ORIGINAL PAPER Relations between several traits linked to sexual plant reproduction in Theobroma cacao L.: number of ovules per ovary, number of seeds per pod, and seed weight Christian Cilas & Regina Machado & Juan-Carlos Motamayor Received: 3 July 2009 / Revised: 15 September 2009 / Accepted: 17 September 2009 / Published online: 13 October 2009 # Springer-Verlag 2009 Abstract Tropical perennial plants cultivated outside their place of origin call for major germplasm characterization and prebreeding work. For cacao breeding, the selection process has to optimize the weight of cacao beans produced per tree by increasing the number of pods produced, the number of seeds per pod (NoSP), and the mean weight of seeds produced (SW). NoSP and SW were studied over nine consecutive years in a collection of more than 200 clones. The number of ovules per ovary (NoOV) was also examined in a subsample of this collection in order to evaluate the ability to predict NoSP. NoSP and SW showed a relatively normal distribution with heritabilities of 0.29 and 0.51, respectively. The composite trait “mean seed weight per pod” showed a generalized extreme value distribution of intermediate herita- bility (0.43). NoSP and SW were found to be genetically independent. NoOV was highly heritable (h 2 =0.810), but it did not provide good prediction of NoSP. The largest seeds were observed in genotypes derived from crosses between cultivated cacao trees, which had been formerly domesticat- ed. Domestication therefore favored seed size, while for the other traits examined, similar variation was found between wild and domesticated populations. Keywords Domestication . Heritability . Fruit traits . Seed traits . Trait evolution Introduction Perennial plant species from the humid tropical regions can often reproduce asexually (Kinsman 1990), but the produc- tion of viable seeds still remains a necessity for the majority of perennial species. The production of viable seeds and their conservation and germination ability are, therefore, “vital” traits that are regulated through natural selection (Dalling et al. 1998). The quantity of seeds produced can, therefore, be a trait that has a selective advantage in a natural environment (Howe and Smallwood 1982). However, depending on how they are dispersed, seed size is not necessarily a trait under selective pressure, especially when animal species facilitate dispersal (Wehncke et al. 2003). In such cases, successful seed dispersal is dependent on the choice made by the animal carrier (Gautier-Hion et al. 1985). For decades, several tropical perennial plants from the humid forests have been removed from their natural environment for agricultural use. Their targeted traits for human exploitation vary from those that enable the best survival of those species in their natural environment. Most agricultural practices and plant breeding are geared towards adaptation to human needs. Some such plants are cultivated for the production of their seeds, also called beans, such as cacao (Theobroma cacao L.). Genetic improvement of traits involved in sexual reproduction is, therefore, important. In this case, some of the target traits provide a selective advantage in a natural environment. Communicated by J. Davis. C. Cilas (*) CIRAD, UPR “Maîtrise des bioagresseurs des cultures pérennes”, TA A31/02, 34398 Montpellier Cedex 5, France e-mail: christian.cilas@cirad.fr R. Machado MARS Inc., Mars Center for Cocoa Sciences, Itajuipe, Bahia, Brazil J.-C. Motamayor MARS Inc., c/o USDA-ARS, SHRS, 13601 Old Cutler Road, Miami, FL 33158, USA Tree Genetics & Genomes (2010) 6:219–226 DOI 10.1007/s11295-009-0242-9