Intraspecific variation in germination and seedling growth traits of Vitex doniana across two contrasting climate zones in Burkina Faso, West Africa: implications for domestication and agroforestry

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Résumé

Vitex doniana Sweet is a socioeconomically and ecologically important agroforestry species in sub-Saharan Africa. It contributes to traditional medicine and socio-cultural practices and supports rural livelihoods. However, limited knowledge of its reproductive biology and regeneration ecology constrains its domestication and large-scale propagation. This study investigated the effects of seed provenance and pre-germination treatments on seed germination and seedling growth of V. doniana from four provenances distributed across two contrasting climate zones in Burkina Faso. A total of 1200 seeds were subjected to three pre-germination treatments (control, water soaking, and scarification) using a splitplot design with four replicates. Mixed-effects models were used to assess the effects of provenance, pre-germination treatments, and their interaction on germination performance and seedling growth traits. Germination performance varied significantly among provenances. Seeds from Bontioli and Dinderesso
showed higher germination percentages, whereas seeds from Gonsé and Ouilingoré germinated earlier and had shorter mean germination times. The effects of pre-germination treatments varied significantly among provenances, indicating provenancespecific responses to dormancy-breaking methods. Relative growth rates were significantly affected by
provenance and pre-germination treatment. Seedlings from Gonsé and Ouilingoré exhibited greater height growth and collar diameter, whereas those from Bontioli and Dinderesso produced more branches. These findings reveal provenance-level phenotypic differentiation in germination and early seedling growth among V. doniana populations, which is consistent with potential adaptive differentiation in response to local climatic conditions. The results highlight the potential value of provenance selection and provenance-
specific propagation protocols for improving nursery production and supporting the domestication and integration of V. doniana into climate-resilient agroforestry systems.

Mots-clés

Adaptive differentiation, Burkina Faso, Pre-germination treatment, Relative growth rate, Restoration, Seed provenance