IITA Theses and Dissertations
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Item Contribution des pesticides agricole a l’induction de resistance aux insecticides chez le vecteur du paludisme, anopheles gambiae s.l.(diptera : culicidea)(Thesis, 2021) Defo Talom, B.A.La lutte antivectorielle représente actuellement le moyen le plus efficace pour limiter la transmission du paludisme. Cependant, le succès de cette stratégie est menacé par l’expansion de la résistance des vecteurs du paludisme aux insecticides usuels. Des études ont suggéré que l'utilisation de pesticides en agriculture contribuerait à la sélection de la résistance aux insecticides chez Anopheles gambiae (Giles, 1902), le vecteur majeur du paludisme en Afrique. Ici, nous avons étudié l'impact des agro-pesticides utilisés par les maraichers sur l’induction de la résistance aux insecticides usuels chez ce vecteur dans deux zones géographiques, en Afrique de l’Ouest et en Afrique Centrale. L’étude s’est déroulée au Benin (Afrique de l’Ouest) et au Cameroun (Afrique Centrale) dans des sites maraîchères. Au Benin, 4 sites ont été utilisés à savoir 2 sites experimentaux exposés aux pesticides chimiques (Houeyiho et Seme) et 2 sites témoins non exposés aux pesticides (Calavi et Zinvie). Au Cameroun, 3 sites experimentaux (Nkolondom, Famassi et Ezazou) et un site temoin (Mvan) ont été utilisés. Dans les sites experimenaux, une étude CAP (Connaissance, Attitude et pratique) sur l’utilisation des pesticides par les agriculteurs a été menée ; elle était focalisée sur le principal insecticide utilisé, leur fréquence d’application ainsi que les doses utilisées. Au Benin 75 agriculteurs ont été impliqués dans l’enquête à savoir 35 à Houeyiho et 40 à Seme, tandis qu’au Cameroun 50 agriculteurs, dont 19 à Nkolondom, 18 à Ezazou et 13 à Famassi ont participé à l’étude. Ensuite, dans chacun des sites, des larves d’anophèles ainsi que l’eau et les sédiments des gîtes ont été collectés, ramenés au laboratoire où elles ont été élevées jusqu’au stade adulte et les eaux conservées à +4°C. Après l’identification morphologique et moléculaire des moustiques, des bioessais à la λ-cyhalothrine (l'insecticide principal utilisé par les maraichers), ainsi qu’à la permethrine (insecticide utilisé en santé publique) ont été effectués sur les anophèles collectés dans chacun des sites. Ensuite la présence de résidus de λ-cyhalothrine ainsi que leur rémanence dans l’environnement ont été évaluées. L’existence des métaux lourds a également été analysée dans l’eau et les sédiments des gîtes d'anophèles. Une analyse croisée a été faite entre les concentrations des résidus de d’insecticides et les profils de résistance à la λ-cyhalothrine des anophèles d’une part, entre les concentrations des métaux lourds et les profils de résistance à la λ-cyhalothrine des d'anophèles d’autre part. L’implication des enzymes cytochromes P450 et de la mutation L1014F dans la résistance aux pyrethrinoïdes a été investiguée. De plus, la mutation G119S responsable de la résistance aux organophosphorés et aux carbamates a été analysée. Les résultats ont révélé que le principal insecticide utilisé en maraichage dans les 2 pays est la λ-cyhalothrine (97,5% au Benin et 54% au Cameroun) ; seul ou en combinaison avec les organophosphorés (profenofos) et les néonicotinoïdes (acetamipride, imidachloripride). Près de 60% et 66% d’agriculteurs interrogés respectivement au Benin et au Cameroun ont observé la bonne fréquence d’application de ces insecticides (tous les 14 jours), tandis que 59,5% au Benin et 58% au Cameroun ont respecté la dose d’insecticide recommandée par le fabricant (5ml/l). Anopheles coluzzii a été la principale espèce d'anophèles identifiée au Benin, tandis qu’au Cameroun, en plus d’Anopheles coluzzii, An. gambiae ss a aussi été identifiée. Ces espèces de moustiques ont été résistantes (taux de mortalité de 30 à 63% au Benin, et entre 3 et 54% au Cameroun) à la λ-cyhalothrine, ainsi qu’à la permethrine (taux de mortalité de 14 à 52% au Benin et entre 4 et 83% au Cameroun). Environ 16,7% (2/12) des gîtes examinés et positifs en anophèles ont été contaminés par des résidus de λ-cyhalothrine dans les sites du Benin et aucune contamination n’a été relevée dans les sites du Cameroun. La présence de cuivre (provenant probablement d'engrais et /ou du sulfate de cuivre utilisé comme fongicide) a été notée dans 10 des 12 gites de moustiques au Benin, et une corrélation positive (r = 0,81; P = 0,0017) entre cette présence et la résistance à la λ-cyhalothrine, indiquant sa possible contribution à l'évolution de la résistance aux insecticides chez les vecteurs du paludisme. Après préexposition au Piperonyl butoxide (PBO) , la susceptibilité à la λ-cyhalothrine a été totalement ou partiellement restituée (51 à 100% au Benin, 45 à 87% au Cameroun), de même qu’à la permethrine (55 à 100% au Benin, 13 à 87% au Cameroun). Une fréquence élevée de la mutation L1014F a été observée, aussi bien au Benin (0,77) qu’au Cameroun (0,79). La mutation G119S a été détectée à une très faible fréquence aussi bien au Benin qu’au Cameroun (0,20 et 0,22 respectivement). Il ressort de l’étude que le cuivre, est incriminé comme un facteur de l’induction de la résistance d’An. gambiae (Giles, 1902) aux insecticides. De plus, plusieurs mécanismes de résistances ont été retrouvés chez ces vecteurs à savoir les enzymes à cytochromes P450 (résistance métabolique), la mutation du type Kdr (résistance par modification de la cible) pour les pyrethrinoïdes et la mutation du type Ace-1R (résistance par modification de la cible) pour les carbamates et organophosphorés. Même si l’utilisation des insecticides en agriculture seul n’induit pas la résistance aux insecticides chez les anophèles, les métaux lourds provenant du sulfatre de cuivre pourraient avoir un rôle dans la survenue de la résistance. Vector control is currently the most effective means to limit malaria transmission. Howerver, the success of this strategy is threatened by the expansion of resistance of malaria vectors to routine insecticides. Studies have suggested that the use of pesticides in agriculture contributes to the selection of insecticide resistance in Anopheles gambiae (Giles, 1902), one of the vectors of malaria in Africa. Here, we have investigated the impact of the agropesticides used by farmers on the selection of the resistance to common insecticides in this vector in two geographical areas; West Africa and Central Africa. The study took place in Benin (West Africa) and Cameroon (Central Africa) in vegetable growine area. In Benin, 4 sites were used, namely 2 test sites with the use of chemical pesticides (Houeyiho and Seme) and 2 control sites without the use pesticides (Calavi and Zinvie). In Cameroon, 3 test sites (Nkolondom, Famassi and Ezazou) and one control site (Mvan) were used. In the test sites, a Knowledge, Attitude and pratice study (KAP) on the use of pesticides by farmers was carried out and was focused on the main insecticides used, their application frequency as well as the dose. In Benin, 75 farmers were involved in the survey; 35 in Houeyiho and 40 in Seme, while in Cameroon 50 farmers, of which 19 at Nkolondom, 18 at Ezazou and 13 at Famassi were involved. In each of the sites, anopheles larvae as well as the water and sediments of the breeding sites were collected, brought back to the laboratory where the larvae were reared to the adult stage and the water stored at +4°C. After morphological and molecular identification, bioassays with λ- cyhalothrin (the main insecticide used by farmers), but also with permethrin (the main insecticide used in public health) were carried out on the anopheles collected in each of the sites. Thereafter, the presence of λ-cyhalothrin residues as well as their persistence in the environment were evaluated. The presence of heavy metals was also analyzed in the water and sediments of anopheles larval breeding sites. A cross-analysis was performed between the data on pesticide residues and the λ-cyhalothrin resistance profiles of anopheles on one hand and between the data on heavy metals and the λ-cyhalothrin resistance profiles of anopheles on the other hand. The implication of cytochromes P450 enzymes and the L1014F mutation in the resistance to pyrethrinoids was investigated. In addition, the G119S mutation responsible for resistance to organophosphates and carbamates was analysed. The results revealed that the main insecticides used in market gardening is λ- cyhalothrin (97.5% in Benin and 54% in Cameroon) alone or in combination with organophosphates (profenofos) and neonicotinoids (acetamipride, imidachloripride). Nearly 60 and 66% of farmers in Benin and Cameroon respectively observed the correct frequency of application of these insecticides (every 14 days) while 59.5% of farmers in Benin and 58% of farmers in Cameroon respected the dose of insecticide recommended by the manufacturer (5mL/L). Anopheles coluzzii was the main species of anopheles identified in Benin while in Cameroon, in addition to Anopheles coluzzii, An. gambiae ss was also identified. These mosquito species were resistant (mortality rate of 30 to 63% in Benin and between 3 to 54% in Cameroon) to λ-cyhalothrin, as well as to permethrin (mortality rate of 14 to 52% in Benin and between 4 and 83% au Cameroon). About 16.7% (2/12) of the sites examined and posistive for anopheles were contaminated with λ-cyhalothrin residues in the sites of Benin and no contamination was noted in the sites of Cameroon. The presence of copper (probably from fertilizer) was noted in 10 of the 12 mosquito developmental sites in Benin, and a positive correlation (r = 0.81; P = 0.0017) between this presence and the resistance to λ- cyhalothrine showed the possible contribution of non-insecticidal compounds to the evolution of insecticide resistance in malaria vectors. Micro-mapping of the larval breeding sites revealed the heterogeneity of the resistance profiles of the the populations of anopheles from the same market gardening sites. After preexposure to PBO, susceptibility to λ-cyhalothrin was totally or partially restored (51 to 100% in Benin, 45 to 87% in Cameroon), as was permethrin (55 to 100% in Benin, 13 to 87% in Cameroon). A high frequency of the L1014F mutation was observed, both in Benin (0.77) and Cameroon (0.79). The G119S mutation was detected at very low frequency both in Benin and in Cameroon (0.20 and 0.22 respectively). The study shows that copper is incriminated as a factor in the induction of resistance of An. gambiae (Giles, 1902) to insecticides. In addition, several resistance mechanisms have been found in these vectors, namely the cytochrome P450 enzymes, the Kdr mutation and the Ace-1R mutation. Even if the use of pesticides in agriculture alone does not induce insecticide resistance in anopheles, heavy metals may have a role in the development of resistance.Item Effectiveness of bylaws related to sustainable intensification of potatoes in Southwestern Ugandan(Thesis, 2024-09) Makuma-Henry, M.Only one-third of global farms utilise sustainable agriculture. This study examined the bylaws' existence, interaction, implementation, and effectiveness in facilitating sustainable potato crop intensification (SCI) in South Western Uganda. An exploratory sequential research design involved 22 key informants’ interviews, six focus group discussions and 104 potato farmers who responded to a questionnaire. Qualitative and quantitative data were analysed using Atlas.ti 7.5.16 and Stata 13.0. Thematic content analysis was used for qualitative data. Descriptive statistics and multivariate linear regression were used for quantitative data. The study findings revealed positive complementary interactions between formal and informal bylaws to achieve SCI. There was complementary and accommodating interaction between formal and informal bylaws in achieving SCI. The physical environment and socioeconomic conditions posed challenges as well as opportunities for developing and strengthening bylaws. Farmers’: knowledge of bylaws (p = 0.03); participation (p = 0.01), location (p = 0.03); gender (p = 0.001); other occupations (p = 0.01), income (p = 0.02) interaction with local councils to implement bylaws (p = 0.01); and knowledge on soil and water conservation bylaws (p = 0.03) were significantly associated with bylaw implementation. Bylaw effectiveness is mostly manifested in the principles of layered multilayers and participation. The majority of potato farmers (63.46%) reported that the bylaws were ineffective. Implementation of improved and quality seed bylaws was significantly associated with effectiveness (p<0.043). In conclusion, farmers acknowledged a number of formal and informal bylaws. Formal and informal bylaws positively interacted with and benefited potato farmers by providing better seeds, potato yields, prices, and higher incomes. Individual and community factors are vital in bylaw implementation, though limited by their congestion and farmers’ engagement in other activities. The study recommends enhancing positive bylaw interaction by engaging communities and local government, creating awareness amongst potato farmers on bylaws, empowering women, and formalising informal bylaws.Item Effects of gender norms on food security and asset acquisition among cassava value chain actors in Oyo and Ogun States, Nigeria(Thesis, 2024) Adeagbo, D.R.This study identified the gender norms that were common among cassava value chain actors in Oyo and Ogun States, Nigeria; examined food security and asset acquisition among the cassava value chain actors; and determined the effect of gender norms on food security and asset acquisition among the cassava value chain actors. These were with a view to providing additional empirical information on specific gender norms, and their effect on food security and asset acquisition among the cassava value chain actors in Oyo and Ogun States, Nigeria. A multistage sampling technique was adopted in selecting 500 cassava value chain actors which comprise of producers, processors, marketers, and influencers in both Oyo and Ogun States. Primary data were collected on socio-economic characteristics of the respondents, gendered social norms such as information on, financial and material resources, group participation and leadership, technology usage, mobility and division of labour, and gender meta-norms, household characteristics, possession and access to productive assets, access to credit and finance and food insecurity experience. The study employed descriptive statistics, household food insecurity scale, and Poisson regression model in analysing the data collected. The results showed that majority (69.40%) of the respondents in the value chain were females, majority (88%) were married, and had at least primary level of education. The results also showed that common gender norms which restricted women actors in the value chain were norms governing the use of financial resources and relating with extension agents independently from their spouse/partner. Others were: restriction in decision making in groups or organisation, participating in leadership roles, norms on usage of technology, mobility and division of labour. Furthermore, decision-making on major expenditures, control of spouse's assets after death, performing household chores, childcare, and paid work outside the home were prevalent for women in the value chain. Food insecurity was found to be present in the study area, as 67% of the respondents experience little food to eat, 70% could not access healthy and nutritious food, and 48% were hungry and did not eat. Majority (82%) owned agricultural land, 93% possessed non-mechanized farm equipment, 88% had small consumer durables, and 96% owned cell phones. However, ownership of large livestock (11%) and mechanized farm equipment (12%) were relatively low. Additionally, a large percentage of respondents (76%) owned houses or buildings, 71% had large consumer durables, and 50% possessed non-farm business equipment, highlighting their importance. Ownership of other land (68%) and means of transportation (57%) were also noteworthy, reflecting diverse asset acquisition among the respondents. The Poisson regression analysis showed that gender norms have a negative effect on food security (-0.007) and asset acquisition (-0.011) among cassava value chain actors. The study concluded that there were negative effects of gender norms on food security and asset acquisition among cassava value chain actors.Item Influence of seed size, storage and priming on germination, growth and yield of soybean (Glycine max (L) Merrill)(Thesis, 2025-06) Adu-Oppong, R.Experiment was conducted at the Physiology Laboratory of the department of Crop Science, University of Ghana and on the field of the Ghana Atomic Energy Commission, Accra, to evaluate the influence of seed size, storage and priming on seed germination, growth, and yield of soybean. Germination tests were performed at the Physiology laboratory of the University of Ghana at two monthly intervals over 10 months using two priming agents, Vitazyme (at concentrations of 3, 5 and 7 %) and Calcium chloride (at concentrations of 0.5, 1 and 1.5 %) and hydro-priming. The duration of priming was six and 12 hours. Dry unprimed soybean seeds served as control. Treatments were laid in a completely randomised design with four replications. Field experiments were also conducted during Major (April-July, 2023) and Minor (July-November, 2023) planting seasons using soybean seeds graded into three sizes (small, mixed seeds, and large) and a priming agent (most promising priming agent from the Laboratory experiments). The field treatments for the Major planting season consisted of seed size (small, mixed seed, and large) and priming with CaCl2 at a concentration of (0.5 and 1 %). Treatments were laid in a split-plot design with four replications. Seed sizes were assigned to the main plot, while priming agents were assigned to the sub-plots. The seeds used in the major planting season had been stored for five months after seed harvest. The Minor season experiment had similar treatments and experimental design as the Major season experiment, except that Vitazyme at 5% concentration and CaCl2 at 0.5% concentration were used as the priming agents in the Minor season experiment, and seeds used for planting had been stored for seven months after seed harvest. Results from the laboratory experiments indicated that seed quality indicators, like germination and vigour, declined with prolonged storage. Percentage germination ranged from 57% with seeds stored for 11 months after seed harvest to 90% with seeds stored for seven months after seed harvest. Percentage germination for primed seeds varied significantly, ranging from 56% with 1.5% CaCl2 concentration to 85% with the unprimed control. Among the primed seeds, percentage germination ranged from 56% with 1.5% CaCl2 concentration to 78% with 0.5% CaCl2 concentration. The most vigorous seedlings, with a vigour index of 1290, were obtained from seeds primed with CaCl2 at a concentration of 0.5%, while a concentration of 1.5% CaCl2 produced the least vigorous seedlings, with a vigour index of 656. A priming duration of 12 hours led to a three percent reduction in percentage germination compared to six hours priming duration. During the Major planting season, the percentage emergence for primed seeds varied from 15% with CaCl2 at 1% concentration to 75% with dry, unprimed seeds. Priming interacted with seed size to significantly improve the weight of 1000 seeds, ranging from 115 g for large seeds primed with CaCl2 at 1% concentration to 155 g for large seeds that were hydro-primed. The Chlorophyll content varied from 15 μ/m2 in the unprimed control to 21 μ/m2 in seeds treated with CaCl2 at 0.5% concentration. Grain yield ranged from 1.27 to 2.66 Mt/ha for small seeds primed with CaCl2 at 0.5% concentration and mixed seed sizes primed with CaCl2 at 0.5% concentration, respectively. In the Minor planting season, the percentage of seed emergence varied from 66% with seeds primed with 5% Vitazyme concentration to 98% with unprimed seeds. Leaf Area ranged from 20.4 m2 to 30.1 m2 for seeds primed with 0.5% CaCl2 concentration and unprimed respectively. Priming significantly increased the weight of 1000 seeds, with unprimed seeds weighing 515 g and Vitazyme-primed seeds weighing 765 g. Grain yield ranged from 2.33 Mt/ha with small seed size primed with CaCl2 at 0.5% concentration to 3.44 Mt/ha with mixed seed size primed with a 5% Vitazyme concentration. The study suggests that soybean seeds should not be stored beyond seven months after seed harvest to achieve excellent germination. The studies also suggest that soybean seeds of any size could be used for planting, provided they are of good quality.Item Multiple shocks, agroecology and resilience of smallholder food security in Northern Ghana(Thesis, 2024) Dagunga, G.Agroecology offers a sustainable food system approach for the resilience of smallholder food security. Global coinciding shocks such as the Covid-19 pandemic and the Russian-Ukraine conflict coupled with economic downturns in developing countries affected agricultural inputs and food prices. Also, climate shocks continue to affect the resilience of smallholder food security. Against this backdrop, the study sought to examine how adoption of agroecological practices moderate the impact of price and climate shocks on the resilience of smallholder food security. To achieve this broad objective, different analytical approaches were adopted. First, a systematic literature review was employed to assess the reported impact of agroecology in fostering the resilience of smallholder food security. Second, econometric approaches were employed to assess smallholder agroecological practices adoption behaviour to shocks as well as the moderation role of agroecology on the shock-resilience nexus in northern Ghana. Finally, the study simulated how projected changes in rainfall and temperature could affect the resilience of smallholder food security and the potential of agroecology to moderate the resulting impacts. The results showed that flood, food and input price shocks significantly affect both initial and consistent adoption of agroecological practices. Meanwhile, agroecology was found to moderate the impact of flood, food and input price shocks. The simulation results also showed that a policy aimed at promoting agroecology could help moderate extreme drought and heat stress. The study concluded that agroecology should be promoted and upscaled in northern Ghana as a mechanism for enhancing the resilience of smallholder food security to shocks. Meanwhile the second phase of the Planting for Food and Jobs policy should include a component of agroecology to help maximize its resilience and ecological synergistic benefits.Item Foodgravity: understand food flows using classic gravity model and explainable artificial intelligence techniques(Thesis, 2024-07) Dusabe, B.Mapping food flows from production areas to consumption areas is essential and often challenging, especially at local scales (Moschitz & Frick, 2021). Knowing how food moves over space and time is crucial for policy-making to maintain food and nutrition security across scales. Nevertheless, there is a tendency to prioritize flows between countries at the global level i.e., Food and Agriculture Organization trade data (FAO, 2023a) whereas the internal food flows within a country are often neglected. This oversight can lead to less efficient spatial planning and agricultural interventions, particularly in less-developed areas where food and nutrition security remains a critical challenge. However, the food flow is a complex issue resulted from socio-ecological characteristics of both origin and destination areas, as well as the linkages in between. To untangle this complexity, this research combined concepts of classic gravity model with machine learning techniques, relying on Explainable Artificial Intelligence techniques (xAI) to enhance the transparency of the predictive models. The Irish potato was chosen as the focus crop to study its flow distribution among 30 districts of Rwanda. Objectives included compiling a comprehensive database of socio-economic and environmental factors along with district pair food flows, and leveraging machine learning methods to predict whether a particular district pair presents Irish potato food flows or not. Specifically, Random Forest (RF) and Support Vector Machine (SVM) were trained to predict Irish potato food flows, while the Local Interpretable Model-agnostic Explanations (LIME) xAI technique was used to further investigate particular district pair instance prediction and its most influencing features. Both RF and SVM models demonstrated high overall accuracy (both above 90%) in predicting district level Irish potato flow. However, it is important to note that the dataset presented imbalanced classes where district pairs that contained Irish potato flows were about 7% of the total data samples, while the remaining dataset comprised the absence of Irish potato flow. F1 score, which is the harmonic mean of precision and recall, was used to evaluate the class prediction accuracy of the models. On the both RF and SVM models, F1 score of class 0 (absence of flow) was 0.96 whereas on class 1 (Presence of flow) was 0.61 for RF and 059 for SVM. These F1 scores shows that both models were accurate at predicting the absence of Irish potato flows (class 0) than the presence of flow (class1), reflecting an imbalance in the dataset where instances of Irish potato flows were less frequent. Using Local Interpretable Model-agnostic Explanations (LIME) xAI technique it was observed that environmental factors notably at the origin district were the most flow influencers compared to socio-economic features. The study recommends the integration of market level flow data, the scope and temporal expansion for a more granular analysis.Item Foodgravity: understand food flows using classic gravity model and explainable artificial intelligence techniques(Thesis, 2024-07) Dusabe, B.Mapping food flows from production areas to consumption areas is essential and often challenging, especially at local scales (Moschitz & Frick, 2021). Knowing how food moves over space and time is crucial for policy-making to maintain food and nutrition security across scales. Nevertheless, there is a tendency to prioritize flows between countries at the global level i.e., Food and Agriculture Organization trade data (FAO, 2023a) whereas the internal food flows within a country are often neglected. This oversight can lead to less efficient spatial planning and agricultural interventions, particularly in less-developed areas where food and nutrition security remains a critical challenge. However, the food flow is a complex issue resulted from socio-ecological characteristics of both origin and destination areas, as well as the linkages in between. To untangle this complexity, this research combined concepts of classic gravity model with machine learning techniques, relying on Explainable Artificial Intelligence techniques (xAI) to enhance the transparency of the predictive models. The Irish potato was chosen as the focus crop to study its flow distribution among 30 districts of Rwanda. Objectives included compiling a comprehensive database of socio-economic and environmental factors along with district pair food flows, and leveraging machine learning methods to predict whether a particular district pair presents Irish potato food flows or not. Specifically, Random Forest (RF) and Support Vector Machine (SVM) were trained to predict Irish potato food flows, while the Local Interpretable Model-agnostic Explanations (LIME) xAI technique was used to further investigate particular district pair instance prediction and its most influencing features. Both RF and SVM models demonstrated high overall accuracy (both above 90%) in predicting district level Irish potato flow. However, it is important to note that the dataset presented imbalanced classes where district pairs that contained Irish potato flows were about 7% of the total data samples, while the remaining dataset comprised the absence of Irish potato flow. F1 score, which is the harmonic mean of precision and recall, was used to evaluate the class prediction accuracy of the models. On the both RF and SVM models, F1 score of class 0 (absence of flow) was 0.96 whereas on class 1 (Presence of flow) was 0.61 for RF and 059 for SVM. These F1 scores shows that both models were accurate at predicting the absence of Irish potato flows (class 0) than the presence of flow (class1), reflecting an imbalance in the dataset where instances of Irish potato flows were less frequent. Using Local Interpretable Model-agnostic Explanations (LIME) xAI technique it was observed that environmental factors notably at the origin district were the most flow influencers compared to socio-economic features. The study recommends the integration of market level flow data, the scope and temporal expansion for a more granular analysis.Item Host plant resistance to infestation of Fall armyworm, Spodoptera frugiperda (J. E. Smith), in tropical maize, (Zea mays L.), germplasm(Thesis, 2024) Udah, O.The study evaluated early and extra-early maturing maize inbred lines to identify adaptive traits for resistance to Fall armyworm (FAW); determined the genetic control of resistance to FAW among selected early and extra early maturing maize inbred lines; identified the most critical stage(s) of different maize genotypes to FAW infestation; evaluated the effects of selected secondary metabolites on food preference of FAW; and determined the inhibitory efficacy of selected early maturing maize inbreds and hybrids against digestive enzymes of FAW. These were with a view to improving maize output and food security in Nigeria. A three-year study at Obafemi Awolowo University in Nigeria screened 1037 maize inbred lines for FAW damage. Early and extra-early maturing lines were divided into eleven groups based on maturity and endosperm color. Artificial infestation with FAW larvae was carried out two weeks after planting, with an average of four larvae per plant stand. Resistance was evaluated throughout the plants' growth stages using a rating scale. The study also included experiments on secondary metabolites and enzyme inhibition assays. Data from both resistant and susceptible lines were analyzed at the OAU Enzymology laboratory. Data obtained for each objective were subjected to analysis of variance and significant means were compared using least significant difference at p ≤ 0.05. Specifically, the adaptive traits were identified based on their significant relationships with the insect’s damage parameters using correlation and stepwise multiple regression analyses. The study identified 150 FAW resistant inbred lines as potential trait donors for breeding programmes. Nine adaptive traits were identified, with the number of days to anthesis and silking significantly correlated with FAW damage (p ≤ 0.05). The study revealed significant ((p ≤ 0.01) genetic variability among inbred lines, with both additive and non-additive gene actions influencing FAW damage. All tested maize hybrids contained flavonoids, triterpenes, and phenolics, while saponins were absent in all samples. The secondary metabolite profile of maize plant materials screened will be useful for selecting resistant germplasms, particularly for flavonoids. The genetic makeup of inbred lines and hybrids significantly influenced enzyme inhibition, with variability primarily due to genetic differences. Alpha amylase inhibition percentages in pro-vitamin A maize inbreds and hybrids revealed TZEIOR 192 as the most effective inbred line. TZEIOR 70, a FAW susceptible inbred parent, performed better than some potentially resistant lines, indicating multiple defense mechanisms may be responsible for resistance in the maize inbreds and hybrids studied. In conclusion, the study identified potential FAW resistant maize inbred lines. Male parents had additive gene action controlling FAW damage parameters, while pro-vitamin A maize inbred lines had non-additive gene action. Secondary metabolites played a crucial role in defense mechanisms against FAW, with flavonoids, triterpenes, and phenolics influencing FAW larvae's feeding preferences. Extracts from selected maize lines showed inhibitory activity against FAW digestive enzymes.Item Effects of urbanization on avian diversity and human-nature interactions in tropical environments(Thesis, 2025-03) Awoyemi, A.G.Urbanization is a rapidly expanding global phenomenon that poses significant threats to biodiversity. Despite its importance, the impacts of urbanization on biodiversity in certain regions remain understudied. Recent studies have highlighted the need for more research on the topic, particularly in Africa, where unprecedented urbanization overlaps with vast biodiversity. Thus, this thesis investigated the impacts of urbanization on socioecological systems in the Afrotropics, providing data useful in achieving sustainable urban development in line with SDG Goal 11 (Sustainable Cities and Communities) in the region. This thesis began with a comprehensive systematic literature review to assess the current state of urban ecology in Africa (Chapter 1). The review revealed a striking knowledge gap, with only 795 relevant papers published in the last century (1920—2020), much less than those from other continents. Notably, a disproportionate number of these studies (40%) were conducted in South Africa, indicating a significant geographical bias in our current knowledge on the topic. This review found that research efforts are driven by economic wealth (GDP) and the importance of conservation in African urban ecology. However, the review also exposed a surprising oversight: the Afrotropics, which is the most urbanized and biodiverse-rich African region, is not a primary focus of study. Furthermore, most urban ecology studies in Africa were conducted in a single city (55%), with substantial knowledge gaps persisting across taxonomic groups, scientific fields, and ecoregions. To partially address these important gaps, this thesis focused on investigating different research questions in multiple cities in Nigeria (Chapters 2—5), a typical Afrotropical country experiencing rapid urbanization. These additional chapters investigated the impacts of urbanization on bird taxonomic, functional and phylogenetic diversity (Chapters 2—3), avian-mediated regulating ecosystem services, including pest control, seed dispersal, pollination, and scavenging (Chapter 4), and human-nature interactions (Chapter 5). The results of these studies unequivocally demonstrated that urbanization has profound negative impacts on bird diversity and ecosystem services in the Afrotropics. Compared to non-urban areas, urban areas exhibited significantly lower bird taxonomic diversity (Chapter 2) and reduced provisioning of essential ecosystem services provided by wildlife, including pest control, seed dispersal and pollination (Chapter 4). Scavenging was the only bird-mediated ecosystem service enhanced by urban development (wet season). Furthermore, certain urban attributes, such as the presence of vehicles and pedestrians, were found to compromise bird phylogenetic divergence and ecosystem service provision, particularly pollination and seed dispersal. However, the results also highlight the potential for targeted conservation efforts to mitigate these negative impacts. Notably, the presence of water bodies and specific vegetation types, such as canopy and bush cover, can significantly enhance multiple components of bird diversity and crucial bird-mediated regulating ecosystem services (Chapters 2 and 4). By preserving and restoring these key habitat features, it may be possible to reverse the decline of bird diversity and the associated regulating ecosystem services in Afrotropical cities, particularly seed dispersal and pollination. Chapter 3 presents a novel application of machine learning and remote sensing techniques in estimating local habitat variables influencing bird diversity components across urban and non-urban areas. This study revealed that the Modified Chlorophyll Absorption Ratio Index (MCARI) is the most effective indicator of taxonomic and phylogenetic bird diversity in the Afrotropics. In contrast, the Normalized Difference Water Index 2 (NDWI2) and Soil Adjusted Total Vegetation Index (SATVI) were found to be the best predictors of functional diversity and phylogenetic divergence, respectively. Interestingly, the Normalized Difference Vegetation Index (NDVI), a commonly used predictor across regions and topics, ranked relatively low (25th percentile) in most cases. These results recommended the use of these alternative predictors (MCARI, NDWI2 and SATVI) rather than the NDVI in predicting bird biodiversity in urban and non-urban areas of the Afrotropics. This is likely due to NDVI's limitations, including scaling issues, saturation in high-biomass areas, and sensitivity to soil brightness, which can compromise its accuracy in diverse Afrotropical environments. The remote sensing approach employed in this study offers a potentially more efficient and cost-effective method for estimating local habitat variables compared to traditional manual estimation techniques. By leveraging machine learning algorithms and remotely sensed data, this approach can help reduce the labor, expense, and investigator error associated with manual data collection. In addition to the ecological impacts, urbanization also has significant social implications. By investigating the extinction of experience concept among urban dwellers in Nigeria, Chapter 5 found that most citizens had little or no contact with nature. The main reasons cited for this disconnection were lack of time, money, and nearby natural areas. The study also found that respondents with higher nature contact were more connected to nature, and that the perception of neighborhood safety was an important factor promoting nature contact. Furthermore, the study also found that respondents living in Lagos, and those with lower levels of income and education, showed greater dissociation from nature. These findings could be useful to fight against the worrying extinction of experience in the region, providing potential factors to consider and implement in future urban development plans in the Afrotropics. Overall, the Chapters of this thesis highlight the need for more research on the impacts of urbanization on biodiversity and ecosystem services in the Afrotropics. They also emphasize the importance of promoting nature contact and experience among urban dwellers, particularly in regions with rapid urbanization such as the study area (i.e. Nigeria). By addressing these knowledge gaps and promoting nature experience, we can work towards creating more sustainable and resilient urban ecosystems that will benefit both people and the environment.Item Effect of hygiene status in maize storage facilities on pests, molds and aflatoxin contamination in Nakuru Country, Kenya(Thesis, 2022) Makinya, K.J.Infestation of harvested agricultural produce with pests, pathogens or contamination with mycotoxins during storage negates efforts to eradicate food and nutrition insecurity. Preventive measures, primarily suitable storage structures and cautious adherence to hygiene constitute key actions for effective control of pests and pathogens. However, contribution of recommended postharvest handling and hygiene practices as avenues for timely mitigation have never been examined. The aim of this study was to assess the effect of hygiene in maize storage facilities on pest infestation, mold and aflatoxin contamination. A cross-sectional survey was conducted in 2017 to assess postharvest handling practices, levels of hygiene and their effect on the magnitude of losses in maize farmers’ storehouses. A total of 342 rural farmers spread across the high potential moist transitional agro-ecological zone in Nakuru County were interviewed and data recorded in a semi-structured questionnaire and a checklist. In addition, the hygiene status of 40 storehouses where shelled maize grain was stored in bags was assessed and the grains sampled. The stores were ranked into ‘poor’, ‘average’ or ‘good’ hygiene categories depending on the level of adherence to recommended storage hygiene practices. Maize grains that had been harvested and stored in farmer’s stores were sampled at intervals of two months beginning April to October 2017. The samples were analyzed for moisture content, quality compliance, insect population, grain damage, weight loss, mold incidence and aflatoxin levels. The main storage bags were polypropylene used by 98.2% of the farmers. Bagged maize was stored either in granaries or designated rooms within dwelling houses. Overall, 90% of the farmers cleaned their storehouses before the most recent harvest was loaded, while only 50% cleaned the storehouses after the harvest had been loaded. Farmers reported 8.3 ± 0.5% weight losses resulting from insects, rodents, molds and theft. Laboratory analysis of maize sampled from farmers’ storehouses revealed a significant (P = 0.002) increase (from 12.2 to 14.2%) in moisture content of maize stored under poor hygiene conditions beginning from the second month of storage. Interaction between hygiene status, population of Sitophilus zeamais and storage time was highly significant (P <0.001). Good hygiene practices slowed the rate of grain damage and corresponding weight loss. The total population of molds across all the stores increased significantly after four (P < 0.001) and six (P < 0.001) months of storage. Additionally, stores adhering to good hygiene practices recorded significantly lower incidence of Aspergillus spp. at the fourth (P = 0.002) and sixth (P < 0.001) months of storage, respectively. This was followed by corresponding significantly (P = 0.041) lower levels of total aflatoxin (range 7 – 64 ppb) after four months of storage. Total aflatoxin levels increased approximately four fold for maize stored under hygienic conditions, six fold for storehouses characterized by average hygiene practices, and seven fold for grain stored under conditions of poor hygiene throughout the storage period. At the commencement of the trial, 15% and 22% of samples from hygienic and unhygienic stores respectively had total aflatoxin levels beyond the 10 ppb threshold set by the Kenya Bureau of Standards (KEBS). This proportion increased to 100% and 71% in unhygienic and hygienic stores respectively four months after commencement of the trial. From the Fractional Response Model, high hygiene scores correlated significantly with lower grain losses. Storing maize grains in the bedroom or living room correlated with lower losses by 2.8 and 4.6 percentage points, respectively; compared to storage in granaries, while storage in the kitchen correlated with higher losses by a margin of 19 percentage points. Storage of maize together with other grains or farm equipment was associated with higher losses by 2.8 percentage points. Storage of maize in hermetic containers did not result in significantly lower losses. In addition, repairing or disinfecting the store before introducing a new harvest did not significantly reduce grain losses. Training in grain storage did not have a significant effect either, while maize farming experience and younger age were associated with lower losses by 2.8 and 5.9 percentage points, respectively. Stores where majority of the postharvest handling decisions were made by women had lower losses by 2.8 percent points. This study demonstrates that storing grain under hygienic conditions can help smallholder farmers retard proliferation of molds, aflatoxin contamination and storage pests and consequently prolong safe storage duration of maize grains.Item Physiological basis for yield differences in maize (Zea mays L.) under varying nitrogen rates and planting windows in the savannas of Nigeria(Thesis, 2024-06) Ahmad, N.M.Maize Production in the savannas of West and Central Africa (WCA) is limited by intermittent drought during cropping season and low soil fertility which affects its productivity and the overall livelihood of smallholder farmers. This study aimed to determine the physiological basis of differential yield response of some maize varieties under varying level of nitrogen and different sowing windows in Guinea and Sudan savannas of Nigeria and identify stress surrogate traits for yield improvement in maize. Field experiments were conducted at Bayero University, Kano (11058`38.63892N, 80 25`7.01868E), altitude 451m above sea level in the Sudan savanna and Zaria (11.16050610N, 7.64535890E) in Northern Guinea Savanna. Treatments consisted of three sowing windows at two weeks intervals, two levels of nitrogen (30 and 100 Kgha-1) and four improved maize varieties (SAMMAZ15, SAMMAZ 16, SAMMAZ 40 and SAMMAZ 51). These were laid out in a Split-split plot design with three replications. Sowing window was allocated to the main plot, varieties to the sub plot and Nitrogen to the sub-sub plot. The results indicated that the most favorable sowing window identified for planting of maize is the mid-June to late June for Sudan Savanna and mid-June to early July for Northern Guinea Savanna. Furthermore, the choice of maize variety emerges as a critical factor influencing yield, irrespective of location. SAMMAZ 40 and SAMMAZ 51 varieties demonstrated superior performance in terms of both yield (3,814 kg/ha and 3,873 kg/ha, respectively) and biomass accumulation at both study locations. Additionally, while higher nitrogen application rates contribute to increased biomass, this effect is contingent on the interplay between planting period and variety selection, highlighting their combined influence on maize yield in terms of both quantity and weight. In instances of low nitrogen, specific surrogate traits such as leaf area index for grain yield, Intercepted photosynthetic active radiation for harvest index, and electrical conductivity, total dissolve salt, chlorophyll content, and leaf area index for hundred seed weight were identified as key indicators.Item Performance of cassava planting materials produced using the "Semi Autotrophic Hydroponic" technology in the laboratory and across locations in the Democratic Republic of Congo(Thesis, 2024) Binzunga, M.M.Cassava (Manihot esculenta Crantz)) is a crucial food crop in D.R. Congo, sustaining over 70% of the population and serving as a primary income source. However, the cassava seed system faces the challenge of a low propagation rate associated with an extended growing cycle. This research aimed to contribute to the improvement of the cassava seed system in D.R. Congo using stem cuttings provided by SAH technology. Two experiments assessed plantlet performance using two types of substrates. Experiment 1, employing a split-plot design, used four genotypes (IB961089A, MM060083, Nase14, and Albert28) and four single substrates: KlasmannTS3 (K), Vermiculite (V), Local Peat (P), and Sawdust (S). It involved three subculture periods lasting four weeks, with data collection on survival, height, leaf, internode, and cutting numbers. Experiment 2, following a similar design, investigated the performance of three genotypes (IB961089A, IBA070520, and IBA980555) under single substrates (K, V, and P) and their combinations (K25P75, V25P75, and V10P90). The field experiment in Mulungu and Kiliba utilized SAH-derived plantlets employing a 4 x 4 split-plot design. Data were collected on survival, growth parameters, and stem length at different months after planting. Finally, a simple cost analysis was carried out, comparing the production cost of SAH-derived plantlets to that of producing cutting sunder the conventional propagation method. Experiment 1 revealed substrate significantly influenced survival rates, surpassing 90% (p<0.05), showing the highest number of cuttings of 70.4 in three months, representing a ratio of 1:4 with the genotype MM060083 (p<0.001). Experiment 2 showed K25P75 did not differ from single KlasmannTS3, with the highest survival rate and an increase of 80.5 cuttings, representing a ratio of 1:4 with IBA961089A. The superior effect of the substrates was attributed to their favorable properties, allowing rapid plantlet growth. Field results indicated that Kiliba recorded a higher survival rate of 81.3% compared to Mulungu's73.8%. Across locations, MM060083 had the highest survival, exceeding 80%, whileNase14 had the lowest. The check-cutting method demonstrated the highest survival of over 90% compared to SAH-derived plants, but KlasmannTS3 had the highest among the SAH at Kiliba (85.4%). The highest stem length was obtained at Mulungu (17.5 m) compared to Kiliba's 10.5 m at 12 MAPs. Nase14 achieved the highest stem length of 17.7 m per plot, while IBA961089A had the lowest at 9.3 m at 12 MAPs. SAH-derived plants caught up with conventional checks across locations by 12 MAPs. The use of combined substrates, particularly K25P75, demonstrated an equal unit cost to that of the conventional mini stem, both amounting to USD 0.07. These findings provide relevant insights into policymakers' decisions to promote efficient cassava propagation method for sustainable agriculture, enhance food security, and promote economic development in D.R. Congo.Item Harnessing the potential of selected bio-agents for sustainable management of plant parasitic nematodes in coffee(Thesis, 2024) Anyango, O.C.East Africa confronts multiple challenges in coffee production, including aging plantations, subpar inputs, climate change, and pest-related issues. Among these threats, plant parasitic nematodes (PPN) pose a significant concern, contributing to estimated global losses of up to 15% in coffee production. Despite their impact, PPN often remain overlooked or underestimated as a major factor causing damage to coffee crops. In Kenya, specific symptoms of PPN damage are poorly understood, leading to their gradual manifestation over years and resulting in enduring losses to the industry. Biocontrol has been explored in management of PPN on other crops like horticultural, ornamental and other annual crops but has not been registered in coffee, a perennial crop. This study aimed to assess the potential of microbial antagonists in suppressing PPN and improving coffee production in Kenya. The effectiveness of three biocontrol agents namely Trichoderma asperellum, Purpureocillium lilacinum, and Bacillus subtiliswas evaluated under pot and field conditions, targeting Meloidogyne hapla, a prevalent nematode species affecting coffee in the Ruiru region of Kenya. In pot experiment, nematode-infested soil and roots from Chania Coffee Farm was utilized. Three Biocontrol agents, namely Bacillus subtilis, Trichoderma asperellum and Purpureocilium lilacinum were tested. Each of biocontrol agent was administered at three different rates: 6.67 × 103, 6.67 × 104, and 6.67 × 105 spores/ml, using a randomized complete block design with 20 treatments and five replicates. Drenching with 150 ml of the biocontrol agent occurred every two weeks for six months after transplanting, with assessments conducted at the experiment's termination. Two biocontrol agents, Trichoderma asperellum and Purpureocilium lilacinum, were tested in the field experiment. The recommended dose for other annual crops, 2 × 107 spores/ml, was applied in seven fields, each with three treatments and four replicates, spanning for two years. Drenching each plant with 40 ml of the respective product in 20 liters of water was done monthly after subsequent soil sampling. Monthly activities included soil sampling, nematode extraction, quantification, and identification, as well as fungal re-isolation. The nematode survey revealed ten genera of plant parasitic nematodes; Meloidogyne spp., Tylenchorhynchus spp., Helicotylenchus spp., Longidorus spp., Pratylenchus spp., Trichodorus spp., Scutellonema spp., Rotylenchulus spp., Paratylenchus spp., and Hemicycliophora spp., with varying densities based on coffee cultivar. Ruiru 11 exhibited a lower mean density of PPN, with 40, as compared to cv French Mission, which recorded 62, with the control group having 43 nematodes per 100cc of soil and 5 g of roots. Similarly, Ruiru 11 had a lower count of free-living nematodes, with 276, compared to cv French Mission, which recorded 326 nematodes per 100cc of soil and 5 g of roots. Trichoderma asperellum significantly colonized coffee roots with 2.45 × 106 cfu/g of soil and roots, a higher count compared to P. lilacinum, which recorded 3.22 × 103 cfu/g of soil and roots. In cv Ruiru 11, the percentage mean of PPN recorded per treatment was significant, with the untreated group having 36.7%, P. lilacinum 32.5%, and T. asperellum 30.8%. The study suggests that older plants associated with French Mission may contribute to this difference. Pot experiment results indicated a significant reduction in M. hapla on coffee with all bio-control agents at spore concentrations of 6.67 × 104 spores/ml and 6.67 × 105 spores/ml. Coffee cultivar Ruiru 11 exhibited higher efficacy in biocontrol agent uptake, resulting in a lower root galling index compared to French Mission. However, the galling index showed no significant variation among the bio-control agents. Trichoderma, at a spore concentration of 6.67 × 105 spores/ml, significantly reduced M. hapla densities in plant roots compared to P. lilacinum at a similar concentration. Additionally, the study demonstrated increased plant biomass in plants treated with biocontrol agents. This study recommends use of B. subtilis, T. asperellum, and P. lilacinum at a spore concentration of 6.67 × 104 spores/ml to effectively manage plant parasitic nematodes in coffee plantations. Further research should explore the use of different coffee cultivars and determine the optimal stage for exposing coffee to biocontrol agents. Additionally, there is a need to investigate the integration of these biocontrol agents into existing control practices for more effective and sustainable nematode management.Item Evaluation of agronomic performance and genotypic mapping using SNP markers of grain iron and zinc content among rice accessions in Eastern Democratic Republic of Congo(Thesis, 2024) Bukomarhe, C.B.Rice (Oryza sativa L.) is among the most important food crop in the Democratic Republic of Congo (DRC). The crop has historically been neglected by local researchers. However, recent urbanization and changes in dietary habits have elevated its significance. The identification of rice varieties with high yield and reasonable micronutrient contents, especially iron (Fe) and zinc (Zn), could be important in rice varieties for the DRC. This study aimed to (a) determine agronomic performance of a subset of 36 rice accessions to identify high yielding and stable genotypes for cultivation in eastern DRC and (b) associate SNP markers with Fe and Zn content in rice grains for application in marker assisted selection. For the molecular markers study, 85 diverse rice accessions from the DRC maintained at the Kalemie were analysed for variation in Fe, Zn and SNP markers. The data were analysed using rMVP package of R software for Genome Wide Association Study (GWAS) to identify genomic regions linked to grain Fe and Zn content. Candidate genes associated with Fe and Zn content were identified and annotated from the Oryza sativa reference genome version 7.0 of the MSU-Rice Genome Annotation Project (RGAP) database. In the evaluated rice grains, Fe content ranged from 0.95 to 8.68 mg/100g (dry weight basis), while Zn content ranged from 0.87 to 3.8 mg/100g. Two significant SNPs were identified, with one on chromosome 11 associated with Fe and another on chromosome 4 associated with Zn. Candidate genes involved in transcription regulation and transporter activities related to Fe and Zn homeostasis, including the bZIP family genes and MYB family genes were pinpointed. For the agronomic trial, 36 rice accessions were evaluated in a 6x6 triple lattice design with three replications in Bwegera and Sange sites, in Eastern DRC. Data on various agronomic traits such as Day to Flowering (DTF), Plant Height (PH), Effective number of Tiller (ET), Panicle Length (PL), Grain per Panicle (GP), Thousand Grain weigh (TGW), Grain Length (GL), Grain Width (GW), Ratio Grain Length and Grain Weight (RGLGW), Grain Yield (GY) were recorded during growth and analysed using R software. Across locations, no significant differences were recorded in various agronomic variables, except for 1000-grain weight (TGW). Within locations, significant differences were observed for the evaluated variables except for panicle length, grain length, grain width, and the ratio of grain length to grain weight. Based on grain yield, accessions IR990-48-B-B-12, IR841, IR88638 and MR254 were the best across and within individual sites making them favorable recommendations for farmers. The identified markers and candidate genes can be utilized in Marker Assisted Selection (MSA) in rice breeding programs, aiming to enhance Fe and Zn content. The study is offering opportunitiesItem Evaluation of agronomic trait of some cassava (Manihot esculenta Crantz) genotype using ground penetraiting radar(Thesis, 2023-06) Omole, D.A.The main economic value of the cassava rests in its starchy storage root, but limited information is available on the growth patterns of cassava roots as compared to the shoot. A non-destructive protocol that captures root bulking rate could facilitate selection and optimize varietal response to management practices. Therefore, this study aimed to evaluate the capability of ground penetrating radar (GPR) to estimate root bulking rate six months after planting. Ten varieties were planted in Ibadan and Ikenne in the 2021/2022 cropping season using a Randomized Complete Block Design (RCBD) with 3 replications in a mixed model with variety and harvest time as a fixed factor and location as a random factor. The plot size was 30 m2, with a plant spacing of 0.8m X 1m. Data were collected on the number of roots (n), dry matter content (%), Cassava Mosaic Disease (CMD) on a scale of 1 (no visible symptom) to 5 (severe mosaic, severe leaf distortion, and stunting), plant height(cm), shoot weight (kg), root volume (lt), root girth (cm), root length (cm), total root weight (kg) and Harvest Index (HI). Fresh yield (t/ha) and dry yield (t/ha) were estimated for each variety. GPR scanning was done to obtain GPR data and was processed using "RELEASE” software, a demo version produced by IDS Georadar. Data were subjected to ANOVA using R software at α0.05. Pearson’s product-moment correlation tests were performed to compare the relationship between GPR and agronomic data sets. Multiple linear regression was used to identify traits that are significantly related to fresh root yield. Results showed a significant correlation between root volume measured by GPR and root volume measured at harvest (r=0.90***), while the number of roots measured by GPR had a significant correlation with root number measured at harvest (r=0.60***). Regression analysis indicated that root volume and dry yield had a higher coefficient of determination multiple R-squared: 0.9837. Harvest time was also significant for all traits except root volume and fresh yield. Interaction between Variety and Location was significant for CMD, root length and HI. Interaction between Variety and Harvest time was significant for all traits except plant height, root number, and dry matter. Interaction between Location and Harvest time was significant for all traits except plant height, root number and dry yield. The three-way interaction between Variety, Location and Harvest time was significant between CMD and HI. Varieties such as Arubielu, Egecoutonou, and TMEB693 had the highest plant heights range of 240cm- 260cm. Arubielu and TMS13F1160P0004 had the highest harvest index (HI) values of 0.62. VarietyTMS13F1160P0004 had the highest dry matter content of 39%. Variety IITA-TMS- IBA000070 recorded the highest fresh yield of 26 t/ha. Variety TMS13F1343P0022 had the highest dry yield of 10.10 t/ha.Item Biomass accumulation and partitioning in cacao (Theobroma cacao Linn.) as affected by age, fertilizer application and canopy exposure(Thesis, 2023) Ajibona, O.A.Cacao is a plant known widely for its beans used in the production of chocolate and cocoa powder. Biomass production dynamics in cacao is an important process that needs to be understood for best management practices that guarantee maximum bean yield. This study investigated the accumulation and distribution of biomass in cacao as affected by age, fertilizer application and canopy exposure at the Cocoa Research Institute of Nigeria (CRIN) (7.36oN, 3.85oE) and the International Institute of Tropical Agriculture (IITA) (7.49oN, 3.90oE) in Ibadan, Oyo state, Nigeria in 2020. Principal Component Analysis was used as a selection tool to ensure that the trees used for the study fairly represented the whole plot. Fertilizer (300g of N.P.K 15:15:15 per tree) was applied using ring method to half of the selected trees while the other half had no fertilizer application. Split plot design was used with three replicates. A total of 18 trees of 8, 12 and 47 year old were harvested and measured. Data collected on shoot, root and leaf parameters were subjected to Analysis of Variance and means were separated using Least Significant Difference at 5% probability level. Regression analysis was carried out to establish allometric relationship between non-destructively obtained plant parameters (stem diameter, mean canopy diameter, height) and the total tree biomass and the biomass of specific tree organs. The age of the tree had significant effect on height (534.90 cm, 723.90 cm and 735.8 cm), leaf fresh weight (2.75 g/leaf, 2.99 g/leaf and 4.07 g/leaf) and leaf dry weight (1.22 g/leaf, 1.35 g/leaf and 1.88 g/leaf) of the 8-year, 12-year and 47-year old trees, respectively. Fertilizer application influenced total dry biomass of leaves (6.36kg/tree), leaf fresh weight (3.47 g/leaf) and leaf dry weight (1.58 g/leaf) with the non-fertilized trees having the highest values irrespective of their position in the canopy. Biomass accumulation in the leaves and branches decreased from 14-4% and 48-36% respectively. However, stem biomass increased from 20-33% and root biomass was maintained at 20% for the 8-year, 12-year and 47-year old trees. The highest contributor to total biomass were in the order of branch > stem > roots > leaves. The allometry between the components and the whole cacao revealed that the best predictor of biomass was stem diameter (R2 = 0.634-0.872). The position of the leaf in the canopy was discovered to have a significant effect on Specific Leaf Area (SLA) with leaves in the lower canopy portion of the tree showing a higher SLA than those in the upper portion. Leaf production in cacao was influenced jointly by their position in the canopy and exposure to sunlight. It was concluded that biomass accumulation increased with tree age and the woody organs were the major contributors to the total biomass. Stem diameter is recommended for use in predicting total biomass using allometric equation. Application of fertilizer to aged cacao trees is not recommended.Item Mechanism of yield compensation in some accession of cowpea grown at different plant densities and environments(Thesis, 2024-01) Odesina, I.S.Grain yield of cowpea [Vigna unguiculata (L.) Walp.] in Nigerian savannas are low despite the cultivation of improved accessions. Amongst a host of production constraints, missing plant stand has been suggested to contribute to yield loss in cowpea. Gap-filling could be used as alternative to mitigate yield losses caused by stand reduction. This study, which was carried out in 2020, was aimed at investigating the mechanism of yield compensation in some accessions of cowpea in two savannah agro-ecologies at Minjibir and Shika in Northern Nigeria. The randomised complete block design in a split-plot arrangement in three replicates was used. The main plot consisted of four plant densities (33,333, 66,666, 99,999 and 133,333 plants ha-1) while the sub-plots consisted of six cowpea accessions (DANILA, IT08K-150-27, IT89KD-288, IT93K-452-1, IT98K-205-8 and IT99K-573-1-1). Results showed that plant density and environment affected grain yield. Total grain yield increased with increasing plant density. Generally, total grain yield was higher at Minjibir than at Shika. The highest total grain yield of 1,793.3 kg ha-1 was observed in the accession DANILA at 99,999 plants ha-1, while the lowest(1,100 kg ha-1) was observed in the accession IT98K-205-8 at 33, 333 plants ha-1. Stand count at harvest, leaf area index and intercepted photosynthetically active radiation and pod weight were positively correlated with total grain yield at both locations, suggesting that these traits could be considered for cowpea improvement. Cowpea growers and breeders could consider erect accessions (IT93K-452-1 and IT98K-205-8) and semi-erect accessions (IT99K-573-1-1 and IT08K-150-27) for cultivation at 133,333 plants ha-1 and prostrate accessions (IT89KD-288 and DANILA) at 99,999 plants ha-1 at Minjibir. The accession IT93K-452-1-1, IT98-205-8, IT99K-573-1-1 and IT08K-150-27 could be considered for cultivation at Shika, irrespective of plant density.Item Genetic diversity in Nigeria taro [Colocasia esculenta (L.) Schott] germplasm(Thesis, 2025-01) Oladimeji, J.J.Taro is a resilient, underexploited tropical corm-producing crop that plays a vital role in the nutritional and economic livelihoods of many households in Nigeria. However, its production and productivity are constrained by the incidence of diseases, low-input farming practices and inadequate genetic improvement efforts. To improve the yield and quality of taro in Nigeria, adequate information is needed on the presence of heritable genetic variation among available collections. However, limited information is available on the level of variability among cultivated taro in Nigeria. This study was carried out to assess the extent of phenotypic and molecular diversity among some taro accessions collected from major taro-growing agroecologies in Nigeria. Four hundred and ninety taro landraces comprising 215 Dasheen and 275 Eddoe gene pools were assembled from farms and markets across seven States (Oyo, Kwara, Ekiti, Ondo, Akwa Ibom, Ebonyi and Anambra) in humid forest and derived savanna agroecologies in Nigeria. The 490 landraces were genotyped using 4,748 Diversity Array Technology sequence-based Single Nucleotide Polymorphism (DArTseq-SNP) markers, 3,047 of which were retained after quality filtering. A subset (114) comprising 65 landraces from the first collection and 49 landraces from the second collection were planted in September 2021 and March 2022 respectively, following their collection times using 27 agromorphological descriptors. Phenotypic data were subjected to descriptive statistics, cluster analysis and analysis of variance, while hierarchical clustering, population structure and analysis of molecular variance were carried out on the molecular data. The phenotypic and molecular characterization of the taro landraces revealed higher genetic diversity among the Eddoes than among the Dasheens. For all the quantitative traits, the estimates of genetic variance were higher than those of environmental variance. The total yield (TY) of the landraces ranged from 100 to 32,200 kg/ha (mean = 10,600kg/ha) for the phenotyped September 2021 set while the range was from 100 to 23,300kg/ha (mean = 6,800 kg/ha) for the March 2022 set. The taro landraces in both planting clustered into four groups based on 10 phenotypic traits at a threshold of 1.5. Highest yield was recorded in K-I-O1-S1 and A-I-IE Cormel 1 (32,200 kg/ha) from the September 2021 planting and AKN 1-P5 (23,300 kg/ha) from the March 2022 planting. Estimates of gene flow (Nm = 0.353) revealed intermixing of landraces among the States of collection. Gene flow was highest (1458.98) between landraces from Anambra and Ondo States and lowest (0.06) between Anambra and Kwara States. The population structure and hierarchical clustering based on the DArTseq-SNP markers delineated four clusters, one which comprised Dasheens, while three comprised Eddoes. The variation between gene pools (49%) was higher than within gene pools (32%). The variation among the States of collection was high (41%), while the variation among individuals within the gene pools (18%) and States of collection (19%) were relatively low. A wide level of genetic diversity was found between the taro gene pools and among the taro landraces from Nigeria. The findings constitute a valuable resource for the genetic improvement of taro in Nigeria.Item Caractérisation de la diversité génétique des bactéries Xanthomonas phaseoli pv. manihotis et Xanthomonas cassavae en RD Congo(Thesis, 2024) Luzolo Tulomba, A.Le manioc est l'une des principales cultures en République Démocratique du Congo, malheureusement il est affecté par divers agents pathogènes. Cette étude a exploré la diversité génétique des souches de Xanthomonas phaseoli pv. manihotis (Xpm) et Xanthomonas cassavae (Xc) en utilisant initialement la technique d'amplification de l'ARNr 16S pour confirmer l'identité des souches, puis la méthode MLVA (Multi-Locus Variable number tandem repeat Analysis) pour comparer les souches récentes aux anciennes souches du laboratoire SAVE, isolées en RD Congo dans les années 1970. La technique MLVA a permis de mettre en évidence la diversité au sein des souches comparées, tout en montrant certaines limites, notamment dans la comparaison des souches Lomami6 et UPB008, qui ont présenté des profils similaires. Le séquençage du génome entier de ces deux souches particulières a ensuite permis d'obtenir des informations plus précises. Les résultats ont confirmé que Lomami6 n'est pas une Xanthomonas cassavae, mais plutôt une Xanthomonas phaseoli pv. manihotis, tandis que UPB008 est effectivement une Xanthomonas cassavae. Par contre, aucun isolat de l’espèce Xanthomonas cassavae n’a pu être mise en évidence dans les souches récentes. Les résultats montrent que LOMAMI6 se rapproche de souches isolées en Colombie, au Nigeria et en Ouganda, tandis que UPB008 est génétiquement distinct des autres génomes de Xanthomonas cassavae déjà publiés sur la base des données NCBI. Les informations génomiques obtenues dans cette étude enrichissent notre compréhe...Item Validation of single nucleotide polymorphism trait-markers and characterization of biofortified cassava (Manihot esculenta Crantz)(Thesis, 2024-05) Ogungbesan, A.O.Cassava (Manihot esculenta Crantz) is a vital industrial and staple crop in Sub-Saharan Africa (SSA) where it is valued for food security and consumer acceptability. Consumers with preference for white-fleshed cassava that lack Pro-vitamin A are prone to diseases associated with vitamin A deficiency. Biofortified cassava has great nutritional benefits in addressing micronutrient deficiency in resource-poor households. However, lack of adequate genomic information on local genetic resources has impeded the efficient conservation and improvement of biofortified cassava. The objectives of this study were to characterize 376 cassava accessions using Single Nucleotide Polymorphism (SNP) markers and to validate trait markers linked to Total Carotenoid Content (TCC), Dry Matter Content (DMC), and resistance to Cassava Mosaic Disease (CMD) for marker-aided selection in biofortified cassava breeding pipeline. In this study, 376 cassava accessions from three breeding programmes (International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria, International Center for Tropical Agriculture, CIAT-Cali, and the University of Hawaii, USA – the origins) were phenotyped and genotyped to achieve the study objectives. The cassava accessions were selected from the clonal evaluation trial (219), elite parents (108), advanced yield trial (30), high-priority genotypes (14), and released biofortified varieties (3) established at IITA-Ibadan, Nigeria. The accessions were phenotyped for resistance to Cassava Mosaic Disease (CMD), Total Carotenoid Content (TCC), and Dry Matter Content (DMC). The accessions were also genotyped with Kompetitive allele-specific primer procedure using 46 SNP markers comprising 36 quality control and 10 traits-linked markers. Phenotypic data were subjected to descriptive statistics, normality tests, and trait relationships. Genotypic data were subjected to population structure, phylogenetic analysis, and F-statistics. Marker validation was done using the Kruskall-Wallis test. The mean performance of the color chart score was 3.37 with total carotenoid content being 10.83μg/g fresh weight basis. The average percent dry matter content was 34.31% while for cassava mosaic disease severity recorded was 1.5. Further results revealed a significant negative correlation between TCC and DMC (-0.64**), and CMD (-0.18**). Twenty-eight accessions combined lower than mean population CMD severity score, high DMC (>30%), and high TCC (>15μg/g). Genotyping results showed that the highest expected heterozygosity (He= 0.493) was found in the genotypes that originated from Hawaii which was comparable to genotypes from IITA breeding programmes (He= 0.43). The Principal Component Analysis (PCA) and hierarchical clustering revealed two genetic sub-populations within the 376 cassava genotypes with accessions connected to the accession origins. The analysis of molecular variance results based on origin and sub-population revealed higher genetic variations in accessions within origin and subpopulations than among origin and subpopulations. The CMD three resistance markers, one DMC marker, and the three PVA markers showed a good predictive ability indicating their usefulness in cassava forward breeding programmes. These results showed a high level of genetic variation among cassava accessions with good levels of prediction for the CMD, DMC, and PVA markers tested in this study. This will facilitate the incorporation of marker-assisted selection in accelerating the improvement for these traits.