Morphological variability of fruits of Cola millenii K. Schum. from seven phytogeographical districts in Benin: opportunity for domestication

Abstract

Cola millenii K. Schum. is a wild edible fruit tree of high socio-economic importance in Sub-Sahara Africa. Its fruit pulp is used for food and nutritional purposes. Other parts of the tree are locally used against several diseases. Given the current threats to natural stands of this species, its domestication has been suggested as one of the methods for its sustainable management. The present study analyzed the domestication potential of this species through evaluation of morphological variability of its fruits across seven phytogeographical districts in Benin. Morphological data on fruits were collected on 1750 fruits from 175 trees distributed among the phytogeographical districts. Univariate and multivariate statistical methods were used for data analyses. The morphological traits of the fruits varied significantly among the phytogeographical districts. Among others, the weight of the pulp fluctuated between 4.18 and 15.55 g and the Bassila phytogeographical district presented the highest value. Variation in quantitative traits was greater between phytogeographical districts (55.44–89.13%) than among individuals within phytogeographical districts (9.52–34.32%). Qualitative descriptors such as shape and the color of the fruits and seeds also unfolded noticeable variation among phytodistricts (Shannon diversity: 0.14–1.46). However, there was no evidence of significant link between the morphological characteristics and the climatic variables considered (rainfall, relative humidity, minimum temperature and maximum temperature). Clustering suggested three fruit morphotypes. Fruits of morphotype 3, in majority from the Bassila and Zou phytogeographical districts had interesting characteristics (e.g. high fruit and pulp weight, and large fruit and seed size) for selection programs.