Overcoming food and nutritional insecurity with the ever-growing population size remains a real challenge for African countries, mainly in sub-Saharan Africa, despite the fact that the continent abounds in a rich agricultural and nutritional diversity that can significantly contribute to the reduction of poverty and hunger in this region of the world. In Africa most food plants are cultivated and consumed locally. For many years, crop, food nutrition and technology sciences in Africa have focused on major crops such as maize [1], cassava, rice and yam leaving behind hundreds of crops and species relevant for the local economy and the nutrition of millions of rural and urban populations [2].

Although major crops feed 60% of the African population, they represent just 1% of the huge diversity used by farmers to adapt to climate hazards and ensure food and nutrition security of their households. For instance, more than 7000 species, frequently referred to as orphan crops, minor crops, or underutilized species, are used by rural and urban dwellers to alleviate hunger and promote healthy and balanced diets [3]. Unfortunately, most of those plant resources are by-and-large overlooked and very limited research programs focus on them. Moreover, very few researchers are trained for processing and promoting those locally adapted crops like leafy vegetables, indigenous fruits, old cereals, and pulses.

Among these crops we find a tuber plant called “Taro”. It is an important crop species widely consumed in Côte d’Ivoire. It is cultivated in various agro-ecological areas for its tubers or leaves [4]. Despite its importance, taro is still marginal and few documented. The cropping system is not developed and sustainable, mainly due to the crops’ natural characteristics and to current human practices. To enhance plant breeders’ capacity to respond to climate challenges, it is acknowledged that they need to be able to access and use as much genetic diversity as they can get. In Côte d’Ivoire, knowledge of taro cultivated, its genetic diversity and differentiation are very weakly documented. In order to fill up this gap, it is crucial to collect the genetic resource available at country level and to characterize the genetic diversity of the collected accessions on the basis of several markers. In this context we initiated a survey and collection of taro accessions in various agroecological zones of Côte d’Ivoire to evaluate the diversity level and genetic structuration.

This survey allowed us to make a first regrouping of these accessions collected in seven morphotypes based on peasant knowledge [4]. But the name taro describes several genera and confusion exists among scientists. In this study we focused our analysis on the leaf’s shapes to extent the knowledge of taro diversity cultivated in Côte d’Ivoire. Diversity in leaf characteristic and shape is considered to be most important as it is the primary criteria frequently used to characterize each of the diverse taro genera and to distinguish them visually [5].

The objective of this study was to characterize the collection of taros from different geographical zones available and identify the genera of taro cultivated. They could provide insights into the patterns of species divergence within taro cultivated in Côte d’Ivoire.

According to FAO [12], sustainable use of plant genetic resources is fundamental for a progressive realization of the right to food. This human right is realized when every man, woman, and child, alone or in community with others, always has physical and economic access to adequate food or means for its procurement. To face this challenge, it is important to rely on local resources. The access to quantitatively and qualitatively adequate and sufficient food focused to the cultural traditions of the people to which the consumer belongs is necessary for African countries. Today, 150 species are under cultivation in the world but only 12 of them provide 80 percent of our food needs. Hence the term neglected or orphan plant or still underutilized. The lack of adequate policies of promotion or conservation leads to the continued extinction of some crops. The goal of conservation genetics is to maintain genetic diversity at many levels and to provide tools for population monitoring and assessment that can be used for conservation planning.

To guarantee the full success for sustainable management of plant resources it’s necessary to knowledge genetic diversity. In fact, the importance of plant genetic diversity (PGD) is now being recognized as a specific area since exploding population with urbanization and decreasing cultivable lands are the critical factors contributing to food insecurity in developing world [13]. Diversity in plant genetic resources (PGR) provides opportunity for plant breeders to develop new and improved cultivars with desirable characteristics, which include both farmer-preferred traits and breeders preferred traits.

Genetic diversity of crop plants is the foundation for the sustainable development of new varieties. So, there is a need to characterize the diverse genetic resources using different markers and utilize them in the breeding programme. Morphological data in conjunction with molecular data are used for precise characterisation of germplasm resources [14]. A first approach to evaluate genetic diversity is morphological characterization based on phenotypic data. Two main parameters are analyzed, the quantitative and the qualitative data. They allow highlighting the divergence intra and inter accessions or population collected. These tools were successfully used in germplasm characterization of several crops [15] [16]

Despite the importance of taro in Côte d’Ivoire, it is weak documented. A recent study realized by [4] revealed 7 morphological types. But a study on plant genetic resources in Côte d’Ivoire [17] revealed that two genera of taro were cultivated. The conservation and characterization of taro genotype are crucial to fulfil the needs of breeders for both present and future generations. In this study, the morphological characteristics of genotypes were determined using Colocasia esculenta descriptors for leaf structure and shape. These characteristics could assist breeders in genotype selection dependent on phenotype, as well as in genetic improvement program.

Traits used in this study to evaluate our germplasm diversity have been very discriminants. Six of the seven parameters studied strongly contributed to the formation of the first two axes of the MCA. A total of 63% of variability was described by these axes. This result showed a significant contribution of leaf related characters to morphological variability of taro.

In the first time, the accessions analyzed were grouped into six groups. According to axe 1, four groups (I, II, III, IV) are very close while group V is closer to group VI. This result suggested that the 213 accessions could belong to two distinct genetic groups. Combination of Hierarchical Ascending Classification (HAC) and Factorial discriminant Analysis (FDA) confirmed the existence of two major groups. Main group 2 is subdivided into two subgroups that are very close.

The morphological traits analyzed highlighted an important variability and allowed a clear distinction of the accessions studied. A total of 20 variants were observed on seven traits analyzed. Several authors have reported similar results for the same traits or others [18] [19]. These results indicate that a high phenotypical diversity exists within the taro cultivated in Côte d’Ivoire. The similar result was found by [18] to taro in Burkina Faso. The qualitative traits used in evaluation of diversity were carried out by some author too. Taking into account modalities of the variants three clusters were highlighted. Cluster 2 and cluster 3 have more variants in common compared to cluster 1. This result shows that both clusters would be very close. This conclusion is supported by result of Hierarchical Ascending Classification (HAC). Hereby, the shape of the base of the leaf more frequent is peltate [19] [20] and sagittal [21] which could indicate that at least two genera of Araceae are cultivated in Côte d’Ivoire and called “taro”. It could be Colocasia and Xanthosoma. Characteristics of each cluster allow us to suggest that main group 1 could belong to genus Xanthosoma, main group 2 could belong to genus Colocasia. Separation of individuals of group 2 into two subgroups could indicate existence of various varieties or species into genus Colocasia [22]. In a study conducted on a species of taro, Colocasia esculenta in Côte d’Ivoire, authors revealed presence of cinq varieties. These results show the diversity of taro cultivated in Côte d’Ivoire. A high diversity in the position of the leaf blade surface was observed among accessions collected. Such a variation has been described by [19]. According to these authors drooping leaves are characteristic of Colocasia and hastate leaves to Xanthosoma. Based on these observations our study showed that the most cultivated genus in Côte d’Ivoire would be Xanthosoma.

The observable characteristics or traits of leaves have been used to describe the accessions of taro collected in various agro-ecological areas in Côte d’Ivoire. Our study showed the existence of more variants of each trait of taro. Two major groups have been highlighted based on traits analyzed. Result allows us to suggest that two genera of taro are cultivated in Côte d’Ivoire. The large group consisted of accessions presenting the characteristic to the genus Xanthosoma. But the highest diversity seems to be observed with accessions describing Colocasia. The genetic characterization by SSR markers in progress could help us with the identification of clones and the establishment of a breeding program of taro in Côte d’Ivoire.

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

Koffi, J.-M.N., Koffi, K.K., Bonny, S.B. and Bi, A.I.Z. (2021) Genetic Diversity of Taro Landraces from Côte d’Ivoire Based on Qualitative Traits of Leaves. Agricultural Sciences, 12, 1433-1446. https://doi.org/10.4236/as.2021.1212091