MOLECULAR CHARACTERIZATION AND DIVERSITY ASSESSMENT OF COCOA GERMPLASM IN THE AMERICAS
Location: Sustainable Perennial Crops
Title: Microsatellite fingerprinting in the International Cocoa Genebank, Trinidad: Accession and plot homogeneity information for germplasm management
Submitted to: Plant Genetic Resources
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 27, 2011
Publication Date: April 20, 2011
Citation: Motilal, L., Zhang, D., Pathmanathan, U., Mischke, B.S., Pinney, S.M., Meinhardt, L.W. 2011. Microsatellite fingerprinting in the International Cocoa Genebank, Trinidad: Accession and plot homogeneity information for germplasm management. Plant Genetic Resources. 9:430-438.
Interpretive Summary: Cacao is an important tropical tree crop since it is the source of cocoa butter and powder for the confectionery and chocolate industries. Genetic resources of cacao are important for breeding new cacao varieties and thus are of great importance for sustainable cacao production. The International Cocoa Genebank, Trinidad (ICG,T) is the largest public domain field gene bank collection of cacao and the correct identity of each tree is crucial for germplasm movement, evaluation and phenotypic characterization. In the present study, we verified the genetic identity of 1480 trees from 525 cocoa using DNA finger printing technology. Based on their genetic profile, the mislabeled trees were identified and the error rate within plot, within field, and within cacao accession groups were estimated. These results improve our understanding of the genetic identity of the cacao germplasm in the international collection and will contribute to a more efficient management of cacao germplasm and will improve the breeding of better cacao varieties. These results will be useful to plant breeders, germplasm curators and cacao farmers and will benefit chocolate consumers.
The International Cocoa Genebank, Trinidad (ICG,T) is the largest public domain field gene bank collection of cacao and the correct identity of each tree is crucial for germplasm movement, evaluation and phenotypic characterization. Nine microsatellite loci were used to assess the identity of 1480 trees from 525 cocoa (Theobroma cacao L.) accessions representing approximately 17% of the trees and 30% of the accessions within the gene bank. An average error rate of 27.6% was found in the gene bank. Heterogeneous plots (plots containing more than one genotype group) averaged 25% in the ICG,T with maximal admixture (33%) being recorded in Field 5. The error rate did not significantly differ among different fields. The extent of mislabelling also varied depending on the accession groups, ranging from 23 – 50% with an average error rate of 27% within accession groups. Synonymous accessions were estimated to account for 14.4% of the field gene bank. The results of present study provides essential information for further identification of intra-accession mislabelling in ICG,T by genotyping each single tree in this collection.