Emile Cros

A genomewide admixture mapping study for yield factors and morphological traits in a cultivated cocoa (Theobroma cacao L.) population

The selection of productive varieties of modern Criollo cocoa, showing fine aromatic qualities in their beans, is of major interest for some producing countries, such as Venezuela. Cultivated populations of Modern Criollo or Trinitario varieties may be suitable for admixture mapping analysis, as large blocks of alleles derived from two identified divergent ancestors, recently admixed, are still preserved, after a few generations of recombination, similar to experimental mapping progenies. Two hundred and fifty-seven individuals from a cultivated population of Modern Criollo were selected and analysed with 92 microsatellite markers distributed along the genome. This population exhibited a wide range of variability for yield factors and morphological features. Population structure analysis identified two main subgroups corresponding to the admixture from the two ancestors Criollo and Forastero. Several significant associations between markers and phenotypic data (yield factors and morphological traits) were identified by a least squares general linear model (GLM) taking into account the population structure and the percentage of admixture of each individual. Results were compared with classical QTL analyses previously reported for other cacao populations. Most markers associated to quantitative traits were very close to QTLs detected formerly for the same traits. Associations were also identified between markers and several qualitative traits including the red pigmentation observed in different organs, mainly associated to common markers in linkage group 4.

The use of near infrared spectroscopy to determine the fat, caffeine, theobromine and (-)-epicatechin contents in unfermented and sun-dried beans of Criollo cocoa

Cocoa is an important raw material in international trade, for which the highest quality is demanded. Venezuelan Criollo cocoa beans from the south of Lake Maracaibo or Chuao are of very high quality and are considered to be Venezuelas finest beans. It is therefore important to characterise and define that quality, or its precursors, in the different primary cocoa processing stages. Given the large number of samples to be analysed, new analytical techniques providing fast and reliable quality data are essential. Near infrared (NIR) spectroscopy utilises wavelengths from 780–2500 nm to measure the absorbance by a sample, compute organic functional groups and quantitatively predict a particular factor. It has been extensively used to analyse food quality and to determine the main alkaloids of coffee. Fat, caffeine, theobromine and (−)-epicatechin contents are related to cocoa bean “flavour” quality. These parameters are usually determined using conventional methods, which are time consuming, destructive and expensive. The goals of this study were to use NIR spectroscopy to develop a fast and non-destructive tool to determine compounds in unfermented and sun-dried cocoa beans of high quality. Calibration coefficients of determination (R2) and standard errors of cross-validation were 0.94 and 0.89%, 0.94 and 0.05%, 0.88 and 0.08% and 0.96 and 0.18% for fat, caffeine, theobromine and (−)-epicatechin contents (% dry matter), respectively. The results confirmed the good predictability of the models and showed that NIR spectroscopy can be used as a rapid method for determining these compounds in cocoa beans.

Diversity of Cacao Trees in Waslala, Nicaragua: Associations between Genotype Spectra, Product Quality and Yield Potential

The sensory quality and the contents of quality-determining chemical compounds in unfermented and fermented cocoa from 100 cacao trees (individual genotypes) representing groups of nine genotype spectra (GG), grown at smallholder plantings in the municipality of Waslala, Nicaragua, were evaluated for two successive harvest periods. Cocoa samples were fermented using a technique mimicking recommended on-farm practices. The sensory cocoa quality was assessed by experienced tasters, and seven major chemical taste compounds were quantified by near infrared spectrometry (NIRS). The association of the nine, partially admixed, genotype spectra with the analytical and sensory quality parameters was tested. The individual parameters were analyzed as a function of the factors GG and harvest (including the date of fermentation), individual trees within a single GG were used as replications. In fermented cocoa, significant GG-specific differences were observed for methylxanthines, theobromine-to-caffeine (T/C) ratio, total fat, procyanidin B5 and epicatechin, as well as the sensory attributes global score, astringency, and dry fruit aroma, but differences related to harvest were also apparent. The potential cocoa yield was also highly determined by the individual GG, although there was significant tree-to-tree variation within every single GG. Non-fermented samples showed large harvest-to-harvest variation of their chemical composition, while differences between GG were insignificant. These results suggest that selection by the genetic background, represented here by groups of partially admixed genotype spectra, would be a useful strategy toward enhancing quality and yield of cocoa in Nicaragua. Selection by the GG within the local, genetically segregating populations of seed-propagated cacao, followed by clonal propagation of best-performing individuals of the selected GG could be a viable alternative to traditional propagation of cacao by seed from open pollination. Fast and gentle air-drying of the fermented beans and their permanent dry storage were an efficient and comparatively easy precondition for high cocoa quality.

Bean quality traits and sensory evaluation of wild Guianan cocoa populations (Theobroma cacao L.)

Naturalized cocoa populations originating from the Oyapok and Tanpok basins in French Guiana were studied for their technological characters (bean count, fat content, purine content) and sensory characters (overall aroma intensity, cocoa flavour, acidity, bitterness, astringency, fruity or floral tastes, aftertaste, etc.), along with three controls (Amelonado and Ecuadorian varieties). The bean count in Guianan cocoa was higher than that of the controls, but it generally remained acceptable (below 100). Caffeine content was much higher than that of the Amelonado control. The overall aroma intensity and cocoa flavour of the chocolates made with the dry cocoa beans from Guianan trees were statistically superior to those of the industrial reference, the West African Amelonado. The other criteria studied, particularly the fat content, did not reveal any significant differences from the controls.