante sauvage; variété indigène; theobroma cacao; guyane française; lignée parentale

Thématique : Génétique et amélioration des plantes; Anatomie et morphologie des plantes

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