Use of floral descriptors to study variability in wild cocoa trees (Theobroma cacao L.) in French Guiana

Abstract

155 clones of wild cocoa trees (Theobroma cacao L.) in French Guiana, belonging to 16 populations identified by surveyors in two different river basins (three sub-basins), along with four international clones used as controls, were characterized with four floral descriptors: petal ligule width, sepal width, gynoecium length and number of ovules per ovary. The data underwent an analysis of variance and a factorial discriminant analysis, and the Mahalanobis distances between the populations were calculated. Significant differences existed between the populations for the four descriptors and the discriminant analysis revealed two main groups among the Guianan cocoa trees. It also isolated them from the controls. The populations in the two basins were not homogeneous, and the sub-basin of origin did not seem to be the main factor structuring the variability of the study populations. There proved to be substantial genotypic variability in the Guianan material for the floral descriptors. Variation within the same family (trees derived from the same pod) was low.