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To exploit the full value of the International Cocoa Genebank Trinidad (ICGT), each accession must be characterised. Morphological characterisation provides information for the identification of accessions and to recognise important traits related to economic yield and potential constraints to yield. Judicial use of data from Cocoa Research Centre's characterisation studies will allow selection of genotypes for future breeding/germplasm enhancement programmes which consider genetic diversity, bean size, and pod index (as an indicator of yield potential) in addition to other traits quantified in evaluation studies.

Some of the major achievements of our team include

  • Completed empirical studies to generate a concise list of 25 morphological descriptors for cacao based on Bioversity International's (formerly IBPGR's) list of 65 descriptors to improve the efficiency of data collection.
  • Compiled and analysed complete morphological data on 1945 primary (not improved) accessions using the concise list (April, 2019).
  • Developed a training module on morphological characterisation to teach interested persons the process and application of this genebank activity. It will be available online in the future.
  • Contributed to the publication of the Field Guide to the ICS Clones of Trinidad and the Field Guide to the UF clones of Costa Rica.
  • Completed studies on environmental effects on cacao fruit and seed characters,
    pod wall hardness variation (significant for Cocoa Pod Borer resistance),
    and characters of economic interest: Pod Index (an indicator of yield potential), bean and cotyledon traits.
  • Identified cacao accessions and populations with good yield potential as well as resistance to Black Pod and Witches' Broom Diseases.
  • Compared cacao classifications obtained using morphological and biochemical/molecular data.
  • Investigated correspondence between phenotypic diversity and geographic origin.
  • Developed a machine to semi-automate removal of pulp/mucilage from cacao seeds.
  • Trained and provided support/outreach to farmers, students, entrepreneurs and other stakeholders in the cocoa industry.  Such training was provided to Ministry of Agriculture staff from 2002 to 2010 and resulted in the production of a Bulletin describing the commercial Trinidad Selected Hybrids.
  • Contributed to the preparation of the Cacao Clones Manual CD-ROM* and compilation of Botanical Notes on the cacao accessions conserved and characterised at the ICGT, in a user-friendly format.

 

Morphological characterisation is an ongoing process and full characterisation is a long, painstaking procedure, requiring significant resources. We continue to make every effort at CRC to improve the efficiency of the task.

A short list of 25 descriptors was adopted in 1998 (https://www.bioversityinternational.org/e-library/publications/detail/working-procedures-for-cocoa-germplasm-evaluation-and-selection/ and we reduced the size of samples of pods and beans, while still ensuring adequate accuracy in the quantitative data.

For the benefit of farmers and researchers in the field, CRC is seeking resources to produce Field Guides with full colour photographs of cacao varieties and accompanying botanical data that would be useful for identification, as well as guide selection based on information on traits of economic interest.

Current activities also involve association studies to identify genetic markers linked to phenotypic traits to facilitate cacao improvement via genomic selection.


Selected publications

Bekele, F. and Bekele, I. (1996). A sampling of the phenetic diversity in the International Cocoa Genebank, Trinidad. Crop Science 36 (1):57–64.

Bekele, F.L. and Bidaisee, G.G. (2009). Assessment of morphological traits in 1180 accessions from the International Cocoa Genebank, Trinidad. Proceedings of the 15th International Cocoa Research Conference, San Jose, Costa Rica, October 9–14, 2006. COPAL, Nigeria, pp. 67–77.

Bekele, F.L., A.D. Iwaro, Butler, D.R. and Bidaisee, G.G. (2008b). Upper Amazon Forastero cacao (Theobroma cacao L.) 2: An overview of Parinari clones from a breeder’s perspective. Tropical Agriculture (Trinidad). Vol 85 No. 1 January 2008: 16-33.

Bekele, F.L., Bekele I., Butler, D.R.B. and Bidaisee, G.G. (2006). Patterns of morphological variation in a sample of cacao (Theobroma cacao L.) germplasm from the International Cocoa Genebank, Trinidad.  Genetic Resources & Crop Evolution 53 (5): 933–948.

Bekele, F.L., Butler, D.R. and Bidaisee, G.G. (2008a). Upper Amazon Forastero cacao (Theobroma cacao L.) 1: An assessment of phenotypic relationships in the International Cocoa Genebank, Trinidad. Tropical Agriculture (Trinidad) Vol 85 No. 1 January 2008: 1-15.

Bekele, F.L., Kennedy, A.J., Mc David, C., Lauckner, F.B., and Bekele, I. (1994). Numerical taxonomic studies on cocoa (Theobroma cacao L.) in Trinidad.  Euphytica 75: 231–240.

Bhola, J., Sreenivasan, T.N., Bekele, F.L. and Motilal, L.A (2013). Two fruits per pedicel in cacao (Theobroma cacao L.) – a rare phenotype.  Plant Genetic Resources: Characterization and Utilization 12 (2): 259–262.

Iwaro, A. D., Bekele, F.L. and Butler, D.R. (2003). Evaluation and utilisation of cacao (Theobroma cacao L.) germplasm at the International Cocoa Genebank, Trinidad. Euphytica 130: 207-221.

Johnson, E., Bekele, F., Brown, S., Zhang, D., Meinhart, L. and Schnell, R. (2009). Population structure and genetic diversity of the Trinitario cacao (Theobroma cacao L.) from Trinidad and Tobago. Crop Science 49: 564–572.

Khan, N. Motilal, L.A. Sukha, D.A., Bekele, F.L., Iwaro, A.D., Bidaisee, G.G., Umaharan, P., Grierson, L.H. and Zhang, D. (2008). Variability of butterfat content in cacao (Theobroma cacao L.): combination and correlation with other seed–derived traits at the International Cocoa Genebank, Trinidad. Plant Genetic Resources: Characterization and Utilisation 6 (3): 175–186. doi:10.1017/S1479262108994132.

Maharaj, K.., Maharaj, P., Bekele, F.L., Ramnath, D., Bidaisee, G.G., Bekele, I., Persad, C., Jennings, K., and Sankar, R. (2011). Trinidad selected hybrids: An investigation of the phenotypic and agro–economic traits of 20 selected cacao cultivars. Tropical Agriculture (Trinidad) Volume 88 (4): 175–185.

Sankar, A. A., Motilal, L. A., Johnson, E., Bidaisee, G. G., Bekele, F. L., Boccara M., and Butler, D. R. (2008). Cacao Clones Manual Version 1.1 Trial CD– ROM, St. Augustine: Cocoa Research Unit, Trinidad and Tobago.

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