Browsing by Author "Christian Cilas"

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    Effect of genotype of cocoa (Theobroma cacao) on attractiveness to the mirid Sahlbergella singularis (Hemiptera: Miridae) in the laboratory
    (2008) Luc Dibog; Regis Babin; Joseph Amang A. Mbang; Bernard Decazy; Salomon Nyasse; Christian Cilas; Albertus B. Eskes
    BACKGROUND: Mirids are a major constraint to cocoa growing in Africa. Cocoa breeding for tolerance/resistance could be effective in an integrated pest management system. Attractiveness is one aspect of tolerance/resistance, and decreasing the attractiveness of cocoa trees should be a good way of reducing damage. RESULTS: Small-scale laboratory tests were carried out in Cameroon to assess differences in the attractiveness to mirids of eleven cocoa genotypes. The genotypes were ranked according to their attractivenes* score and a distance from a mean value. An analysis of variance was performed and revealed significant differences between cocoa genotypes (F = 3.15, P < 0.001). The cocoa genotype groupings revealed three major categories, with BE10 and SNK413 proving to be the most attractive. In contrast, five genotypes, IMC60, the Catongo Trinitario genotypes, Playa Alta2 (from Venezuela), SIC5 and SNK614, proved to be less attractive than the mean. Four genotypes (PA107, SNK619, UPA134 and T60/&87) displayed similar attractiveness to the mean. CONCLUSION: The circular microtest offered the advantage of not needing a reference cocoa genotype. The least -attractive clones, such as IMG60, were also the most tolerant in the field. Comparisons with the results of other studies are proposed.
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    Effect of genotype of cocoa (Theobroma cacao) on attractiveness to the mirind sahlbergella singularis(Hemiptera: Miridae) in the laboratory
    (2008) Luc Dibog; Regis Babin; Joseph Amang A. Mbang; Bernard Decazy; Salomon Nyasse; Christian Cilas; Albertus B. Eskes
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    Genetic diversity and structure of farm and GenBank accessions of cacao (Theobroma cacao L.) in Cameroon revealed by microsatellite markers
    (2008) Ives Bruno M. Efombagn; Juan C. Motamayor; Olivier Sounigo; Albertus B. Eskes; Salomon Nyasse; Christian Cilas; Ray Schnell; Maria J. Manzanares-Dauleux; Maria Kolesnikova-Allen
    The genetic diversity of 400 accessions collected in cacao farms, 95 GenBank, and 31 reference accessions was analyzed using the 12 microsatellite markers. The GenBank and reference accessions were subdivided into 12 accession groups (AG) that belong to the traditional cacao genetic groups (GG) Lower Amazon Forastero (LA), Upper Amazon Forastero (UA), Trinitario, and Criollo (Cr). The 12-microsatellite loci revealed a total of 125 alleles, 113 of which were present in the farm accession group (FA). The within and between group variation for all AGs accounted respectively for 81% and 19% of the total molecular variation. The average Fis for the FAwas 0.15 suggesting a moderate level of inbreeding. Significant differences for the level of gene diversity were found between the farm (0.50), GenBank (0.42 to 0.62), and reference (0.10 to 0.60) AGs. Genetic differentiation among AGs was variable with Fst values varying between 0.14 and 0.57 for the different AGs. Analysis using a Bayesian model-based method showed the existence of a high level of admixture for the farm accessions group. The LA genes were most represented in the FA (54%), followed by UA (33%) and Cr (7%). The genes of LAwere also the most represented in the GenBank (48%), followed by UA (24%) and Cr (14%). Only 14% and 6% of the genes of the GenBank and farm accessions, respectively, could not be attributed to any of the reference GGs. The results suggest the predominating presence of LA genes in the Cameroon farm accessions and a high level of admixture, with apparent presence of genes of more than three GGs in most accessions. The traditional Trinitario types appear to have almost disappeared from farmers fields. The admixture must be the result of hybridization and recombination of these genes from the different GGs in seed gardens and in farmers’ fields. The use of selected farm accessions will depend on the GG that it belongs to and also on their level of heterozygosity. Further implications of the results for breeding and for introduction of new germplasm into the Cameroon GenBank are discussed.
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    Study of the genetic diversity of cocoa populations (Theobroma cacao L.) of Martinique (FWI) and potential for processing and the cocoa industry
    (2020) Sandra Adenet; Franc¸oise Regina; Dominique Rogers; Sarah Bharath; Xavier Argout; Katia Rochefort; Christian Cilas