Genetic Characterization of the Cacao Cultivar CCN 51: Its Impact and Significance on Global Cacao Improvement and Production

Abstract

<jats:p>Cacao (<jats:italic>Theobroma cacao</jats:italic> L.) is an important cash crop in tropical growing regions of the world and particularly for small cacao farmers. Over the past two decades, ‘CCN 51’ has become one of the most planted cultivars in Ecuador, mainly as a result of 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. The primary goals of this study were to determine the genetic identity, structure, and allelic richness of ‘CCN 51’, its maternal origin and to compare ‘CCN 51’s’ agronomic characteristics against a composite group of Nacional cultivars. To investigate the complex genetic background of this cultivar, 70 simple sequence repeat loci were used. The high heterozygosity observed (56 of 70 loci) for ‘CCN 51’ is not characteristic of traditional Nacional cultivars. Comparison of agronomic characteristics between ‘CCN 51’ and several Nacional cultivars indicates significant differences in cacao dry bean weight, yield potential, production efficiency, percent healthy pods, and witches' broom [<jats:italic>Moniliophthora perniciosa</jats:italic> (Stahel) Aime &amp; Phillips-Mora] 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%) genetic groups. A lesser proportion of its genome was accounted for by genetic groups 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 yielding high bootstrap values strongly support the relatedness of ‘CCN 51’ with Iquitos, Criollo, and Amelonado genetic groups. Moreover, seven mitochondrial simple sequence repeat 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.</jats:p>

A disease and production index (DPI) for selection of cacao (Theobroma cacao) clones highly productive and tolerant to pod rot diseases

“…Identifying superior recombinants can require both extra time and effort because disease tolerance, productivity, and quality are considered quantitative traits. As observed in this experiment, the crosses of CCN‐51, a highly productive clone but of questionable organoleptic traits (Kadow et al , ; Boza et al , ), with National clones with varying production potentials, disease tolerance, and organoleptic traits (Amores et al , ; Kadow et al , ) has led to the selection of clones with both high production and significant tolerance to FPR and other diseases as observed in clones T1 and T24. These two clones also rank high among the clones tested based on DPI.…”

“…Clone T26 has the lowest seed fresh weight per pod of all clones as can be seen by the ratio of numbers of healthy pods/tree compared to seed fresh weight per tree. Regardless, clone T26 is interesting because its parents are both National cacao type, which might imply good organoleptic quality (Deheuvels et al , ; Boza et al , ). The hierarchical clustering after PCA of multiple variables associated with disease and yield grouped three of the top four clones (T1, T24, and T26) identified by DPI.…”

QTL mapping and identification of SNP-haplotypes affecting yield components of Theobroma cacao L.

“…In contrast, the second haplotype T2 (GGA) grouped with three varieties belonging to Iquitos genetic cluster, i.e., 'IMC 12', 'IMC 47', and 'IMC 50' 13 . These results were expected, since another variety from Iquitos cluster 14 , 'IMC 67', is part of the 'TSH 1188' lineage 15,16 . In turn, the first paternal haplotype, C1 (AAA), grouped with the first haplotype of 'CCN 10'.…”

Moniliophthora roreri, causal agent of cacao frosty pod rot

“…The annual FPR incidence of ICS-95 ranged from 13% to 51%, and was intermediate to the reactions obtained by the most R/T (CATIE-R6, 3%-7%) and most susceptible (Pound-7 and SCA-6, 38%-99%) clones (W. Phillips-Mora, unpublished results). CCN-51, an offspring of the cross 'IMC-67 3 ICS-95', is a productive, R/T and precocious clone widely used in crosses because of its high general and specific combining ability (Boza et al, 2014). In field trials at CATIE's La Lola farm, CCN-51 had an FPR incidence of 38%.…”