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ItemPre-and post-flowering drought resistance and recovery strategies of sorghum(Makerere University, 2025)With ongoing climate change, characterized by increasing frequency and intensity of droughts, developing drought-adaptable crops has become a critical focus in recent decades. Sorghum, a key crop for addressing food and nutritional insecurity, is particularly vulnerable to both pre- and post-flowering drought under rain-fed farming systems. Effective screening and phenotyping techniques are essential for breeding drought-resilient sorghum varieties. This study aimed to generate knowledge for the selection of drought-adaptable sorghum genotypes for targeted use in drought resilience breeding. Specifically, it sought to (i) determine the response of sorghum genotypes to pre- and post-flowering drought stress and (ii) determine the response of selected genotypes to rewatering after drought. In the screen house, eighty sorghum genotypes from the national sorghum breeding program were assessed under different moisture regimes. The moisture regimes included: well-watered, pre-flowering drought and post-flowering drought, arranged as a split-plot design with watering regimes as whole plots, while sorghum genotypes as subplots, with three replications. Subsequently, a field trial arranged as a 10 x 8 alpha-lattice with three replications was established at Nabuin-ZaRDI-Karamoja to assess the effect of natural drought on the entire sorghum trial population. A subsequent screenhouse experiment assessed the drought recovery potential of sixteen selected genotypes and two checks, subjecting them to drought stress followed by rewatering. Results showed that pre-flowering drought was more detrimental, reducing yield by 98%, compared to a 76% yield reduction due to post-flowering drought. Key traits for pre-flowering drought resistance included higher chlorophyll content, larger green leaf area, reduced biomass yield and a higher survival ability. In contrast, plant height, low relative growth, reduced leaf inclination angle, flag leaf dimensions and genotype’s good agronomic robustness (plant vigour and agronomic score) were associated with post-flowering drought resistance. Leveraging drought selection indices and survival probabilities, genotypes were ranked by resistance. Genotypes ASARECA 13-1 x Framida -1-1-3-1/2022B, ICSX 162719-1-4-1-1-1, ICSX152666-B-2-7-3-1-1-1, SSGA/RAP/349 and IESV16 143-1-3-1 exhibited superior resistance to both pre- and post-flowering drought. Strong recovery abilities along with high breeding values were observed in genotypes ASARECA 13-1 x Framida -1-1-3-1/2022B, NAROSORGH1 x NAROSORGH3-1-1-5-1/2022B, ASARECA 13-1 x NAROSORGH3-1-1-1-1/2022B, GE16/2/20B x IESV92041SH (SSEA 18B#6) and NAROSORGH1 x NAROSORGH3 -1-1-1-1/2022B, whereas IESV 214006DL and ICSX152005-SB-5-3-2-1 were highly susceptible and showed the poorest recovery. Notably, genotypes ASARECA 13-1 x Framida -1-1-3-1/2022B, ASARECA 13-1 x NAROSORGH3-1-1-1-1/22B and ICSX152666-B-2-7-3-1-1-1 combined both strong resistance and robust recovery, making them promising parental lines for breeding drought-adaptable sorghum, while the most susceptible genotypes may serve as local negative checks.
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ItemSoil erosion tolerance rates in contrasting land uses and soil types in the Rwenzori Highlands of Uganda(Makerere University, 2026)Soil erosion is a primary factor contributing to environmental deterioration in the 21st century. High erosion rates experienced in the Rwenzori highlands undermine the soils' capacity to sustain productivity once the soil loss tolerance threshold is surpassed. Erosion rates differ across different land uses and soil types, and how these variations relate to soil loss tolerance thresholds remains poorly understood in the region. This study, therefore, aimed to assess the soil erosion tolerance thresholds of Ferralsols and Andosols under different agricultural land uses in the upper slopes of the Rwenzori highlands. Two case studies with the quasi-experimental research design were used in this research: one case study done in Kabarole on Andosols and the other in Kasese on Ferralsols, both under annual, woodland, grasslands, and perennial land use at slopes between 25% and 27%. Soil erosion rates were estimated using the RUSLE and measured using closed runoff plots. Runoff samples were collected after every rainfall event for 12 months. Soil loss tolerance thresholds were determined from a method developed by the USDA, which uses favourable rooting depth and bio-physical soil properties (bulk density, soil erodibility, pH, organic carbon, and infiltration rate) linked to erosion. While using runoff plots, Andosols had the highest mean erosion rate in annual land use (14.21 ± 2.15 tha-1yr-1) at 26% slope and the lowest in woodlands (7.06 ± 3.78 tha-1yr-1) at 25% slope. Similarly, Ferralsols had the highest mean erosion rate in annual land use (8.50 ± 1.26 tha-1yr-1) at 26% slope, and the lowest in woodlands (4.49 ± 2.05 tha1yr-1) at 27% slope. Mean erosion rates estimated with the RUSLE were highest in annuals under Andosols at 26% slope (78.33 ± 5.36 tha-1yr-1) and were lowest in woodlands under Ferralsols at 27% slope (2.52 ± 0.26 tha-1yr-1). There are evident disparities between observed soil loss from runoff plots and estimations from the Revised Universal Soil Loss Equation (RUSLE). The average tolerance thresholds of Andosols were highest in grasslands (11.67 ± 1.29 tha-1yr-1) at 27% slope and lowest in annual (8.33 ± 1.29 tha-1yr-1) at 26% slope. For Ferralsols, the tolerance thresholds were highest (8.75 ± 1.37 tha-1yr-1) and lowest (6.25 ± 1.37 tha-1yr-1) in grasslands at 26% slope and perennials at 25% slope, respectively. Although annual land use was the only land use with soil erosion rates exceeding tolerance thresholds, grasslands, woodlands, and perennials are at risk of losing productivity due to the very small margin left for the erosion rates to exceed the tolerance thresholds. Thus, the soils in this study are vulnerable to degradation in the future. Therefore, there is a critical need to implement sustainable land management practices in order to curb degradation and prevent further soil erosion and future threshold exceedance.
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ItemVulnerability of indigenous chicken scavenging production system to climate variability(Makerere University, 2026-01-11)Indigenous chickens (ICs) reared under scavenging production system are central to food security and poverty alleviation among rural households in Uganda. However, climatic variability threatens their productivity by altering the availability and quality of scavengeable feed resources and compromising chicken welfare. Farmers’ limited ability to modify the open scavenging environment further heightens chickens’ vulnerability to environmental fluctuations. This study assessed farmers’ knowledge and perceptions of climate variability, its effects on indigenous chickens, coping strategies employed, and factors influencing adoption of these strategies. It further evaluated seasonal variation in Scavengeable Feed Resources (SFR) and examined the effects of elevated ambient temperature on the physiology and thermoregulatory behavior of ICs. Data were collected in Soroti District through a cross-sectional survey of 271 indigenous chicken farmers, 10 key informant interviews, four focus group discussions, and analysis of local climate records (2003–2022). In addition, 120 ICs aged 4–5 months were obtained across four seasons for crop content characterization and chemical analysis. Two indigenous chicken ecotypes one from the cooler Kabale (KAB) and the other from the hotter Soroti (SOR) regions were assessed for thermal responses. These pullets were sequentially exposed to ambient temperatures of 30, 33, 36, and 39 °C in a controlled heat chamber, with thermoregulatory behaviors recorded and rectal temperature measured. Quantitative data were analyzed using descriptive statistics, chi-square tests, ordered probit regression, the Modified Mann–Kendall test, and linear mixed-effects models, while qualitative data were analyzed thematically. Most farmers perceived decreases in annual rainfall (63.8%) and rainy-season duration (>50%), alongside increases in dry (91.1%) and rainy-season (71.2%) temperatures and drought frequency (79.3%). Meteorological data showed a significant rise in monthly minimum temperatures but no significant trends in rainfall or average and maximum temperatures. Farmer perceptions of rising temperatures aligned with observed minimum temperature trends, while perceived rainfall declines did not. Perceived impacts of high temperature on ICs included reduced egg production (56%), hatchability (63.4%), increased disease incidence (58.6%), and higher mortality (45.1%). Coping strategies mainly involved provision of drinking water, shade, and feed supplementation, with adoption significantly influenced by gender, age, flock size, weather information access, training in poultry management and resource access. Seasonal variation significantly (P<0.05) affected feed availability and quality. Insects dominated (P=0.032) crop contents, with higher proportions during wet seasons which was followed by food waste, while dry seasons had more cereals and legumes. Nutrient levels in crop contents were generally below age-specific requirements for protein, calcium, and metabolizable energy during the first dry season and both wet seasons. Whereas crude fiber consistently exceeded recommended levels. Thermoregulatory responses differed by ecotype, with KAB chickens exhibiting earlier and longer heat-dissipating behaviors and greater increases in body temperature than SOR chickens. Overall, climatic variability imposes both nutritional and thermal stress on indigenous chickens, increasing their vulnerability under the scavenging production system. The findings highlight the need for integrated adaptation strategies, including climate literacy, localized weather information, season-specific low-fiber feed supplementation, provision of cool, clean drinking water under shaded areas, and practical training in climate-resilient poultry management to enhance the resilience of IC scavenging production system.
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ItemPhenotypic variation and genetic diversity of East African sandalwood trees (Osyris lanceolata Hochst. & Steud.) in Uganda(Makerere University, 2025)East African Sandalwood tree (Osyris lanceolata Hochst. & Steud) is an aromatic tree species at risk of extinction due to over-exploitation for its essential aromatic oil. Moreover, limited information on its phenotypic variation, genetic diversity, and population structure, is a great impediment to its effective management in Uganda. Thus, the objectives of this study were (i) to characterize phenotypic variation and (ii) to estimate the level of genotypic diversity and population structure within and among O.lanceolata populations in Uganda. Samples were taken from three (3) natural populations in Amudat, Moroto, and Nakapiripirit districts. Eight (8) phenotypic traits were used to characterize the variation, while 5 SSR markers were optimized to estimate the level of genetic diversity and population structure. Phenotypic data were analyzed using R, FigTree and PAST software. Significant differences were revealed in 3 of the 8 traits, including LAA, LL, and LW. Trees in Moroto and Amudat districts were the tallest. LL and LW had the greatest contribution in differentiating phenotypes. Significant correlations were found between RCD and TH, CD, LL, and PL. The genetic data analysis was done using GenAlEx 6.5, Power Marker, FigTree, and PAST software. At the locus level, all genetic diversity indices were high (Ne=1.971, Na=2, Hs=0.493, Fis=-0.020, Fst=0.006, Nm=50.89). At the population level, the means of all genetic diversity indices ranged from moderate to high (Na = 2, Ne = 1.48, I = 0.48, %P = 100%). Based on the Shannon index, Amudat and Moroto populations showed the highest level of genetic diversity; Amudat (I=0.372, h=0.55, %P=100%); Moroto (I=0.48, h=0.31, %P = 100%). There was more variation (98%) within populations compared to variation among populations (2%), and differentiation was low (PhiPT=0.023). The ΔK was plotted against various values of K, and the optimum value of K was 4, indicating that 4 was the most likely number of clusters. The high level of genetic diversity is attributed to the outcrossing nature of Osyris lanceolata and gene flow. The lowest level of genetic divergence was observed between Amudat and Nakapiripirit populations, while the highest level of divergence was observed between Moroto and Nakapiripirit populations. The Moroto and Amudat populations have shown a unique genetic signature and should be managed as in situ conservation areas. Meanwhile, an ex-situ conservation program should also be initiated, targeting healthy trees from all populations. Key words: Conservation, Genetic differentiation, Genetic diversity, Molecular markers, Osyris lanceolata, phenotypic traits, Variation.
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ItemFinger millet host plant resistance and associated changes in plant metabolites as a response to blast disease infection(Makerere University, 2025)Finger millet blast, caused by fungus Magnaporthe grisea, is a highly devastating disease affecting all growth stages and causing a severe economic impact on the crop. Host plant resistance remains the most cost-effective and reliable management strategy. This study aimed at (i) determining new stable sources of blast resistance in selected finger millet genotypes in Uganda, and (ii) determining finger millet metabolites produced in response to infection by Magnaporthe grisea on susceptible and resistant genotypes. For the first objective, ninety-seven diverse finger millet genotypes were evaluated for resistance to leaf, neck, and finger blast across two locations (NaSARRI and Ikulwe) during the 2023A and 2023B seasons, using an alpha-lattice design with three replications in 2-meter row plots. For the second objective, a screen-house experiment was conducted using three finger millet varieties (resistant, moderately resistant, and susceptible) selected from field evaluations and arranged in a completely randomized design (CRD) with three replications. Controlled pathogen inoculation was done, and blast-infected tissues (leaf, neck, and finger) were sampled at seedling, booting, flowering, and maturity stages for metabolite analysis using spectrophotometry and HPLC. Disease severity was assessed periodically using a 1-9 scale for leaf blast, 1-5 for neck, and visual percentage of blast florets for finger blast that was adjusted to a 1-5 scale. These were later converted to Area Under Disease Progress Curve (AUDPC) before analysis. A significant variation was observed across genotypes, and genotype by environment (GxE) interaction, for leaf, neck, and finger blast severity. The stability analysis revealed twenty-two finger millet genotypes with stable resistance to at least leaf, neck, and/or finger blast. The selected finger millet genotypes demonstrated a significant difference in metabolite concentrations across the different sampling times with progress in blast infection. The study further identified saponins, salicylic acid (SA), and phenolics such as tannins, among others, as key metabolites associated with low blast severity in finger millet. These accumulated at higher levels in resistant and moderately resistant genotypes relative to the susceptible one. The study therefore, identifies new stable blast resistance and key biochemical indicators that may guide breeding efforts for disease resistance in finger millet.