Location: Subtropical Horticulture ResearchTitle: Genetic characterization of the cacao cultivar CCN 51: its impact and significance on global cacao improvement and production) Author
|Livingstone iii, Donald|
Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/24/2014
Publication Date: 3/1/2014
Citation: Boza, E.J., Motamayor, J.C., Amores, F.M., Sergio, C., Tondo, C.L., Livingstone Iii, D.S., Schnell, R.J., Gutierrez, O.A. 2014. Genetic characterization of the cacao cultivar CCN 51: its impact and significance on global cacao improvement and production. Journal of the American Society for Horticultural Science. 139(2):219-229. Interpretive Summary: Cacao (Theobroma cacao L.) is the plant from which chocolate is obtained. It is an important cash crop in tropical growing regions of the world. Cacao production in the Americas constitutes ~13.0% of global production and Ecuador is the second largest producer in South America. Ecuador produces cacao beans known as the Nacional type that are well known for fine flavors, aroma, and fat content. But, over the past 10 years the cacao variety CCN-51 has become one of the most planted varieties in Ecuador. Its genetic background is complex and beans of CCN-51 are often mixed with the Nacional type beans, which reduces the overall bean quality. Uncertainty regarding the bean type of CCN-51 lead to investigation of its genetic makeup. To investigate the genetic background of CCN-51 simple sequence repeat (SSR) molecular markers were used. The molecular markers detected high heterozygocity for CCN-51, whereas Nacional genotypes have low heterozygocity. There were also significant agronomic differences found when comparing CCN-51 and several Nacional clones, such as differences in cacao dry bean weight, yield potential, production efficiency, healthy pods, and witches' broom disease incidence. Additionally, physical, chemical, and sensory qualities suggest that CCN-51 is different from those of Nacional type. Population structure analysis revealed the genetic ancestry of CCN-51 to be primarily of Iquitos, Criollo, and Amelonado genetic type, and demonstrated that Nacional type constitutes only 1.1% of its ancestry. Results of phylogenetic analyses strongly supports the relatedness of CCN-51 with Iquitos, Criollo and Amelonado genetic types. CCN-51 constitutes a valuable cacao genetic resource that is currently used in its country of origin, as well as in many other national breeding and selection programs worldwide.
Technical Abstract: Cacao (Theobroma cacao L.) is an important cash crop in tropical growing regions of the world and particularly for small cacao farmers. Cacao production in the Americas constitutes ˜13.0% of global production. Ecuador is the second-largest cacao producer in South America and its Nacional beans are recognized for fine flavors, aroma and high fat content. Over the past two decades, ‘CCN 51’ has become one of the most planted cultivars in Ecuador mainly due to its high productivity and disease resistance. Intermixing of Nacional fine flavor Ecuadorian beans with beans of ‘CCN 51’ has become common practice, reducing overall bean quality and decreasing value. To investigate the complex genetic background of this important cultivar, seventy simple sequence repeat (SSR) loci were used. The high heterozygosity observed (56 of 70 loci) for ‘CCN 51’ is not characteristic of Nacional types. Comparison of agronomic characteristics between ‘CCN 51’ and several Nacional clones indicates significant differences in cacao dry bean weight, yield potential, production efficiency, percent healthy pods and witches' broom disease incidence. Additionally, physical, chemical, and organoleptic characteristics suggest that ‘CCN 51’ is different from those of Nacional lineage. Based on population structure analysis, the predominant ancestries for ‘CCN 51’ are Iquitos (45.4%), Criollo (22.2%), and Amelonado (21.5%). A lesser proportion of its genome was accounted for by Contamana (3.9%), Purús (2.5%), Marañon (2.1%) and Nacional (1.1%) admixtures. Results of phylogenetic analyses using the unweighted pair group method with arithmetic mean (UPGMA) yielding high bootstrap values strongly support the relatedness of ‘CCN 51’ with Iquitos, Criollo and Amelonado. Moreover, seven mitochondrial SSR loci revealed that ‘CCN 51’ maternally inherited the ‘IMC 67’ cytotype. ‘CCN 51’ constitutes a valuable cacao genetic resource that is currently used not only in its country of origin, but also in many other national breeding and selection programs worldwide.