Gravimetric sorting to improve germination of Anogeissus leiocarpa seed lots

Anogeissus leiocarpa is an important economical and cultural species which is used for dyeing cotton fabric and for reforestation and restoration plantings in West Africa, where it is protected. Its natural regeneration is nearly non-existent and the species is continually exploited. Hence, propagation has emerged as an alternative to its conservation, although limited by the very low germination of its seeds. We aimed to increase the quality of seed lots to support community forestry, investigating how mechanical gravimetric and immersion seed sorting influence germination rate, and we correlated germination responses with physical characteristics to better typify a quality seed lot. For immersing, water was the best separation medium, resulting in a seed lot with 19% germination against 9% for the unsorted seeds. Mechanical sorting through air-flows allowed separating initial seed lots into sorted lots that were on average 4% by weight of the initial, unsorted seed lot. The final sorted batches had 89% germination and an additional sulphuric acid pre-treatment improved germination of these seeds to 100%, which has never been obtained for this species before. The gravimetric mechanical and immersion sorting are efficient in separating out highly viable seeds and could be used for large seed lots