Should we keep trusting cacao varieties in Côte d'Ivoire?
2022
Wibaux, Thomas | Diallo, Djenabou | Tokannou, Isabelle Erhudice Tachégnon
In Côte d'Ivoire, farmers and extension officers often refer to cacao “varieties” using names such as Trinitario, Amelonado, Togolese, Ghanaian, or Mercedes. This habit of naming cacao germplasm based on geographical origin, commercial name, or conventional cultivar classification has traditionally helped distinguish cocoa populations with distinctive agronomic characteristics. This was particularly useful when selected hybrid germplasm began to replace traditional cacao types, with each germplasm type associated with specific agronomic or quality traits. Today, the numerous crosses and recombinations that have occurred between trees of diverse genetic backgrounds - first in breeding programs and later in farmers' fields - have led to a widespread increase in genetic diversity within smallholder farms. It is now common to find highly heterogeneous cacao phenotypes in a typical farmer's orchard, with substantial variability in both vegetative and reproductive traits among trees. However, it remains a widespread practice to infer the "variety" of a cacao tree based on specific morphological traits, primarily pod shape and color. This intuitive categorization is often used to predict a tree's agronomic performance and quality features and may influence crop-management decisions. Yet, given the high phenotypic variability now present in smallholder orchards and the likely recombination events since the introduction of the original parental "varieties," this practice is questionable. To address this issue, we studied two contrasting orchards in an industrial cocoa plantation in Gagnoa, center Côte d'Ivoire. The two orchards were planted in 1999 and 2010 with seeds provided by the national agency for support of rural development (ANADER), supposedly mixes of controlled hybrids or open-pollinated progenies of selected hybrids. A sample of 174 trees were characterized using common morphological descriptors employed in phenotypic classification. We then analyzed the relationship between these descriptors and various growth and yield traits, measured over four-years. The results revealed substantial variability in combinations of morphological traits among trees. No consistent relationship was found between morphological descriptors and performance traits, indicating that morphological characterization alone cannot reliably predict agronomic performance. We conclude that the practice of evaluating cacao trees based on superficial morphological descriptors and classifying them into “varieties,” as commonly done by farmers and technical advisors, can be misleading. This approach should be discouraged in the context of seed-based cacao populations involving broad genetic diversity. We advocate that terms such as “variety” and “cultivar” should be reserved for populations with well-defined genetic lineages or narrowly defined agronomic and/or quality characteristics.
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