2.2. Villages and Institutions Surveyed

For the country to be sufficiently covered and for an exhaustive species inventory, 50 villages (Table 1; Figure 1) located in diverse agroecological (humid, semiarid, and arid) and ethnic zones were randomly selected for the study.

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Figure 1

Benin map showing the geographical location of the villages and institutions surveyed.

In Republic of Benin, the agricultural research is globally managed by INRAB (Institut National des Recherches Agricoles du Benin), IRDCAM (Institut de Recherche et de Développement sur la Biodiversité des Plantes Cultivées, Aromatiques et Médicinales), and the national universities (Parakou and Abomey-Calavi) while the popularisation is mainly the prerogative of the Ministry of Agriculture and its divisions. INRAB has four Agricultural Research Centres (CRA) working on subsistence crops and located at Agonkanmè (CRA-Agonkanmè), Niaouli (CRA-Sud), Savè (CRA-Centre), and Ina (CRA-Nord) (Figure 1). It also has a special vegetable programme (PCM) based at Agonkanmè and a Research and Development team (RD) based at Natitingou. The Ministry of Agriculture has a principal division (CeRPA) in all the departments and a subdivision (CeCPA) in all the districts. In addition, the Ministry of Agriculture also has a Department of Agriculture (DAGRI) located at Porto-Novo and a national society for the promotion of agricultural products (SONAPRA) located at Parakou. The two universities through their Faculties of Agriculture and the Faculty of Sciences and Technology (FAST) of the University of Abomey-Calavi through its Laboratory of Agricultural Biodiversity and Tropical Plant breeding (LAAPT) and Laboratory of Genetic and Biotechnology, highly contribute to capacity building in crop science. All these delocalised institutions were also selected for the study. In addition the associations of the producers of the districts of Savalou, Aplahoué, Cobli, and Kandi (Figure 1) were also surveyed. Also, the associations of the market women of the most important national agricultural markets (Glazoué, Bohicon, Parakou, and Tanguiéta) were considered as commercialisation of agricultural products in Benin is most exclusively a female enterprise. At total 50 villages, 17 research and development institutions and 11 local farmers and market women organizations were surveyed (Table 1; Figure 1).

3.2. Reasons of Negligence of the Species

The reasons behind the current status of the NUCS vary according to the agricultural technicians (researchers and extensionists) and the farmers which are also consumers (Table 4). The great majority (95.88%) of the agricultural technicians highlighted the lack of financial supports for research oriented on the neglected crops that no farmer interviewed listed (Table 4). This is widely justified since most of the institutions that support research in developing countries directly or indirectly specify “major crops” in their grant announcements. In republic of Benin, it has been recently that the government is thinking about diversification of the production. Hitherto, the main focus of the national research fund has always been the major crops such as Cotton, sorghum, cassava, maize, yam, rice, and beans. Both farmers and agricultural technicians listed as important reasons of neglect the lack of a national promotion policy of the neglected crops, the lack of organised markets as it is the case for cotton and maize, the susceptibility to pests and diseases and the lack of improved cultural practices and varieties (Table 4). Contrary to technicians, farmers underline two other important reasons which are low yield and laborious production. The listed reasons well-examined revealed that agronomic constraints are in majority and would result from the lack or insufficiency of scientific research and could justify, as indicated by many interviewees, the economically not profitable production of neglected crop species. For this last reason producers of the young generation interviewed said to be mostly interested in cash crops like Cotton, sorghum, and cassava that can provide them with a lot of money in a short time.

Also, some cultural believes weigh heavily on the production of some species. For many producers, voluntary digging out (most often by the children) of a plant of Kersting's groundnut in a given cultivated field to check maturity of the seeds provokes an immediate drying out of the whole field in two to three days hence leading to the loss of the year in case seeds are immature. Should the opposite occur, you will have to rapidly harvest the entire field and this is, as they said, painful, labour consuming and costly. In the Fè ethnic area (District of Bantè in central Benin), seeds of African yam beans Sphenostylis stenocarpa should be cooked only in the fields and never at home. When this happens, it leads to an epidemic of varicella engendered by the divinity Sagbata (God of the earth). Cultivation and consumption of Launaea taraxacifolia is proscribed to the adepts of this same divinity throughout the country. Because of all these, the production of many priority NUCS is globally being abandoned with as consequence, the disappearing of local varieties (genetic erosion).

3.3. Nutritional Value of the Species

Key data available from the Internet and other sources on the nutritional values of the 19 priority NUCS revealed that most of the species have interesting nutritional value and, if promoted, will surely help to combat malnutrition in Benin. For example, chemical evaluation [41], revealed that 100g edible portion of dried seeds (part consumed) of Macrotyloma geocarpum contain water 9.7g, energy 1457kJ (348kcal), protein 21.3g, fat 1.1g, carbohydrate 66.6g, fibre 5.5g, Ca 103mg, P 392mg, Fe 15.0mg, zinc (4.42 to 4.92mg), potassium (235.73 to 341.94mg), thiamin 0.76mg, riboflavin 0.19mg, and niacin 2.3mg. The same authors [41] reported that the content of essential amino acids per 100g food is arginine (9.3g), histidine (2.1g), and phenylalanine (3.2g), tryptophan 155mg, lysine 1280mg, methionine 267mg, phenylalanine 1125mg, threonine 738mg, valine 1209mg, leucine 1485mg, and isoleucine 871mg. The seed of M. geocarpum is therefore a high source of crude protein and very low in crude fat. Arginine, an amino acid for pediatric growth, is the most concentrated amino acid in the seed. Arginine, histidine, and phenylalanine concentrations in the seed are higher than the recommended Food and Agricultural Organisation/World Health Organisation amino acid requirement pattern for the preschool age group [41]. The total essential amino acid content in M. geocarpum seed is 42.0%. The lysine/arginine ratio calculated to estimate the seed atherogenic potential is 0.3 showing that M. geocarpum seed protein will not exert a hypercholesterolemia effect on the consumer.

Similarly, seed of egussi (Cucumeropsis mannii) used as vegetable is also a rich source of protein (31.4%), essential amino acids, fat (52.5%), essential fatty acids, minerals, and vitamins making it a nutritive food for consumers in developing countries, especially in West Africa where it is widely cultivated [42–44]. The fatty acids that it contains in abundance are linoleic (62.42%), oleic (15.90%), palmitic (10.27%), and stearic (10.26%) [44]. The high content of polyunsaturated fatty acids and essential amino acids it contains demonstrates that seed of Cucumeropsis mannii has potential health benefits and can be incorporated in many African diets and also used in poultry and animal feed [42–44]. Gbolo (Crassocephalum sp.) is one of the key traditional leafy vegetables wildly consumed in Benin [10].

In Benin, two species (Crassocephalum rubens and C. Crepidioides) are used. According to Yehouenou et al. [45], and Adjatin et al. [46], the nutritional values of these two species are slightly different but of high importance. Adjatin et al. [46] reported that the contents of the leaves in raw protein and in crude lipids expressed in % of dry matter are, respectively, 27.13%, 3.45 for C. crepidioides; 26.43% and 2.75% for C. rubens. The content of vitamin C for 100g of fresh leaf is of 9.17mg for C. crepidioides and 3.60mg for C. rubens. The content of ash is of 19.76% and 19.02% for C. rubens and C. crepidioides, respectively. The contents for sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), iron (Fe), Manganese (Mn), and copper (Cu) are 2129.04mg, 4469.91mg, 434.13mg, 3845.88mg, 1.6mg, 8.22mg, and 2.6mg, respectively, for C. rubens and these are higher than those in C. crepidioides.

Tigernut (Cyperus esculentus) was reported to be an excellent source of some useful minerals such as iron and calcium which are essential for body growth and development [47]. It is high in dietary fibre content, which could be effective in the treatment and prevention of many diseases including colon cancer, coronary heart diseases, obesity, diabetes, and gastrointestinal disorders. In addition, Tigernut has been demonstrated to be a rich source of quality oil and to contain higher essential amino acids than those proposed in the protein standard by the FAO/WHO for satisfying adult needs [47].

The chemical compositions and the nutritional values of other priority NUCS (Cajanus cajan, Ceratotheca sesamoides, Corchorus olitorius, Citrullus lanatus, Cleome gynandra, Pennisetum glaucum, Sphenostylis stenocarpa, Vigna subterranea, and Sesamum indicum) compiled in Table 5 shows that Africans in general and Beninese in particular suffer or die of malnutrition in the midst of a great diversity of highly nutritive food crops by ignorance or negligence.

Table 5

Known nutritional values of some priority NUS in Benin.

Species	Nutritional values
Cajanus cajan	The levels of crude protein, crude fiber, K, Ca, P, and Mg reported on pigeon peas by Amarteifio et al. [30] were dry matter 86.6–88.0%, crude protein 19.0–21.7%, crude fat 1.2-1.3%, crude fiber 9.8–13.0%, and ash 3.9–4.3%. Minerals ranges (mg/100g dry matter) were K 1845–1941, P 163–293, Ca 120–167, Mg 113–127, Na 11.3–12.0, Zn 7.2–8.2, Fe 2.5–4.7, and Cu 1.6–1.8. These data indicate that pigeon peas would positively contribute protein and could be valuable in the diet of the people in Benin.
Ceratotheca sesamoides	According to Fasakin [31] the leaves of Ceratotheca sesamoides used as vegetable contain low calories (soluble carbohydrates and fat) as well as high levels of protein (29.35–29.85%) and two of the elemental nutrients needed in large amounts by the human body, that is, calcium (2.60–2.62%) and phosphorus (0.25–0.27%). This vegetable is, therefore, a potent supplement to the starchy staple foods with which it is traditionally consumed and its consumption should be promoted, especially in families that can ill afford the prohibitive cost of animal protein.
Citrullus lanatus	The seeds consumed as vegetable is an excellent source of energy, protein, mineral salt, and vitamins. According to Das et al. [32], the composition of dried seed without shell per 100g is water 5.1g, energy 2340kJ (557kcal), protein 28.3g, fat 47.4g, carbohydrate 15.3g, Ca 54mg, P 755mg, Fe 7.3mg, thiamin 0.19mg, riboflavin 0.15mg, niacin 3.55mg, and folate 58μg. The seed oil consists of glycosides of linoleic, oleic, palmitic, and stearic acids. It is a rich natural source of lycopene, a carotenoid of great interest because of its antioxidant capacity and potential health benefits [32].
Cleome gynandra	100g edible portion of fresh leaves contain water 9.7g, energy 34kcal, protein 4.8g, fat 0.4g, carbohydrate 66.6g, fibre 1.2g, Ca 288mg, P 111mg, Fe 6.0mg, and ascorbic acid 13mg. It is a highly recommended meal for pregnant and lactating women [33].
Corchorus olitorius	Corchorus Olitorius leaves are rich sources of potassium, iron, copper, manganese and zinc as well as high energy values essential in human and animal nutrition. Idirs et al. [34] reported for 100g of leaves: 18.38g ash, 12.54g crude protein, 11.99g crude lipid, 19.56g available carbohydrate, high energy value of 200.78 ± 3.54kcal, potassium (2814.15 ± 8.08mg) and magnesium (76.69 ± 0.13mg), Na (54.56mg), Ca (30.55mg), P (6.68mg), Cu (2.52mg), Fe (19.53mg), Mn (5.95mg), and Zn (4.71mg).
Pennisetum glaucum	The grain of pearl millet contains per 100g edible portion: water 12.0g, energy 1428kJ (341kcal), protein 10.4g, fat 4.0g, carbohydrate 71.6g, fibre 1.9g, Ca 22mg, P 286mg, Fe 20.7mg, β-carotene traces, thiamin 0.30mg, riboflavin 0.22mg, niacin 1.7mg, and ascorbic acid 3mg. The content of essential amino acids per 100g food is tryptophan 189mg, lysine 332mg, methionine 239mg, phenylalanine 467mg, threonine 374mg, valine 535mg, leucine 927mg, and isoleucine 397mg [35]. Compared to that of other millets, the protein of pearl millet is rich in tryptophan [35].
Sesamum indicum	Proximate composition and physicochemical analyses of the Sesamum seeds [36] used in Benin as frying vegetables showed that the seed contains 5.7% moisture, 20% crude protein, 3.7% ash, 3.2% crude fiber, 54% fat, and 13.4% carbohydrate. The seeds are good sources of minerals. Potassium (851.35 ± 3.44mg/100g) was the highest, followed in descending order by Phosphorus (647.25 ± 3.52mg/100g), Magnesium (579.53 ± 0.42mg/100g), Calcium (415.38 ± 3.14mg/100g), and Sodium (122.50 ± 4.21mg/100g). The physical properties of the oil extracts showed the state to be liquid at room temperature. The oil was found to contain high levels of unsaturated fatty acids, especially oleic (up to 38.84%), and linoleic (up to 46.26%). Sesamum indicum L. oil can be classified in the oleic-linoleic acid group. The dominant saturated acids were palmitic (up to 8.58%) and stearic (up to 5.44%). The oil extracts exhibited good physicochemical properties and could be useful as edible oils and for industrial applications.
Sphenostylis stenocarpa	African yam bean is a crop with food security potentials for Africa. The average composition of the seeds (whole grains) is as follows: protein 20.51%, fat 12.20%, carbohydrate 50.24%, ash 2.60%, fibre 6.00%, and moisture 8.36%. The seeds are rich in potassium and phosphorus (625.43mg/100g), and (206.35mg/100g) respectively [36, 37]. The content of crude protein in AYB seeds is lower than that in soybean, but the amino acid spectrum indicated that the level of most of the essential amino acids especially lysine, methionine, histidine, and isoleucine in AYB is higher than those in other legumes including soybean [36]. The seed is rich in minerals. The value of minerals per 100g is: 4.2g for P; 0.80g for Ca; 1.7g for Mg; 12.0g for K; 0.06g for Na; 46.2mg for Mn; 44.0mg for Zn; 63.0mg for Fe 11.8mg for Cu [36, 38].
Vigna subterranea	Following Amarteifio et al. [39] 100g edible portion of dried seeds contain: water 10.3g, energy 1537kJ (367kcal), protein 18.8g, fat 6.2g, carbohydrate 61.3g, fibre 4.8g, and ash 3.4g. The ranges (mg/100g dry matter) of the macrominerals in bambara groundnut are Ca 37–128, K 1545–2200, Mg 159–335, Na 16–25, and P 313–563. For the microminerals (ppm): Cu 3.0–13.2, Fe 23.0–150 and Zn 13.9–77.0, β-carotene 10μg, thiamin 0.47mg, riboflavin 0.14mg, niacin 1.8mg and ascorbic acid traces. The content of essential amino acids per 100g food is tryptophan 192mg, lysine 1141mg, methionine 312mg, phenylalanine 991mg, threonine 617mg, valine 937mg, leucine 1385mg, and isoleucine 776mg [40]. This legume is a good source of Ca, K, Mg, P, and Fe and its concentration in minerals indicates that it could be useful in the diets of consumers.

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3.4. Medicinal Value of the Species

Some neglected and underutilized crop species have many important medicinal properties beside their nutritional value and can be used as nutraceutical. Local populations of the surveyed sites believe that Crassocephalum sp. has antibiotic, antihelminthes, anti-inflammatory, antidiabetic, anti-malaria and blood regulation properties and also treats indigestion, liver complaints, colds, intestinal worms, and hepatic insufficiency. Recent chemical analysis [46] of leaves extract of this species revealed quite rightly the presence of tannins, flavonoïds, steroids, mucilage, reducing compounds, coumarins, and the C-heterosis that are recognized as possessing pharmacological properties intervening in the prevention and the treatment of several human pathologies such as hypertension, headaches, breast cancer, burns, inflammations, injuries, liver complaints, infections, and sexually transmitted diseases [48, 49].

Leaf of Cleome gynandra consumed as leafy vegetable has anti-inflammatory and lysosomal stability actions [50], potent dose-dependent anticancer activity comparable to that of 5-fluorouracil [51] and free radical scavenging activity [52, 53]. It is also believed to improve eyesight and provide energy [33]. Similarly, Launaea taraxacifolia is locally believed (indigenous knowledge) to have, through simple and regular consumption as leafy vegetable, lactogenic, aphrodisiaque, antibiotic, and antimalaria properties, a wonderful blood pressure regulating and haemorrhoids treatment capacity [10]. Recently Obi [54] reported that leaves extract of the species has virucidal potential. Gill et al. [55] reported that Citrullus lanatus has good antioxidant, anti-inflammatory, and analgesic potential and may be used as a future food medicine. Surprisingly, tuber of Dioscorea dumetorum is said to have antidiabetic properties [56, 57]. The leaves of Bidens pilosa highly consumed as leafy vegetable in Adja cultural area in the southwest of Benin are reported by the local population to possess antibacterial, antidysenteric, anti-inflammatory, antimicrobial, antimalarial, diuretic, hepatoprotective, and hypotensive activities with most of them being confirmed by scientific research [58]. Tubers of Tigernut (Cyperus esculentus) are said to be aphrodisiac, carminative, diuretic, emmenagogue, stimulant, tonic and have potent antioxidant and anti-inflammatory properties [59]. Tigernut tuber has also been reported to be used in the treatment of flatulence, indigestion, diarrhoea, dysentery, and excessive thirst [59]. Therefore, there is the need for increased utilization and awareness about the health benefits of the use of these species.

3.5. Economic Importance of the Species

In Benin, no information or data regarding the economic importance of the priority NUCS identified and particularly their income generation role for the poor is available for use. Market survey revealed that all the species are sold in the markets (Table 6) but their market value are highly variable. According to the women association of Glazoué market (the most important agricultural market of central Benin), the price of one kg of Macrotyloma geocarpum varies during the year between 2 $and4$ FCFA (which is about 3 to 5 times the price of rice) while the one of Crassocephalum rubens varies between 1 $to1.5$ (Table 6). At Bassila (Figure 1) roundabout also known as one of the numerous egussi (Cucumeropsis edulis and Citrullus lanatus) selling point in Benin, 10 women interviewed reported to individually sell, on average, 30 bags of 2 $perdayhencemakingatotalbusinessof18000$ per month. At the road market of Sèhouè where leafy vegetables are among the dominant products sold and during the raining season, Launaea taraxacifolia generates to rural market women about 200 $perdayandapproximately6000$ per month. At the international market of Dantokpa (Cotonou), Corchorus olitorius like the other NUCS, is sold through a well-established network of wholesalers and retailers. Rapid survey of 10 women wholesalers revealed an average of 1000 $ income per month and per individual.

At a Tigernut (Cyperus esculentus) wholesaling point of this same market, one of the women wholesalers interviewed on the economic importance of this NUC declared: “I will never leave Tigernut business for other things. During its period of availability, loincloth sellers cannot compete with me with regard to what I spent on and what I gain from in a short time. Look! Apart from Sunday, I paid 20 $ each day and 80 $ all Saturday for tontine. When in a given week wholesalers from Gabon and Cameroun come to the market for buying Tigernut bags, I can easily realize a net benefit of 400 $ this week. Per day I earn about 80 $ on average and we are 15 at this selling point. Make the calculation yourself and see!” This statement clearly highlighted the economic importance of the species.

Although these data gathered on some species from some selected markets are not results of sound economic analysis, they clearly indicate that the neglected crop species are important source of household incomes and substantially contribute to poverty reduction mostly in rural areas in Benin. In order to provide policy makers with more detailed, robust, and convincing economic data, it is recommended that a scientifically well-designed socioeconomic study be conducted on the identified species.

3.6. Gender Role in the Production and Marketing of the Neglected and Underutilized Crop Species

The gender role in the production, diversity preservation, and use of the priority NUCS has to be documented as no data regarding this aspect is available for use. According to the interviewees, the gender role would mostly vary according to the crops and the regions and sometimes the ethnic areas. According to the data collected and summarised in Table 7, leafy vegetables species are produced most exclusively by women while Dioscorea dumetorum is essentially men crop. In the north, the production of the pulses Vigna subterranea and Macrotyloma geocarpum would be women prerogative while in the south and in the centre their production was said to be under the control of both men and women. For all the species apart from Pennisetum glaucum, Sesamum indicum, and Sphenostylis stenocarpa in the north, the marketing is almost exclusively a female-dominated enterprise. They gain a lot of money through commercialisation of the priority NUCS and this helps them to improve their position within the society. Species which highly contribute to women's empowerment cited are Macrotyloma geocarpum, Vigna subterranea, Corchorus olitorius, Citrullus lanatus, Cucumeropsis mannii, and Launaea taraxacifolia. The results obtained globally indicate, and as reported by many authors [60–64] for crop production in general, that female farmers contribute more significantly to the production of the priority NUCS species in Benin than their male counterparts. However, the promotion of sustainable production of these species in Benin would require that the needs of both rural male and female farmers be deeply examined and addressed in a comprehensive and systemic manner.

This research was sponsored by EU-ACP Science and Technology Programme through the project “Building human and institutional capacity for enhancing the conservation and use of Neglected and Underutilized Species of crops in West Africa, and Eastern and Southern Africa” and by the Laboratory of Agricultural Biodiversity and Tropical Plant Breeding of the University of Abomey-Calavi. The authors are grateful to Drs. Per Rudebjer and Stefano Padulosi of Bioversity International (Rome) and Wellington Ekaya of Regional Universities Forum for Capacity Building in Agriculture (RUFORUM, Uganda) who provided useful scientific guidance for the implementation of the work. They thank Drs. Adéoti K. and Eteka A. and Ir P. Ajassè and B. Kpèki (University of Abomey-Calavi) for their technical assistance during the survey. They express Their sincere thanks to all the scientists, agricultural technicians and farmers they met or interviewed during the survey.