Caractérisation phénotypique des plantules de quatre populations de Sclerocarya birrea (A. Rich.) Hochst. au Burkina Faso

Sclerocarya birrea (A. Rich.) Hochst. is an African oleaginous fruit tree. High post-plantation mortality is due to planting in inappropriate ecological zones. This study characterised the seedling phenotypes in order to determine their ecologically adapted traits from a very early stage. A total of 494 seedlings were analysed, from populations in You, Yarci, Gonse and Diapangou-Peulh in Burkina Faso, four locations that fall within three different climatic zones. The study results show that grouped seedling emergence ensures that overlapping generations are present within each population. Variance analysis showed differences within and between populations for most variables, reflecting the diversity of phenotypes among the seedlings. Principal Component Analysis showed characteristics specific to each population. The dendrogramme for ranked classification in ascending order identified three groups of individual seedlings with similar phenotypes: G1 for Gonse (55.88%), Yarci (23.52%) and You (20.58%); G2 for You (46.15%), Yarci (42.30%), Diapangou-Peulh (7.69%) and Gonse (3.84%); G3 for Diapangou-Peulh (90%), Yarci (5%) and You (5%). These results show the existence of genetic gains in selection at the individual and population level. They also show that these populations are not in danger of coming to an evolutionary dead-end in the short term. The study of heritability showed that the most heritable traits are stem height (28.31%), length of the primary root (44.30%), number of secondary roots (81.89%), fresh weight of the roots (73.47%) and dry weight of the roots (28.86%). The root system architecture reflects the adaptation capacity of Sclerocarya birrea to different soil types. In view of these results, selective breeding for adaptive traits may be considered at an early stage.