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Title: Microsatellite-aided detection of genetic redundancy improves management of the International Cocoa Genebank, Trinidad

item MOTILAL, LAMBERT - Cocoa Research Unit - Trinidad
item Zhang, Dapeng
item Mischke, Barbara
item Meinhardt, Lyndel
item UMAHARAN, PATHMANATHAN - Cocoa Research Unit - Trinidad

Submitted to: Tree Genetics and Genomes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/25/2013
Publication Date: 7/20/2013
Citation: Motilal, L., Zhang, D., Mischke, B.S., Meinhardt, L.W., Umaharan, P. 2013. Microsatellite-aided detection of genetic redundancy improves management of the International Cocoa Genebank, Trinidad. Tree Genetics and Genomes. 9:1395-1411.

Interpretive Summary: Cacao is an important tropical crop because it is the source of cocoa butter and powder for the confectionery industry. An understanding of the genetic variability within the International Cocoa Genebank is important for improving the efficiency of genebank management, for breeding new cacao varieties, as well as for rehabilitation and rejuvenation of old unproductive trees. This study looked at 387 selections of cacao and analyzed their pedigree relationship and genetic diversity. The results allow for the selection of a core set of unique accessions or types that represent the composite genetic diversity of the tested group. The selected core set can be more efficiently evaluated and used in breeding. This information will be used by plant curators, breeders, scientists and extension people to improve cacao production around the world.

Technical Abstract: Cacao (Theobroma cacao L.), the tree from which cocoa butter and chocolate is derived, is conserved in field genebanks. The largest of these ex situ collections in the public domain is the International Cocoa Genebank, Trinidad (ICG,T). Reduction of genetic redundancy is essential to improve the accuracy and efficiency of genebank management. This study examined the pedigree and genetic diversity in a subset of 387 accessions in this collection. Sibship reconstruction of this subset revealed 56 full-sib families nested within 189 half-sib families. Sixteen centers of interconnectivity were identified, which suggested a high level of genetic redundancy in the collection. Generally, consistent phylogenetic trees were obtained using different genetic distance measures. However, a principal coordinate analysis of the best differentiation measure elicited the best representation of accession group clustering, and we recommend this approach when probing fine-scale genetic differentiation among cacao accessions. The composite genetic diversity of 414 cacao accessions was contained in a core set of 59 unique accessions. These results have significant implications in the conservation of genetic resources of the ICG,T and other cacao genebanks. The approach developed in this study is recommended as a strategy to curators in guiding conservation management practices of cacao and other similar ex situ genebanks.