Browsing by Author "Buah, Stephen"

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    Analysis of Genetic Diversity of Banana Weevils (Cosmopolites sordidus) (Coleoptera: Curculionidae) Using Transcriptome-Derived Simple Sequence Repeat Markers
    (Journal of Economic Entomology, 2022) Milton, Ali; Muhanguzi, Dennis; Male, Allan; Kajubi, Ali; Buah, Stephen; Kubiriba, Jerome; Tumuhimbise, Robooni
    The banana weevil, Cosmopolites sordidus (Germar) (Coleoptera: Curculionidae) is an economically important insect pest of bananas. It causes up to 100% yield losses and substantial lifespan reduction in bananas. Advances in genomics, proteomics, and sequencing technologies have provided powerful pathways to genotyping disastrous pests such as C. sordidus. However, such technologies are often not available to the majority of rural subtropical African banana growers and pest control managers. This study was therefore motivated by the need to create cheap and easily accessible C. sordidus genotyping methods that could be deployed by banana pest control managers to the benefit of C. sordidus control programs in the tropics where such advanced technologies are not readily accessible. We used an in-house C. sordidus transcriptome from the an-ongoing study from which we mined an array of simple sequence repeat (SSR) markers. Of these, six highly polymorphic transcriptome-derived SSR markers were used to successfully genotype within and among banana weevil population genetic diversity of 12 C. sordidus populations collected from four bananagrowing agro-ecological zones (AEZs) in Uganda. The developed transcriptome-derived SSR markers can be used by researchers in population genetics for characterization of the C. sordidus and identification of new genes that are linked to traits of particular interest. The significant genetic diversity revealed in C. sordidus provides pertinent information for integrated pest management strategies.
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    Biofortified East African Highland Bananas to Alleviate Vitamin A Deficiency in Uganda
    (Gates Open Res, 2019) Buah, Stephen; Tindamanyire, Jimmy M.; Namanya, Priver; Kubiriba, Jerome; Paul, Jean-Yves; Dale, James L.; Tushemereirwe, Wilberforce
    Micronutrient deficiency, also referred to as hidden hunger, is a global public health problem that affects over two billion people (Tulchinsky, 2010). In Uganda, micronutrient deficiency is the third most important public health problem after HIV/AIDS and malaria. Vitamin A deficiency (VAD) and Iron Deficiency Anaemia (IDA) are the major causes of anaemia in Uganda. VAD affects 20-35% of children below five years of age and the same proportion of women of child-bearing age. The aim of the Banana 21 project is to alleviate vitamin A deficiency through biofortification of Uganda’s major staple food, banana.
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    Genetic diversity of aflatoxin-producing Aspergillus flavus isolated from groundnuts in selected agroecological zones of Uganda
    (BMC microbiology, 2020) Acur, Amos; Arias, Renée S.; Odongo, Steven; Tuhaise, Samuel; Ssekandi, Joseph; Muhanguzi, Dennis; Adriko, John; Buah, Stephen; Kiggundu, Andrew
    Background Aspergillus is the main fungal genus causing pre- and post-harvest contamination of groundnuts. Aspergillus flavus belongs to section Flavi, a group consisting of both the aflatoxigenic species (A. flavus, A. parasiticus and A. nomius) and non-aflatoxigenic species (A. oryzae, A. sojae and A. tamarii). Aflatoxins are food-borne toxic secondary metabolites produced by Aspergillus species, causing hepatic carcinoma and stunting in children and are the most toxic carcinogenic mycotoxins ever identified. Despite the well-known public health problems associated with aflatoxicosis in Uganda, information about the genetic diversity of the main aflatoxin causing fungus, Aspergillus flavus in this country is still limited. Results A cross-sectional survey was therefore carried out in three main groundnut-growing agro-ecological zones (AEZs) of Uganda; West Nile farming system, Lake Kyoga basin mixed farming system and Lake Victoria basin farming system. This was to assess the genetic diversity of A. flavus and to establish the contamination rates of groundnuts with Aspergillus species at pre- and post-harvest stages. Out of the 213 A. flavus isolates identified in this study, 96 representative isolates were fingerprinted using 16 insertion/deletion microsatellite markers. Data from fingerprinting were analyzed through Neighbor Joining while polymorphism was determined using Arlequin v 3.5. The pre- and post-harvest contamination rates were; 2.5% and 50.0% (West Nile farming system), 55.0% and 35.0% (Lake Kyoga basin mixed farming system) and 32.5% and 32.5% (Lake Victoria basin farming system) respectively. The Chi-square test showed no significant differences between pre- and post-harvest contamination rates among AEZs (p = 0.199). Only 67 out of 96 isolates produced suitable allele scores for genotypic analysis. Analysis of genetic diversity showed higher variation within populations than among populations. Two major clusters (aflatoxigenic and non-aflatoxigenic isolates) were identified as colonizing groundnuts at pre- and postharvest stages. Conclusions These findings provide a first insight on the existence of non-aflatoxigenic strains of A. flavus in Uganda. These strains are potential candidates for developing local Aspergillus biocontrol agent.
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    Genetic variation, Heritability estimates and GXE effects on yield traits of Mesoamerican common bean (Phaseolus vulgaris L) germplasm in Uganda
    (Plant Genetic Resources, 2018) Okii, Dennis; Mukankusi, Clare; Sebuliba, Sulaiman; Tukamuhabwa, Phinehas; Tusiime, Geoffrey; Talwana, Herbert; Odong, Thomas; Namayanja, Annet; Paparu, Pamela; Nkalubo, Stanley; Otim, Michael; Ugen, Michael; Buah, Stephen; Gepts, Paul
    Germplasm of common beans from the Mesoamerican gene pool races: Durango, Jalisco, Mesoamerica and Guatemala have highest genetic variation for the crop’s improvement. The objective was to assign 50 common bean germplasm in Uganda into its gene pool races based on analyses of population structure. Secondly, to estimate heritability and effects of genotype environment (GXE) interaction on common bean agronomic and yield traits in space and time. Sample genomic DNA was amplified in 2011 with 22 Simple sequence repeat markers (SSRs) and alleles separated using capillary electrophoresis. Field evaluations were conducted in 2010 and 2011 at NaCRRI and 2015 at CIAT – Kawanda. Multivariate analyses of SSRs data identified four subgroups within the germplasm: K4.1–K4.4, with corresponding Wrights fixation indices (FST) as 0.1829 for K4.1, 0.1585 for K4.4, 0.1579 for K4.2 and least for K4.3 at 0.0678. Gene pool race admixtures in the population (14%) were notable and attributed to gene flow. Four superior parents currently used in improving resistance to major diseases grouped as; Jalisco for MLB49-89A; Mesoamerica for MCM5001 and G2333; Durango for MEXICO 54. Heritability values for yield traits estimated using phenotypic data from above fixed parents, was above 0.81. Season and location had significant effect (P < 0.05) on numbers of: flower buds per inflorescence, pod formation and weight of 100 seeds. The findings will improve understanding of co-evolutionary relationships between bean hosts and pathogens for better disease management and will broaden the germplasm base for improving other tropical production constraints.
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    Pro-vitamin A carotenoid content of 48 plantain (Musa AAB genome) cultivars sourced from eastern Democratic Republic of Congo
    (Theoretical medicine and bioethics, 2008) Blomme, Guy; Ocimati, Walter; Nabuuma, Deborah; Sivirihauma, Charles; Davey, Mark; Buah, Stephen; Bergh, Inge Van den; Vutseme, Lusenge; Bahati, Liliane; Ekesa, Beatrice
    Vitamin A deficiency (VAD) is widespread in sub-Saharan Africa (SSA). Unlike in developed countries, where the main source of vitamin A comes from meat, the diet of poor populations in SSA is largely plant based. It is thus important to identify local / popular plants with higher vitamin A content for combating VAD. Banana (including plantains) is an important staple food crop in this region. The identification and promotion of vitamin A-rich banana cultivars could contribute significantly to the alleviation of VAD in areas heavily dependent on the crop.We assessed pro-vitamin A carotenoid (pVACs) content in the fruit pulp of 48 local plantains from eastern Democratic Republic of Congo, to identify cultivars that could help reduce VAD, especially among young children and women of reproductive age. RESULTS: Mean pVACs content varied from 175–1756 𝛍g/100 gfw in ripe fruits. Significant increases (P <0.001) in total pVACs content occurred after ripening in all cultivars except ‘UCG II’. Retinol activity equivalents (RAE) in ripe fruits ranged from 12–113 𝛍g/100 gfw. Fifteen plantain cultivars, including ‘Adili II’, ‘Nzirabahima’, ‘Mayayi’, ‘Buembe’,and‘Sanza Tatu’ (associated with RAE values of 44 𝛍g/100 gfw and above) can be considered as good sources of pVACs. Modest consumption (250 or 500 gfw) of the fruit pulp of the five best plantain cultivars at ripening stage 5meets between 39–71% and 44–81% of vitamin A dietary reference intake (DRI) respectively, for children below 5 years old and women of reproductive age. CONCLUSION: The 15 best plantain cultivars (especially the top 5) could potentially be introduced / promoted as alternative sources of pro-vitamin A in banana-dependent communities, and help to reduce cases of VAD substantially.
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    The quest for golden bananas: Investigating carotenoid regulation in a Fe’i group Musa cultivar
    (Journal of agricultural and food chemistry, 2016) Buah, Stephen; Mlalazi, Bulukani,; Khanna, Harjeet,; Dale, James; Mortimer, Cara
    The regulation of carotenoid biosynthesis in a high carotenoid accumulating Fe’i group Musa cultivar, ‘Asupina’, has been examined and compared to that of a low carotenoid accumulating cultivar, ‘Cavendish’, to understand the molecular basis underlying carotenogenesis during banana fruit development. Comparisons in the accumulation of carotenoid species, expression of isoprenoid genes and product sequestration are reported. Key differences between the cultivars include greater carotenoid cleavage dioxygenase 4 (CCD4) expression in ‘Cavendish’ and the conversion of amyloplasts to chromoplasts during fruit ripening in ‘Asupina’. Chromoplast development coincided with a reduction in dry matter content and fruit firmness. Chromoplasts were not observed in ‘Cavendish’ fruits. Such information should provide important insights for future developments in the biofortification and breeding of banana.