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Abstract
Knowledge of available variability in a crop species provides a guide for the utilization and conservation of useful variation. Seventeen agro-morphological traits were studied in 184 accessions of cacao, Theobroma cacao L. collected from farmers' fields (138) and field genebank collections (46). Descriptive statistics—univariate analysis of variance (ANOVA)—were used to determine variation among accessions. Multivariate analysis with principal component analysis (PCA) was done and a cluster dendrogram was generated based on the unweighted pair group mean with arithmetic average (UPGMA). The first three principal component axes accounted for 43.6% of total variation observed among accessions studied. Quantitative bean traits—dry bean weight, nib weight, fresh weight, cotyledon length and cotyledon width—and qualitative fruit traits—basal constriction, apex form, ridge colour, fruit shape, flush colour and cotyledon shape—were the most important traits accounting for the variability observed. Six groups of accessions were obtained from cluster analysis. Fruit and bean traits of Upper Amazon Forasteros observed in farmers' accessions provided evidence of a shift from previously grown local ‘West African Amelonado’ from the Lower Amazon Forastero population. In conclusion, this study revealed some accessions with useful trait combinations in farmers' plantations and indicated a need to conserve the local ‘Amelonado’ landrace variety to avoid extinction and to preserve the unique flavour of ‘West African Amelonado’ in cocoa breeding programmes.
Acknowledgements
The field assistance of Messrs. Lateef Raji, Marcus Efunla, Segun Adeyanju, Sunday Njoku, Victor Enagu and Sunday Taiwo; financial support from the USAID/USDA-ARS, Mars Inc and three anonymous referees are gratefully acknowledged.