Browsing by Author "Nakabonge, Grace"
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Item Celoporthe Dispersa gen. et sp. nov. from Native Myrtales in South Africa(Studies in Mycology, 2006) Nakabonge, Grace; Gryzenhout, Marieka; Roux, Jolanda; Wingfield, Brenda D.; Wingfield, Michael J.In a survey for Cryphonectria and Chrysoporthe species on Myrtales in South Africa, a fungus resembling the stem canker pathogen Chrysoporthe austroafricana was collected from native Syzygium cordatum near Tzaneen (Limpopo Province), Heteropyxis canescens near Lydenburg (Mpumalanga Province) and exotic Tibouchina granulosa in Durban (KwaZulu-Natal Province). The fungus was associated with dying branches and stems on S. cordatum, H. canescens and T. granulosa. However, morphological differences were detected between the unknown fungus from these three hosts and known species of Chrysoporthe. The aim of this study was to characterise the fungus using DNA sequence comparisons and morphological features. Pathogenicity tests were also conducted to assess its virulence on Eucalyptus (ZG 14 clones), H. natalensis and T. granulosa. Plants of H. canescens were not available for inoculation. Results showed distinct morphological differences between the unknown fungus and Chrysoporthe spp. Phylogenetic analysis showed that isolates reside in a clade separate from Chrysoporthe and other related genera. Celoporthe dispersa gen. et sp. nov. is, therefore, described to accommodate this fungus. Pathogenicity tests showed that C. dispersa is not pathogenic to H. natalensis, but that it is a potential pathogen of Eucalyptus and Tibouchina sppItem A Deep Learning-based Detector for Brown Spot Disease in Passion Fruit Plant Leaves(arXiv preprint arXiv, 2020) Katumba, Andrew; Bomera, Moses; Mwikirize, Cosmas; Namulondo, Gorret; Ajeroy, Mary Gorret; Ramathaniy, Idd; Nakayima, Olivia; Nakabonge, Grace; Okello, Dorothy; Serugunda, JonathanPests and diseases pose a key challenge to passion fruit farmers across Uganda and East Africa in general. They lead to loss of investment as yields reduce and losses increases. As the majority of the farmers including passion fruit farmers, in the country are smallholder farmers from low-income households, they do not have sufficient information and means to combat these challenges. While, passion fruits have the potential to improve the well-being of these farmers given their short maturity period and high market value [1], without the required knowledge about the health of their crops, farmers can not intervene promptly to turn the situation around. For this work, we partnered with the Uganda National Crop Research Institute (NaCRRI) to develop a dataset of expertly labeled passion fruit plant leaves and fruits, both diseased and healthy. We made use of their extension service to collect images from five districts in Uganda to create the dataset. Using the dataset, we are applying state-of-the-art techniques in machine learning, specifically deep learning at scale for object detection and classification for accurate plant health status prediction. While deep learning techniques have been applied to various disease diagnosis contexts with varying degrees of success([2], [3], [4], [5], [6]), there has not been any significant effort, to the best of our knowledge, to create a dataset or apply machine learning techniques to passion fruits despite their obvious financial benefits. With this work, we hope to fill this gap by generating and making publically available an image dataset focusing on passion fruit plant diseases and pest damage and training the first generation of machine learning-based models for passion fruit plant disease identification using this dataset. The initial focus is on the locally prevalent woodiness (viral) and brown spot (fungal) diseases.Item Diversity of Arbuscular Mycorrhizal Fungi Associated with Maize in the Eastern Part of Uganda(MDPI, 2022) Fall, Abdoulaye Fofana; Nakabonge, Grace; Ssekandi, Joseph; Founoune-Mboup, Hassna; Badji, Arfang; Balde, Issa; Ndiaye, Pape MalickImproving maize yield is an utmost important objective for food security in Uganda. In the evaluation of soil microorganisms to crop production, it is important to assess the composition and diversity of Arbuscular Mycorrhizal Fungi (AMF) species at different agroecosystems. AMF play an important role in improving crop growth and yield. We present a study of the morphological diversity of native AMF species associated with the rhizosphere of maize in two locations in eastern Uganda (Amuria and Serere districts). The effects of soil chemical properties on this diversity were also assessed. AMF diversity was assessed by morphological identification of the spores extracted from soils samples by the wet sieving method. Spores abundance, species richness, and diversity were determined. A total of 19 AMF morphotypes were distributed in 7 genera (Gigaspora, Scutellospora, Glomus, Acaulospora, Archaospora, Entrophosporaa, and Paraglomus) were observed. Glomus species were abundant in all sites. Spores densities were higher in Amuria than in Serere. Soil pH, CEC, and phosphorus content influenced AMF distribution. Finding the species in various agroecological environments indicates that they are adapted to the environments. Maize grown in eastern Uganda is associated with a diversity of AMF that could be selected as a bio-fertilizer to improve crop production.Item Fat Content and Fatty Acid Profiles of Shea Tree (Vitellaria paradoxa subspecies nilotica) Ethno-Varieties in Uganda(Forests, Trees and Livelihoods, 2012) Gwali, Samson; Nakabonge, Grace; Okullo, John Bosco Lamoris; Eilu, Gerald; Forestier-Chiron, Nelly; Piombo, Georges; Davrieux, FabriceFat content and fatty acid composition are important nutritional properties of shea fruits. Farmers in Uganda report the presence of local shea tree ethno-varieties, but it is necessary to investigate their relative fat content and fatty acid composition to evaluate the economic importance of these ethno-varieties. Near infrared spectrophotometry (NIRS) was used to determine the fat content as well as the fatty acid composition of 44 ethno-varieties. Wet chemistry (soxtec petroleum – ether fat extraction and gas chromatography) methods were used to validate the results from NIRS. Fat content ranged from 43.9% to 58.4% while fatty acid composition was dominated by oleic (47–62%) and stearic acid (25–38%). Other fatty acids present were palmitic, vaccenic, linoleic, linolenic and arachidic acids. There was no significant difference in stearic, palmitic and oleic acid composition between ethno-varieties. However, significant variation of fat content, vaccenic and linoleic acids was observed between some ethno-varieties, perhaps due to locality, climatic and tree-to-tree differences. These findings can be utilized for the selection of ethno-varieties that are suitable for commercial production of shea oil in Uganda.Item Folk Classification of Shea Butter Tree (Vitellaria paradoxa subsp. nilotica) Ethno-varieties in Uganda(Ethnobotany research and applications, 2011) Gwali, Samson; Okullo, John Bosco Lamoris; Eilu, Gerald; Nakabonge, Grace; Nyeko, Philip; Vuzi, PeterFolk knowledge has been the basis for selection and improvement of many food crops such as potatoes, sorghum, yams, cassava and rice. In Uganda, there is strong potential to utilize folk knowledge to select and domesticate the shea butter tree (Vitellaria paradoxa C.F. Gaertn.subsp. nilotica (Kotschy) A.N. Henry & Chithra & N.C. Nair), an important economic tree species. Farmers report high variation in fruit yield, tree form and pulp taste. In this study, we documented shea tree folk classification by interviewing 300 respondents, 15 focus groups and 41 key informants across three farming systems of Uganda. Data were analyzed using Kruskall-Wallis and Spearman’s tests, Chi-square, Multivariate, Factor and Discriminant Function Analyses. Folk classification and nomenclature of shea tree ethno-varieties is based on fruit/nut organoleptic (color and taste) and morphological attributes. Interestingly, despite the socio-cultural importance of shea oil, it does not feature as a factor in the folk classification and nomenclature of shea tree ethno-varieties. There was no significant difference in classification knowledge across the three farming systems (Kruskal – Wallis χ2 = 28, df = 28, p > 0.05; Spearman’s R > 0.8, p < 0.0001) although there was significant influence from ethnicity of the respondents (Pillai’s trace = 0.817, p < 0.001). While this study provides a record of shea tree ethno-varieties and associated classification criteria, there is need to validate these ‘ethno-varieties’ using detailed morphological, biochemical and molecular analyses.Item Genetic Diversity in Shea Tree (Vitellaria Paradoxa Subspecies Nilotica) Ethno-Varieties in Uganda Assessed with Microsatellite Markers(Forests, Trees and Livelihoods, 2015) Gwali, Samson; Vaillant, Alexandre; Nakabonge, Grace; Okullo, John Bosco Lamoris; Eilu, Gerald; Muchugi, Alice; Bouvet, Jean-MarcShea trees (Vitellariaparadoxa C. F. Gaertn.) are classified locally into several folk or ethno-varieties by farmers in Uganda. It is, however, not clear whether this folk classification is supported by genetic differentiation between ethno-varieties. Genetically linked traits from folk classification are useful in conservation and breeding programmes. A total of 118 individual shea trees constituting 28 ethno-varieties sampled from three farming systems of Uganda were analysed using microsatellite markers. The number of alleles amplified per microsatellite locus ranged from 6 to 13 with an average of 9.5, with a total of 106 alleles identified. Observed (Ho) and expected heterozygosity (He) per locus ranged from 0.366 to 0.934 and 0.580 to 0.840, respectively. Mean Ho and He values for all loci across all ethno-varieties were 0.633 and 0.727, respectively. Analysis of molecular variance indicated that most of the variation (86.28%) occurred within individual trees; 11.25% was found among individual trees within ethno-varieties while 2.47% was found among ethno-varieties. The in-breeding index (f = 0.130), fixation index (θP = 0.025), gene flow value (Nm = 6.56) and cluster analysis show that all shea tree ethno-varieties were a single out-crossing population with very low genetic differentiation and high gene flow. The low differentiation in shea tree ethno-varieties was most likely due to the utilization of non-genetic traits in folk classification. However, while ethno-variety genetic structure was very weak, overall spatial population structure indicated the presence of three populations (West Nile, Northern and Teso). The West Nile population was more distantly related to the other two most likely due to isolation barriers such as the Rift Valley, Lake Albert and River Nile.Item Local Varieties of Cassava: Conservation, Cultivation and Use in Uganda(Environment, Development and Sustainability, 2018) Nakabonge, Grace; Samukoya, C.; Baguma, Y.The study explored the theory that on-farm conservation of cassava germplasm is influenced by farmers’ traditional and cultural preferences of particular varieties. Traditional knowledge practices that are used for on-farm conservation of cassava germplasm as well as cassava attributes for selection were assessed. The findings obtained from the study indicated that farmers use traditional knowledge to select and preserve cassava germplasm for future use. It was also clear that farmers have their preferences such as culinary attributes, storability in the ground, early maturity and cooking quality to mention but a few that influence the decisions taken to retain or abandon cultivation of varieties. Therefore, by planting varieties in multiples plots, replanting immediately after harvesting, sharing with others in the community and planting disease-free materials, farmers ensure that they preserve varieties of interest for decades. The information generated during this study could inform development policies tailored toward ensuring sustainable on-farm conservation of cassava genetic resources.Item Manual for Collection of Cassava Germplasm and Associated Farmer Knowledge in Eastern and Southern Africa(International Institute of Tropical Agriculture, Ibadan, Nigeria, 2014) Cox, T. Paul; Nakabonge, Grace; Ferguson, MoragCassava germplasm and associated farmer knowledge from southern, eastern and central Africa is under represented in national and international germplasm collections. This germplasm consists mainly of farmer varieties (landraces) which have been grown for many years and harbor valuable adaptive gene complexes that have evolved under human and environmental selection pressures. The current situation of lack of a repository means that (1) local landraces are not readily available to breeders (2) some farmer landraces contain genetic variation and are not ‘clonal’ as researchers and breeders assume, and no ‘type specimen’ exists so breeders are often not sure of what they are breeding with, (3) disease-free farmer landraces are not available, preventing the movement and sharing of germplasm, (4) landraces and the adaptive gene complexes they harbor are vulnerable to genetic erosion from the spread of improved varieties with increased breeding activities in the region and in the face of devastating diseases such as cassava brown streak disease which may cause the total loss of susceptible landraces, and (5) there is no germplasm database concerning the various attributes of particular clones, geographical location and farmer perceptions for use as a decision-making tool. This lack of ‘farmer-centric’ information means that breeders may not fully understand the subtleties of farmer preferences with implications for varietal adoption of improved germplasmItem Morphological Variation among Shea Tree (Vitellaria paradoxa subsp. nilotica) ‘Ethnovarieties’ in Uganda(Genetic resources and crop evolution, 2012) Gwali, Samson; Nakabonge, Grace; Okullo, John Bosco Lamoris; Eilu, Gerald; Nyeko, Philip; Vuzi, PeterVitellaria paradoxa C. Gaertn. (shea butter tree) is an indigenous African tree species that is widely distributed in the dry areas of northern and eastern Uganda. The species is widely known for its oil which is used in cooking, cosmetics and traditional medicine. Local folk classification recognises the presence of different ethno-varieties on the basis of fruit and nut characters. In the present study, 176 trees representing 44 ethno-varieties from three farming systems of Uganda were assessed to determine the patterns of morphological variation and establish the congruence between morphological variation and folk classification. The results show high variation in pulp weight (CV = 35.9 %), stem diameter (CV = 28.48 %), fruit weight (CV = 27.81 %) and canopy diameter (CV = 26.69 %). There was a strong positive correlation between pulp and fruit weight (r = 0.963, p < 0.001), leaf length and leaf width (r = 0.652, p < 0.001) and between petiole length and leaf length (r = 0.788, p < 0.001). There was no underlying quantitative morphological structuring among the 44 ethno-varieties. Hierarchical cluster analysis using quantitative morphometric data produced three groups without clear aggregation based on ethnographic or geographic separation. However, a combination with qualitative traits as perceived by farmers provided good congruence with folk classification. Quantitative morphological data alone does not resolve any discrete forms of V. paradoxa that are related to folk classification. There is need to utilise biochemical and molecular markers to unravel the underlying variation for use in selection and improvement of shea butter tree ethno-varieties.Item Morphological variation among shea tree (Vitellaria paradoxa subsp. nilotica) ‘ethnovarieties’ in Uganda(Genetic resources and crop evolution, 2012) Gwali, Samson; Nakabonge, Grace; Lamoris Okullo, John Bosco; Eilu, Gerald; Nyeko, Philip; Peter, VuziVitellaria paradoxa C. Gaertn. (shea butter tree) is an indigenous African tree species that is widely distributed in the dry areas of northern and eastern Uganda. The species is widely known for its oil which is used in cooking, cosmetics and traditional medicine. Local folk classification recognises the presence of different ethno-varieties on the basis of fruit and nut characters. In the present study, 176 trees representing 44 ethno-varieties from three farming systems of Uganda were assessed to determine the patterns of morphological variation and establish the congruence between morphological variation and folk classification. The results show high variation in pulp weight (CV = 35.9 %), stemdiameter (CV = 28.48 %), fruit weight (CV = 27.81 %) and canopy diameter (CV = 26.69 %). There was a strong positive correlation between pulp and fruit weight (r = 0.963, p\0.001), leaf length and leaf width (r = 0.652, p\0.001) and between petiole length and leaf length (r = 0.788, p\0.001). There was no underlying quantitative morphological structuring among the 44 ethno-varieties. Hierarchical cluster analysis using quantitative morphometric data produced three groups without clear aggregation based on ethnographic or geographic separation. However, a combination with qualitative traits as perceived by farmers provided good congruence with folk classification. Quantitative morphological data alone does not resolve any discrete forms of V. paradoxa that are related to folk classification. There is need to utilise biochemical and molecular markers to unravel the underlying variation for use in selection and improvement of shea butter tree ethno-varieties.Item Pathogenicity of Teratosphaeria species on Eucalyptus grandis and selected hybrids in Uganda(Journal of Forest Research, 2021) Syofuna, Agatha; Nakabonge, Grace; Namayengo, Sarah; Tumwebaze, Susan; Banana, AbwoliTeratosphaeria stem canker is one of the most important diseases to have emerged on non-native plantation-grown Eucalyptus trees cultivated globally. The study assessed the pathogenicity of two Teratosphaeria species associated with Teratosphaeria stem canker and the susceptibility of Eucalyptus grandis and six commonly grown Eucalyptus hybrids to these fungal species in Uganda. The inoculation trials indicated that Eucalyptus species and hybrids were susceptible to fungal pathogens used. A comparison of Eucalyptus species and hybrids for each fungal species showed that GC 540 and GC 796/2 are the most susceptible hybrids to T. zuluensis and T. gauchensis respectively while hybrid clone GU 8 had a higher tolerance to both fungal species. GC 540 was also tolerant to T. gauchensis while F2 and GC 550 were tolerant to T. zuluensis. Eucalyptus grandis sourced from Australia (F2) showed a higher tolerance than Eucalyptus grandis from South Africa (F1). The results further revealed that both Teratosphaeria zuluensis and Teratosphaeria gauchensis are pathogenic to Eucalyptus species and hybrids. The generated information indicates that there is an opportunity to sustainably manage Teratosphaeria stem canker disease if tolerant species are grown in areas with high disease impact.Item Population Structure of the Fungal Pathogen Holocryphia Eucalypti in Australia and South Africa(Australasian Plant Pathology, 2008) Nakabonge, Grace; Burgess, Treena; Gryzenhout, Marieka; Wingfield, Brenda; Wingfield, Michael J.; Roux, JolandaHolocryphia eucalypti is a fungal pathogen that causes stem cankers on Eucalyptus species in South Africa and Australia. In South Africa it is considered opportunistic but in Australia it has been associated with occasional but serious disease problems. The aim of this study was to determine the genetic structure of a South African population of H. eucalypti and compare it with three Australian populations of the fungus. Seventy-two isolates from Eucalyptus spp. and clones in South Africa were compared with 30 isolates from E. globulus and 24 isolates from Corymbia calophylla in the south of Western Australia and 23 isolates from E. dunnii in eastern Australia.DNA of these isolates was amplified using eight pairs of microsatellite markers previously developed for H. eucalypti. Nei’s gene diversity (H) showed that the eastern Australian population is the most genetically diverse and the Western Australian populations from Corymbia and Eucalyptus are somewhat less diverse. The South African population displayed the lowest genetic diversity. The high genetic diversity in the Australian populations supports the view that H. eucalypti is native to that region and was introduced into South Africa.Item Production of Virus-free Cassava through Hot Water Therapy and Two rounds of MeristemTip Culture(Cogent Food & Agriculture, 2020) Nakabonge, Grace; Nangonzi, R.; Tumwebaze, B.S.; Kazibwe, A.; Samukoya, C.; Baguma, Y.Cassava genetic resources are highly threatened by devastating viral diseases. It is therefore important to conserve the specifically farmer-preferred landraces/cultivars that are highly susceptible. The study assessed the efficiency of hot water therapy and meristem tip culture techniques in the elimination of cassava mosaic disease (CMD) and cassava brown streak disease (CBSD) causal viruses. Stems of symptomatic cassava genotypes confirmed infected with cassava brown streak viruses (CBSV) and cassava mosaic viruses (CMV) were subjected to hot water therapy at varying temperatures (25°C—60°C) followed by two rounds of meristem tip culture (MTC). Data on sprouting in the screen house and response in vitro were recorded and weaned plants were indexed for CMV and CBSV. The results indicated 100% elimination of CMV and a significant reduction in the viral load of CBSV. Thus, these techniques could be integrated into the cassava conservation strategy, for sustainable management of cassava genetic resources.Item Roles of Arbuscular Mycorrhizal Fungi on soil fertility and its importance in phytoremediation of polluted soil(Preprints, 2021) Fall, Abdoulaye Fofana; Nakabonge, Grace; Ssekandi, Joseph; Apori, Samuel ObengA single paragraph Arbuscular mycorrhizal fungi (AMF) establish symbiotic relationships with many crops. These soil microbiotas improve the soil fertility through the soil physical, chemical and biological properties. extending the root absorbing area. In return, the symbiont receives plant carbohydrates for the completion of its life cycle. AMF also helps plants to cope with biotic and abiotic stresses such as extreme temperature, heavy metal, diseases, and pathogens. For soil physical properties, the mechanisms used by AMF are the production of a glycoprotein, glomalin, which creates a high quality of soil macro-aggregations. These macro-aggregations control soil erosion, nutrients and organic matter losses. For soil chemical properties, AMF produce acids and an enzyme called phosphatase. This enzyme hydrolyzes the inorganic phosphorus and the rock phosphate (RP) hence making P available in the soil for plant uptake. AMF also are involved in soil nitrogen, carbon and trace element cycling. Regarding the biological component of the soil, AMF influence the composition, diversity and activity of microbial communities in the hydrosphere. They also work in synergy with others soil microorganisms to improve soil fertility, plant growth and resistance against some diseases. In this review, we present the contribution of AMF on soil fertility and importance in polluted soils.Item Susceptibility of Eucalyptus Hybrid Clones to Botryosphaeria Canker in Uganda(Journal of Sustainable Forestry, 2020) Nakabonge, Grace; Namukasa, Evelyn; Tumwebaze, Susan B.The study assessed the susceptibility of the nine commonly grown Eucalyptus clones to Neofusicoccum species associated with Botryosphaeria canker in Uganda. The inoculation trials indicated that susceptibility of Eucalyptus hybrids differed significantly (p = .000), clones GU609, GU7, GC578, and GC796 exhibiting a higher tolerance than GC784, GC550, GU8, GC514, and GC540. The results further revealed that N. parvum was more pathogenic than N. kwambonambiense. The generated information can be exploited in sustainable forest management by expanding the growing of tolerant hybrids in areas with high Botryosphaeria canker disease pressure.Item Traditional management and conservation of Shea trees (Vitellaria paradoxasubspeciesnilotica) in Uganda(Springer, 2016) Gwali, Samson; Okullo, John Bosco Lamoris; Eilu, Gerald; Nakabonge, Grace; Nyeko, Philip; Vuzi, PeterTraditional practices are universally recognised as a basis for conservation ofbiodiversity. However, such practices are often not included in natural resource conser-vation policies. This study assessed local conservation practices of shea trees (Vitellariaparadoxa) within different farming systems in Uganda and developed conservationguidelines for the species. The assessment involved 300 respondents, 15 focus groups and41 key informants. Content analysis was used to identify the most important managementand conservation practices. Local uses were categorised on the basis of shea tree productswhile differences in conservation practices were analysed using the Friedman test. Theresults show that eight shea tree products are used for 36 different purposes. Respondents’age significantly influenced their knowledge about the shea tree. Traditional conservationpractices include on-farm retention during cultivation and the use of folklore (mainly taboos), customs and rituals. Traditional management practices include weeding, bushburning, pollarding and pruning. Based on the current management and traditional con-servation practices, a framework for the conservation of shea trees is proposed for inte-gration into conservation policy decisions.Item Variation in Susceptibility of Eucalyptus Grandis and Selected Hybrid Clones to two Termite Species Macrotermes Bellicosus and M. Subhyalinus in Uganda(All Life, 2021) Nakabonge, Grace; Matovu, BrianThe maximum productivity of plantation forestry and its role in climate change mitigation, adaptation and resilience cannot be met without proper management. Termites in the genus Macrotermes have been reported as a major challenge to Eucalyptus plantation forestry establishment. The current study evaluated the susceptibility of four Eucalyptus hybrid clones: GU 7, GC 796, GC 550 and GC 796/2, and E. grandis Hill ex Maid. to the most damaging Macrotermes bellicosus (Smeathman) and Macrotermes subhyalinus (Rambur) to identify tolerant material that can be planted in high incidence areas. The study involved exposure of moisture dry pieces of wood from E. grandis and the four hybrid clones to damage by M. bellicosus and M. subhyalinus. Results confirmed that M. bellicosus is the most aggressive. Results further revealed that E. grandis and GC 550 are the most susceptible whereas GC 796 is the most tolerant clone. The findings from the study will contribute to improved management of termites by planting tolerant material in high risk areas.