2018 ASHS Annual Conference

The current USDA ARS Tropical Agriculture Research Station’s (TARS) cacao (Theobroma cacao L.) collection in Mayaguez, Puerto Rico, consists of 262 clonally propagated accessions. Each accession is represented by six individual trees grafted onto a common ‘Amelonado’ seedling rootstock and planted in a completely randomized block design with three blocks and two trees per block. Most of the accessions were established in 2001 and all are established with a spacing of 2 m between plants and rows under irrigation and in full sun. Data being collected include: black pod disease reaction, production, pod index, as well as liquor and chocolate qualities. Phenotypic traits such as the length, width, weight, shape, and color of pods, husk weight and number of seeds per pod are also measured. In 2010, all replicate trees for the existing 154 clones in the collection at the time were fingerprinted using 15 microsatellite markers. Intra-plant error (mislabeling among replicate trees) and synonymous sets (unique accessions with identical genotypes) were identified. The average number of alleles and gene diversity estimates indicate good genetic diversity representativeness in the collection. Several genetic gaps in coverage have been identified, including underrepresented genetic populations and efforts are currently underway to introduce diverse accessions into the collection. Twenty ancient Criollo accessions were recently incorporated into the collection to fill a specific gap. Fingerprint profiles for cacao accessions as well as voucher images showing flowers, pod shape, color, texture and size as well as bean shape color and size for most accession are available through the USDA, National Plant Germplasm System, Germplasm Resources Information Network (GRIN-Global) database (http://www.ars-grin.gov/). Recent cacao research focused on field experiments to compare performance of 12 cacao varieties propagated by grafting vs. somatic embryogenesis. This work showed that although there were significant differences between plant propagation treatments for some of the variables measured, these were not of a magnitude that would preclude the use of somatic embryogenesis as a viable propagation system. Ongoing collaborative work on evaluation of new disease-resistant clones for yield performance and bean/chocolate quality along with the contribution of propagative material from the USDA-ARS cacao germplasm collection in assisting cacao growers in Puerto Rico recover from damages caused by Hurricane Maria are discussed herein.