Submitted to: Proceedings of the International Cocoa Producer's Conference
Publication Type: Proceedings
Publication Acceptance Date: 10/2/2009
Publication Date: 11/1/2010
Citation: Irish, B.M., Goenaga, R.J., Schnell Ii, R.J., Motamayor, J., Brown, J.S., Zhang, D. 2010. CACAO (THEOBROMA CACAO L.) GENETIC RESOURCES RESEARCH AT THE USDA-ARS TROPICAL AGRICULTURE RESEARCH STATION. Proceedings of the International Cocoa Producer's Conference. PP. 417-423.
Technical Abstract: The current USDA ARS Tropical Agriculture Research Station’s cacao (Theobroma cacao) collection consists of 154 clonally propagated accessions. Each accession is represented by six individual trees grafted on Amelonado rootstocks and planted in a completely randomized block design with three blocks and two trees per block. The collection was established in 2001-2004 with a spacing of 2 meters between plants and rows in full sun. Field characterization efforts began January 2007 with data being collected on production and disease resistance. Other important agronomic traits being collected include the individual accessions pod index values as well as liquor and chocolate qualities. Phenotypic traits such as pod length and width, weight of the pod, weight of the shell, shape, color and number of seeds per pod are also being collected. Furthermore, all 924 trees in the entire germplasm collection (154 accessions x 3 blocks x 2 trees/block) were fingerprinted using a high throughput genotyping system with 15 microsatellite loci. Intra-plant error (mislabeling among multiple trees within the same accession) and synonymous sets (accessions that have identical fingerprint profiles but different names) were identified. The average number of alleles and gene diversity estimates indicate good genetic diversity representativeness in this collection. A distance-based cluster analysis showed that the cacao accessions in this collection can be classified into four distinct clusters, with their geographical origins covering most of the cacao growing regions in the Americas. Several genetic gaps were identified gaps, including underrepresented genetic populations and particular economic/agronomic traits and efforts are currently under way to introduce approximately 60 accessions once released from quarantine. Fingerprint profiles for cacao accessions as well as voucher images showing flowers, pod shape, color, texture and size as well as beans shape color and size for all accession have been loaded and are available through the USDA, National Plant Germplasm System, Germplasm Resource Information Network (GRIN) database http://www.ars-grin.gov/ with production, disease resistance and phenotypic data coming online in the near future.