Indigenous knowledge and valorisation of ackee products
B. sapida is well known in Benin. It has been utilized for centuries and is still an important plant genetic resource today. Each ethnic group has different names for the species indicating age-old knowledge and uses. In general, by providing different products, services and having a commercial value, ackee is conserved for its multipurpose properties.
Apart from the use as vegetable in the Natemba ethnic group mentioned above, others utilizations of the aril have been reported also in West Africa [15–18] and in the Caribbean [19, 20]. Farmers managed the species firstly to meet their own needs and also for the commercial value of arils and soap [3, 4].
Future researches on the technological characteristics of the fruits and the design of small storage techniques are needed to help farmers to improve the conservation and long-term storage of arils. The best way to do that would be to establish small processing units managed by farmers in villages or at the communal level. The exact knowledge of composition is the basis for any successful technological process . Preliminary analyses of the physical composition of arils from Toukountouna (North-West Benin) have shown that it includes 46% of oil, 47% of fibres and 3% of proteins . The food value of 100 g of raw arils from Mexico is as follows: Moisture (57.60 g), Protein (8.75 g), Fat (18.78 g), Fibre (3.45 g), Carbohydrates (9.55 g), Ash (1.87 g), Calcium (83 mg), Phosphorus (98 mg), Iron (5.52 mg), Thiamine (0.10 mg), Riboflavin (0.18 mg), Niacin (3.74 mg) and Ascorbic Acid (65 mg) .
Characterization of ackee seed oil and defatted cake of seeds from Southern Benin compared to seeds from Nigeria and Côte d'Ivoire revealed differences in chemical properties and composition of seeds oils (saponification value, iodine value, oleic acidity, peroxide value); fatty acid composition, proximate composition (moisture, fat, crude fibre, total sugars, starch, proteins) and mineral composition (K, N, P, Ca, Mg, Na, Cu, Zn, Mn, Fe, Fe, Ash) and 17 amino acids [22–24]. Those results highlighted the potential of ackee seeds for industrial use as lubricants, surfactants and as oil for consumption that should be further explored. Feeding trial experiments conducted in savannas areas of Nigeria have shown that ackee leaves are good fodder resource for West African Dwarf goats especially in the dry season . This is probably good news for animal breeders in the region because ackee trees flush during dry seasons in many part of West Africa when the availability of grasses to feed ruminants decreases drastically.
Some of the medicinal values attributed to ackee in Benin are known in other countries where the species occurs as well. The bark is used in Ivory Coast together with some spices to relieve pains; leaves and barks are used in association to treat sore stomach, epilepsy and yellow fever in Columbia . In Ghana, the bark is one of the ingredients used in a concoction administered for epilepsy; leave juice is used for washing or as drops for sore eyes, conjunctivitis and trachoma; the pulp of twiggy leaves is applied on the forehead to treat migraine/headache . B. sapida is also a natural source of carboxycyclopropylglycine used in pharmacy. The extraction of this non-proteinogenic amino acid from ackee offers the possibility of avoiding the expensive synthetic procedures . Furthermore, B. sapida has antidiabetic activity . The use of this important traditional medicinal knowledge in a rational way remains a challenge to modern scientific disciplines such as pharmacology. More research is necessary to analyze the properties and therapeutic virtues attributed to the soap as a preliminary step to the mechanization of the production. The confirmation of the virtues of ackee soap can boost its production and contribute to a better valorisation of the enormous quantity of capsules and seeds that are usually thrown away.
Ackee is not well known in Benin for its utility as repellent. However, experiments conducted in Trinidad and Tobago had shown that other fruit parts (epidermis, aril and seed) have repellent properties against stored-product insect pests, namely, Callosobruchus maculatus, Cryptolestes ferrugineus, Tribolium castaneum and Sitophilus zeamais [29, 30].
Traditional management and domestication of ackee
The various differentiation criteria of ackee trees mentioned above calls for an appropriate characterization to investigate the existence of eventual varieties, and/or to detect the effect of the ongoing domestication process practiced by farmers in their different land-use systems. For instance, the positive correlation reported between fruit size and aril size needs to be tested by morphometric study to characterize the diversity of ackee fruits traits.
All traditional silvicultural management practices to improve the production were reported for other important agroforestry parkland species such as Vitellaria paradoxa and Parkia biglobosa (Jacq.) R.Br. ex Benth. in West Africa . There is a consensus among local people that these management practices favour the abundance of better phenotypes, in this case fruits with preferred traits. This link between management techniques and the perception of variation suggests that there is selection going on with a tendency to increase phenotypes producing desired fruits in managed populations. However, reasons for the "superior" perception of trees under management need further analyses. It is particularly challenging and important to distinguish genetic from environment impacts on phenotypes.
Evidence that farmers have domesticated other African indigenous trees has been reported for Dacryodes edulis H.J. Lam and Irvingia gabonensis (Aubry-Lecomte ex O'Rorke) Baill. [32–34]; Vitellaria paradoxa C.F. Gaertn.  and Sclerocarya birrea (A. Rich.) Hochst. subsp. caffra (Sond.) Kokwaro. Processes of plants domestication associated to silvicultural management were also documented for many species in the Tehuacán Valley of Mexico including Stenocereus stellatus (Pfeiff.) Riccob.  and Ceiba aesculifolia (Kunth) Britten & Baker .
Implications for improvement and conservation of ackee genetic resources
In general, the ethnobotanical survey revealed clearly that indigenous knowledge about ackee varies according to ethnic group and gender. Particularly three ethnic groups (Batombu, Otamari and Natemba) had a great knowledge about the species. In addition, the multivariate analysis showed also clearly the separation between the knowledge of men and women within the Otamari, Batombu and Yoruba communities.
Selection or breeding programs should focus on ackee trees with preferred traits important for local populations. For instance when looking at preferred fruit traits, this study showed that ackee fruit size is the most important trait for men (Batombu, Otamari and Yoruba). Fruit shape, aril colour, aril size and aril taste were the preferred fruit traits for Batombu women, Otamari men and all Yoruba and Natemba. Those differences needs to be taken into account in any research/development programs related to germplasm sampling and ackee improvement.
Domestication can reduce the genetic diversity of wild populations if cultivars replace autochthonous populations on a large scale. It can also increase the level of variability at desired traits in semi-domesticated populations suggesting that varieties may have multiple origins [1, 34]. The effect of the artificial selection reported in this study on the genetic diversity and structure of ackee is not yet known and needs to be evaluated properly. This prerequisite is essential to avoid that the intensification of the domestication process will lead to a progressive elimination of individuals with non-desired quality, and a subsequent loss of genetic diversity.
Conservation of ackee genetic resources can be done effectively through cultivation of the species in agroforestry systems, its maintenance on protected areas where they occurs and maintenance of seeds in gene banks. Since preferred traits vary among ethnic groups and gender, the strategy should be specific and should target not only the morphotypes recognized by local populations but should also integrate the population genetics information.