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Not AvailableNot AvailableDepartment of Science and Technolog

Not Available

Not AvailableNot AvailableDepartment of Science and Technolog

Assessment of genetic diversity and structure in cocoa trees (Theobroma cacao L.) in Cte d'Ivoire with reference to their susceptibility to Cocoa swollen shoot virus disease (CSSVD)

International audienceResistance to Cocoa Swollen Shoot Virus disease (CSSVD) is becoming an increasingly important criterion for selection of new cocoa cultivars in Cte-d'Ivoire, where the disease resurfaced since 2003. This virus can seriously affect the yield of trees with a loss of 25%, 1 year after infection, to around 100% 3 years after. In order to find tolerant plant material, 337 farm accessions have been collected on fields affected by CSSVD, according to the status of accessions potentially tolerant (APT) or susceptible (APS). Both phenotypic groups were genotyped using 30 microsatellite markers (SSR) in the presence of representative clones of the ten genetic groups of cocoa. This study revealed 214 alleles with the set of primer pairs used. The number of alleles per locus was between 3 and 16 with an average of 7.13 alleles per locus. The results showed a high contribution of genetic diversity within population (H (s) = 0.51) to the total genetic diversity (H (t) = 0.53) for the two studied groups. There was no significant difference between tolerant and susceptible groups (Fst = 0.05). These results suggest that APT could be a potential genetic reservoir for other traits of interest associated with virus resistance. The phylogenetic tree, as the STRUCTURE analysis of Ivorian cocoa population, showed a distribution of individuals following four groups marked by a high contribution of group 4 (Nanay, Maranon, Guiana) followed by group 2 (Criollo), and group 1 (Amelonado), and a lower contribution of group 3 (Iquitos, Purus, Nacional, Curaray, Contamana)

The genome of Theobroma cacao.

We sequenced and assembled the draft genome of Theobroma cacao, an economically important tropical-fruit tree crop that is the source of chocolate. This assembly corresponds to 76% of the estimated genome size and contains almost all previously described genes, with 82% of these genes anchored on the 10 T. cacao chromosomes. Analysis of this sequence information highlighted specific expansion of some gene families during evolution, for example, flavonoid-related genes. It also provides a major source of candidate genes for T. cacao improvement. Based on the inferred paleohistory of the T. cacao genome, we propose an evolutionary scenario whereby the ten T. cacao chromosomes were shaped from an ancestor through eleven chromosome fusions