Analysis of the morphological diversity of elite Shea trees (Vitellaria paradoxa, C. Gaertn.) identified in the Bagoué and Tchologo counties, Côte d'Ivoire

Shea tree (Vitellaria paradoxa C. Gaertn) is one of the most important economically and
socially important tree species in the Sudano-Sahelian region and it is used in cooking,
cosmetics, chocolate making and traditional medecine. It is wildly distributed in the northern Côte d’Ivoire. However, it is the object of many pressures such demography, bushfires, and misuse of trees which cause genetic erosion of the species. The knowledge and understanding the genetic variation of elite shea trees genotypes identified in farmers land is essential for conservation and improvement. The aim of this study was to determine the relevant agro-morphological traits of elite shea tree in Côte d’Ivoire.
It was carried out on 220 shea trees randomly selected from a population of 639 elite shea
trees in the Bagoué and Tchologo counties, northern Côte d’Ivoire. We assessed phenotypic variability based on 11 qualitative and 10 quantitative traits. The results showed significant variability for most of the characteristics studied. Thus Shannon diversity index in the order of 0.98; 0.97; 0.95; 0.89 and 0.85 were found respectively for Shaft carrying, crown’s shape, branching, blade apex shape and nut’s shape. Results also showed high variation of number of fruit per tree (CV=39.9%), stem circumference (CV=30.71%), nut weight (CV=28.51%) and petiole length (CV=24.41%). Correlation was positively strong between nut yield and stem circumference (r=0.772; p˂0.001), leaf length and leaf width (r=568; p˂0.001), nut weight and nut width (r=0.808; p˂0.001) and nut length and nut weight (r=0.580; p˂0.001). The stem circumference was the only one quantitative morphological variable that structuring elite shea trees into three groups.
A combination of both quantitative and qualitative traits had identified 10 relevant descriptors that could describe efficiently elite shea trees in Côte d’Ivoire. Those morphological traits include 5 qualitative (nut color, nut shape, crown shape, young leaf color and limb shape) and 5 quantitative traits (stem circumference, nut length, nut weight, limb length and width). In order to complete the study of shea tree genetic diversity in Côte d’Ivoire, molecular markers will be use.