Academic submissions (CAES)
Permanent URI for this collection
Browse
Recent Submissions
1 - 5 of 113
-
ItemGenomics of multiple-insect resistance in maize(Makerere University, 2021-01)Maize, a food security crop, is attacked from the fields to the storage facilities by a plethora of insect pests on all parts of the plant. Most studies that were conducted to understand maize defense mechanisms to incorporate resistance in new varieties focused on single insect attacks. The phenotypic correlations and co-localizations of quantitative trait loci (QTL) for maize resistance to stem borers (SB), the fall armyworm (FAW), and storage pests (SP) on the one hand, and with cell wall constituents (CWC) and benzoxazinoids, on the other hand, suggested the existence of single and multiple-insect resistance (MIR) mechanisms. Therefore, this research aimed to investigate the feasibility of MIR in maize through the application of genomic-aided breeding (GAB) technologies for mapping and selection by establishing the genetic architecture and genomic predictability of maize resistance to multiple insect pests. A QTL meta-analysis for resistance to stem borers, FAW, and storage pests along with CWC and Benzoxazinoids revealed 42 stem (SIR), 24 leaf (LIR), and 20 kernel (KIR) insect resistance meta-QTL (MQTL) with CWC and Benzoxazinoids involved in most, suggesting a defensive role played by CWC and BXs in resistance. A genome-wide association analysis conducted on a diverse association mapping panel (AMP) planted in three locations during three seasons and genotyped with 34509 diversity array technology (DArT) single-nucleotide polymorphism (SNP) markers revealed sixty-two quantitative trait nucleotides (QTNs) for resistance to FAW and MW, majorly located within or near the insect resistance genomic regions (IRGRs). Seventy-nine genes were located around the QTNs, and 64 were functionally related to plant defense mechanisms through an array of In-silico interspecific comparative functional analyses. A network-based candidate gene identification that used these 64 genes as guides identified an additional set of 107 candidate genes differentially expressed under various stress conditions located within the IRGRs. These MQTL, QTNs, and genes could be incorporated in molecular breeding or gene editing and transgenic programs targeting single or combined insect resistance. Also, benchmarking of genomic prediction (GP) strategies was conducted using 17 GP algorithms, and two training (TS) and breeding set (BS) determination approaches were performed for FAW and MW resistance traits. The prediction accuracies (PA) were high for FAW (up to 86%) and MW (up to 82%) resistance traits, even with moderately-sized TS. The GP models performed differentially on both FAW and MW resistance traits. However, the determination of the TS size and its relationship with the BS were more influential. These results give hope for the application of GS in breeding for resistance to insect pests in Africa.
-
ItemOccurrence of cassava mosaic disease and characterization of casual viruses in Mozambique(Makerere University, 2021-11)Cassava mosaic disease (CMD) is one of the major constraints to cassava production in Mozambique. In this research, two studies were carried out to monitor the incidence and severity of CMD and its causal viruses in the country. Field surveys were conducted in seven major cassava-producing provinces in 2013 and 2015. The disease was found in all seven provinces. Incidence ranged from 14.4% to 81.3% and 19.3% to 40.8% in 2013 and 2015, respectively. In comparison to previous surveys conducted in 2003, 2005 and 2006 results of this study suggest that the disease is generally decreasing. This trend could be attributed to increased use of disease-free planting material of local or improved CMD resistant varieties, as well as increased farmer knowledge on how to manage the disease. The second objective of the study was to investigate the genetic diversity of cassava mosaic begomoviruses (CMBs) based on partial genomes analyses of 45 isolates. Collection of CMD symptomatic leaves was done in May 2016 followed by molecular analysis using PCR-specific primers. PCR findings revealed the presence of East Africa cassava mosaic virus - Uganda Variant (EACMV-UG2) in Maputo province, southern Mozambique. This is the first report of EACMV-UG2in Maputo. PCR also detected East Africa cassava mosaic virus (EACMV), Africa cassava mosaic virus (ACMV) as well as mixed infections of the two viruses in the Southern provinces of Mozambique, except in Maputo; EACMV was the most widely distributed virus. Results from Sanger sequencing also revealed the presence of South Africa cassava mosaic virus (SACMV), East Africa cassava mosaic Cameron virus (EACMCV), East Africa cassava mosaic Kenyan virus (EACMKV) in addition to ACMV. This is the first detection of EACMKV in Mozambique. The virus isolates clustered together with reference isolates for the four species derived from GenBank in phylogenetic analyses. These results indicate a relatively high level of diversity of CMBs affecting cassava in Mozambique. The existence of different CMBs poses a threat to the sustainable production of cassava and consequently food security for cassava-dependent rural households. The high viral genetic diversity calls for more surveillance and due diligence in quarantine or restriction of material movement at entry points, coupled with cassava breeding programmes that should continuously develop new resistant varieties to viral diseases.
-
ItemEvaluation of application regimes and rates of biological control agents for the management of root knot nematodes and bacterial wilt of tomato(Makerere University, 2021-10)Trichoderma asperellum and Bacillus subtilis have been used as biological control agents (BCAs) for root knot nematodes (Meloidogyne spp.) and bacterial wilt (Ralstonia solanacearum), two of the most problematic soil borne pathogens in tomato production. Unfortunately, use of these BCAs is hindered by lack of protocols that farmers can adopt and adapt to their production spheres. The current study developed a working protocol for the appropriate use of T. asperellum strain TRC 900 (1 × 109 spores/ml) and B. subtilis strain BS-01 (1 × 1010 CFU/ml) in the management of root knot nematodes and tomato bacterial wilt disease. Specifically, the appropriate application interval and amount of T. asperellum and B. subtilis that individually or in combination can effectively control RKNs and bacterial wilt in tomatoes were developed. Experiments were established with three application rates of a T. asperellum and B. subtilis (1 ml/L, 2 ml/L and 4 ml/L) and three application interval (3 days, 7 days and 14 days); tested alongside a positive check of Velum Total® (AI: Imidacloprid and Fluopyram) and a negative check where water was used. Bacillus subtilis was tested in the field, screen house and in-vitro whereas T. asperellum and the combination of the two BCAs were tested only in the screen house. The in-vitro trial aimed at determining the potential of B. subtilis to inhibit growth of R. solanacearum included a positive control of an antibiotic Chlortetracycline hydrochloride and water as the negative control. Trichoderma asperellum used at 4 ml/L water every 7 days was the most appropriate for the control of RKNs. However, use of B. subtilis at all the rates and intervals tested had a very low biocontrol efficacy against R. solanacearum. The strain of B. subtilis used did not effectively control bacterial wilt and hence not feasible for use against this particular pathogen at any of these application rates and intervals. When the two biocontrol agents were used in combination, RKNs were effectively managed but bacterial wilt disease was not effectively controlled.
-
ItemAssessing the socio-cultural determinants of adoption of biogas technology in Mpigi district, Uganda(Makerere University, 2021-10-11)The increasing energy poverty in Uganda is seen as a limitation to sustainable development. Hence attempts are made to disseminate and promote the relevance of clean renewable energy resources such as Biogas technology in Mpigi District to fulfill the domestic energy need. However, its use and uptake is still low and likely to keep dropping year after year. This gap prompted the study to assess the socio-cultural determinants of the adoption of biogas technology in Mpigi District. The study was to assess the determinants of adoption of biogas technology in Mpigi District and to assess the feasibility of biogas technology on the households in Mpigi District. The study obtained primary data with the help of questionnaires and interview checklists. Photography was used to show the types of biogas digesters installed. Random and purposive sampling techniques were used to select the respondents. The mean, frequency and percentages described the characteristics of the households. Multiple linear regression model in SPSS was used given by equation 2. Results indicated that education level, income level, access to subsidies, proximity of the farm and cattle heads were found significant with positive and negative beta coefficient on the adoption of Biogas technology. The classification of adopters in the study was consistent with the assumptions of the Diffusion of Innovation Theory hence categories such as; innovators (17.8%), early adopters (25.7%), early majority (33.7%), late majority (15.8%) and laggards (6.9%), were identified. Cost-benefit analysis with the help of Net Present Value and Benefit Cost Ratio were used to analyze the profitability of 3 biogas digester capacities (6m3, 9m3, and 13m3). The Discount Rate of 7 % and the period of 20 years lifespan of biogas digesters were considered in the economic evaluation of each biogas digester. The 9m3 biogas digesters were found as the most profitable with the highest Benefit Cost Ratio=7.8, 6.5 for 6m3 and 2 for 13m3. Besides, 6m3 mostly dominate the area for being affordable in terms of dung and costs required. In addition, estimations indicated Mpigi Town Council with a total reduction of 182,613 kg CO2e from biogas use in a year, better than other Sub Counties. The study highlighted the need for the government to promote 9m3 biogas digester if adopters are to benefit from biogas technology and increase access to subsidies and credit to potential adopters to reduce on initial costs by the government policy makers and biogas companies. The study recommends further research on why biogas from other (human excreta and pig manure) feedstock are less utilized at the household level.
-
ItemLecheate physico-chemical parameters removal efficiency and possible alternative treatment options to Kiteezi landfill treatment facility(Makerere University, 2021-09)Sanitary landfills generate large quantities of highly polluted leachate, which is a major environmental, economic and social concern. Further, the treatment of landfill leachate constitutes a challenge that may vary considerably depending on the age of the landfill. This study was aimed at evaluating the removal efficiency and determine a best treatment option for the landfill leachate to meet Uganda's national standards for safe effluent discharge to the surrounding environment. The specific objectives were to; determine the efficiency of the current treatment plant at Kiteezi in terms of leachate quality and determine the best treatment option for the treatment of the leachate from the Kiteezi landfill. The performance evaluation of the Kiteezi activated sludge facility included, a weekly assessment of the physico-chemical parameter reduction efficiency of the raw, and treated leachate from March 5 to July 23, 2020. The best treatment option was established by comparing two treatment options: lateritic soil and activated carbon amended with sand, by varying the combination of their particle sizes (0.25-0.5 mm, 0.5-1 mm, and 1-4 mm) with their column lengths (30 cm, 45 cm, 60 cm, and 75 cm).The study showed that the current Kiteezi landfill activated sludge treatment was only effective for the treatment of the turbidity (90.4 ± 6.4 %). This was due probably to the halving of the total phosphorus (TP) and total suspended solids (TSS), which were very high in the raw leachate. For other Physico-chemical parameters, the values in the effluent increased. For example, the value of the pH was 8.75 ± 0.13 at the inlet and 9.67 ± 0.17 at the outlet. The concentration of total nitrogen (TN) was 190 ± 50.2 mg/L and increased to 6,749 ± 1,595 mg/L. For the chemical oxygen demand (COD) and the color of the leachate, their values remained more or less the same before and after treatment; color was 15,182 ± 2,649 PtCo at the inlet and 16,008 ± 1,710 PtCo at the outlet, and COD was 31,362 ± 5,844 mg/L at the inlet and 32,218 ± 963 mg/L at the outlet. This poor treatment efficiency could be due to the composition of the sludge as well as the lack of oxygen in the aeration tank. For the best treatment option, this study showed that lateritic soil was more effective than activated carbon in reducing all the Physico-chemical parameters of the leachate. The effluent quality met the effluent discharge standards set by the National Environment Management Authority of Uganda. The maximum reduction efficiency was achieved with the combination column length of material of 75 cm associated with particle size range 0.25-0.5 mm.