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Assessment of genetic diversity in cocoa in farms of Southern Cameroon using SSR markers

Efombagn M.I.B., Sounigo O., Nyassé S., Eskes A., Kolesnikova-Allen M.. 2006. In : Denamany G. (ed.), Kelvin Lamin H. (ed.), Ling Albert (ed.), Navies Maisin (ed.), Azmi Che Ahmad (ed.), Bakar Saripah (ed.), Nuraziawati Mat Yazik (ed.). Sustainable cocoa economy through increase in productivity, efficiency and quality : Proceedings of 4th Malaysian International Cocoa Conference (MICC) 2005. Kuala Lumpur, Malaysia, 18th-19th July 2005. Kota Kinabalu : MCB, p. 325-338. Malaysian International Cocoa Conference. 4, 2005-07-18/2005-07-29, Kuala Lumpur (Malaisie).

The range of polymorphism of about 194 cocoa accessions collected in farms in Southern Cameroon during field surveys and 71 Trinitario and Upper Amazon clones available in genebanks on-station was assessed using 13 SSR markers. The gene diversity, genetic differentiation and genetic similarities were analysed for the different populations. In total, 282 alleles were detected within all the populations studied. The farm accessions were strongly differentiated based on their geographical origin, with accessions coming from the East province clustering together with local Trinitario accessions from the genebank. Accessions from the Centre-South provinces clustered with Amazon and hybrid accessions, suggesting more uptake of seed garden materials in farms in these provinces. The genetic diversity parameters indicate that the farmers' planting material is not highly diverse, and is genetically close to parental genotypes available in genebanks. However, some promising Upper Amazon clones (T-clones) that have also been used as parents of released hybrid varieties were genetically distant from the accessions. This result suggests that the progenies of these parents have so far been poorly used in the cocoa farms surveyed. The consequences of these findings for cocoa breeding in Cameroon are discussed.

Mots-clés : theobroma cacao; polymorphisme génétique; marqueur génétique; variété; hybride; amélioration des plantes; cameroun

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