Socio-demographic characteristics of D. praehensilis farmers
Of the 560 D.
praehensilis producers surveyed, 98.74% were men with 1 to 3 wives. Their households had 4 to 22 members. They belong to five ethnic groups: Abron, Agni, Abbey, Attié, and Baoulé. The Agni are the most common, at 57.80%. The
D.
praehensilis farmers interviewed have a shallow level of education. Most (76.34%) have never been to school. Only 2.6% attended secondary school. The rest (21.06%) attended primary school (Fig 2A). They had no training or support in cultivating
D.
praehensilis. The main activity of these respondents in all study areas was farming (97%). Some farmers had off-farm income-generating activities such as trade and civil service. The age data show that 6.07% of respondents were young (age<35). 53.26% were adults (35<age<50). 40.67% were old (age>50). The mean age was 48 years (Fig 2B). The farmers’ experience in
D.
praehensilis cultivation ranged from 7 to 60 years, with a mean of 19 years.
D.
praehensilis yam is mainly grown by men because they own the cocoa and coffee plantations where
D.
praehensilis is intercropped. This observation confirms the results of studies in Togo and Ghana
(Gnamkoulamba et al., 2002). Sixty years of experience cultivating
D.
praehensilis has confirmed the idea of recent traditional selection methods proposed by
Zoundjihekpon (1993) and
Hamon (1988). En revanche la culture de D. praehensilis en Côte semble être plus récente qu’au Ghana d’ou elle aurait été introduite.
D. praehensilis folk taxonomy and classification
Farmers in the study know
D.
praehensilis by different names depending on their sociolinguistic group. Within each sociolinguistic group, there are several indigenous names. As a result, 18 cultivars were recorded in all the study sites. The local and generic names of
D.
praehensilis cultivars and the farmers’ criteria for categorizing and naming cultivars by ethnic group surveyed in Côte d’Ivoire are presented in Table 2. Globally, by combining correspondence analysis between cultivar names with their main characteristics described by farmers, the 18 inventoried cultivars could be broadly classified into four main morphotypes. Table 3 summarizes the
Dioscorea genus descriptors used by farmers to name a cultivar. In all the villages studied, farmers frequently used phenotypic characteristics related to tubers (48.60%) and stem (40.90%) and less frequently the descriptors related to inflorescences (9.42%) and leaves (1.08%) to recognize, identify and classify or describe
D.
praehensilis landraces. Identification of landraces based on these characters varied among sociolinguistic groups. Furthermore, there was a significant difference in the phenotypic markers used to characterize these cultivars within each sociolinguistic group. This suggests that individuals within the same sociolinguistic group may differ in the criteria they use to characterize landraces (c2=149.482; p<0.05). A factorial correspondence analysis (Fig 3) showed that Agni and Baoulé farmers named their
D.
praehensilis landrace by referring to the density of spines on the stem, the color of the tuber flesh and the presence of spines on the tuber roots.
D.
praehensilis landraces are defined by the Abron ethnic group in terms of stem spine density and tuber flesh color. The Abbey ethnic group distinguishes cultivars based on flowering type and tuber shape. The Attiés rarely use phenotypic characters to identify
D.
praehensilis landraces. They refer to them under the generic name “cocoassié”. 18 recorded
D.
praehensilis morphotypes were grouped into four classes based on tuber flesh color: pure white, yellow, spotted white and purple (Fig 4). The white morphotype includes cultivars with irregularly shaped tubers that develop an irregular shape and pure white flesh color. The stem is densely spined and colored at the base. The off-white morphotype usually has cylindrical tubers that are smooth on the rootlets and have either mottled purple or yellow flesh. The purple morphotype consists of elongated or rounded tubers with many rootlets and purple flesh. The yellow-fleshed morphotypes can be either completely yellow or have a mottled red appearance. All four morphotypes have very similar characteristics in their aerial parts, including leaves and stems and in their reproductive structures, such as inflorescences. Because of this similarity, it is difficult to distinguish them by these characteristics.
Farmers classified
D.
praehensilis landraces into four categories based on the color of the tuber flesh pure white, spotted white, yellow and purple. Farmers also use phenotypic traits such as stem spine density, stem color and spine presence on tuberous roots to name and classify
D.
praehensilis landraces. Farmers in the study area, particularly from the Agni, Abron and Baoulé ethnic groups, have developed a good knowledge of
D.
praehensilis. Tuber flesh color, spine development on tuber roots and spine density on the stem are stable traits that better characterize
D.
praehensilis landraces. Farmers indicated that stem color and tuber shape, are less useful for distinguishing landraces because these traits are affected by environmental factors. The linguistic polymorphism observed in this study could lead to confusion about the diversity of
D.
praehensilis. This is because different landraces may have the same local name and one may be known by several local names (
Adoukonou-Sagbadja et al., 2006). Therefore different landraces can share the same name and other names can know a single landrace among the 18 local landraces identified by farmers.
Otabo et al., (2016), Agre et al., (2015) and
Kombo et al., (2012) have highlighted that homonyms and synonyms are also found in other tuber crops, including cassava. In addition,
D.
praehensilis diversity is significantly lower than that of
D.
cayenensis and
D.
rotundata in Côte d’Ivoire (
Zoundjihekpon, 1993;
Hamon, 1988). This difference may be due to more recent traditional selection practices.
Diversity of D. praehensilis across surveyed regions in Côte d’Ivoire
A summary of the diversity indices and the number of cultivars in the surveyed villages is presented in Table 4. The results show that
D.
praehensilis diversity distribution in the study area is uneven. Shannon’s diversity index ranges from 0.84 to 1.15 at the regional level, while Pielou’s evenness ranges from 0.77 to 0.88. Diversity is highest in the East region (H’=1.15), closely followed by the Midwest (H’=1.11). The Southwest region has slightly lower diversity (0.84) than the other regions. All seven cultivars identified were found in the eastern part ofCôte d’Ivoire.Dédia, Abongoua, Assindi, Kotosso and Massakro are the five villages with the highest diversity. The Shannon diversity indices range from 2.034 to 2.389. The villages have a moderately equitable distribution of cultivars, with all equitability index values above 0.85. Ottawa has the lowest varietal diversity (H’=0.503).
Shannon’s diversity index, equitability and Margalef species richness indices revealed moderate genetic diversity among
D.
praehensilis morphotypes in the regions studied.
D.
praehensilis diversity recorded in our study is significantly lower than that reported by
Adewum et al., (2021) in Ghana. This suggests that farmers in Côte d’Ivoire made less intensive traditional selections during the domestication of
D.
praehensilis. Eastern Côte d’Ivoire has the greatest diversity. This region plays a crucial role in the production, consumption and market of
D.
praehensilis. The east region is likely where
D.
praehensilis was domesticated, as noted by
Hamon (1988). The limited diversity of
D.
praehensilis in the Southwest and Midwest may be due to its recent arrival as a result of population movements. The heterogeneity of
D.
praehensilis diversity can be attributed to two main factors. The first is human influence. Farmers select
D.
praehensilis landrace based on agronomic traits such as high yield, early maturity, good production and organoleptic traits such as taste and ease of cooking. The second factor is favorable agroecological conditions, including consistent and abundant rainfall and moderate humidity, which promote the growth and development of various yam species, including
D.
praehensilis.
Constraints related to D. praehensilis production
D.
praehensilis production faced biotic and abiotic constraints based on farmers’ responses and perceptions. Table 5 shows the main constraints associated with reducing the production and utilization of
D.
praehensilis morphotypes in Côte d’Ivoire. The identified abiotic factors contributing to 97.54% of the issues include agricultural practices, market conditions and the characteristics of the tubers. The specific tuber characteristics are rapid oxidation of the flesh (18.7%), short shelf life after harvest (15.46%), a fibrous texture (4.26%) and poor taste (1.62%). Agronomic factors also significantly impact production and utilization, accounting for 57.05% of the challenges reported by farmers. Major agronomic problems include long dormancy (8.76%), low productivity (1.84%), difficulty in harvesting (2.62%), being affected by erratic rainfall (30.73%) and challenges in growing in poor soils (2.76%). In addition, challenges related to abiotic factors, such as the loss of coffee and cocoa plantations (7.55%) and low market value, account for 3.24% of the problems. Biotic factors such as pests and diseases represent 2.91%. The challenges varied significantly among the different villages studied (c2 = 86.1934, p = 0.000***), indicating clear differences in ranking these problems among the villages. A factorial correspondence analysis revealed a relationship between the constraints related to
D.
praehensilis and the specific villages studied (Fig 5).
The three main factors that affect the crop of
D.
praehensilis are a short shelf-life after harvest, quick oxidation of the flesh and erratic rain. Erratic rain is the most important abiotic constraint that seems to spare no region of Côte d’Ivoire
(Dekoula et al., 2018). However, these constraints can be overcome by electing and using local varieties that are more efficient in terms of drought tolerance and good post-harvest conservation, as with some crops, such as cassava, to circumvent these various constraints
(Agre et al., 2015). In addition,
in vitro culture techniques through micropropagation can be used to multiply these selected varieties, as was the case for cassava, a greatly appreciated tuber in Côte d’Ivoire
(Cacai et al., 2012).
Economic and social importance of D. praehensilis
Most farmers (81.63%) reported growing
D.
praehensilis for their consumption. They prepare it by pounding, boiling, or stewing. In August and September, over 70% of meals included it. Farmers do not have rituals for eating
D.
praehensilis yam. But they do for
D.
cayenensis and
D.
rotundata yams. Only 18.37% of the farmers surveyed sold some of their produce at local markets, in the fields, or at home (Fig 6). The tuber’s price depends on its size, shape, color, texture, moisture, flesh and skin. The relationship between seller and buyer, as well as the season, also matters. Prices drop with stronger seller-buyer ties. They rise in lean seasons. Women primarily sell
D.
praehensilis yams. They make between 30 and 60 USD a year. Most of this money goes to food. From August to September, women lead the marketing of
D.
praehensilis yams.
Yam (
Dioscorea spp.
) is a food security crop of great economic and sociocultural importance for millions of people in sub-Saharan Africa
(Wembou et al., 2017). This important role was confirmed by the current study conducted on
D.
praehensilis. This yam is mainly used for food in the study area. This shows that producers are aware of the product’s high nutritional value and how its value can contribute to the community’s food security. Studies conducted in Togo and Ghana confirmed that
D.
praehensilis is consumed directly as foutou, boiled, or stewed. Its use helps to regulate the use of other foodstuffs of more commercial interest
(Gnamkoulamba et al., 2002). D.
Praehensilis tubers are a major source of income for farmers, particularly in eastern Côte d’Ivoire. Despite its status as a neglected plant, local populations attach great importance to this yam.
Indigenous post-harvest storage techniques
Post-harvest storage of
D.
praehensilis tubers has three main purposes. Consumption accounts for 98.42% of cases, sales (1.46%) and use as seed (0.12%). Farmers have developed various techniques to optimize post-harvest tuber storage conditions to achieve these aims. These techniques protect against heat and pests, particularly termites and rodents. We identified and described four advantages and disadvantages of postharvest storage techniques (Table 6). The most common technique is pit storage, used by 92.76% of farmers, followed by storage in damp places (5.63%), in packaging (0.12%) and in sheds or trees (1.49%). Regardless of the technique, fresh tubers generally last between 7 and 20 days after harvest. These post-harvest storage techniques are different from those used for
D.
alata,
D.
cayenensis and D.
rotundata yams, as described by
Digbeu et al., (2009).
