Natural assets of Côte d’Ivoire (quality and availability of cultivable land, hydraulic system, favorable climate and varied vegetations) have favored the diversification of its agriculture, pillar of national economy. The success of this agricultural economy depends on the diversification of crop production, including cash or industrial crops (coffee, cocoa, rubber, pineapple, cotton, cashew nuts, etc.) and starchy food crops (sorghum, millet, beans, yams, manioc, taro, plantain bananas, corn, rice, etc.) [1] that guarantee financial and food security. In the margins of both categories, appear native but underutilized plant species. They belong to the traditional production category, specifically the sector of minor crops. Minor farms are characterized by low productivity, small size of cultivated areas, the hardness of work due to its manual nature, difficult access to agricultural inputs because their financing is scarce and an almost exclusively female workforce. At the heart of Côte d’Ivoire’s neglected food heritage are many legumes whose dry seeds are used as a sauce ingredient.

In Côte d’Ivoire, they are generally referred to “beans” because they are characterized by a vinescent habit. Legumes are a part of the Fabaceae, generally annual, for food purposes and whose seeds are contained in pods. Groundnuts, cowpeas, voandzou, pigeon pea… are the most common pulses and are grown in larger areas [2]. Like these plants, little-known legumes, which are qualified as orphan and/or minor plants, play an important part in a sustainable diet. Many studies highlight their nutritional, agronomic, environmental and economic interest. Indeed, legume seeds are characterized by a high energy and nutritional content. Their high protein content (18% to 30%, two to three times more than the seeds of major cereals), carbohydrates and minerals [3] [4] are the dietary assets available in the context of a healthy and balanced diet. In addition, their consumption pattern supports long storage without loss of nutritional value and adapt to droughts and marginal environments. Some of them contribute to improving the biological renewal of phosphorus. Moreover, thanks to their symbiotic nitrogen fixation capacity, they contribute to preserving soil fertility and improving the productivity of nutrient-poor sub-Saharan soils. Legumes reveal a wide variety of phenotypes. In fact, the color of the seed, the shape and the size of the pods are the units of diversity on which farmers classify local varieties. As a result of natural and human selection, these local varieties have accumulated genetic diversity that has been little studied and is therefore poorly exploited in the management of available plant genetic resources. In addition, due to changes in culinary practices, the cultivation of orphan legumes is rapidly declining in traditional production systems and yields are low and irregular. Only a few women farmers have kept the habit of cultivating them, but mainly on very small surfaces or in hut farming, just for domestic consumption needs. These changes in practices could lead to significant erosion of the genetic diversity of these legumes with consumable seeds. And insufficient genetic diversity increases risks for food security and nutrition. Knowledge of the genetic diversity of a resource is the pillar, the foundation of food security.

The rise of underutilized legumes therefore requires a better preservation of its genetic diversity. Very few studies of valorization of these species in Côte d’Ivoire have been carried out and do not enable to assess the level of genetic diversity of these minor plants. Indeed, the taxonomy is not updated, the collection of genetic resources, the genetic characterization and the agronomic evaluation are fragmented or trivial. There is therefore an urgent need to prospect the country in order to assess the genetic variability and to constitute a germoplasm of these legumes for sustainable management of these resources.

This study was carried out in the context of the conservation of under-exploited plants genetic resources in Côte d’Ivoire. This is the first report characterizing the morphotypes of minor and endangered legumes seeds collected in Côte d’Ivoire. It enabled to assess the current state of the variability of these resources in their main production areas in Côte d’Ivoire, an essential step in assessing the diversity and genetic improvement of the resource [7] [8]. It makes it possible to provide plants genetic resources improvers and managers with vital information necessary for their work [7].

The data set obtained after a survey enabled to assess the variability within the “neglected legumes” resource. Farmers’ management of this resource in its production area in Côte d’Ivoire has revealed 22 morphotypes of consumable legumes seeds. These morphotypes were identified by the Centre National de Floristique, which grouped them into five species: Phaseolus lunatus, Phaseolus sp., Mucuna pruriens, Canavalia ensiformis and C. gladiata. A collection of 254 accessions was selected to represent the diversity of morphotypes collected from 47 localities and five Ivorian administrative regions.

The collected accessions were characterized using morphological descriptors. Results of seeds quantitative traits analysis, namely seed length, seed width and thickness, and qualitative traits showed significant variability among morphotypes. Morphotypes are defined on the basis of seeds colour, shape and size. The cultivation of the identified minor legumes seeds is not uniformly distributed over the five surveyed regions. Also, species show morphological variability. P. lunatus is represented by nine morphotypes for 146 accessions, Phaseolus sp includes two morphotypes for six accessions, M. pruriens is represented by four morphotypes for 64 accessions, C. ensiformis contains two morphotypes for 15 accessions, C. ensiformis large seeds includes 1 morphotype for 13 accessions, C. ensiformis small seeds is represented by 1 morphotype for 23 accessions and C. gladiata includes 5 morphotypes for 26 accessions.

While P. lunatus is the most representative of collected species, it is present in varying proportions in each of the surveyed regions, idem for morphotypes. Indeed, morphotype M3 with only (9 accessions) is present in the five surveyed regions while morphotype M7 represented by 47 accessions is present in only four of the five surveyed regions. Some regions have a greater number of morphotypes than others, this is the example of Indénié-Djuablin region, which has collected the largest number of species and morphotypes (130 accessions for the five species of minor seeded legumes used in sauces, some are the main food or consumed as a treat or snack. The Moronou region is the only one where accessions of Canavalia ensiformis with large seeds, C. gladiata and the morphotypes M9 and M14 of M. pruriens have been collected. The greater variability of morphotypes from one region to another could also be explained by different social factors. Legumes are deeply integrated into the socio-cultural life and diet of local populations, and their large number in the Indénié-Djuablin region could be due to trade with neighbouring Ghana, a country where seed legume cultivation is more sustained. This would contribute to increasing the genetic diversity of local types in the region [9].

The analysis of variance showed a significant difference between the seeds of the accessions on all the parameters analyzed. The Principal Component Analysis, hierarchical bottom-up classification and discriminant factor analysis confirmed this important morphological variability. A strong phenotypic structuring of the studied material into three sets is highlighted. The first group includes 117 accessions characterized by large and thick seeds but a low index shape. The second group includes 62 accessions characterized by seeds of small width and thickness, but a high shape index, the 3^rd group includes 75 accessions.

However, ANOVA and the LSD test indicate that all traits vary from one morphotype to another, suggesting that legumes studied have been ecologically adapted [10]. The ACM has shown that the cumulative portion of information provided on the first two axis is 66.16%, which is relatively high, allowing a better representation of the relationship among all the variables. This analysis confirms the variability of morphotypes within legume seeds groups. The study of seed variability for variety identification is common [11] [12] among Fabaceae. Parameters such as integument staining, eye and hilum appearance and staining are widely documented [13] [14], indicating the importance of seed characteristics in the study of systematics in the Fabaceae. [15] [16] [17] have shown that the variability of patterns on the seed surface is very useful for species recognition in the Fabaceae. Many differences in colouring, appearance within the same species, could be the result of an adaptive process. The great diversity that generally characterizes the Fabaceae indicates the presence of several mutations controlling morphological traits within the family itself. Ecologically, the Fabaceae family colonized all habitats (forests, deserts, plains to mountains). They are forage, ornamental, wild, domesticated, woody, as well as herbaceous... The emergence of variability in organisms can be explained by the fact that diversity ensures survival following evolution and sets the potential for an adaptive response to fluctuations in environmental conditions. Thus, the morphological differences observed among different morphotypes within a species or between species suggest that morphotypes are created and maintained under very different evolutionary processes within the same agroecosystem. At the population level, evolutionary processes can indeed lead to variations in morphological characteristics. And evolutionary processes could include anthropogenic factors. Indeed, anthropogenic factors are likely to exert highly variable selective pressures on genotypes [18]. They tend to modify genetic diversity. For example, the mode of seeds management influences morphotypes diversity. Morphotype choices and selections, as well as cultural practices, lead to a diversified selection resulting in the acquisition or maintenance of significant phenotypic diversity [19]. This morphological differentiation observed may be compromised by the gradual disappearance of species due to changes in farming practices. Many of the practices identified could ensure that diversity is maintained. Indeed, the acquisition of seeds by inheritance or donation, the poly-varietal culture, the eating habits of certain peoples, the culture mainly ensured by indigenous people, those who have kept in mind the ancestral eating habits of minor seed legumes are factors that can perpetuate the conservation of the resource’s diversity. The age of producers indicates that adult and senior producers have more expertise in growing, consuming and producing pulses than younger generations. The lack of interest of younger generations in minor seed legumes in favour of crops with improved varieties hinders their maintenance and promotes their disappearance. According to interviewees, production appears to have declined over the years, due to the popularity of other legumes such as cowpea, groundnuts and soybeans. This study was also carried out with the objective of looking for the morphological characteristics that best explain the variety of diversity observed among producers among legumes seeds identified in Côte d’Ivoire. The identification of the peasant diversity management unit as an analytical unit can be an important tool for diversity assessment [20] [21]. The use of seed colour as a unit of diversity within the legume collection is an important differentiation criterion in farming environments. The grouping of genotypes within each diversity group generally shows a structuring of morphological variability according to the colour of the genotype and seems to confirm the peasant classification.

It is undeniable that several local varieties of neglected and underutilized legumes are available in the hands of farmers. In Côte d’Ivoire, producers in five resource-producing regions recognize 22 morphotypes. Certain varieties have their own qualitative and quantitative characteristics. Our results have highlighted the heterogeneity of the collection legumes collected. Significant differences among accessions, relating to the length, width, thickness and shape index of these morphotypes have been revealed by ANOVA. It was also possible in terms of quantitative traits (width, thickness and shape of the seed) and qualitative features (uniformity of coloring, patterns on the seed coat, appearance of the hilum, coloring and the appearance of the eye) to reveal groups of different sizes and morphologies within our germoplasm, thanks to multivariate analyzes (FDA, AHC, ACM).

The authors declare no conflicts of interest regarding the publication of this paper.

Kouonon, L.C., Koffi, K.G., Adjoumani, K. and Goba, K.A.E. (2020) Morphological Variability of Neglected and Underutilized Legumes (NULs) Collection from Côte d’Ivoire. American Journal of Plant Sciences, 11, 226-244. https://doi.org/10.4236/ajps.2020.112018