Onion production is low in Côte d'Ivoire. The country is therefore dependent on producer countries in the sub-region. One of the solutions would be to select adapted varieties to the growing conditions of the production areas. It is for this purpose that this study was conducted. This study aims to determine the agronomic and morphological characteristics of five varieties of onion in order to select the best ones. The experiment was carried out in a block with three replications. Data’s used was vegetative characteristics and bulb yield components. Multivariate analysis were performed on the collected data. The results revealed three agromorphological groups. The first group, composed of the varieties BATI and KARIBOU, is characterised by a high seed germination rate (85.65%), heavier bulbs (40.19 g), large size (bulb diameter=4.26 cm), a greater number of thick (0.14 cm) scales (6 scales) and a high bulb yield (4.02 kg/m2). The second (Group 2) consisting of the varieties CARA and DAMANI recorded the highest plant height (42.19 cm), longer leaves (40.19 cm) and longer bulbs (4 cm). The third (Group 3) consisting of the variety SAFARI gave intermediate morphological characteristics to the two previous groups. Based to the measured characteristics, the varieties BATI and KARIBOU with interesting agronomic characteristics are to be recommended to farmers in Korhogo to make onion cultivation profitable.
Onions (Allium cepa L. ) are grown all over the world, especially in hot regions. In the list of the world's most grown vegetables, onions are ranked second, afetr tomatoes. Global production has increased from 82,850,000 tonnes per year in 2012 to 99,90.106 tonnes per year in 2019 1. The main producing countries are China with 24,600,000 tonnes per year, India with 22,308,990 tonnes per year and the United States of America (USA) with 3,277,460 tonnes per year 1.
In Africa, onions are used both for their gustatory qualities and for their pharmacological properties 2. According to 3, total onion production in Africa, estimated at 5.3 million tonnes, has almost tripled in the last three decades. The main producing countries are Egypt with 2,024,881 tonnes per year, Algeria with 1,183,268 tonnes per year, Morocco with 855,764 tonnes per year and Nigeria with 618,000 tonnes per year 3.
In West Africa, onions are commonly consumed and account for 10-25% of vegetable consumption 4. Average annual onion production in West Africa, estimated at about 1.1 million tonnes, represents less than 2% of world production. The largest producer in the West African region is Nigeria. It is also the largest net importer because of its large population, which consumes the local annual production 5.
The growth of onion imports is particularly strong in Côte d'Ivoire compared to a national production that has remained very low until now. In 2018, with an estimated annual production of between 5,000 and 8,000 tonnes, Côte d'Ivoire remains one of the smallest onion-producing countries in West Africa despite significant production potential in both savannah and forest areas 6. Economically, Côte d'Ivoire imports more than 100,000 tonnes of onions each year, which corresponds to 30,000,000,000 F CFA, which represents a shortfall for the country's domestic needs 7.
Côte d'Ivoire's dependence on the external market is a handicap. Indeed, in the event of the appearance of cultural constraints (diseases, pests, climatic factors, etc.) in importing countries, Côte d'Ivoire would find itself out of supply with onions on its various markets 6. To remedy this situation, studies are needed to increase onion production by identifying adapted varieties for the production areas. It is in this context that this study was conducted. It evaluates the diversity of five onion varieties in order to make available to farmers those with good agromorphological aptitudes.
The experiment was conducted at the experimental site of the Peleforo GON COULIBALY University (UPGC) in Korhogo, northern Côte d'Ivoire (Figure 1). The altitude in relation to sea level is 360 m. The site is characterised by a tropical Sudanese-Guinean climate, marked by two main seasons. A rainy one that extends from May to October and a dry season from November to April 8. The average annual temperature is 27°C and the average rainfall is about 1200 mm/year.
Five onion varieties were studied (Table 1, Figure 2). These are the varieties named DAMANI, CARA, SAFARI, KARIBOU and BATI bought on the local market.
2.3.1.1. Sowing onion seeds in the nursery
The nursery was conducted in well plate with industrial substrate as recommended by 9. Each onion variety was sown in two plates. Three seeds were sown in each hole. In sum, 10 plates were used for the five onion varieties (Figure 3 and Figure 4). A total of 432 seeds of each variety were sown and each seedling plate contained 216 seedling holes. Watering was done in the morning and evening using a sprayer. The seedlings were transplanted to the field after 40 days in nursery.
2.3.1.2. Experimental design and conduct of the field trial
The trial was conducted in a three-repeat design (Figure 5. The elementary plots were made up, according to measurements, of square planks or furrows of dimensions 100 cm x 100 cm x 15 cm (L x W x H) or 1 m2 and 15 cm high. On the day of transplanting, the beds were watered to facilitate the operation. On each seedlings trays 100 plants were transplanted and seed in 10 lines. Each line was seed with 10 plants at 10 cm intervals. Three days before transplanting, each bed received one (01) kilogram of compost. To prevent attacks by fungi and certain insect pests, the beds were treated with pesticide to eliminate soil parasites. Maintenance consisted of regular weeding of the planting beds to avoid competition between the young plants and weeds. The plants were watered every day with 15 litres of water per bed until bulb formation.
Data were collected in the nursery and in the field. In the nursery only the germination rate per variety was determined. In the field, 10 plants was randomly sampled per bed, which correspond to 30 plants for each onion variety. In sum, 150 onion plants were sampled for the five varieties.
The agromorphological variables used are listed in the Allium descriptor proposed by IPGRI (2001). Table 2 presents the descriptors used and the measurement methods.
2.3.5.1 Analysis of quantitative data
Descriptive statistics (means, standard deviations.) and analysis of variance (ANOVA) were performed for each descriptor. For the data collected in the nursery, a one-sample T-test with a threshold of 5% was performed to compare the germination rate obtained in our trial with those indicated on the seed package. For each descriptor, the Newman and Keuls post ANOVA test was performed to make comparisons between the mean values of each variety at the 5% threshold.
The links between the different variables were assessed using the Pearson correlation coefficient. A Hierarchical Ascending Classification (HAC) was performed to structure the onion varieties studied. It was done on the basis of Euclidean distances and using the Unweighted Pair-Group Method Using Arithmetic Average (UPGMA) as a rule for linking distances between groups. An variance analysis between the classes obtained from the AHC was carried out to identify the descriptors that discriminate the populations studied. The analyses were performed using SPSS software version 22.00 and Statistica version 7.0.
The seeds of the varieties studied germinated three to four days after sowing and reached their maximum germination rate between 13 and 16 days after sowing (Figure 10). The varieties CARA, SAFARI showed statistically lower germination rates (66.20 %) than those reported on their labels (80 %) (Table 3). The varieties BATI and DAMANI had statistically identical germination rates (78.95 % and 81.71 %) to the rates reported on the packages. The variety KARIBOU gave a germination rate of 89.58 % statistically higher than that mentioned on the label (80 %).
The germination rate differed significantly between the onions varieties studied. The variety KARIBOU got the best germination rate (89.55%) followed by DAMANI and BATI which hat germination rates ranging from 78.95% to 81.71%. The varieties SAFARI and CARA had lowest germination rates in seedling plate (66.20%) (Table 4).
With the exception of the number of leaves per plant, all other variables did not significantly differentiate the onion varieties studied.
All the varieties studied expressed statistically identical height growth ranging from 37.80 cm to 42.23 cm. The maximum leaf length was similar among all onion varieties and ranged from 36.00 cm to 40.23 cm. In all onion varieties, the maximum leaf diameter ranged from 0.97 cm to 1.23 cm (Table 4). the leaves number of per plant of varieties BATI, DAMANI, KARIBOU and SAFARI showed highest values (5 to 6 leaves). The variety CARA expressed a lower average value of number of leaves per plant (5 leaves).
Bulb length significantly (F= 22.42; p<0.001) differentiated onion varieties (Table 5) and classified them into two groups. The first group consisted of the variety CARA with the longest bulbs (4.28 cm). A second group consisting of BATI, DAMANI, KARIBOU and SAFARI which had shorter bulbs (3.23 and 3.5 cm). The diameter of the bulbs makes it possible to form three different groups of varieties. A first group consisting of the variety KARIBOU presented bulbs with the largest diameters (4.34 cm). A second group consisting of the varieties CARA and SAFARI had the smallest bulbs (3.83 cm to 3.92 cm). The third group contains the varieties BATI and DAMANI which have bulbs with an intermediate diameter (4.18 cm to 4.34 cm) between the first two groups. For the variable number of scales per bulb, two groups could be distinguished. The first group, BATI, DAMANI and SAFARI, had highest number of scales (6 scales) and the second group, CARA and KARIBOU, had a lower number of scales (5 scales).The variable thickness of the scales of each bulb made it possible to differentiate two groups. One group is composed of the varieties BATI, KARIBOU, SAFARI and DAMANI, which had thinner scales (0.12 cm to 0.15 cm). The second one composed of the CARA variety with thicker scales (0.2 cm). The weight of the bulbs did not allow differentiation between varieties. It varies from 35g to 40g. The bulb yield did not also distinguished onion varieties. It varied from 3.5 to 4 kg/m2.
The Pearson correlation matrix presents the different relationships between the measured variables (Table 6). Plant height is positively linked to the number, length and of leaves diameter with correlation coefficient values of 0,510.99 and 0.52 respectively.
The leaf length of is positively correlated with the number of leaves (r = 0.51) and the diameter (r = 0.52). The weight of the bulb depends on its length (r = 0.45) and diameter (r = 0.92). Yield is positively linked to bulb characteristics with correlation coefficients ranging from 0.45 to 0.99.
The Hierarchical Ascending Classification (HAC) revealed three groups (Figure 11). The simultaneous analysis of Figure 11 and Table 7 shows that:
- Group 1 consists of the varieties BATI and KARIBOU, which have high germination rate (85.65%), heaviest bulbs (40.19 g), larger sizes (DB=4.26 cm), greater number of thick (0.14 cm) scales (6 scales) and a high yield (4.02 kg/m2)
- Group 2 consists of the varieties CARA and DAMANI which have the largest plants (42.19 cm high), with large leaves (40.19 cm), long bulbs (3.89 cm), thick scales (0.17 cm) and high bulb yield (3.74 kg/m2)
- Group 3 includes the variety SAFARI, which has vegetative and production characteristics intermediate to groups 1 and 2 (Table 7).
3.1.6. Variability of Quality Characteristics in the Five Onion Varieties
This study revealed that germination rate varies with variety. Since the germination trial was conducted under the same conditions, the genotype effect could explain the variability in germination rates observed in onion. Also, the germination substrate would have an influence on the germination of onion seeds since the germination rates observed in some varieties were statistically different from those reported on the labels. In order to optimise onion seed germination, the search for a variety-specific germination substrate would be an avenue to explore. According to 11 the seed may appear healthy but not germinate because it has not been fertilised or has entered a dormant state due to internal factors. In addition, 12 reveled that the presence of fungus on the sown seed causes they rotting.
The results of the elemental statistics for the agromorphological descriptors showed variability for the characters number of leaves per plant, bulb length, bulb diameter, bulb scale thickness and number of bulb scales. This result could be explained by environmental factors, such as day length, humidity and temperature. Indeed, the expression of morphological traits is influenced by both genes and the environment. These environmental factors could lead to variable effects on vegetative development and onion production depending on the variety. These results are in line with those of 13 and 14 obtained on different onion varieties.
Significant correlations were observed between plant height and leaf dimensions and between vegetative traits and those expressing bulb production. This could be explained by photosynthesis which takes place mainly in the leaves of the plant. The onion does not have a true leaf. Increasing the size of the leaves to carry out photosynthesis in order to meet these organic needs also promotes the growth in height of the plant and bulb production. Indeed, the varieties with high bulb yields are those with high height growth, with a high number of large leaves and larger bulbs. These results are in agreement with those of 15.
The structuring of diversity observed in the onion varieties studied through Hierarchical Ascending Classification (HAC) constitutes a tool for assessing the relative contribution of the different characters to the total diversity and for evaluating the degree of similarity between the different genotypes studied 16. On the basis of the eleven quantitative variables studied, the five onion varieties were separated into three morphological groups by Hierarchical Ascending Classification (HAC).
The aims of the study was to evaluate the agromorphological potential of five onion varieties. The results shown that, on the basis of the descriptors used, a high morphological variation was observed in the onion varieties. Significant correlations were also observed between the different quantitative variables. Such correlations will help to identify important variables that can be used for varietal improvement. From the quantitative traits three morphological groups were formed, group 1 of which is composed of the varieties BATI and KARIBOU, group 2 witch contains the varieties DAMANI and SAFARI and group 3 fomed only with the variety CARA. On the basis of quantitative characteristics, the BATI and KARIBOU varieties have interesting agronomic characteristics and should be recommended to farmers in Korhogo in order to make onion cultivation profitable. Indeed, these varieties have a high seed germination rate (85.65%), heavier bulbs (40.19 g), large sizes (bulb diameter = 4.26 cm), a greater number of scales (6 scales) thick of 0.14 cm and a high bulb yield (4.02 kg/m2).
The authors thank the Korea Africa Food & Agriculture Cooperation Initiative (KAFACI) for funding this study.
The authors declare that they have no competing interests.
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| In article | View Article | ||
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| In article | View Article | ||
| [10] | IPGRI, ECP/GR, AVRDC. Descriptors for Allium (Allium spp.). International Plant Genetic Resources Institute, Rome, Italy; European Cooperative Programme for Crop GeneticResources Networks (ECP/GR), Asian Vegetable Research and Development Center, Taiwan, 2001. | ||
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| [11] | N’dri AA, Irie VB, Kouamé PL, Zoro Bi IA. Bases génétiques et biochimiques de la capacité germinative des graines : implications pour les systèmes semenciers et la production alimentaire. Sciences & Nature 8 (1). 119-137. 2011. | ||
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| [12] | Dedi. J, Allou K. Etude du pouvoir germinatif de quatre variétés de riz que sont GIZA 178, WAB 56-50, LOHININI, DANANE et identification des champignons présents sur les grains en germination Afrique SCIENCE 11(3): 161-171. 2015. | ||
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| [13] | Currah L. Onions in the Tropics: Cultivars and Country Reports. In: Rabinowitch H.D. and Currah L., eds. Allium Crop Sci.: Recent adv., CABI Publ., Wallingford, Oxon, UK, New York, NY, USA, 2002, 379-408. | ||
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| [14] | Abdou R. Caractérisation de la diversité génétique de cultivars d'oignon (Allium cepa L.) du Niger en vue de leur conservation in situ et de leur amélioration. Thèse de doctorat. Université de Liège-Gembloux Agro-Bio Tech. 2014. | ||
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| [15] | Hammadi. H. Étude de l'aspect dynamique de la photosynthèse par l’analyse des oscillations complexes de la fluorescence chlorophyllienne induites sous lumières sinusoïdales, 2013. | ||
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| [16] | Tiendrebeogo FK, Sawadogo N, Nanema KR, Traore RE, Bationo-Kando P, Zongo J, Sawadogo M. Evaluation de la diversité génétique du pourghere (Jatropha Curcas L.) au Burkina Faso. International Journal of Innovation and Applied Studies 16 (1). 155-165. 2016. | ||
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Published with license by Science and Education Publishing, Copyright © 2022 KOFFI Eric-Blanchard Zadjéhi, DIARRASSOUBA Nafan, KONAN N’guessan Ysidor, YAO Saraka Didier martial, SAHI Gonkapeu Achille and SIE Raoul Sylvère
This work is licensed under a Creative Commons Attribution 4.0 International License. To view a copy of this license, visit
https://creativecommons.org/licenses/by/4.0/
| [1] | Faostat. Base de données statistiques agricoles FAO, 2019a, https://faostat3.fao.org,/browse/rankings/countries_ by_commodity/. | ||
| In article | |||
| [2] | Molas C. Intoxications des carnivores domestiques dues aux denrées alimentaires consommées par l'homme. Thèse de doctorat Vétérinaire dans la Faculté de Médecine de Créteil (France), 2009. | ||
| In article | |||
| [3] | Faostats. Base de données statistiques agricoles de la FAO, 2019b. https://www.faostat3.fao.org. | ||
| In article | |||
| [4] | Dupaigre B, Baris P, Liagre L. Etude sur la compétitivité des filières agricoles dans l'espace UEMOA. IRAM, 2006. | ||
| In article | |||
| [5] | Nana WL. Evaluation agromorphologique d'une collection d'accessions d'oignon (Allium cepa. L) du Burkina Faso. Mémoire de fin de cycle Université polytechnique de bobo-dioulasso, Burkina Faso, 2016. | ||
| In article | |||
| [6] | RONGEAD. Diagnostic de la filière oignon en côte d’ivoire. Projet « Redynamiser les productions, l’accès au marché et le conseil agricole pour les filières vivrières et commerciales du Nord de la Côte d’Ivoire ». Coopération Union Européenne – République de Côte d’Ivoire Programme FLEX-FED/2013/324 233, 2014. | ||
| In article | |||
| [7] | Djè Bi. La culture d’oignon en Côte d’Ivoire reste encore timide (Interprofession), 2015 https://WWW.koffi.net/. | ||
| In article | |||
| [8] | Boko-Koiadia ANN, Cisse G, Koné B, Séry D. Variabilité climatique et changements dans l’environnement à Korhogo en Côte d’Ivoire: mythes ou réalité? European Scientific Journal 12 (5). 158-176. 2016. | ||
| In article | View Article | ||
| [9] | Koffi E-B Z, Diarrassouba N, Yao SDM, Sié RS. Effet des doses de semis et de la méthode de conduite de la pépinière sur les caractéristiques morphologiques des plantules de cinq variétés d’oignon (Allium cepa L.) en Côte d’Ivoire. European Scientific Journal 17 (34). 208-222. 2021. | ||
| In article | View Article | ||
| [10] | IPGRI, ECP/GR, AVRDC. Descriptors for Allium (Allium spp.). International Plant Genetic Resources Institute, Rome, Italy; European Cooperative Programme for Crop GeneticResources Networks (ECP/GR), Asian Vegetable Research and Development Center, Taiwan, 2001. | ||
| In article | |||
| [11] | N’dri AA, Irie VB, Kouamé PL, Zoro Bi IA. Bases génétiques et biochimiques de la capacité germinative des graines : implications pour les systèmes semenciers et la production alimentaire. Sciences & Nature 8 (1). 119-137. 2011. | ||
| In article | |||
| [12] | Dedi. J, Allou K. Etude du pouvoir germinatif de quatre variétés de riz que sont GIZA 178, WAB 56-50, LOHININI, DANANE et identification des champignons présents sur les grains en germination Afrique SCIENCE 11(3): 161-171. 2015. | ||
| In article | |||
| [13] | Currah L. Onions in the Tropics: Cultivars and Country Reports. In: Rabinowitch H.D. and Currah L., eds. Allium Crop Sci.: Recent adv., CABI Publ., Wallingford, Oxon, UK, New York, NY, USA, 2002, 379-408. | ||
| In article | View Article | ||
| [14] | Abdou R. Caractérisation de la diversité génétique de cultivars d'oignon (Allium cepa L.) du Niger en vue de leur conservation in situ et de leur amélioration. Thèse de doctorat. Université de Liège-Gembloux Agro-Bio Tech. 2014. | ||
| In article | |||
| [15] | Hammadi. H. Étude de l'aspect dynamique de la photosynthèse par l’analyse des oscillations complexes de la fluorescence chlorophyllienne induites sous lumières sinusoïdales, 2013. | ||
| In article | |||
| [16] | Tiendrebeogo FK, Sawadogo N, Nanema KR, Traore RE, Bationo-Kando P, Zongo J, Sawadogo M. Evaluation de la diversité génétique du pourghere (Jatropha Curcas L.) au Burkina Faso. International Journal of Innovation and Applied Studies 16 (1). 155-165. 2016. | ||
| In article | |||
