Effect of provenance and traits of fruit on the seed germination of Senegalia macrostachya in Burkina Faso, West Africa

Senegalia macrostachya is a multipurpose native shrub in West Africa that faces challenges in natural regeneration due to pests and overharvesting. This study evaluates seed germination and early seedling growth according to provenance, maturity stage, and the number of seeds in the fruit. Fruits were collected from four sites in two climate zones, considering two maturity stages (full and medium maturity) and four fruit types (containing 2 to 5 seeds). Seeds were weighed and their water content was measured before germination trials in alluvial sand and composite soil substrates. Germination was recorded every two days. Starting 65 days after sowing, seedling growth was measured biweekly over a period of 145 days. Data were analyzed using ANOVA. The weight of the seeds ranged from 0.27 ± 0.02 g to 0.45 ± 0.02 g and varied significantly (p < 0.001) between the provenances and between the types of fruit. Seeds with lower water content (6.93 ± 0.33%) exhibited the highest germination rates. Germination rates varied significantly (p < 0.001) according to substrate type, maturity stage, and number of seeds in the fruit. Seeds from mature fruits, from the Sissili provenance in the Sudanian zone, and 2-seeded fruits showed the highest mean germination rates (73 ± 15.45%, 73 ± 5.79%, and 90 ± 9.52%, respectively). At 145 days post-emergence, seedlings had reached a collar diameter of 6.93 mm and a height of 60.8 cm, with significant growth increases observed every two weeks (p< 0.001). Mature fruits, the fruits from Sissili provenance, and the 5-seeded fruits produced the most vigorous seedlings. The number of leaves and branches did not vary significantly among treatments within each study factor. Root biomass allocation was lower than above-ground biomass and did not differ significantly across treatments. These findings provide valuable insights for promoting the cultivation of Senegalia macrostachya through optimal seed selection in natural stands.