Analysis of the population structure of cassava growers, production systems, and plots’ sanitary
state in Côte d'Ivoire
DJAHA Konan Engueran*
1, ABO Kouabenan
2, KONE Tchoa
1, KONE Daouda
3, KONE Mongomaké
1.
1UFR Sciences de la Nature, Laboratoire de Biologie et Amélioration des Productions Végétales, Université Nangui Abrogoua, 02 BP 801 Abidjan 02, Côte d’Ivoire.
2Institut National Polytechnique Félix Houphouët-Boigny, Laboratoire de Phytopathologie et de Biologie Végétale, BP 1313 Yamoussoukro, Côte d'Ivoire.
3UFR Biosciences, Laboratoire de Physiologie et Pathologie Végétales, Université Félix Houphouët Boigny, 22 BP 582 Abidjan 22, Côte d'Ivoire.
*Corresponding author: DJAHA Konan Engueran, tel: (225) 04284659/77958928, email: senadke@yahoo.fr
Keywords: Collection, Cote d’Ivoire, Manihot esculenta, Prospecting, Viral disease.
1 ABSTRACT
These last decades, the cassava (Manihot esculenta, Crantz) sector has become a provider of employment and therefore, a significant source of revenue in Cote d'Ivoire. This economic growth led to changes in the management of cassava cultivation, mainly characterized by diversified farming practices that do not require high technicality.
Unfortunately, information regarding this new production environment is not yet available.
Objective: the present study aims to analyze the environment and the agricultural practices of the cassava sector in Cote d'Ivoire.
Methodology: investigations were carried out from March to October 2014 in different production areas in Cote d'Ivoire. After interchanges and farming plots diagnosis, cuttings of different varieties and symptomatic leaf samples of the mosaic viral disease were collected.
Results: the information gathered revealed that the major growers in the cassava cultivation areas are the men. Fallow practice is inexistent, and plot areas are small (0.25 ha). Pure or associated culture is practiced, and growers prefer cassava varieties with a cycle length of six months. A total of 252 cassava phenotypes have been collected. 40.63% of the farming plots support at least two different varieties. For the renewal and/or the extension of cultivated plots, 87.9% of the farmers use cuttings from previous harvests. Cassava mosaic disease is present in all producing areas, but predominantly in the North Cote d’Ivoire (72%) where the disease severity index is 3.58.
Conclusion and applications of results: Cassava is one of the main food crop grown by local populations in various agroecological areas of Cote d’Ivoire. Its cultivation is mainly practised by men. Cassava mosaic disease is present in all areas of cultivation in the country, but with a higher index of severity in the North zone. The results of this survey can help in sustainable management strategies for cassava cultivation.
2 INTRODUCTION
The Ivorian annual cassava production is estimated at 4.2 million tons (FAO, 2014). This crop ranks second regarding food production.
It can be cultivated in all agro-ecological zones of Cote d'Ivoire. However, the main production zones are located in the south, west, and the centre parts (Anonyme, 2009). A high varietal diversity was discovered, offering a varied range of flavours and cassava-derived products for local feed consumption and sub- Saharan export (N'Zué, 2007). Since its introduction in Côte d'Ivoire from Ghana by the ‘Akan’ peoples (Perrot, 2005), cassava used to be the food during hunger seasons but later became a staple food especially for the Akans living in the south of the country. Growing and food processing were women's activities.
Today, the estimated Ivorian population of 22.8 million inhabitants from an annual growth rate of 2.6% (Anonymous, 2015), induces an increase in demand for cassava-derived products. The increasing demand has driven to economic development in cassava production and processing. Consequently, cassava has moved from a subsistence crop to a cash crop.
The crop is hence grown by many farmers in both favourable and marginal areas. Despite the economic growth, the plant during its
development is confronted with major constraints such as viral diseases. This is a major threat to food security, especially for small farmers who practice agriculture (Segnou, 2002). The sector remains in the informal. Data related to the socio-economic evolution and farming practices are practically non-existent or insufficiently documented. The studies previously carried out in Côte d'Ivoire were just related to the production constraints, namely epidemiology of viral diseases (Pita, 2001), yield improvement by the adoption of best crop technical itineraries (Doubi et al., 2016) and agro-morphological characterization (Djaha et al., 2016). However integrating experiences from farmers, who are at the heart of this activity, is a critical part of undertaking sustainable management strategies of cassava genetic resources and their selection. Therefore, the global objective of the present work was to understand the socio-cultural management and the ecological environment of cassava cultivation. Specifically, the involvement of gender in the production chain of maize will be determined. The adopted crop models and the prevalence of cassava mosaic disease in the different agroecological zones will be established.
3 MATERIALS AND METHODS
3.1 Prospecting and collection of morphotypes: Six prospecting and collection missions were conducted in the cassava producing areas during 2014. One hundred seventy-two cassava plots set up either around human habitats or in village plantations were visited. For each plot, the locality name, the grower’ name and gender, the cultivation mode, the geographical coordinates, the cultivated area, the way of obtaining planting material, weed control level and vernacular names of cultivars were noted during interchanges with growers. After the interchanges, an inspection of the plots was made with the grower, allowing additional questions to complete the information on the survey sheets. At the end of
the investigation, and with the consent of the grower, cuttings of different morphotype of cassava were collected.
3.2 Study of cassava mosaic disease incidence and severity: A total of 75, 28, 14, 21, 32 plots were visited in the South, East, North, Centre, and West respectively (figure 1).
The plots were crossed following two diagonals on which 30 plants were randomly selected for observations (Figure 1). The number of plants with or without symptoms of cassava mosaic disease was recorded, allowing to calculate the disease incidence and severity index per plot.
Regarding the severity index, a grading scale of severity scores from 1 to 5 was used. Plants with mosaic symptoms were grouped into five
classes according to the criteria given in Table 1 (IITA, 1990).
Figure 1: Illustration of the visited cassava plots shapes and the two-diagonals based leaf sampling method (a and b: undefined shaped plots)
Table 1: Grading scale of disease severity of cassava mosaic disease (IITA, 1990).
Score Aspect of symptoms
1 No symptoms
2 Yellowish stain covering 1/5 of the leaf blade
3 Spot covering half of the limb; appearance of foliar deformation 4 Severe curling of deformed leaves; reduced vegetative growth 5 Almost all of the limb curled up, reduced vegetative apparatus Then the severity index (SI) was determined
according to Mignouna et al. (2001):
SI = , with: SI: severity index; Xi:
severity scores; Ni: number of infected plants;
Nt: total number of plants.
The Disease Incidence (DI), was evaluated as follows:
DI% =
4 Statistical analyses: Data derived from survey sheets were subjected to the analysis of frequency distribution using the MS Excel 2010 software. The StatSoft Statistica 7.1 software one-way ANOVA program was run on disease incidence and severity data and Fisher LSD pairwise comparison test was subsequently was performed when p<0.05.
5 RESULTS
5.1 Producer Gender, plot acreage, and cropping antecedence: A total of 172 producers were interviewed, and their cassava farms visited. Producers are mostly male. Data analysis revealed that a significant proportion of
growers are men in the North (64.71%), South (56.34%), East (55.88%) and West (67.7%) areas, 57%) except for the Centre where the proportion of women is higher, (53.85%) (Figure 2).
Figure 2: Repartition of cassava farmers by genera and agroecological zones in Côte d'Ivoire.
Plot cropping antecedent is diverse. The majority of cassava growers use plots previously occupied by other food crops and fallows.
These kinds of plots represent 24% and 17%
respectively (Figure 3). However, 46% of growers did not accurately give information about the cropping history of their plot.
Figure3. Cropping antecedent of the plots Furthermore, the areas devoted to cassava
cultivation vary between one-hundredth of a hectare (1/100 ha) and 4 ha (Figure 4). The most extensive plot (4 ha) was held by only 1%
of the growers investigated. The majority of growers (34.26%), devoted only 0.25 ha to cassava production.
Figure 4: Distribution of cassava growers per cultivated areas 5.2 Weed infestation state of the cassava
plots: In general, weeds in the visited plots were controlled manually or chemically. The best-maintained plots, regardless of the
method, reach a proportion of 70.88% followed by 21.52% of moderately-controlled plots. The poorly-controlled plots, represent 7.6% (Figure 5).
Figure 5: Proportion of weed infestation state 5.3 Cassava cultivation mode: In North
Cote d’Ivoire, cassava was found associated with maize and vegetable crops. In the Centre and East, cassava cultivation was preferably done with yam. In the West zone, cassava was growing with rice and plantain whereas legumes, vegetables, and maize were associated with cassava in the south. In every zone, the frequency distribution of any cultivation mode has been recorded. The results from the data analysis are shown in Figure 6. According to
the cultivation mode, three homogeneous groups stand out. The first group brings together the South and East zones, where pure culture of cassava is predominant, with a frequency of 66.67%. West and North zones compose the second group where 67.57% of cassava plots have a companion planting. The last group comprises the center part of the country where pure culture and association are proportionally present.
Figure 6: Cassava cultivation mode in the production areas 5.4 Planting material supply mode:
Producers obtained planting material (cuttings)
either by purchasing or by donations from friends or the National Agency for Rural
Development (ANADER). The material is also obtained by sampling cuttings from previous cassava plots. 87.91% of cuttings are harvested from old cassava fields whereas 8.1 %; 1.6%
and 1.2%, of cuttings, are respectively are donations, unidentified procurement, purchases, and from neighbouring countries (Figure 7).
Figure 7. Plant material supply mode 5.5 Cassava morphotypes collected: In
this study, the number of cassava phenotypes was recorded in every inspected plot. In all, 242 accessions were collected in the 172 fields visited. The varieties have been identified by the phenotype, by observing stems and leaves of cassava. The results are illustrated in Figure 8. There is a diversity of cassava varieties by
field. Most of the growers (40.63%) cultivated at least two varieties of cassava in the same plot. Moreover, the highest number of varieties recorded in a plot is six and 4.69% of growers conduct this mode of cultivation. The lowest number of varieties recorded by field is one, involving 32.81% of the growers.
Figure 8: Proportions of the number of cultivars per field 5.6 Cycle length of cultivars used: The
growers use cultivars which are harvested within 6 and 24 months (Figure 9). 54.67% of them use the shortest cycle cultivars (6
months). intermediate cycle cultivars (12 months) are grown by 20% of farmers while only 5.33% cultivate long cycle cultivars.
Figure 9. Percentage of growers per cultivar cycle length 5.7 Cassava cultivars identification
mode used by growers: Farmers identify and name the cultivars according to two levels of apprehension. The first level is based on the phenotypic characters. The second is anecdotal.
Concerning the anecdotal names, cassava may be identified according to the locality of origin of the cuttings. For example, the much
appreciated cultivar comes from the department of Bonoua, located in the south- east of Côte d'Ivoire. Some cultivars might bear a human name. For instance, "Diarrassouba"
therefore indicating the name of the person who introduced the cultivar in the locality. In the visited localities, the widely vernacular name is "Yacé", with a frequency of 24% (Figure 10).
Figure 10: Frequencies of common vernacular names 5.8 Phytosanitary status of cassava
fields: Plant health in every plot was assessed through the determination of the incidence and severity index of cassava mosaic disease.
Symptoms of the viral disease have been observed in most of the fields visited. Disease incidence range from 45 to 81% depending on the zone (Table 2). The highest incidence (81.67%) was found in the North and the lowest (45.67%) in West Cote d'Ivoire.
Screening the Ivorian geographical zones for this viral disease incidence revealed four significantly distinct zones or groups. The first, second and third group describe the disease incidence just in the North, South and Centre zone respectively. However, the fourth group comprises the East and West zones. The disease severity index range from 2.56 to 3.58 and also discriminate four producing zones in which the zones statistically similar are the
Center and East (Fig. 11). Figure 11 shows that cassava mosaic was severe in the South-East, centre, and north of the country. However,
some plots in the South-East and the Eastern zone showed no mosaic symptoms.
Table 2: Incidence and severity of cassava mosaic disease in the cultivation areas of Côte d’Ivoire
Agroecological zones Incidence (%) Severity index
South 58,29±2,34 b 3,05 ± 0,11abc
East 50,38±2,18 c 3,38 ± 0,15bc
North 81,67±6,61 a 3,58 ± 0,10a
Center 52,11±3,21 bc 2,94 ± 0,17bc
west 45,67±1,14 c 2,56 ± 0,14c
F 11,52 5,32
P ˂ 0,001 ˂ 0,001
In the same column, the means ± sd followed by the same letter are statistically equal at α risk = 0.05 according to the Fischer LSD test; F = Fischer value, P = Probability.
Figure 11: Geographical distribution of areas and plots visited with prevalence of cassava mosaic disease.
6 DISCUSSION
6.1 Growers population structure and plot history: The present study showed a high proportion of men involved in the cassava production chain. Indeed, fluctuating prices of cash crops such as cocoa and rubber have pushed producers (men) to diversify agricultural products to improve their incomes. In addition,
the growing demand for cassava tubers for the production of attiéké (fermented cassava semolina) has motivated the choice of cassava cultivation to offset the shortfall in traditional cash crops. Added to this is the increased income from cassava production in Côte d'Ivoire. In addition, arable land belongs
primarily to men. The combined effect of all these factors explains the rise in the proportion of man in cassava production. The high number of men in the cassava production chain has already been reported by Agré et al. (2015).
The authors pointed out that 81.33% of farmers in Benin were men. Two facts could explain the absence of fallow period in any farming practices. Firstly, cassava is traditionally planted after the harvest of the main crops.
Secondly, there is a decreasing of arable land for food crops. Eric Mollard (1993) already alerted that mass immigration of growers to Ivorian forest zones was causing increasing deforestation. Generally speaking, under the constraint of the demographic pressure, the extension of cash crops, and some modification in farming systems, the fallow practice is changing. Fallow times are shortened or unusual (Serpantié and Floret, 1994). The proportion of growers cultivating small areas (0.25 ha) is high (34, 26%). Three reasons could explain this proportion: lack of mechanization, decreasing of arable land and the high requirement of workforce (FAO, 2013). In addition, new producing areas (North Cote d’Ivoire) showed up because of increasing and extensive agriculture of export crops in the traditional zones (South Cote d’Ivoire) of cassava.
6.2 Agricultural practices of cassava: Both cultivation modes (pure or associated) are used in cassava agrosystems. The trend for one or the other mode depends on the socio-economic value of cassava in each zone. According to Babo (1997) in Bouaké (Center Cote d'Ivoire), the cassava production system was undergoing a substantial change from the associated culture to the pure culture, the entire production destined for the market. Moreover, pure cultivation facilitates large-scale harvesting.
However, plots reserved for cassava cultivation are not very fertile. Indeed, several other crop cycles are carried out on the land prior cassava is grown. It is one of the few staple crops which does efficiently grow on a small scale and not require any mechanization or inputs on
marginal areas with poor soils and erratic rainfalls (FAO, 2013). This environment is unfavourable for cassava-associated food crops.
6.3 Supply mode of planting material:
Most growers use cuttings from previous harvests. These cuttings are taken either in the cassava field during the harvest; the cuttings are also taken in a growing field at least six months of age. Many growers do not have enough resources to buy cuttings of improved varieties or even ignore their existence (IITA, 1990).
Plating different cuttings of varieties in the same plot help minimize the purchasing cost of improved cuttings. This cultivation mode helps preserve the local cultivars diversity. Also, the significant 30% proportion of farmers that exchange cuttings partly contribute the diversity of cultivars in fields. Boster (1986) have previously specified the exchange of information and planting material within communities as one source of plant genetic resources diversity.
6.4 Identification of collected morphotypes and choice of growers: On an individual scale, the diversity of cultivars ranged from one to six. The management of diversity closely depends on the conservation means of the cuttings and therefore on the readiness or setting up time for planting (Desmoulière, 2001). Although cultivars are planted according to the kind of cassava-derived dishes desired, farmers grow different cultivars to increase chances of reaching a high yield. Indeed, they see diversification in the same plot as a guarantee of food security (Desmoulière, 2001).
Furthermore, farmers identify local cultivars by observed phenotypes and with anecdotal names. The cultivars differ by the type stem branching, petiole and leaf colour, tuber bitterness and skin colour. Boster (1983) suggested that diversity of cultivars would exploit the environment more efficiently than a monoculture crop with uniform architecture.
6.5 Cycle length of the cultivars : Growers prefer a "short-cycle" cultivar for two reasons.
The first reason is to perform two crop cycles per year on rented plots. This choice is
primarily made in the south of the country where rainfall is abundant. However, short cycle cultivar is mainly for the food processing of marketable '' attiéké '' and '' placali ''. The second reason is a climate change and drought avoidance response in the Central, North, and East zones. Indeed, the lasting of the drought period due to climate change not only reduces yields but hardens the soil resulting in a laborious harvest (PNUD, 2013). Leonard and Ibo (1994) reported that soil depletion and shortening of rain cycles favoured the spread of especially short-cycle species such as maize or crop with adaptation to low soil fertility like cassava.
6.6 Distribution, incidence and severity index of cassava mosaic disease: Cassava mosaic is prevalent in all investigated areas.
However, the highest incidence and severity index observed in the northern zone could be explained by the associated crops (Tiendrébéogo et al., 2012). Indeed, the north zone of Côte d'Ivoire is one of the major producing areas of cassava-associated vegetable crops such as chilli pepper, tomato, okra, and eggplant (Fromageot, 2007). These crops are hosts of the whiteflies vectors of Tomato Yellow Leaf Curling Virus (TYLCV) (Kil et al. 2016) and cassava mosaic virus (Fargette 1985).
7 CONCLUSION
Ultimately, this study shows the socio- economic importance of cassava cultivation in Côte d'Ivoire. Men perform most of the cultivation on small areas without prior fallow.
Growers preferentially cultivate the cultivar with a short cycle, and the cuttings for the renewal of the fields come mainly from the
previous harvests. Also, monoculture and associated cultivation are frequent in cassava agricultural practices. In all visited fields, prevalence rates of cassava mosaic disease and severity index are high. The results of this survey can help to plan sustainable management strategies for cassava cultivation.
8 ACKNOWLEDGMENT
The authors are grateful to West African Economic Monetary Union commission for financial support.
9 REFERENCES
Agre AP, Kouchade S, Odjo T, Dansi M, Nzobadila B, Assogba P, Dansi A, Akoegninou A. & Sanni A: 2015.
Diversité et évaluation participative des cultivars du manioc (Manihot esculenta Crantz) au Centre Bénin. International Journal of Biological and Chemical Sciences. 9(1) :388-408.
Anonyme (2009). Rapport national sur l’état des ressources phytogénétiques pour l’alimentation et l’agriculture. Ministère de l’Agriculture, Côte d’Ivoire 63 p.
Anonyme (2015) : Recensement Général de la Population et de l'Habitat de Côte d'Ivoire 2014, Institut national de la statistique de Côte d’Ivoire.
Boster J (1983). A comparison of the diversity of Jivaroan gardens with that of the tropical forest. Human. 2: 47-67.
Boster JS (1986). Exchange of varieties and information between Aguaruna manioc cultivators. American Anthropologist. 88 (2):
428–436. https://doi.org /10.1051/cagri/
2017022.
Desmoulière S (2001). Approche ethnobotanique de la diversité variétale du manioc en Amazonie centrale : gestion et perspectives de conservation. Thèse de Doctorat, Muséum National d’Histoire Naturelle, Paris, Laboratoire d’ethno biologie – biogéographie. 340 p.
Djaha KE, Abo K, Bonny BS, Koné T, Amoakon WJL, Koné D, Koné M (2016).
Caractérisation agromorphologique de 44
accessions de manioc (Manihot esculenta Crantz) cultivés en Côte d’Ivoire.
International Journal of Biological and Chemical
Sciences. 11(1): 174-184.
http://dx.doi.org/10.4314/ijbcs.v11i1.14.
Doubi BTS, Kouassi KI, Kouakou LK, Koffi KK, Baudoin JP, Zoro BIA (2016).
Existing competitive indices in the intercropping system of Manihot esculenta Crantz and Lagenaria siceraria (Molina) Standley. Journal of Plant Interactions.11(1):
178–185. http://dx.doi.org/10.1080/
17429145.2016.1266042.
FAO (2013). Guide pour une intensification durable de la production, Rome.
FAOSTAT (2014). Food and Agriculture Organization of the United Nations.
FAO Database Rome, Italy.
Fargette D, Fauquet C & Thouvenel JC (1985) Field studies on the spread of African Cassava Mosaic. Annals of Applied Biology.
106 : 285-294
Floret C & Serpantié G (1993). La jachère en Afrique de l'Ouest. Paris : ORSTOM, 171-178. (Colloques et Séminaires).
Montpellier (France), 1991/12/02-05.
Fromageot A (2007). Colonisation maraîchère des rives des petits barrages : une nouvelle géographie. In : L’eau en partage : les petits barrages de Cote d’Ivoire. IRD/ Montpellier : 229-243.
IITA (1990). Le manioc en Afrique tropicale : un manuel de référence. IITA, Nigeria. 176 p Kil EJ, Kim S, Lee YJ, Byun HS, Park J, Seo H, Kim CS, Shim J K, Lee JH, Kim JK, Lee KY, Choi HS & Lee S (2016). Tomato yellow leaf curl virus (TYLCV-IL): A seed-transmissible geminivirus in tomatoes. Scientific Reports. 6: 19013. doi:
10.1038/srep19013.
Kouadio KKH, Dao D, Tschannen A & Girardin O (2010). Rentabilité comparative des systèmes de culture à base de manioc à l’Est de la Côte d’Ivoire. Journal of Animal
& Plant Sciences. 9 (1) : 1094-1103.
Léonard E & Ibo JG (1994). Appropriation et gestion de la rente forestière en Côte d’Ivoire. Politique Africaine. 53 : 25-36.
Mignouna HD, Njukeng P, Abang MM, Asiedu R (2001). Inheritance of resistance to Yam mosaic virus genus Potyvirus in white yam (Dioscorea rotundata). Theoretical and Applied Genetics. 103 : 1196-1200.
N’Zué B (2007). Caractérisation morphologique, sélection variétale et amélioration du taux de multiplication végétative chez le manioc (Manihot esculenta Crantz (Euphorbiaceae). Thèse de doctorat, Université de Cocody, Abidjan. 141 p.
Perrot CH (2005). L’importation du « modèle » akan par les Anyi au Ndenye et au Sanwi (Côte d’Ivoire). Journal des africanistes. 75-1, 139-162.
Pita J, Fondong VN, Sangaré A, Otim-Nape GW, Ogwal S, Fauquet CM (2001).
Recombination, pseudo recombination and synergism of geminiviruses are determinant keys to the epidemic of severe cassava mosaic disease in Uganda.
Journal of Général Virology 82 : 655-665.
PNUD (2013). Etude de Vulnérabilité du Secteur Agricole face aux Changements Climatiques en Côte d’Ivoire.
Segnou (2002). Développement végétatif et potentiel de rendement chez le manioc.
Tropicultura. 20(4) : 161-164. www .tropicultura.org/eng/content/v20n4.htm l.
Serpantie GC & Floret (1994). Un mode de gestion des ressources en Afrique tropicale : la jachère longue. Regards différenciés sur une pratique en crise.
Comptes Rendus de l'Académie d'Agriculture de France. 80(8) :73-85.
Tiendrébéogo F, Lefeuvre P, Hoareau M, Harimalala MA, De Bruyn A, Villemot J, Lett JM (2012). Evolution of African Cassava Mosaic Virus by recombination between bipartite and monopartite Begomoviruses. Virology Journal. 9: 67.
